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Palynomorphs are one of the few groups of fossils that provide biostratigraphic control in marine to nonmarine rocks and can be applied as proxies for paleoenvironmental and paleoclimatic interpretations. Their utility is enhanced by their microscopic size, which is usually less than 200 micrometres; they are thus easily recovered from small rock samples. They occur throughout the Phanerozoic and are therefore invaluable in refining biostratigraphic control of Arctic successions in Alaska, Arctic Canada, Greenland, northern Europe, and northern Russia. The objective of the Circum-Arctic Palynological Event (CAPE) Stratigraphy series of papers is to integrate data published on Arctic palynomorphs to delineate palynological events (palynoevents) across the Arctic for the Silurian to Cenozoic. Once the series of papers is complete, the data will also be used to compile a TimeScale Creator datapack that can be updated and calibrated on an ongoing basis. Palynoevents include taxon originations (first occurrences or FOs) and extinctions (last occurrences, or LOs) and some abundance events. The palynoevents are correlated with established chronostratigraphic horizons such as bases of ammonoid zones or stages, and hence their chronostratigraphy is independent of the absolute time scale in millions of years. In addition to the palynostratigraphic papers, the series includes a paper detailing the paleogeography of the circum-Arctic regions, including informative maps, as well as a paper providing a palynological perspective of the Cenozoic shift from greenhouse to icehouse conditions. [ABSTRACT FROM AUTHOR]

Twenty years of gravity observations from various satellite missions have provided unique data about mass redistribution processes in the Earth system, such as melting of Greenland's ice shields, sea level changes, ground and underground water depletion, droughts, floods, etc. The ongoing climate change underlines the urgent need to continue this kind of observations with future gravimetry missions using enhanced concepts and sensors. This paper studies the benefit of enhanced electrostatic and novel optical accelerometers and gradiometers for future gravimetry missions. One of the limiting factors in the current space gravimetry missions is the drift of the Electrostatic Accelerometers (EA) which dominates the error contribution at low frequencies (<1mHz). This study focuses on the modeling of enhanced EAs with laser-interferometric readout, so-called optical accelerometers, and on evaluating their performance for gravity field recovery in future satellite missions. In this paper, we simulate gravimetry missions in multiple scopes, applying various software modules for satellite dynamics integration, accelerometer (ACC) and gradiometer simulation and gravity field recovery. The total noise budgets of the modeled enhanced electrostatic and optical ACCs show a similar sensitivity as the ACC concepts from other research groups. Parametrization w.r.t. the weight of the test mass (TM) of ACCs and the gap between the TM and the surrounding electrode housing confirmed the fact known from previous results that an ACC with a heavier TM and a larger gap will perform better. Our results suggest that the anticipated gain of novel ACCs might at some point be potentially limited by noise from the inter-satellite laser ranging interferometry. In order to present the advantage of the novel sensors, time-variable background models and associated aliasing errors were not considered in our simulations. The utilization of enhanced EAs and optical ACCs shows a significant improvement of accuracy compared to the currently used GRACE-like EA. In addition, their benefit in double satellite pairs in a so-called Bender constellation as well as in the combination of low-low satellite-to-satellite tracking with cross-track gradiometry has been investigated. [ABSTRACT FROM AUTHOR]

Background: To strengthen palliative care for children in the Nordic countries, an updated status of current needs, resources, clinical services, education, and research is necessary to align and consolidate future research. A Nordic research collaboration initiative for children with palliative care needs was assembled in 2023. Building on this initiative, this paper presents an overview of pediatric palliative care (PPC) in the Nordic countries' (a) population characteristics, (b) care models and setting of care, (c) education and training, and (d) research. Methods: The Nordic initiative researchers collaboratively gathered and assessed available data on the characteristics of PPC within Denmark, Finland, Greenland, Iceland, Norway, the Faroe Islands, Sweden, and Åland. Data were compiled in a matrix with population characteristics, models- and setting of care, education and training, and areas of research in a Nordic context. The findings are narratively and descriptively presented, providing an overview of Nordic PPC. Results: In total, the Nordic child population comprises around six million children (0–19 years), of which about 41.200 are estimated to be living with a life-limiting and/or life-threatening condition. Healthcare services are provided through various care models, ranging from specialized care to homecare settings. Overall, there remain few opportunities for education and training with some exceptions. Also, Nordic research within PPC has been shown to be a growing field although much remains to be done. Conclusion: This overview is the first outline of the current PPC in Nordic countries. Although some differences remain important to acknowledge, overall, the strengths and challenges faced within PPC in the Nordic countries are comparable and call for joint action to increase evidence, services, and education to better serve the children, families, and healthcare personnel within PPC. Despite the varying structural premises for PPC, research endeavors aiming to provide evidence in this field seem increasing, timely and relevant for the Nordic countries, as well as the international context. [ABSTRACT FROM AUTHOR]

Ice fractures when subject to stress that exceeds the material failure strength. Previous studies have found that a von Mises failure criterion, which places a bound on the second invariant of the deviatoric stress tensor, is consistent with empirical data. Other studies have suggested that a scaling effect exists, such that larger sample specimens have a substantially lower failure strength, implying that estimating material strength from laboratory-scale experiments may be insufficient for glacier-scale modeling. In this paper, we analyze the stress conditions in crevasse onset regions to better understand the failure criterion and strength relevant for large-scale modeling. The local deviatoric stress is inferred using surface velocities and reanalysis temperatures, and crevasse onset regions are extracted from a remotely sensed crevasse density map. We project the stress state onto the failure plane spanned by Haigh–Westergaard coordinates, showing how failure depends on mode of stress. We find that existing crevasse data are consistent with a Schmidt–Ishlinsky failure criterion that places a bound on the absolute value of the maximal principal deviatoric stress, estimated to be 158±44 kPa. Although the traditional von Mises failure criterion also provides an adequate fit to the data with a von Mises strength of 265±73 kPa, it depends only on stress magnitude and is indifferent to the specific stress state, unlike Schmidt–Ishlinsky failure which has a larger shear failure strength compared to tensile strength. Implications for large-scale ice flow and fracture modeling are discussed. [ABSTRACT FROM AUTHOR]

In an iceberg-choked fjord, meltwater can drive circulation. Down-fjord of the ice, buoyancy and rotation lead to an outflowing surface coastal current hugging one side of the fjord with an inflowing counter-current below. To predict the structure and evolution of these currents, we develop an analytical model – complemented by numerical simulations – that involves a rectangular fjord initially at rest. Specifically, we (i) start with the so-called Rossby adjustment problem; (ii) reconfigure it for a closed channel with stratification; and (iii) generalize the conventional "dam-break" scenario to a gradual-release one that mimics the continual, slow injection of meltwater. Implicit in this description is the result that circulation is mediated by internal Kelvin waves. The analytical model shows that if the total meltwater flux increases (e.g., a larger mélange, warmer water, or enhanced ice–ocean turbulence) then circulation strength increases as would be expected. For realistic parameters, a given meltwater flux induces an exchange flow that is ∼ 50 times larger. This factor decreases with increasing water column stratification and vice versa. Overall, this paper is a step toward making Greenland-wide predictions of fjord inflows and outflows induced by icebergs. [ABSTRACT FROM AUTHOR]

The Green's function approach is well‐established and widely used for modeling the surface mass loading displacements. Global mean Green's functions (MGFs) are commonly applied without considering local variations of the crustal structure. Derived from the modified layered Earth structure, the local Green's functions (LGFs) are theoretically beneficial to generate more accurate deformation, since they consider interior information of the local crust. This paper analyzed the differences among MGFs from Gutenberg–Bullen A model and two sets of LGFs derived from modified PREM Earth models consolidating with two crust models TEA12 and CRUST1.0, hereafter called PREMTEA and PREMCRU, respectively. Utilizing MGFs and two sets of LGFs, we modeled the corresponding 3D atmospheric loading displacements for 984 ITRF2014 stations and compared them with the ITRF2014 residuals. The results show that LGFs from PREMTEA and PREMCRU perform well in further promoting scatter reduction for ∼72%, ∼56%, and ∼85% of stations for the Up, East and North components, respectively. The improvements for the North components are significant (up to 3.6%). In particular, stations in the east coastal areas of North America and the west edge of Greenland exhibit further promoting scatter reduction for the East components (up to ∼2.5%), while those located in west coastline of North America show better performance for the North components. Nevertheless, there are significant anomalies in northern Europe for PREMCRU, the mutation margin of which should be carefully considered when using a resolution higher than 1°. In the area around station MORP (358.31°W, 55.21°N, sited at coastline of Britain), we suggest using PREMTEA model. Plain Language Summary: In any location worldwide, we employ a consistent set of numbers, known as load Green's functions that characterize the elastic properties of the Earth, to model the deformation caused by mass transfer on Earth's surface, which is referred to as surface mass loading effects. Most research and data products adopt same set of global mean Green's functions for any location on Earth, which neglects the differences in elastic properties of various regions of the Earth, leading to modeling errors to some extent. This study aims to optimize the modeling using local load Green's functions, with the objective of obtaining results that are more theoretically valuable. "Local" means that the Green's functions for each site are derived from an Earth model that takes into account the local crustal structure. The modeled atmospheric loading displacements exhibit enhanced alignment with GNSS position time series. This, in turn, further elucidates that deformations can be more attributed to atmospheric loading. Moreover, the model shows improved performance in the horizontal components when compared to the vertical components. Key Points: Local load Green's Functions enable a more precise modeling of loading displacements than global mean Green's FunctionsThe modeled atmospheric loading displacements based on Local Green's Functions can improve scatter reduction of GNSS position time seriesTwo sets of local load Green's Functions, based on CRUST1.0 model and TEA12 model, are compared. We recommend TEA12 for European region [ABSTRACT FROM AUTHOR]

Polar regions and Greenland in particular are highly sensitive to global warming. Impacts on Greenland's glaciers may be observed through the increasing number of calving events. However, a direct assessment of the calving activity is limited due to the remoteness of polar regions and the cloudy weather which makes impossible a recurrent observation through satellite imagery. To tackle this issue, we exploit the seismological network deployed in Greenland which actively records seismic signals associated with calving events, hereinafter referred to as glacial earthquakes. These seismic signals present a broad frequency range and a wide diversity of waveform which make them difficult to discriminate from tectonic events as well as anthropogenic and natural noises. In this study, we start from two catalogues of known events, one for glacial earthquake events which occurred between 1993 and 2013 and one for earthquakes which occurred in the same time period, and we implement a detection algorithm based on the STA/LTA method to extract signals' events from continuous data. Then, we train and test a machine learning processing chain based on the Random Forest algorithm which allows us to automatically associate the events respectively with calving and tectonic activity, with a certain probability. Finally, we investigate 844 selected days spanning time of continuous data from the Greenland regional seismic network which results in a new, more exhaustive, catalogue of glacial earthquakes expanded of 1633 newly detected glacial events. Moreover, we extensively discuss the choice of the features used to describe glacial earthquakes, in particular the 39 new features created in this study which have drastically improved our results with 7 of the 10 best features being in the added set. The perspective of further expansion of the glacial earthquake catalogue applying the processing chain discussed in this paper on different time spans highlights how combining seismology and machine learning can increase our understanding of the spatio-temporal evolution of calving activity in remote regions. [ABSTRACT FROM AUTHOR]

At present, a variety of global remote sensing surface downwelling longwave radiation (SDL) products are used for atmospheric science research; however, there are few studies on the quantitative evaluation of differences among different SDL products. In order to evaluate the differences among different SDL products quantitatively, we have selected three commonly used SDL products—Clouds and the Earth's Radiant Energy System-Synoptic Radiative Fluxes and Clouds (CERES-SYN), the European Centre for Medium Range Weather Forecasts-Surface Radiation Budget (ECMWF-SRB) and the Global Energy and Water Exchanges Project-Surface Radiation Budget (GEWEX-SRB)—to comprehensively study in this paper. The results show that there are significant differences among the three SDL products in some areas, such as in the Arctic, the Antarctic, the Sahara, the Tibet Plateau, and Greenland. The maximum absolute root mean square error (RMSEab) in these areas is greater than 20 Wm−2, the maximum relative root mean square error (RMSEre) is greater than 20%, the maximum and minimum absolute mean bias error (MBEab) are about 20 Wm−2 and −20 Wm−2, respectively, and the maximum and minimum relative mean bias error (MBEre) are about 10% and −10%, respectively. Among the three SDL products, the difference between the ECMWF-SRB and GEWEX-SRB is the most significant. In addition, this paper also analyzed the differences among different SDL products based on three aspects. Firstly, the differences among the three SDL products show that there is significant seasonality, and the differences among different months may vary greatly. However, the differences are not sensitive to years. Secondly, there are some differences in cloud-forcing radiative fluxes (CFRFs) of different SDL products, which is also an important factor affecting the difference between different SDL products. Finally, in the process of converting high temporal resolution SDL products into monthly SDL products, data processing also affects the difference between different SDL products. [ABSTRACT FROM AUTHOR]

Over the past 20 years, the Gravity Recovery and Climate Experiment (GRACE), and its successor mission, GRACE‐Follow On (GRACE‐FO) have made significant contributions to time‐variable gravity field modeling. A Chinese low‐low satellite‐to‐satellite tracking gravimetry mission (i.e., Chinese future gravimetry mission) has been confirmed to be selected as the polar‐orbiting satellite gravimetry mission for China, because of the capability to collect gravity data globally. However, the analysis of potential contributions to geosciences from GRACE‐FO coupling with the Chinese future gravimetry mission is still limited. This study combines GRACE‐FO and Chinese future gravimetry missions as the Dual GRACE‐like Polar satellite Constellation (DGPC). By carefully choosing the initial orbit parameters of the Chinese future gravimetry mission with the differential evolution algorithm, the DGPC is expected to mitigate the temporal aliasing effects by improving the temporal resolution of time‐variable gravity solutions (i.e., 1‐day and 3‐day solutions). Regarding the spectral‐domain evaluation, zonal, tesseral, and sectorial coefficients estimated by the DGPC show approximately 6.01%–13.42% noise reductions compared with GRACE‐FO. Regarding the spatial‐domain evaluation, the DGPC can suppress noises of about 39.44% and 31.12% in annual amplitude and long‐term trend, respectively. On this basis, this paper analyzes the effectiveness of the DGPC in potential contributions to geosciences (e.g., hydrology, glaciology, and seismology). Specifically, the DGPC can improve accuracy by about 36.96%, 25.85%, and 33.16% with respect to GRACE‐FO for signals in the subhumid basin, signals of ice‐sheet mass balance over Greenland, and coseismic displacement of the fault zone, respectively. In general, the potential capability for high‐frequency signals recovery of the DGPC would facilitate contributions of satellite gravimetry to geosciences. Plain Language Summary: The Gravity Recovery And Climate Experiment (GRACE) mission and its successor GRACE Follow On (GRACE‐FO) have made significant contributions to time‐variable gravity field modeling. A polar gravity satellite mission (i.e., Chinese future gravimetry mission) has been confirmed to be selected as the polar‐orbiting satellite gravimetry mission for China because of its capability to collect gravity data globally. Including the GRACE‐FO mission, it is expected that there will be two polar pairs of gravity satellites (i.e., dual GRACE‐like polar satellite constellation) simultaneously within the next few years. What can we expect from the dual GRACE‐like polar satellite constellation? In this study, we introduce an optimization algorithm (i.e., differential evolution algorithm) to carefully choose the initial orbit parameters of the Chinese future gravimetry mission. The dual GRACE‐like polar satellite constellation has been demonstrated to have the potential to mitigate the temporal aliasing effects of time‐variable gravity solutions. It is found that the dual GRACE‐like polar satellite constellation can improve accuracy by about 36.96%, 25.85%, and 33.16% with respect to GRACE‐FO for signals in the subhumid basin, signals of ice‐sheet mass balance over Greenland, and coseismic displacement of the fault zone, respectively. The temporal improvement of Earth's mass transport estimated by coupling GRACE‐FO with a Chinese polar gravity satellite mission would facilitate contributions of satellite gravimetry to geosciences. Key Points: This paper introduces the differential evolution algorithm into the design of the dual Gravity Recovery And Climate Experiment (GRACE)‐like polar satellite constellationImproving the temporal resolution of time‐variable gravity solutions can potentially contribute to mitigating the temporal aliasing effectsThe dual GRACE‐like polar satellite constellation has high‐frequency signal recovery capabilities and stimulates potential contributions to geosciences [ABSTRACT FROM AUTHOR]

Microfade testing (MFT) was used to examine standardized wool samples dyed with 14 natural historic dyes, each prepared with five different mordants, to determine whether the lightfastness and colourimetric properties of these dyes vary as a function of the mordant. The addition of mordants changed the original colour of the dyes as well as potential patterns corresponding to ΔL*, Δa*, and Δb* such that the variation of lightfastness ranges from 0.25–0.70 units of Blue Wool Equivalence (BWE). Disregarding the effect of mordants, MFT showed that all dyes have lightfastness equivalent to BW3, indicating that they belong in the category of 'high sensitivity to light'. All dye-mordant combinations vary in lightfastness, such that even the least lightfast dye will have a mordant combination that is more lightfast than the most lightfast dye combined with a mordant that renders it less lightfast. The effect of mordants varies by dye: while one dye may demonstrate a difference in lightfastness of 0.56 units of BWE between the least and most lightfast mordant combination, another may show little or no difference (as low as 0.07 units of BWE). Overall, alum based mordants tend to produce the least lightfast combinations, followed by tin and iron, with copper and chromium producing the most lightfast combinations. This paper shows that there are no simplistic patterns of lightfastness between mordant-dye combinations with these 14 natural dyes. Identifying both dye and mordant is useful to better estimate the lightfastness of a dyed textile. [ABSTRACT FROM AUTHOR]

The article offers world news briefs related to meteorology. The subrotors and the internal structure of the parent rotor lifts off the surface and breakdown along the edge of the lee wave through Kelvin-Helmholtz like instability. Greenland extends one quarter of the distance between the North Pole and Equator averaging 1.5 kilometer (km) in height and reaching skyward more than 3.5 km. The Global Precipitation Climatology Project (GPCP) offers the opportunity to analyze climate variation.

Numerical modeling of ice sheet motion and hence projections of global sea level rise require information about the evolving subglacial environment, which unfortunately remains largely unknown due to its difficulty of access. Here we advance such subglacial observations by reporting multi‐year observations of seismic tremor likely associated with glacier sliding at Helheim Glacier. This association is confirmed by correlation analysis between tremor power and multiple environmental forcings on different timescales. Variations of the observed tremor power indicate that different factors affect glacial sliding on different timescales. Effective pressure may control glacial sliding on long (seasonal/annual) timescales, while tidal forcing modulates the sliding rate and tremor power on short (hourly/daily) timescales. Polarization results suggest that the tremor source comes from an upstream subglacial ridge. This observation provides insights on how different factors should be included in ice sheet modeling and how their timescales of variability play an essential role. Plain Language Summary: The Greenland Ice Sheet has lost ice increasingly in the past few decades, contributing significantly to global sea level rise. However, large uncertainties remain in computer simulations of such ice mass loss and hence sea level rise. This uncertainly is mainly attributed to the lack of information on what is happening at the bottom of the ice sheet and how that affects ice sheet movement. For example, how much water is there and whether it is in isolated pockets or is well distributed as a thin sheet can have an important effect on ice movement. In this paper, we observe small ground motions that are generated during glacier movement at a marine‐terminating glacier in Greenland. By analyzing the energy variation of the small ground motions over multiple years as well as observing the reasons that cause the variations, we learn that subglacial water pressure may control ice flow speeds on a seasonal/annual scale, and that ocean tides can change ice flow on an hourly/daily scale. This observation provides important constraints for computer simulations of future sea level rise in terms of the impacting factors and their respective timescales. Key Points: Multi‐year seismic records reveal glacial slip and tremor variability at Helheim GlacierTremor correlates with high effective pressure at tidal timescales, opposite to the expectation at longer timescalesThe tremor source points to an upstream subglacial ridge [ABSTRACT FROM AUTHOR]

The ionosphere can impair the accuracy, availability and reliability of satellite-based positioning, navigation and timing. The Arctic region is particularly affected by strong ionospheric gradients and phase scintillation, posing a safety issue for critical infrastructure and operations. Ionospheric warning and impact maps can provide support to Arctic operations, but to produce such maps threshold values have to be determined. This study investigates how such thresholds can be derived from the GPS and Galileo satellite signals. Rapid changes in total electron content (TEC) or scintillation-induced receiver tracking errors could result in cycle slips or even loss of lock. Cycle slips and data outages are used as a measure of impact on the receiver in this paper. For Galileo, 73.6% of the impacts were cycle slips and 26.4% were outages, while for GPS, 29.3% of the impacts were cycle slips and 70.7% were outages. Considering the sum of cycle slips and outages, it is worth noting that the sum of impacts for Galileo signals is larger than for GPS. A range of possible explanations have been examined through hardware-in-the-loop simulations. The simulations showed that the GPS L2 signal was not adequately tracked during rapid TEC changes and TEC changes were underestimated, thus the GPS cycle slips, derived from L1 and L2 derived TEC changes, were not all registered. These results are important in designing threshold values for TEC and for scintillation impact maps as well as for the operation of GNSS equipment in the Arctic. In particular, the results show that ionospheric changes could be underestimated if GPS L1 and L2 were used in isolation from other dual frequency combinations. It is the first time this analysis has been made for Greenland and the first time that the dual frequency derivation of ionospheric delay using GPS L1 and L2 has been shown to underestimate large TEC gradients. This has important implications for informing GNSS operations that rely on GPS to provide reliable estimates of the ionosphere. [ABSTRACT FROM AUTHOR]

The negative surface mass balance of glaciers and ice caps under a warming climate impacts local ecosystems, influencing the volume and timing of water flow in local catchments, while also contributing to global sea level rise. Peripheral glaciers distinct to the Greenland ice sheet respond faster to climate change than the main ice sheet. Accurate assessment of surface mass balance depends on in-situ observations of near-surface climate and ice ablation, but very few in-situ observations of near-surface climate and ice ablation are freely available for Greenland’s peripheral glaciers. The transect of three automated weather and ablation stations on the peripheral A. P. Olsen ice cap in northeast Greenland is an example of this much needed data. The transect has been monitored since 2008, and in 2022 the old weather and ablation stations were replaced by a new standardized setup. In order to ensure comparable data quality from the old and new monitoring station setups, it was necessary to re-evaluate the data collected between 2008 and 2022. This paper presents the fully reprocessed near-surface climate and ablation data from the A. P. Olsen ice cap transect from 2008 to 2022, with a focus on data quality and the usability for ice ablation process studies. The usability and some quality issues are exemplified by using the data in an energy balance melt model for two different years. We showed that the inherent uncertainties of the data resulted in an accurate reproduction of ice ablation for just one of the two years. A transect of three automatic ablation and weather stations of this length is unique for Greenland’s peripheral glaciers and it has a broad scale of usage from input to climate reanalysis to detailed surface ablation studies. The dataset can be downloaded here: https://doi.org/10.22008/FK2/X9X9GN (Larsen and Citterio, 2023). Future refinements will be uploaded as new versions and the continuation of the transect time series are available via. [ABSTRACT FROM AUTHOR]

Digital elevation models (DEMs) are currently one of the most widely used data sources in glacier thickness change research, due to the high spatial resolution and continuous coverage. However, raw DEM data are often misaligned with each other, due to georeferencing errors, and a co-registration procedure is required before DEM differencing. In this paper, we present a comparative analysis of the two classical co-registration methods proposed by Nuth and Kääb (2011) and Rosenholm and Torlegard (1988). The former is currently the most commonly used method in glacial studies, while the latter is a seminal work in the photogrammetric field that has not been extensively investigated by the cryosphere community. Furthermore, we also present a new residual correction method using a generalized additive model (GAM) to eliminate the remaining systematic errors in DEM co-registration results. The performance of the two DEM co-registration methods and three residual correction algorithms (the GAM-based method together with two parametric-model-based methods) was evaluated using multiple DEM pairs from the Greenland Ice Sheet and mountain glaciers, including Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEMs, ZiYuan-3 (ZY-3) DEMs, the Shuttle Radar Topography Mission (SRTM) DEM, and the Copernicus DEM. The experimental results confirm our theoretical analysis of the two co-registration methods. The method of Rosenholm and Torlegard has a greater ability to remove DEM misalignments (an average of 4.6 % and 13.7 % for the test datasets from Greenland Ice Sheet and High Mountain Asia, respectively) because it models the translation, scale, and rotation-induced biases, while the method of Nuth and Kääb considers translation only. The proposed GAM-based method performs statistically better than the two residual correction methods based on parametric regression models (high-order polynomials and the sum of the sinusoidal functions). A visual inspection reveals that the GAM-based method, as a non-parametric regression technique, can capture complex systematic errors in the DEM co-registration residuals. [ABSTRACT FROM AUTHOR]

The total air content (TAC) of polar ice cores has long been considered a potential proxy for past ice sheet elevation. Recent work, however, has shown that a variety of other factors also influence this parameter. In this paper we present a high-resolution TAC record from the South Pole ice core (SPC14) covering the last 54 000 years and discuss the implications of the data for interpreting TAC from ice cores. The SPC14 TAC record shows multiple features of interest, including (1) long-term orbital-scale variability, (2) millennial-scale variability in the Holocene and last glacial period, and (3) a period of stability from 35 to 25 ka. The longer, orbital-scale variations in TAC are highly correlated with integrated summer insolation (ISI), corroborating the potential of TAC to provide an independent dating tool via orbital tuning. Large millennial-scale variability in TAC during the last glacial period is positively correlated with past accumulation rate reconstructions as well as δ15 N-N 2 , a firn thickness proxy. These TAC variations are too large to be controlled by direct effects of temperature and too rapid to be tied to elevation changes. We propose that grain size metamorphism near the firn surface explains these changes. We note, however, that at sites with different climate histories than the South Pole, TAC variations may be dominated by other processes. Our observations of millennial-scale variations in TAC show a different relationship with accumulation rate than observed at sites in Greenland. [ABSTRACT FROM AUTHOR]

This paper reports on an observation of three-dimensional (3D) arrivals for which the change in the direction of horizontally refracted sound is nearly 180°. The experimental site is Jan Mayen Channel (JMCh), which connects the Greenland and Norwegian Seas. During the experiment, signals from a moored source transmitting a 500–1500 Hz sweep every 4 h were recorded by three surface drifters equipped with hydrophone arrays. Over a 3-day period, the drifters moved north across JMCh toward the moored source. In each recording, an in-plane arrival is identified. In a subset of these recordings, a second arrival is observed, having travel time consistent with propagation from the moored source, turning at the ridge on the south side of the channel, and arriving at the drifters. In a smaller subset of recordings, a third arrival is also observed having travel time consistent with a turning point on the face of the bathymetric rise on the west end of the channel that forms the Jan Mayen volcano. A 3D ray trace is employed to show the change in direction results from repeated reflections from the seafloor such that it is classified as horizontal refraction and not a single-bounce reflection. [ABSTRACT FROM AUTHOR]

This paper summarizes the physical and human geography of the southwestern part of Greenland, stretching from Upernavik at the southern end of Melville Bay in approximately 73° N latitude, southward to Cape Farewell in approximately 60° N latitude. It is along this southwestern coast of Greenland that modernization has token place, and it is here that development is proceeding rapidly. Since about six-sevenths of Greenland is buried under ice, only a narrow strip of land is exposed along the coastline, never exceeding one hundred miles. Most of the 22,000 people live along this coastal fringe. Of mixed Eskimo and European origin, these "Greenlanders" have increased rapidly in numbers in the last half-century, and are now straining the restricted natural resources of the country. Denmark, which has governed the country for almost two centuries, has traditionally maintained a strict policy of isolating Greenland from outside contacts. This has protected the natives and given them a high standard of education, reasonably good health, and a carefully planned economy insulating them from the vagaries of world prices. Today this traditional policy is being questioned. Intensive efforts are now being made to modernize West Greenland through building efficient harbors, power stations, fish processing plants, by raising still higher educational standards, and by speeding up Greenland's self-government. [ABSTRACT FROM AUTHOR]

This paper analyzes the origins of two 1946 sightings of Soviet submarines in the Davis Strait, placing the various reports about them into an international and interservice framework. It shows how the Davis Strait and the surrounding area (Greenland, the Canadian Arctic, and Newfoundland and Labrador) fit into early post-World War II war plans for strategic deterrence. The Davis Strait sightings combined with American and British appreciations to spur Canada to endorse postwar joint defense plans with the Americans; to pursue trilateral intelligence, research, and defense work; and to agree to defense preparations in the north, including supporting American plans to establish strategic air forces in Goose Bay, Labrador. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of the first investigation into the effect of particle‐laden plumes on glacier melting using laboratory experiments. We find that the melt rate, when the ice is exposed to a particle‐laden plume, can be larger than when exposed to an equivalent plume without particles. The increased melt rate is linked to an increase in the plume velocity in response to the presence of suspended particles. Including this increased velocity in a plume model improves melt rate predictions from the "three‐equation model" by approximately 45% for the range of particle concentrations used in this study. Plain Language Summary: Ice loss from the Greenland ice sheet is more rapid in locations where fresh water is released at the base of marine terminating glaciers. The fresh water forms a buoyant plume that rises vertically next to the ice face. Previous observations of these plumes have shown that they can contain significant concentrations of suspended sediment. We show, using laboratory experiments, that the melt rate of a vertical ice face can be increased by the presence of suspended particles in the vertically rising plume. This observation suggests that the effect of such plumes could be larger than current modeling studies predict. Key Points: Laboratory experiments show that melting of an ice face can be increased by the presence of sediment in a subglacial discharge plumeThe increased melting is linked to an increase in the plume velocity in response to the presence of suspended particlesAccounting for the increased plume velocity within the three‐equation model significantly improves predictions of the melt rate [ABSTRACT FROM AUTHOR]

This exploratory study presents Greenland as a case of a peripheral destination that complicates and contradicts global definitions of sustainable tourism. Using empirical data that consists of 39 semi-structured interviews, the author employs an inductive approach to discuss the conceptualisation of sustainable tourism according to local stakeholders in Greenland. The key points of conflict surrounding sustainable tourism in Greenland are identified and discussed, with a focus on how local stakeholders contradict each other, and on how the debates prevalent at the local scale can inform tourism development in other peripheral places. The paper contributes to academic literature by offering a deeper understanding of how core-periphery dynamics can influence perceptions of and priorities for sustainable tourism in peripheral places. It benefits the industry by exposing the main debates around the issue of sustainable tourism in Greenland, which can be used to inform the nation's tourism development. [ABSTRACT FROM AUTHOR]

Satellite data have revealed that the Greenland and Antarctic Ice Sheets are changing rapidly due to warming air and ocean temperatures. Crucially, Earth Observations can now be used to measure ice sheet mass balance at the continental scale, which can help reduce uncertainties in the ice sheets' past, present, and future contributions to global mean sea level. The launch of satellite missions dedicated to the polar regions led to great progress towards a better assessment of the state of the ice sheets, which, in combination with ice sheet models, have furthered our understanding of the physical processes leading to changes in the ice sheets' properties. There is now a three-decade-long satellite record of Antarctica and Greenland mass changes, and new satellite missions are planned to both continue this record and further develop our observational capabilities, which is critical as the ice sheets remain the most uncertain component of future sea-level rise. In this paper, we review the mechanisms leading to ice sheets' mass changes and describe the state of the art of the satellite techniques used to monitor Greenland's and Antarctica's mass balance, providing an overview of the contributions of Earth Observations to our knowledge of these vast and remote regions. [ABSTRACT FROM AUTHOR]

A chain of magnetometers has been placed in Antarctica for comparisons with magnetic field measurements taken in the Northern Hemisphere. The locations were chosen to be on magnetic field lines that connect to magnetometers on the western coast of Greenland, despite the difficulty of reaching and working at such remote locations. We report on some basic comparisons of the similarities and differences in the conjugate measurements. Our results presented here confirm that the conjugate sites do have very similar (symmetric) magnetic perturbations in a handful of cases, as expected. Sign reversals are required for two components in order to obtain this agreement, which is not commonly known. More frequently, a strong Y component of the Interplanetary Magnetic Field (IMF) breaks the symmetry, as well as the unequal conductivities in the opposite hemispheres, as shown in two examples. In one event the IMF Y component reversed signs twice within 2 hours, while the magnetometer chains were approaching local noon. This switch provided an opportunity to observe the effects at the conjugate locations and to measure time lags. It was found that the magnetic fields at the most poleward sites started to respond to the sudden IMF reversals 20 min after the IMF reaches the bow shock, a measure of the time it takes for the electromagnetic signal to travel to the magnetopause, and then along magnetic field lines to the polar ionospheres. An additional 9–14 min is required for the magnetic perturbations to complete their transition. Plain Language Summary: Space science research has long relied on magnetometer measurements in the Northern Hemisphere to detect and observe the flow of currents in the ionosphere and magnetosphere. In the past few years it has become possible to acquire magnetic field measurements in the southern polar region as well, as a result of the placement of a chain of magnetometer stations in a remote part of Antarctica. Each of these magnetometers were placed where the Earth's magnetic field connects to an existing magnetometer in the Northern Hemisphere, on the western coast of Greenland. The locations follow a roughly north‐south meridian in geomagnetic coordinates. These "conjugate" magnetometer chains are useful for observing the similarities and differences between the ionospheric currents flowing in opposite hemispheres as a result of the solar wind's interaction with the Earth's magnetosphere. This paper presents results showing how the inter‐hemispheric measurements are very similar in some cases, but only if the signs of two of the vector components are reversed. In other cases the magnetic fields in the two polar hemispheres are different, mainly due to the summer‐winter differences in conductivity. The conjugate measurement will be useful for future space science research. Key Points: Magnetic field measurements are obtained from magnetic conjugate points in both hemispheresUnder optimal conditions the conjugate magnetic fields are very similar, with signs reversed on two components due to coordinate geometriesMore often the fields differ due to different seasonal conductivities and asymmetrical driving by the magnetic field in the solar wind [ABSTRACT FROM AUTHOR]

After the end of World War II, many military air bases in Greenland were abandoned with all the material left in place. One of these sites was the Bluie East Two military air base. A specific feature of this area is that it contained thousands of old barrels formerly used for fuel storage. In 2019, a rehabilitation of this area began. A few months prior to the rehabilitation, our expedition visited the area and mapped it using an unmanned aerial vehicle (UAV). This made it probably the latest documentation before the start of the sanitation. The aim of such mapping was to estimate the number of barrels in a given location. The second objective was to monitor the progress of the rehabilitation over the years. For this purpose, satellite data were acquired for the years 2019 through 2022. A supervised classification was performed to automatically detect sites with barrel occurrences, which enabled subsequent change detection. We conclude that a total of 33,786 old barrels were located in the investigated area in 2019. However, we suggest this number is a lower estimate of the actual number of barrels due to the factors we mention in our paper. The results further indicate that between the years 2019 and 2022 the barrels were removed from more than half of the area. [ABSTRACT FROM AUTHOR]

In the post-WWII decolonization era, the prospect of an open, decolonized Greenland, with unrestricted mobility for inhabitants, intensified medical experts' pre-existing concerns over sexually transmitted diseases. During the colonial phase, medical and administrative authorities could govern Greenlanders as subjects and accordingly control their mobility and interactions with Europeans. However, the decolonization agenda threatened to undermine this situation. Greenland could no longer remain a colony, enclosed and sealed off from the rest of world by trade monopoly and strict limitations on access to the country imposed by the Danish authorities. Doctors were concerned by two impending shifts that threatened to undermine efforts to control sexually transmitted diseases. First, Greenland's decolonized status would entail more or less free access to the country. Second, after decolonization, Greenlanders would have the status as citizens, and authorities could no longer govern them as (colonial) subjects. This paper demonstrates how medical authorities struggled with the Greenlanders' transition from controllable (sexual) subjects to rights-bearing (sexual) citizens. The paper provides a fresh perspective concerning this watershed moment, between colonialism and the process of decolonization in Greenland. [ABSTRACT FROM AUTHOR]

This paper presents new u-channel paleomagnetic secular variation (PSV) data for ODP Site 1233 (Chile margin) for the last 70 ky. This is the highest-resolution, long-term PSV record ever recovered. The u-channel study has carried out detailed af demagnetization of the natural remanence (NRM) and developed a characteristic remanence (ChRM – final PSV direction) for each sampling horizon. The u-channel rock magnetic studies have measured magnetic susceptibility and anhysteretic remanence (ARM) with af demagnetization and used them to normalize the NRM and develop a new, detailed relative paleointensity record. The paleomagnetic record contains three excursions: the Mono Lake Excursion, the Laschamp Excursion, and the Greenland/Norwegian-Sea Excursion. These excursions have nominal sampling intervals of 5–8 years. Both the Mono Lake and Greenland/Norwegian-Sea Excursions involve short duration intervals of excursional directions (<300 years). The excursions are distinctly different from similar excursion records from other parts of the World. The Laschamp Excursion exhibits a full local reversal of the field with fast (<200 yr) movement to/from reversed directions and ∼ 500 years of full reversed polarity directions. This pattern is distinctly different from Laschamp excursion records from other parts of the World. We have carried out a statistical analysis of the Site 1233 u-channel PSV record. Notable specific features of that analysis include documentation that the field spends >1/3 of its time with anomalously large amplitude directional variability (high angular dispersion). These intervals occur at∼25–45 ka and 55–65 ka. These intervals have lower-frequency (more sluggish) directional variability and are associated with lower than average paleointensity. • This paper presents a very detail record of PSV from the Southern Hemisphere. • The record contains detailed records of three excursions. • The Site 1233 PSV record of the Laschamp Excursion is a local field reversal. That is different from its detailed character elsewhere in the world. [ABSTRACT FROM AUTHOR]

The Arctic climate is influenced by the interaction of shortwave (SW) and longwave (LW) radiation with the atmosphere and the surface. The comprehensive evolution of the Surface Radiative Fluxes (SRF) on different time scales is of paramount importance to understanding the complex mechanisms governing the Arctic climate. However, only a few sites located in the Arctic region provide long-term time series of SRF allowing for capturing the seasonality of atmospheric and surface parameters and carrying out validation of satellite products and/or reanalyses. This paper presents the daily and monthly SRF record collected at the Thule High Arctic Atmospheric Observatory (THAAO, 76.5° N, 68.8° W), in North-Western Greenland. The downwelling components of the SW (DSI) and the LW (DLI) irradiances have been measured at THAAO since 2009, while the collection of the upwelling SW (USI) and LW (ULI) irradiance was started in 2016, together with additional measurements, such as e.g., meteorological parameters and column water vapour. The datasets of DSI (Meloni et al., 2022a; https://doi.org/10.13127/thaao/dsi), USI (Meloni et al., 2022b; https://doi.org/10.13127/thaao/usi), DLI (Meloni et al., 2022c; https://doi.org/10.13127/thaao/dli), ULI (Meloni et al., 2022d; https://doi.org/10.13127/thaao/uli), and near surface air temperature (Muscari et al., 2018; https://doi.org/10.13127/thaao/met), can be accessed through the THAAO web site (https://www.thuleatmos-it.it/data). DSI is absent (solar zenith angle=90°) from 29 October to 13 February, assuming maxima in June (monthly mean of 277.0 Wm-2), when it is about half of the total incoming irradiance. The USI maximum occurs in May (132.4 Wm-2) due to the combination of moderately high DSI values and high albedo. The shortwave surface albedo (A) assumes an average of 0.16 during summer, when the surface is free of snow. Differently, during months of snow-covered surface, when solar radiation allows estimating A, its values are greater than 0.6. A large interannual variability is observed in May and September, months characterized by rapidly changing surface conditions, which appear to be linked with air temperature anomalies. DLI and ULI maxima occur in July and August, and minima in February and March. ULI is always larger than DLI and shows a wider annual cycle. ULI is well described by a fourth-order polynomial fit to the air temperature (R²>0.99 for monthly data and R²>0.97 for daily data). The surface radiation budget (SRB) is positive from April to August, when absorption of solar radiation exceeds the infrared net cooling, with a maximum value of 153.2 Wm-2 in June. From November to February, during the polar night, the LW net flux varies between -34.5 and -43.0 Wm-2. In March and September, the negative LW net flux overcomes the positive SW contribution, producing a negative SRB. THAAO measurements show clear evidence of the influence of several regional weather/climate events, which appear strongly linked with SRF anomalies. These anomalies are found for example during summer 2012, when a large ice melting event took place over Greenland, and during winter 2019-2020, extraordinarily cold in the Arctic region. [ABSTRACT FROM AUTHOR]

The Gravity Recovery and Climate Experiment (GRACE) and its successor GRACE Follow-On mission have been estimating temporal gravity field models for various geoscience applications since 2002. While the errors in atmospheric and oceanic de-aliasing (AOD) model are still the key limitation for GRACE-type missions especially taking advantages of improved laser ranging interferometer (LRI), this paper explores the realistic assumption of continuously reducing AOD model error in global scale and regional scale (e.g. ocean, Greenland, Qinghai-Tibet plateau and South America) in the anticipated future. For this, using a realistic orbit scenario and error assumptions both for instrument and background model errors, the 5-yr full-scale simulations are implemented in the context of 26 scenarios with different AOD model errors. Our overall simulation results demonstrate that: (1) when the AOD model errors are reduced in the global scale, the corresponding gain in temporal gravity field determination is significant, with the cumulative geoid height error decrease from 11.28 to 6.25 mm in spectral domain, as well as 26.3–65.2 per cent noise reduction in terms of mean RMS residuals over ocean in spatial domain. (2) When the AOD model errors are reduced in the regional scale, the improvements of temporal gravity field estimations are diverse in different simulation scenarios. The most notable noise reduction, with 22.9–43.9 per cent noise reduction in spatial domain, is observed when the AOD model error decreases in ocean. The limited noise reductions (0.1 per cent and 1.3 per cent respectively in spectral and spatial domain) are observed in the temporal gravity field estimations if the AOD model is refined in other typical regions such as the Qinghai-Tibet plateau, the Greenland and the South America. (3) However, when the satellites passing over the AOD model refined regions, the along-orbit range rate analysis indicates that, there are visible differences by about 50.0 nm s−1 in terms of range rate residuals as well as 11.0–48.5 nm s−1 in terms of the mean RMS of range rate residuals. These results reflect the benefits of reducing AOD model error in both global and regional scale for improving GRACE-type temporal gravity estimation, especially considering the development of LRI technology. [ABSTRACT FROM AUTHOR]

In studying the mass balance of polar ice sheets, fluctuations in firn density near the surface is a major uncertainty. In this paper, we explore these variations at locations on the Greenland Ice Sheet and at the Dome C location in Antarctica. Borehole in situ measurements, snow radar echoes, microwave brightness temperatures, and modeling results from the Community Firn Model (CFM) are used. It is shown that firn density profiles can be represented using three processes: "long-scale" and "short-scale" density variations and "refrozen layers". Consistency with this description is observed in the dynamic range of airborne 0.5–2 GHz brightness temperatures and snow radar echo peaks in measurements performed in Greenland in 2017. Based on these insights, a new analytical partially coherent model is implemented to explain the microwave brightness temperatures using the three-scale description of the firn. Short- and long-scale firn processes are modeled as a 3D continuous random medium with finite vertical and horizontal correlation lengths as opposed to past 1D randomly layered medium descriptions. Refrozen layers are described as deterministic sheets with planar interfaces, with the number of refrozen-layer interfaces determined by radar observations. Firn density and correlation length parameters used in forward modeling to match measured 0.5–2 GHz brightness temperatures in Greenland show consistency with similar parameters in CFM predictions. Model predictions also are in good agreement with multi-angle 1.4 GHz vertically and horizontally polarized brightness temperature measured by the Soil Moisture and Ocean Salinity (SMOS) satellite at Dome C, Antarctica. This work shows that co-located active and passive microwave measurements can be used to infer polar firn properties that can be compared with predictions of the CFM. In particular, 0.5–2 GHz brightness temperature measurements are shown to be sensitive to long-scale firn density fluctuations with density standard deviations in the range of 0.01–0.06 gcm-3 and vertical correlation lengths of 6–20 cm. [ABSTRACT FROM AUTHOR]

GRACE‐D accelerometer data show significant bias jumps since one month after the launch of the GRACE Follow‐On (GRACE‐FO) satellites in May 2018, making them inapplicable for correcting GRACE‐FO products for non‐gravitational accelerations. The GRACE‐FO Science Data System (SDS) compensated this issue by transplanting the GRACE‐C accelerometer data toward that of GRACE‐D. Recently, GRACE‐FO SDS implemented an updated transplant method, used in the latest release of GRACE‐FO data. Here, we examine the impact of updated accelerometer transplant data (ACH) on GRACE‐FO measurements at all levels: (a) Level‐1B inter‐satellite laser ranging residuals measured along satellite orbit, (b) Level‐2 time‐variable gravity solutions from all SDS centers (JPL, CSR, and GFZ), and (c) Level‐3 mascon solutions. We show that inter‐satellite laser ranging residuals are modified at low frequencies below 1 mHz, affecting the along‐orbit analysis of large‐scale time‐variable gravity signals. When mapped into monthly Level‐2 spherical harmonic coefficients of geopotential, the low‐frequency change in inter‐satellite ranging residuals leads to substantial improvement of coefficients associated with resonant orders (i.e., 15, 30, 45, etc.) and C30. We also present an improved SLR‐derived C30 which significantly improves the agreement with updated GRACE‐FO C30 at seasonal and interannual timescales. Moreover, we demonstrate the noise reduction in mass change estimates from new GRACE‐FO Level‐2 data over oceans, Greenland, and Antarctica for all SDS solutions. GRACE‐FO mascon solutions show a moderate change in the updated release. Our comprehensive analyses demonstrate high‐quality estimates of non‐gravitational accelerations by the updated transplant method, resulting in more accurate GRACE‐FO time‐variable gravity and mass change observations. Plain Language Summary: GRACE Follow‐On (GRACE‐FO) consists of two satellites that orbit around the Earth at ∼500 km altitude, following each other at a distance of ∼200 km. The inter‐satellite distance between the two satellites changes because of the gravitational as well as non‐gravitational forces (e.g., air drag), and it is measured by high‐precision sensors. To estimate time‐variable gravity caused by mass change in the Earth system from inter‐satellite ranging data, the effect of non‐gravitational forces is reduced using on‐board accelerometer measurements. The accelerometer on‐board the GRACE‐D satellite started to return erroneous measurements about 1 month after the launch. The GRACE‐FO Science Data System (SDS) compensated this issue by transplanting the GRACE‐C accelerometer data toward that of GRACE‐D. An updated transplant accelerometer data set for GRACE‐D was recently released by the GRACE‐FO SDS and, consequently, new time‐variable gravity and mass change solutions were released. In this paper, we demonstrate the improved accuracy of the new GRACE‐FO time‐variable gravity and mass change solutions caused by high‐quality estimates of non‐gravitational accelerations by the updated transplant method. Key Points: GRACE Follow‐On (GRACE‐FO) laser ranging residuals are modified at low frequencies by ACH, affecting the along‐orbit analysis of large‐scale mass changesGeopotential spherical harmonic coefficients associated with resonant orders (i.e., ∼15, 30, 45, etc.) show the largest improvement by ACHMonthly gravity fields show significantly lower noise for months when the angle between GRACE‐FO orbital plane and Sun‐Earth direction is ∼0 [ABSTRACT FROM AUTHOR]

The variability and dynamics of the Asian monsoon (AM, hereafter indicates both of the summer and winter monsoons.) at orbital and millennial timescales has attracted wide interest. Chinese loess deposits, covering an area of ~500 × 103 km2 and with a thickness of several tens to more than three hundred meters, is an ideal continental archive to reconstruct AM variations during the Quaternary epoch. Over the past thirty years, since the earliest paper published in an international journal that linked the Asian monsoon and Chinese loess deposits, many studies have been undertaken focusing on this research topic. These results have greatly deepened our understanding of the variations of the AM climate and their driving mechanisms during the past ~2.6 Myr. In this paper, we emphasize recent progress on the AM variability and dynamics revealed by Chinese loess records; in particular, we discuss the reliability and precision of the timescale and the monsoon proxy indicators for the loess-paleosol sequences, which are two fundamental aspects for understanding AM behavior. We analyze what we know and discuss what we do not know about the AM. We refine the timescale for the typical loess-paleosol sequence in the central Chinese Loess Plateau (CLP), which can be used as a new timescale to study palaeoclimate and palaeoenvironmental changes in the monsoonal Asia. We conclude that low-latitude insolation changes induced by precession, and global ice volume, temperature at high-latitudes, as well as sea-level changes forced variations of the AM at orbital time scales. High-latitude cooling events and low-latitude hydroclimate process at millennial time scales, such as climate changes associated with Heinrich events and Dansgaard-Oeschger cycles in Northern Atlantic and Greenland, have also modulated AM variability. We suggest that high-latitude forcing of AM variations occurs through ocean and atmospheric circulation linkages, although the roles of atmospheric CO 2 , ocean and vegetation feedbacks need further investigation. In future study, high-resolution independent dating, novel proxy indices and transient numerical simulations are still basic tools to understand the loess deposition and AM variations that require considerably more work. Issues such as reliable spatial comparison and regional linkages of records (dependent on precise and accurate numerical chronologies), and quantitative reconstruction of the AM variations, should be given priority in the study the past climate change in Asia, and low-latitude hydroclimate process. [ABSTRACT FROM AUTHOR]

Basal conditions directly control the glacier sliding rate and the dynamic discharge of ice. Recent glacier destabilization events indicate that some marine-terminating glaciers quickly respond to lubricated beds with increased flow speed, but the underlying physics, especially how this vulnerability relates to glacier geometry and flow characteristics, remains unclear. This paper presents a 1D physical framework for glacier dynamic vulnerability assuming sudden basal lubrication as an initial perturbation. In this new model, two quantities determine the scale and the areal extent of the subsequent thinning and acceleration after the bed is lubricated: Péclet number (Pe) and the product of glacier speed and thickness gradient (dubbed J0 in this study). To validate the model, this paper calculates Pe and J0 using multi-sourced data from 1996 to 1998 for outlet glaciers in the Greenland ice sheet and Austfonna ice cap, Svalbard, and compares the results with the glacier speed change during 1996/1998–2018. Glaciers with lower Pe and J0 are more likely to accelerate during this 20-year span than those with higher Pe and J0 , which matches the model prediction. A combined factor of ice thickness, surface slope, and initial flow speed physically determines how much and how fast glaciers respond to lubricated beds in terms of speed, elevation, and terminus change. [ABSTRACT FROM AUTHOR]

Background: Research suggests that head‐mounted displays (HMD) can spark situational interest when they are used to provide science learning experiences that are not possible in traditional classroom settings. However, few studies have investigated the lasting effects of using HMDs in an authentic instructional intervention. Objectives: We investigated the effects of a one‐time experience of a virtual field trip to Greenland in a sample of 105 middle school students. Methods: Students used either a standard 2D video (video condition; N = 50) or an HMD (HMD condition; N = 55) as part of a six‐lesson educational activity on the topic of climate change. Informed by social cognitive career theory (SCCT), we investigated the effects of the different conditions (video vs. HMD) on the outcomes of self‐efficacy, outcome expectations, interest, and science intentions across three time points. Results and Conclusions: The results showed that using the HMD‐based virtual field trip, compared to the video, had a positive immediate effect on self‐efficacy and interest, and total later effects on self‐efficacy, outcome expectations, and interest an average of two and a half weeks after the virtual field trip. The results suggest that HMD‐based virtual field trips can influence self‐efficacy, outcome expectations, and interest more than a video‐based virtual field trip when measured approximately two and a half weeks after the intervention. Lay Description: What is currently known about the subject matter: Social Cognitive Career Theory provides a framework for understanding students' learning.Few studies have examined the effect of head‐mounted displays on science interest in the framework of Social Cognitive Career Theory. What this paper adds: The results suggest that virtual field trips based in head‐mounted display can foster self‐efficacy, outcome expectations, and interest more than video‐based virtual field trips. Implications of the findings for practitioners: Fostering learning through head‐mounted displays may increase students' interest in science. [ABSTRACT FROM AUTHOR]

The bulk crystal orientation in ice influences the flow of glaciers and ice streams. The ice c -axes fabric is most reliably derived from ice cores. Because these are sparse, the spatial and vertical distribution of the fabric in the Greenland and Antarctic ice sheets is largely unknown. In recent years, methods have been developed to determine fabric characteristics from polarimetric radar measurements. The aim of this paper is to present an improved method to infer the horizontal fabric asymmetry by precisely determining the travel-time difference using co-polarised phase-sensitive radar data. We applied this method to six radar measurements from the East Greenland Ice-core Project (EastGRIP) drill site on Greenland's largest ice stream to give a proof of concept by comparing the results with the horizontal asymmetry of the bulk crystal anisotropy derived from the ice core. This comparison shows an excellent agreement, which is a large improvement compared to previously used methods. Our approach is particularly useful for determining the vertical profile of the fabric asymmetry in higher resolution and over larger depths than was achievable with previous methods, especially in regions with strong asymmetry. [ABSTRACT FROM AUTHOR]

The geophysical effects are the main factor that causes the nonlinear motion of the station, and a comprehensive analysis of the relationship between the GRACE seasonal load deformation and the GPS station coordinates is helpful to study the physical mechanism that causes the nonlinear motion of the station. Aiming at the continuous GPS coordinate time series in Greenland, this paper comprehensively analyzes the correlation between GRACE seasonal load deformation and GPS station coordinates. First, in order to improve the accuracy of GPS station coordinates, the principle component analysis (PCA) method was used to eliminate the common mode error (CME) of the station coordinates. The results show that this method effectively reduces the uncertainty of the station coordinates time series. Secondly, when extracting seasonal signals, it is found that the singular spectrum (SSA) method can effectively obtain the time-varying part of seasonal signals, and its extraction effect is better than that of the least square fitting (LSF) method. Finally, the seasonal relationship between GRACE load deformation and GPS station coordinates is analyzed from the aspects of time series change, correlation, and WRMS reduction. It is found that there are differences in the amplitude and phase parts of the time series. The mean value of correlation is 0.73, the maximum reduction of WRMS is 55.20% (QAQ1 station), and the minimum is −22.69% (KMJP station), indicating that most stations mainly exhibit seasonal load deformation, while individual stations cannot effectively reflect. In addition, the influence of GRACE seasonal load deformation on the station coordinate parameters is quantitatively analyzed. The results show that the best noise model of the station is mainly WN + FN, which effectively reduces the velocity uncertainty of the station coordinate, and weakens the seasonal term oscillation. [ABSTRACT FROM AUTHOR]

At the Pingorsuit Glacier in North‐West Greenland, an organic‐rich deposit that had recently emerged from the retreating ice cap was discovered at an elevation of 480 m above sea level. This paper reports on macrofossil analyses of a coarse detritus gyttja and peaty soil, which occurred beneath a thin cover of till and glacifluvial deposits. The sediments contained remains of vascular plants, mosses, beetles, caddisflies, midges, bryozoans, sponges and other invertebrates. The flora includes black spruce, tree birch, boreal shrubs and wetland and aquatic taxa, which shows that mires, lakes and ponds were present in the area. We describe a new extinct waterwort species Elatine odgaardii. The fossils were deposited in a boreal environment with a mean July air temperature that was at least 9 °C higher than at present. The fossil assemblages show strong similarities with others from Greenland that have been assigned an Early Pleistocene age, and we suggest a similar age for the sediments found at the margin of the Pingorsuit Glacier. At the Pingorsuit Glacier in North‐West Greenland, an organic‐rich deposit was discovered at an elevation of 480 m above sea level. The sediments contained remains of vascular plants, mosses, beetles, caddisflies, midges, bryozoans, sponges and other invertebrates. The fossils were deposited in a boreal environment with a mean July air temperature that was at least 9 °C higher than at present. [ABSTRACT FROM AUTHOR]

The North Atlantic islands of the Faroe Islands, Iceland and Greenland have always been relatively poor in terms of native timber resources, due to their cold climate and exposed topography. Nevertheless, timber was vital to the material culture of the Norse settlers of these islands, and driftwood often met this need. As in subarctic Norway, where trees are also scarce, driftwood use and ownership were prescribed in medieval law codes. Historical documentary evidence shows that wealthy landowners bought driftwood rights as valuable assets, and ethnohistorical sources reveal a wide range of local and regional customs related to driftwood exploitation. However, driftwood was an unstable resource, and its delivery depended on a range of unpredictable factors related to climate and ocean currents. There is also ongoing debate regarding the relative importance of imported timber, which is for example often referenced in the Icelandic sagas. The use of driftwood is difficult to demonstrate through macroscopic, microscopic, or (geo-)chemical analysis. Similarities in the microscopic anatomy of boreal wood taxa preclude definitive provenancing through taxonomic analysis, and material traces of immersion in seawater are often either impermanent or ambiguous, especially in archaeological wood remains. This paper presents a comprehensive review of current historical and archaeological research on the exploitation of driftwood timber in the Medieval North Atlantic and explores potential future directions in this field. Furthermore, it asserts that this line of research should be pursued with some urgency, as anthropogenic climate change threatens both driftwood delivery and the preservation of archaeological wood remains. [ABSTRACT FROM AUTHOR]

In largely treeless Arctic and subarctic environments driftwood is a key raw material, and this was no less so in Norse Greenlandic society (AD 985–1450). Driftwood was used for various purposes such as construction, transport, tools, utensils and for decoration. It has been argued that driftwood was a non-renewable resource which by the fourteenth century led to timber shortage in Norse Greenland. This paper presents data from taxonomic identifications on wood remains from five farmsteads in Norse Greenland where excavations have produced large collections of wood artefacts and wood debris. The study shows that 67% of the combined assemblage (total of 8552 pieces) are non-native coniferous taxa, the majority of which came to Greenland as drift. The Norse farms had more or less equal proportions of driftwood. In addition, this study finds no significant change in driftwood availability throughout the Norse period in Greenland nor does the composition of driftwood taxa change. [ABSTRACT FROM AUTHOR]

To evaluate the performance of the eXtensible Bremen Aerosol/cloud and surfacE parameters Retrieval (XBAER) algorithm, presented in the Part 1 companion paper to this paper, we apply the XBAER algorithm to the Sea and Land Surface Temperature Radiometer (SLSTR) instrument on board Sentinel-3. Snow properties – snow grain size (SGS), snow particle shape (SPS) and specific surface area (SSA) – are derived under cloud-free conditions. XBAER-derived snow properties are compared to other existing satellite products and validated by ground-based and aircraft measurements. The atmospheric correction is performed on SLSTR for cloud-free scenarios using Modern-Era Retrospective Analysis for Research and Applications (MERRA) aerosol optical thickness (AOT) and the aerosol typing strategy according to the standard XBAER algorithm. The optimal SGS and SPS are estimated iteratively utilizing a look-up-table (LUT) approach, minimizing the difference between SLSTR-observed and SCIATRAN-simulated surface directional reflectances at 0.55 and 1.6 µm. The SSA is derived for a retrieved SGS and SPS pair. XBAER-derived SGS, SPS and SSA have been validated using in situ measurements from the recent campaign SnowEx17 during February 2017. The comparison shows a relative difference between the XBAER-derived SGS and SnowEx17-measured SGS of less than 4 %. The difference between the XBAER-derived SSA and SnowEx17-measured SSA is 2.7 m 2 /kg. XBAER-derived SPS can be reasonably explained by the SnowEx17-observed snow particle shapes. Intensive validation shows that (1) for SGS and SSA, XBAER-derived results show high correlation with field-based measurements, with correlation coefficients higher than 0.85. The root mean square errors (RMSEs) of SGS and SSA are around 12 µm and 6 m 2 /kg. (2) For SPS, aggregate SPS retrieved by XBAER algorithm is likely to be matched with rounded grains while single SPS in XBAER is possibly linked to faceted crystals. The comparison with aircraft measurements, during the Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP) campaign held in March 2018, also shows good agreement (with R=0.82 and R=0.81 for SGS and SSA, respectively). XBAER-derived SGS and SSA reveal the variability in the aircraft track of the PAMARCMiP campaign. The comparison between XBAER-derived SGS results and the Moderate Resolution Imaging Spectroradiometer (MODIS) Snow-Covered Area and Grain size (MODSCAG) product over Greenland shows similar spatial distributions. The geographic distribution of XBAER-derived SPS over Greenland and the whole Arctic can be reasonably explained by campaign-based and laboratory investigations, indicating a reasonable retrieval accuracy of the retrieved SPS. The geographic variabilities in XBAER-derived SGS and SSA both over Greenland and Arctic-wide agree with the snow metamorphism process. [ABSTRACT FROM AUTHOR]

With global warming, supraglacial lakes play an important role in ice sheet stability and climate change. They are not only the main factors affecting mass balance and sea-level rise but also the key units of surface runoff storage and mass loss. To automatically map the spatiotemporal distribution of supraglacial lakes in Greenland, this paper proposes an attention-based U-Net model with Sentinel-1 SAR imagery. The extraction results show that compared with the traditional network, this method obtains a higher validation coefficient, with an F1 score of 0.971, and it is spatiotemporally transferable, able to realize the extraction of supraglacial lakes in complex areas without ignoring small lakes. In addition, we conducted a case study in the Jakobshavn region and found that the supraglacial lake area peaked in advance between spring and summer due to extreme melting events from 2017 to 2021. Meanwhile, the supraglacial lakes near the 79°N Glacier tended to expand inland during the melting season. [ABSTRACT FROM AUTHOR]

This paper reports results of the first range-wide study of the behaviors of free-living wolves in the High Arctic in response to human presence and discusses these behaviors from a conservation perspective. The study focused on wolves believed to have had little, if any, contact with humans and excluded data from areas where wolves have become habituated to people. Data consisted of incidental sightings of wolves on the Canadian Arctic Archipelago and in Greenland from 1819 to 2019. A total of 325 behavioral observations were identified: 163 from Greenland and 162 from Canada. The most commonly reported behaviors (71.4%) involved wolves seeking out humans: coming to campsites, following traveling dog teams, closely approaching a person, and following people. These behaviors are not typical of canids in lower latitudes and have the potential to create conflicts with people who might feel threatened owing to the centuries-old belief that wolves are dangerous. Some Arctic wolves have been shot in perceived self-defense, when in all likelihood the animals were only curious. In addition, aggression directed towards domestic dogs was the most common form of wolf-dog interaction and produced another source of conflict. The findings are important from a conservation perspective because of the small wolf population and the fact that vanishing sea ice is increasing human access to the Arctic wolf range. Appropriate and humanely used hazing techniques and outreach to stakeholders on what constitutes normal Arctic wolf behavior can mitigate the risk of conflict and contribute to the conservation of Arctic wolves on the Canadian Arctic Archipelago and in Greenland, while minimizing the risk that the natural behavior of this subspecies is altered by increased human activity. [ABSTRACT FROM AUTHOR]

Accurately modelling the contribution of Greenland and Antarctica to sea level rise requires solving partial differential equations at a high spatial resolution. In this paper, we discuss the scaling of the Ice-sheet and Sea-level System Model (ISSM) applied to the Greenland Ice Sheet with horizontal grid resolutions varying between 10 and 0.25 km. The model setup used as benchmark problem comprises a variety of modules with different levels of complexity and computational demands. The core builds the so-called stress balance module, which uses the higher-order approximation (or Blatter–Pattyn) of the Stokes equations, including free surface and ice-front evolution as well as thermodynamics in form of an enthalpy balance, and a mesh of linear prismatic finite elements, to compute the ice flow. We develop a detailed user-oriented, yet low-overhead, performance instrumentation tailored to the requirements of Earth system models and run scaling tests up to 6144 Message Passing Interface (MPI) processes. The results show that the computation of the Greenland model scales overall well up to 3072 MPI processes but is eventually slowed down by matrix assembly, the output handling and lower-dimensional problems that employ lower numbers of unknowns per MPI process. We also discuss improvements of the scaling and identify further improvements needed for climate research. The instrumented version of ISSM thus not only identifies potential performance bottlenecks that were not present at lower core counts but also provides the capability to continually monitor the performance of ISSM code basis. This is of long-term significance as the overall performance of ISSM model depends on the subtle interplay between algorithms, their implementation, underlying libraries, compilers, runtime systems and hardware characteristics, all of which are in a constant state of flux. We believe that future large-scale high-performance computing (HPC) systems will continue to employ the MPI-based programming paradigm on the road to exascale. Our scaling study pertains to a particular modelling setup available within ISSM and does not address accelerator techniques such as the use of vector units or GPUs. However, with 6144 MPI processes, we identified issues that need to be addressed in order to improve the ability of the ISSM code base to take advantage of upcoming systems that will require scaling to even higher numbers of MPI processes. [ABSTRACT FROM AUTHOR]

Exact information on the calving front positions of marine- or lake-terminating glaciers is a fundamental glacier variable for analyzing ongoing glacier change processes and assessing other variables like frontal ablation rates. In recent years, researchers started implementing algorithms that can automatically detect the calving fronts on satellite imagery. Most studies use optical images, as calving fronts are often easy to distinguish in these images due to the sufficient spatial resolution and the presence of different spectral bands, allowing the separation of ice features. However, detecting calving fronts on synthetic aperture radar (SAR) images is highly desirable, as SAR images can also be acquired during the polar night and are independent of weather conditions (e.g., cloud cover), facilitating year-round monitoring worldwide. In this paper, we present a benchmark dataset of SAR images from multiple regions of the globe with corresponding manually defined labels providing information on the position of the calving front (https://doi.org/10.1594/PANGAEA.940950). With this dataset, different approaches for the detection of glacier calving fronts can be implemented, tested, and their performance fairly compared so that the most effective approach can be determined. The dataset consists of 681 samples, making it large enough to train deep learning segmentation models. It is the first dataset to provide long-term glacier calving front information from multi-mission data. As the dataset includes glaciers from Antarctica, Greenland, and Alaska, the wide applicability of models trained and tested on this dataset is ensured. The test set is independent of the training set so that the generalization capabilities of the models can be evaluated. We provide two sets of labels: one binary segmentation label to discern the calving front from the background, and one label for multi-class segmentation of different landscape classes. Unlike other calving front datasets, the presented dataset contains not only the labels but also the corresponding preprocessed and geo-referenced SAR images as PNG files. The ease of access to the dataset will allow scientists from other fields, such as data science, to contribute their expertise. With this benchmark dataset, we enable comparability between different front detection algorithms and improve the reproducibility of front detection studies. Moreover, we present one baseline model for each kind of label type. Both models are based on the U-Net, one of the most popular deep learning segmentation architectures. In the following two post-processing procedures, the segmentation results are converted into 1-pixel-wide front delineations. By providing both types of labels, both approaches can be used to address the problem. To assess the performance of different models, we suggest first reviewing the segmentation results using the recall, precision, F1 score, and the Jaccard index. Second, the front delineation can be evaluated by calculating the mean distance error to the labeled front. The presented vanilla models provide a baseline of 150 m ± 24 m mean distance error for the Mapple Glacier in Antarctica and 840 m ± 84 m for the Columbia Glacier in Alaska, which has a more complex calving front, consisting of multiple sections, compared with a laterally well constrained, single calving front of Mapple Glacier. [ABSTRACT FROM AUTHOR]

During the past 20 years, multi-channel radar emerged as a key tool for deciphering an ice sheet's internal architecture. To assign ages to radar reflections and connect them over large areas in the ice sheet, the layer genesis has to be understood on a microphysical scale. Synthetic radar trace modelling based on the dielectric profile of ice cores allows for the assignation of observed physical properties' variations on the decimetre scale to radar reflectors extending from the coring site to a regional or even whole-ice-sheet scale. In this paper we rely on the available dielectric profiling data of the northern Greenland deep ice cores: NGRIP, NEEM and EGRIP. The three records are well suited for assigning an age model to the stratigraphic radar-mapped layers, and linking up the reflector properties to observations in the cores. Our modelling results show that the internal reflections are mainly due to conductivity changes. Furthermore, we deduce fabric characteristics at the EGRIP drill site from two-way-travel-time differences of along and across-flow polarized radarwave reflections of selected horizons (below 980 m). These indicate in deeper parts of the ice column an across-flow concentrated c-axis fabric. [ABSTRACT FROM AUTHOR]

The Northeast Greenland Ice Stream (NEGIS) is the main artery for ice discharge from the northeast sector of the Greenland Ice Sheet (GrIS) to the North Atlantic. Understanding the past, present and future stability of the NEGIS with respect to atmospheric and oceanic forcing is of global importance as it drains around 17% of the GrIS and has a sea-level equivalent of 1.6 m. This paper reconstructs the deglacial and Holocene history of Nioghalvfjerdsbræ (or 79N Glacier); a major outlet of the NEGIS. At high elevation (>900 m asl) autochthonous blockfield, a lack of glacially moulded bedrock and pre LGM exposure ages point to a complex exposure/burial history extending back over half a million years. However, post Marine Isotope Stage 12, enhanced glacial erosion led to fjord incision and plateaux abandonment. Between 900 and 600 m asl the terrain is largely unmodified by glacial scour but post LGM erratics indicate the advection of cold-based ice through the fjord. In contrast, below ∼600 m asl Nioghalvfjerdsfjorden exhibits a geomorphological signal indicative of a warm-based ice stream operating during the last glacial cycle. Dated ice marginal landforms and terrain along the fjord walls show initial thinning rates were slow between ∼23 and 10 ka, but post-10 ka it is evident that Nioghalvfjerdsfjorden deglaciated extremely quickly with complete fjord deglaciation below ∼500 m asl between 10.0 and 8.5 ka. Both increasing air and ocean temperatures were pivotal in driving surface lowering and submarine melt during deglaciation, but the final withdrawal of ice through Nioghalvfjerdsfjorden was facilitated by the action of marine ice sheet instability. Our estimates show that thinning and retreat rates reached a maximum of 5.29 ma−1 and 613 ma−1, respectively, as the ice margin withdrew westwards. This would place the Early Holocene disintegration of this outlet of the NEGIS at the upper bounds of contemporary thinning and retreat rates seen both in Greenland and Antarctica. Combined with recent evidence of ice stream shutdown during the Holocene, as well as predictions of changing ice flow dynamics within downstream sections of the NEGIS catchment, this suggests that significant re-organisation of the terminal zone of the ice stream is imminent over the next century. • The Northeast Greenland Ice Stream (NEGIS) thinned slowly between 23–10ka as ice retreated across the continental shelf. • At the opening of the Holocene rising air & ocean temperatures drove surface lowering & basal melt. • Between 10-8.5ka marine ice sheet instability further enhanced grounding line retreat rates into Nioghalvfjerdsfjorden. • During the Early Holocene thinning and retreat rates reached a maximum of 5.29 ma-1 and 613 ma-1 respectively. • Such rates are at the upper bounds of contemporary ice stream thinning and retreat rates in Greenland and Antarctica. [ABSTRACT FROM AUTHOR]

In this paper, we propose a multi-RREH (Remote Renewable Energy Hub) based optimization framework. This framework allows a valorization of CO 2 using carbon capture technologies. This valorization is grounded on the idea that CO 2 gathered from the atmosphere or post combustion can be combined with hydrogen to produce synthetic methane. The hydrogen is obtained from water electrolysis using renewable energy. Such renewable energy is generated in RREH, which are locations where RE is cheap and abundant (e.g., solar PV in the Sahara Desert, or wind in Greenland). We instantiate our framework on a case study focusing on Belgium and 2 RREH, and we conduct a techno-economic analysis under uncertainty. This analysis highlights, among others, the interest in capturing CO 2 via Post Combustion Carbon Capture (PCCC) rather than only through Direct Air Capture (DAC) for methane synthesis in RREH. By doing so, a notable reduction of 10% is observed in the total cost of the system under our reference scenario. In addition, we use our framework to derive a carbon price threshold above which carbon capture technologies may start playing a pivotal role in the decarbonation process of our industries. • We demonstrate PCCC technology potential for reducing RREH's CH4 production cost. • We derive a carbon price threshold for crucial industrial decarbonization. • An uncertainty analysis has been carried out on the reference scenario. [ABSTRACT FROM AUTHOR]

Arctic driftwood can be used as an alternative source of wood as construction timber and furniture material, especially in Iceland and Greenland. The use of Arctic driftwood can help in the fight against climate change, by developing land reforestation processes and reducing the volume harvested wood from forests and sustainability of harvesting processes. In this paper the results of an analysis of the effect of long-term residence of pine (Pinus sylvestris L.) and larch wood (Larix sibirica L.) stay in Arctic ice and seawater on the granulation of wood sawdust and the distribution of fine wood dust particles during the frame sawing process are presented. The distribution of wood chips and dust was analysed using sieve and laser diffraction methods. The results confirmed that Arctic driftwood, compared to normal wood for both analysed species, generate slightly more fine wood dust particles during the frame sawing process, which can be harmful to human health. However, these differences are not significant, indicating that the same dust extraction systems can be used for both sawing processes. • The particle size of larch driftwood dust is similar that of normal larch wood. • Increasing the feed per tooth increases the proportion of smaller particles. • The distribution of fine dust particles (<20 μm) is stronger in pine driftwood. • In the process of sawing driftwood, more the finest sawdust fractions were obtained. [ABSTRACT FROM AUTHOR]

Extreme climate events are hotspots in global change. However, research on the changes in future compound events and population exposure is still limited. Leveraging from the data of the sixth phase of the Coupled Model Intercomparison Project (CMIP6), this paper aims to analyze the temporal and spatial changes of global compound temperature and precipitation extreme events in the future. We also predict the risk of population exposure and quantify the contribution of different factors to exposure. The results show that: (1) In the next 80 years, compound hot-dry event (CHDE) will increase at a rate of 0.02, 0.03, and 0.08 days per decade under the three scenarios of SSP1–2.6, SSP2–4.5 and SSP5–8.5, respectively. By comparison, compound hot-humidity event (CHHE) shows a downward trend under the three scenarios, with a downward rate of 0.01, 0.02, and 0.11 days per decade, respectively. (2) Under the SSP1–2.6 and SSP2–4.5 scenarios, CHDE and CHHE have two or more mutation points. Under the SSP5–8.5 scenario, CHDE shows a significant upward and CHHE shows a significant downward trend in the middle and late 21st century. These two indices exhibit periodic changes in all three scenarios (3) South Asia, West Asia, and Northeast Africa have higher CHDE values, while regions with higher CHHE values are located in North Asia and Greenland. (4) Climate change is a major factor affecting population exposure. For CHDE, climate, population, and their synergistic effects contribute about 75%, 20%, and 5% to the exposure, respectively. For CHHE, the contributions of these three factors are 85%, 10%, and 5% respectively. These findings provide scientific guidance for the rational formulation of population policies, the effective avoidance of climate disaster risks and the protection of human health. • Frequency of hot-dry events and hot-humidity events will increase and decrease, respectively, in the future. • There are abrupt points and periodicity in the future time series of compound temperature and precipitation extremes. • Asia is projected to have the greatest exposure and climate change contributes the most to exposure. [ABSTRACT FROM AUTHOR]

Exact information on calving front positions of marine-or lake-terminating glaciers is a fundamental glacier variable for analyzing ongoing glacier change processes and assessing other variables like frontal ablation rates. In recent years, researchers started implementing algorithms that could automatically detect the calving fronts on satellite imagery. Most studies use optical images, as in these images, calving fronts are often easy to distinguish due to sufficient spatial resolution and the presence of different spectral bands, allowing the separation of ice features. However, detecting calving fronts on SAR images is highly desirable, as SAR images can also be acquired during the polar night and are independent of weather conditions, e. g., cloud cover, facilitating all-year monitoring worldwide. In this paper, we present a benchmark dataset of SAR images from multiple regions of the globe with corresponding manually defined labels to train and test approaches for the detection of glacier calving fronts. The dataset is the first to provide long-term glacier calving front information from multi-mission data. As the dataset includes glaciers from Antarctica, Greenland and Alaska, the wide applicability of models trained and tested on this dataset is ensured. The test set is independent of the training set so that the generalization capabilities of the models can be evaluated. We provide two sets of labels: one binary segmentation label to discern the calving front from the background and one for multi-class segmentation of different landscape classes. Unlike other calving front datasets, the presented dataset contains not only the labels but also the corresponding preprocessed and geo-referenced SAR images as PNG files. The ease of access to the dataset will allow scientists from other fields, such as data science, to contribute their expertise. With this benchmark dataset, we enable comparability between different front detection algorithms and improve the reproducibility of front detection studies. Moreover, we present one baseline model for each kind of label type. Both models are based on the U-Net, one of the most popular deep learning segmentation architectures. Additionally, we introduce Atrous Spatial Pyramid Pooling to the bottleneck layer. In the following two post-processing procedures, the segmentation results are converted into one-pixel-wide front delineations. By providing both types of labels, both approaches can be used to address the problem. To assess the performance of the models, we first review the segmentation results using the recall, precision, F1-score, and the Jaccard Index. Second, we evaluate the front delineation by calculating the mean distance error to the labeled front. The presented vanilla models provide a baseline of 150m±24m mean distance error for the Mapple Glacier in Antarctica and 840m±84m for the Columbia Glacier in Alaska, which has a more complex calving front, consisting of multiple sections, as compared to a laterally well constrained, single calving front of Mapple Glacier. [ABSTRACT FROM AUTHOR]