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Antarctic meltwater discharge has been largely emphasized for its potential role in climate change mitigation, not only by reducing global warming, but also by stabilizing the Atlantic Meridional Overturning Circulation (AMOC). Despite the tremendous impact of the AMOC on the climate system, its temporal evolution in response to the meltwater remains poorly understood. Here, we investigate the meltwater impacts on the AMOC based on the GFDL CM2.1 experiments and discover its fast weakening and slow strengthening to the Antarctic meltwater discharge. Cold ocean surface caused by meltwater spread throughout the globe and eventually strengthened the AMOC. However, in the early stages, the tropical temperature response could stimulate the Rossby wave teleconnection, modulating atmospheric circulation in the North Atlantic, and weakening convection and even the AMOC. This counterintuitive evolution implies a potential destabilizing effect of Antarctic meltwater, underscoring the importance of the atmospheric dynamics in the interaction between the two poles. Plain Language Summary: The climate system is made up of interactions between different subsystems, so that regional climate changes can have global effects. The freshwater discharge from Antarctica would increase in the future and result in regional cooling. Atmospheric and oceanic dynamics extend this local effect to the globe, reducing global surface temperature and strengthening the large‐scale ocean circulation in the Atlantic. These mitigating effects naturally put the spotlight on Antarctic meltwater. Our study however suggests that the mitigation effect depends on the time scale. Although the global mean temperature is always reduced, the ocean circulation in the Atlantic surprisingly slows down as an early response to Antarctic meltwater; fast atmospheric teleconnection enables it. This non‐monotonic evolution emphasizes the importance of the atmospheric teleconnection between the two poles, which should be carefully considered to understand the polar climate. Key Points: The response of the Atlantic Meridional Overturning Circulation to perennial meltwater‐induced cooling is investigated by GFDL CM2.1 experimentsBefore the cooling spreads out the Atlantic, tropical atmospheric teleconnection could weaken the Greenland ocean convectionThe fast and slow responses imply the importance of the atmospheric teleconnection to regulate polar climate [ABSTRACT FROM AUTHOR]

Background: The regional disparity of heatwave-related mortality over a long period has not been sufficiently assessed across the globe, impeding the localisation of adaptation planning and risk management towards climate change. We quantified the global mortality burden associated with heatwaves at a spatial resolution of 0.5°×0.5° and the temporal change from 1990 to 2019. Methods and findings: We collected data on daily deaths and temperature from 750 locations of 43 countries or regions, and 5 meta-predictors in 0.5°×0.5° resolution across the world. Heatwaves were defined as location-specific daily mean temperature ≥95th percentiles of year-round temperature range with duration ≥2 days. We first estimated the location-specific heatwave-mortality association. Secondly, a multivariate meta-regression was fitted between location-specific associations and 5 meta-predictors, which was in the third stage used with grid cell-specific meta-predictors to predict grid cell-specific association. Heatwave-related excess deaths were calculated for each grid and aggregated. During 1990 to 2019, 0.94% (95% CI: 0.68–1.19) of deaths [i.e., 153,078 cases (95% eCI: 109,950–194,227)] per warm season were estimated to be from heatwaves, accounting for 236 (95% eCI: 170–300) deaths per 10 million residents. The ratio between heatwave-related excess deaths and all premature deaths per warm season remained relatively unchanged over the 30 years, while the number of heatwave-related excess deaths per 10 million residents per warm season declined by 7.2% per decade in comparison to the 30-year average. Locations with the highest heatwave-related death ratio and rate were in Southern and Eastern Europe or areas had polar and alpine climates, and/or their residents had high incomes. The temporal change of heatwave-related mortality burden showed geographic disparities, such that locations with tropical climate or low incomes were observed with the greatest decline. The main limitation of this study was the lack of data from certain regions, e.g., Arabian Peninsula and South Asia. Conclusions: Heatwaves were associated with substantial mortality burden that varied spatiotemporally over the globe in the past 30 years. The findings indicate the potential benefit of governmental actions to enhance health sector adaptation and resilience, accounting for inequalities across communities. Qi Zhao and colleagues modelled the global, regional and national burden of heatwave-related mortality from 1990 to 2019. Author summary: Why was this study done?: Although exposure to heatwave has been associated with increased risk of excess deaths and certain temporal attenuation observed, the evidence mainly comes from limited locations. The regional disparity in heatwave-related mortality burden over a long period has not been adequately quantified across the globe. What did the researchers do and find?: Heatwave-related excess deaths were predicted to each grid cell (0.5°×0.5°) across the globe between 1990 and 2019 using a three-stage modelling framework. During 1990 to 2019 warm seasons, 153,078 deaths were associated with heatwaves (nearly half in Asia), which accounted for 0.94% of all deaths and equated 236 deaths per 10 million residents. The global heatwave-related excess death rate declined by 7.2% per decade in comparison to the 30-year average. Heatwave-related mortality showed complex regional disparities, such that Southern and Eastern Europe or areas had polar and alpine climates, and/or their residents had high incomes had the greatest cumulative burden while certain locations in Oceania or those with tropical climate or low incomes were observed with the greatest decline over decades. What do these findings mean?: These regional disparities suggest the necessity of considering the cumulation and temporal change of mortality burden for evaluating the historical health impact of climate change and developing time-efficient adaptation strategies for a certain area. Localised adaptation planning and risk management should be encouraged across all levels of government, with considering subnational capacities and inequalities. Lack of time-series death data from certain regions, e.g., Arabian Peninsula and South Asia, may reduce the prediction accuracy in those regions. [ABSTRACT FROM AUTHOR]

A fundamental divide exists between previous studies that conclude that polar amplification does not occur without sea ice and studies that find that polar amplification is an inherent feature of the atmosphere independent of sea ice. We hypothesize that a representation of climatological ocean heat transport is key for simulating polar amplification in ice-free climates. To investigate this, we run a suite of targeted experiments in the slab ocean aquaplanet configuration of CESM2-CAM6 with different profiles of prescribed ocean heat transport, which are invariant under CO2 quadrupling. In simulations without climatological ocean heat transport, polar amplification does not occur. In contrast, in simulations with climatological ocean heat transport, robust polar amplification occurs in all seasons. What is causing this dependence of polar amplification on ocean heat transport? Energy-balance model theory is incapable of explaining our results and in fact would predict that introducing ocean heat transport leads to less polar amplification. We instead demonstrate that shortwave cloud radiative feedbacks can explain the divergent polar climate responses simulated by CESM2-CAM6. Targeted cloud locking experiments in the zero ocean heat transport simulations are able to reproduce the polar amplification of the climatological ocean heat transport simulations, solely by prescribing high-latitude cloud radiative feedbacks. We conclude that polar amplification in ice-free climates is underpinned by ocean–atmosphere coupling, through a less negative high latitude shortwave cloud radiative feedback that facilitates enhanced polar warming. In addition to reconciling previous disparities, these results have important implications for interpreting past equable climates and climate projections under high-emissions scenarios. Significance Statement: Polar amplification is a robust feature of climate change in the modern-day climate. However, previous climate modeling studies fundamentally do not agree on whether polar amplification occurs in ice-free climates. In this study, we find in a state-of-the-art climate model that, if ocean heat transport is neglected, the response to an increase in CO2 is not polar amplified, whereas robust polar amplification occurs if ocean heat transport is included. Using targeted model experiments, we diagnose cloud radiative effects as the driver of this divergent behavior. We conclude that polar amplification is a robust feature of the atmosphere–ocean system. Our results have important implications for interpreting past warm climates and future projections under high-emissions scenarios. [ABSTRACT FROM AUTHOR]

Gaining a comprehensive understanding of the characteristics and propagation of precipitation-based meteorological drought to terrestrial water storage (TWS)-derived hydrological drought is of the utmost importance. This study aims to disentangle the frequency–time relationship between precipitation-derived meteorological and TWS-based hydrological drought from June 2002 to June 2017 based on the Standardized Precipitation Index (SPI) and Standardized Terrestrial Water Storage Index (STI) by employing wavelet coherence rather than a traditional correlation coefficient. The possible influencing factors on drought propagation in 28 regions across the world are examined. The results show that the number of drought months detected by the STI is higher than that detected by the SPI worldwide, especially for slight and moderate drought. Generally, TWS-derived hydrological drought is triggered by and occurs later than precipitation-based meteorological drought. The propagation characteristics between meteorological and hydrological droughts vary by region across the globe. Apparent intra-annual and interannual scales are detected by wavelet analysis in most regions, but not in the polar climate region. Drought propagation differs in phase lags in different regions. The phase lag between hydrological and meteorological drought ranges from 0.5 to 4 months on the intra-annual scale and from 1 to 16 months on the interannual scale. Drought propagation is influenced by multiple factors, among which the El Niño–Southern Oscillation, North Atlantic Oscillation, and potential evapotranspiration are the most influential when considering one, two, or three factors, respectively. The findings of this study improve scientific understanding of drought propagation mechanisms over a global scale and provide support for water management in different subregions. [ABSTRACT FROM AUTHOR]

The synoptic cold surge is a weather event that frequently occurs in the Northern Hemisphere, often causing severe damage accompanied with intense winds and precipitation. It is reported that the Arctic Oscillation and the North Atlantic Oscillation can affect the cold surge. However, on interacting with tropical circulation, the cold surge potentially links to the Antarctic sea‐ice loss with influence extending to Tropics. Therefore, this research aims to investigate the potential link between Antarctic sea‐ice loss and Northern Hemisphere cold surges and corresponding wind–precipitation compound events. To study this link, twin numerical experiments using a physically based atmosphere model with a prescribed 30% Antarctic sea‐ice loss scenario were used. The results show that the cold surge occurs more frequently in most regions of the world, except for central North America and central Eurasia. In Europe, the cold surges occur closer to the lower latitudes in the Antarctic sea‐ice loss scenario. Additionally, the Antarctic sea‐ice loss can result in intensified wind and precipitation extremes within compound events. The intensified precipitation extremes are caused by increased moisture transportation by tropical easterlies and higher local temperature after the cold surge occurrence, providing more moisture available for precipitation in East Asia and East North America, respectively. Overall, the results of the numerical experiments provide evidence that Antarctic sea‐ice loss influences cold surges in Northern Hemisphere through atmospheric teleconnections. It is important to continue investigating the link between Antarctic sea‐ice loss and weather events like cold surges, as this research can help improve our understanding of the impacts of polar climate change on lower latitudes. [ABSTRACT FROM AUTHOR]

In a changing climate, drought risk and vulnerability assessments are becoming increasingly important. Following the global call for proactive drought risk management, drought vulnerability assessments are progressively taking their stage in the drought research community. As the manifestation of drought vulnerability is dependent on the social, ecological, and hydroclimatic context in which it occurs, identifying vulnerability factors relevant for specific climatological and ecological regions may improve the quality of vulnerability assessments. Meanwhile, a holistic overview of factors affecting vulnerability in polar and cold climates is currently lacking. These regions are home to large socio-hydrological systems including urban areas, energy systems, agricultural practices, and the boreal forest. By conducting an interdisciplinary systematic literature review, the manifestation and conceptualization of drought vulnerability were identified for forested ecoregions in the Köppen– Geiger D and E climates. Vulnerability factors, as described by several scientific disciplines, were identified and combined into a conceptual framework for drought vulnerability in the study region. The results demonstrate the wide range of conceptualizations that exist for assessing drought vulnerability, and the thematic differences between sectors such as forestry, water supply, and agriculture. The conceptual framework presented herein adopts a novel approach, categorizing vulnerability factors by their location in a socio-hydrological system, and their relation to blue or green water sources. This allowed for identification of systemic vulnerability patterns, providing new insights into regional differences in drought vulnerability and a base for stakeholders performing proactive drought risk assessments in the study region. This article is categorized under: Human Water > Methods Science of Water > Water Extremes Water and Life > Conservation, Management, and Awareness Human Water > Water Governance [ABSTRACT FROM AUTHOR]

With global warming, extreme weather frequently and severely appears globally. Extreme precipitation is one of the extreme weather events that can cause many natural disasters, such as floods and waterlogging. In this study, Global Precipitation Climatology Project (GPCP) daily precipitation data were used to investigate extreme precipitation and its contribution to annual precipitation in different global climate regions and typical river basins. The climate types included equatorial climates (EC), arid climates (AC), warm temperate climates (WTC), snowy climates (SC) and polar climates (PC). R99p, Rx5day, CWD and R20 was selected as extreme precipitation indices in this study; extreme precipitation days were defined by CWD and R20. The results showed that EC and WTC had higher extreme precipitation level; SC and PC had lower extreme precipitation amounts and days than AC. R99p, Rx5day and CWD monitored higher extreme precipitation contribution degrees in AC; however, R20 monitored higher contribution degrees in EC and WTC. R99p, Rx5day and CWD showed higher extreme precipitation contribution degrees in North Africa, the Middle East, Australia and northwestern China; R20 showed higher contribution degrees in South America, the southeastern United States and South Asia. Based on historical observational data, Heilongjiang Basin (HB), Yellow River Basin (YERB), Yangtze River Basin (YARB), Ganges River Basin (GRB), Danube River Basin (DRB) and Mekong River Basin (MERB) had high-frequency extreme precipitation in summer. The research results are helpful for understanding the characteristics of extreme precipitation and provide a reference for flood control and disaster reduction in different climatic regions and main river basins. [ABSTRACT FROM AUTHOR]

Ocean heat exchanges at the marginal ice zone (MIZ) play an important role in melting sea ice. Mixed‐layer eddies transport heat and ice floes across the MIZ, facilitating the pack's access to warm waters. This study explores these frontal dynamics using disk‐shaped floes coupled to an upper‐ocean model simulating the sea ice edge. Numerical experiments reveal that small floes respond more strongly to fine‐scale ocean currents, which favors higher dispersion rates and weakens sea ice drag onto the underlying ocean. Floes with radii smaller than resolved turbulent filaments (∼2–4 km) result in a wider and more energetic MIZ, by a factor of 70% each, compared to larger floes. We hypothesize that this floe size dependency may affect sea ice break‐up by controlling oceanic energy propagation into the MIZ and modulate the sea ice pack's melt rate by regulating lateral heat transport toward the sea ice cover. Plain Language Summary: Sea ice forms as a thin layer of frozen ocean waters, which breaks into individual floes due to the action of waves, ocean currents, and atmospheric winds. At the edge of the pack, these floes are vulnerable to warm waters in the open ocean, which can favor the melt of sea ice. The transport of heat from the open ocean into ice‐covered regions is not well represented in existing climate models, notably due to their poor spatial resolution and their inability to represent the dynamics of individual floes. In this study, we use a regional numerical model to investigate how fine‐scale ocean currents (2–30 km) can help transport heat toward a sea ice pack composed of broken‐up floes. We find that this heat transport is most efficient when floes are small, because they cannot efficiently damp the mechanical energy from the surface currents and they are easily transported into the open ocean by these currents. These two processes combined may lead to sea ice melt feedbacks that are currently not captured by coarser climate models. Key Points: The sensitivity of sea ice dispersion and upper‐ocean energetics to floe size is considered at a mesoscale frontFloes smaller than turbulent filaments disperse more strongly and lead to a wider marginal ice zoneThese small floes allow for stronger eddy kinetic energy propagation and heat transport into the pack [ABSTRACT FROM AUTHOR]

This study analyzes the dynamics of surface melting in Antarctica, which are crucial for understanding glacier and ice sheet behavior and monitoring polar climate change. Specifically, we focus on the Nivlisen ice shelf in East Antarctica, examining melt ponds, supra glacial lakes (SGLs), seasonal surface melt extent, and surface ice flow velocity. Spatial and temporal analysis is based on Landsat and Sentinel-1 data from the austral summers of 2000 to 2023. Between 2000 and 2014, melt ponds and SGLs on the ice shelf covered roughly 1 km2. However, from 2015 to 2023, surface melting increased consistently, leading to more extensive melt ponds and SGLs. Significant SGL depths were observed in 2016, 2017, 2019, and 2020, with 2008, 2016, and 2020 showing the highest volumes and progressive SGL area growth. We also examined the relationship between seasonal surface melt extent and ice flow velocity. Validation efforts involved ground truth data from a melt pond in central Dronning Maud Land (cDML) during the 2022–2023 austral summer, along with model-based results. The observed increase in melt pond depth and volume may significantly impact ice shelf stability, potentially accelerating ice flow and ice shelf destabilization. Continuous monitoring is essential for accurately assessing climate change's ongoing impact on Antarctic ice shelves. [ABSTRACT FROM AUTHOR]

The Ice Pathfinder satellite (code: BNU-1) is the first Chinese microsatellite, designed for monitoring polar climate and environmental changes. The major payload of BNU-1 is the wide-field camera which provides multispectral satellite images with a 73.69 m spatial resolution and a 739 km swath width. However, the color misrepresentation issue can be observed as the BUN-1 image appears yellowish as it gets farther towards the center field of view (FOV). The blue band of the image appears to be higher near the center FOV and declines generously towards both the edge areas of the image, which may cause the color misrepresentation issue. In this study, we develop a relative sensor normalization method to reduce the radiance errors of the blue band of BNU-1 images. This method uses the radiometric probability density distribution of the BNU-1 panchromatic band as a reference, correcting the probability density distribution of the blue band radiance first. Then, the mean adjustment is used to correct the mean of the blue band radiance after probability density function (PDF) correction, obtaining the corrected radiance in the blue band. Comparisons with the ground measurements and the Landsat8 image reveal the following: (1) The radiances of snow surfaces also have good consistency with ground observations and Landsat-8 images in the red, green, and blue bands. (2) The radiance errors of the uncorrected BNU-1 images are eliminated. The RMSE decreases from 80.30 to 32.54 W/m2/μm/sr. All these results indicate that the on-orbit relative correction method proposed in this study can effectively reduce the radiance errors of the BNU-1 images. [ABSTRACT FROM AUTHOR]

Lisa E. Bloom's book, "Climate Change and the New Polar Aesthetics: Artists Reimagine the Arctic and Antarctic," explores how contemporary artists challenge and critique traditional colonial aesthetics of the polar regions. Bloom focuses on feminist, Black, Indigenous, and non-Western perspectives to demonstrate how these artists reimagine the Arctic and Antarctic as vulnerable and subject to change, rather than exceptional and conquerable. The book includes analyses of various visual media, such as installations, documentary films, and protest art, and features works by Scandinavian artists and filmmakers. Bloom also examines the role of art in documenting cultural and environmental change in the polar regions and highlights the activist agenda of some artists and filmmakers. The book raises important questions about the impact of human activity and climate change on the polar regions and the need for a critical polar aesthetics that considers the complexities of renewable energy projects in these environments. [Extracted from the article]

Sea ice in the polar regions can move several tens of kilometres per day under the actions of winds, ocean currents, and internal stresses. Long-term observations of the rate and patterns of this motion are needed to characterize the full response of the polar environment to climate change. Here, we introduce a new climate data record (CDR) of year-round, global, daily sea-ice drift vectors covering 1991–2020. The motion vectors are computed from series of passive microwave imagery in the winter months and from a parametric free-drift model in the summer months. An evaluation against on-ice buoy trajectories reveals that the RMSEs of the sea-ice drift CDR are small and vary with hemisphere and seasons (2.1 km for Arctic winters, 2.6 km for Arctic summer, 3 to 4 km for the Antarctic sea ice). The CDR is un-biased for Arctic winter conditions. The bias is larger for Antarctic and for summer sea-ice motion. The CDR consists of daily product files holding the dX and dY components of the drift vectors on an Equal-Area Scalable Earth (EASE2) grid with 75 km spacing as well as associated uncertainties and flags. It is prepared in the context of the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF) and is readily available at 10.15770/EUM_SAF_OSI_0012. [ABSTRACT FROM AUTHOR]

Drought monitoring and early detection have improved greatly in recent decades through the development and refinement of numerous indices and indicators. However, a lack of guidance, based on user experience, exists as to which drought-monitoring tools are most appropriate in a given location. This review paper summarizes the results of targeted user engagement and the published literature to improve the understanding of drought across North America and to enhance the utility of drought-monitoring tools. Workshops and surveys were used to assess and make general conclusions about the perceived performance of drought indicators, indices and impact information used for monitoring drought in the five main Köppen climate types (Tropical, Temperate, Continental, Polar Tundra, Dry) found across Canada, Mexico, and the United States. In Tropical, humid Temperate, and southerly Continental climates, droughts are perceived to be more short-term (less than 6 months) in duration rather than long-term (more than 6 months). In Polar Tundra climates, Dry climates, Temperate climates with dry warm seasons, and northerly Continental climates, droughts are perceived to be more long-term than short-term. In general, agricultural and hydrological droughts were considered to be the most important drought types. Drought impacts related to agriculture, water supply, ecosystem, and human health were rated to be of greatest importance. Users identified the most effective indices and indicators for monitoring drought across North America to be the U.S. Drought Monitor (USDM) and Standardized Precipitation Index (SPI) (or another measure of precipitation anomaly), followed by the Normalized Difference Vegetation Index (NDVI) (or another satellite-observed vegetation index), temperature anomalies, crop status, soil moisture, streamflow, reservoir storage, water use (demand), and reported drought impacts. Users also noted the importance of indices that measure evapotranspiration, evaporative demand, and snow water content. Drought indices and indicators were generally thought to perform equally well across seasons in Tropical and colder Continental climates, but their performance was perceived to vary seasonally in Dry, Temperate, Polar Tundra, and warmer Continental climates, with improved performance during warm and wet times of the year. The drought indices and indicators, in general, were not perceived to perform equally well across geographies. This review paper provides guidance on when (time of year) and where (climate zone) the more popular drought indices and indicators should be used. The paper concludes by noting the importance of understanding how drought, its impacts, and its indicators are changing over time as the climate warms and by recommending ways to strengthen the use of indices and indicators in drought decision making. [ABSTRACT FROM AUTHOR]

In situ meteorological data are essential to better understand ongoing environmental changes in the Arctic. Here, we present a dataset of quality-controlled meteorological observations from two automatic weather stations in northwest Greenland from July 2012 to the end of August 2020. The stations were installed in the accumulation area on the Greenland Ice Sheet (SIGMA-A site, 1490 m a.s.l.) and near the equilibrium line of the Qaanaaq Ice Cap (SIGMA-B site, 944 m a.s.l.). We describe the two-step sequence of quality-controlling procedures that we used to create increasingly reliable datasets by masking erroneous data records. Those datasets are archived in the Arctic Data archive System (ADS) (SIGMA-A – 10.17592/001.2022041303, Nishimura et al., 2023f; SIGMA-B – 10.17592/001.2022041306, Nishimura et al., 2023c). We analyzed the resulting 2012–2020 time series of air temperature, surface height, and surface albedo and histograms of longwave radiation (a proxy of cloudiness). We found that surface height increased, and no significant albedo decline in summer was observed at the SIGMA-A site. In contrast, high air temperatures and frequent clear-sky conditions in the summers of 2015, 2019, and 2020 at the SIGMA-B site caused significant albedo and surface lowering. Therefore, it appears that these weather condition differences led to the apparent surface height decrease at the SIGMA-B site but not at the SIGMA-A site. We anticipate that this quality-controlling method and these datasets will aid in climate studies of northwest Greenland and will contribute to the advancement of broader polar climate studies. [ABSTRACT FROM AUTHOR]

Both regional climate models (RCMs) and remote sensing (RS) data are essential tools in understanding the response of polar regions to climate change. RCMs can simulate how certain climate variables, such as surface melt, runoff and snowfall, are likely to change in response to different climate scenarios but are subject to biases and errors. RS data can assist in reducing and quantifying model uncertainties by providing indirect observations of the modeled variables on the present climate. In this work, we improve on an existing scheme to assimilate RS wet snow occurrence data with the "Modèle Atmosphérique Régional" (MAR) RCM and investigate the sensitivity of the RCM to the parameters of the scheme. The assimilation is performed by nudging the MAR snowpack temperature to match the presence of liquid water observed by satellites. The sensitivity of the assimilation method is tested by modifying parameters such as the depth to which the MAR snowpack is warmed or cooled, the quantity of water required to qualify a MAR pixel as "wet" (0.1 % or 0.2 % of the snowpack mass being water), and assimilating different RS datasets. Data assimilation is carried out on the Antarctic Peninsula for the 2019–2021 period. The results show an increase in meltwater production (+66.7 % on average, or +95 Gt), along with a small decrease in surface mass balance (SMB) (-4.5 % on average, or -20 Gt) for the 2019–2020 melt season after assimilation. The model is sensitive to the tested parameters, albeit with varying orders of magnitude. The prescribed warming depth has a larger impact on the resulting surface melt production than the liquid water content (LWC) threshold due to strong refreezing occurring within the top layers of the snowpack. The values tested for the LWC threshold are lower than the LWC for typical melt days (approximately 1.2 %) and impact results mainly at the beginning and end of the melting period. The assimilation method will allow for the estimation of uncertainty in MAR meltwater production and will enable the identification of potential issues in modeling near-surface snowpack processes, paving the way for more accurate simulations of snow processes in model projections. [ABSTRACT FROM AUTHOR]

Science museums are important informal science learning environments which have the potential to shape public discourse around topics such as climate change. Planetariums, which have traditionally provided projected, observational experiences to explore topics in astronomy, have evolved to engage different areas of science in live interaction with planetarium staff. The current study analyzes audience experiences of a planetarium show about polar science and climate change, Earth: Pole to Pole, designed jointly by Pacific Science Center and the University of Washington's Polar Science Center. Post-show survey results from general audiences indicated that over 90% of respondents felt that they learned either "some" or "a lot" about polar science, with a moderate increase in interest observed in all subgroups analyzed, but this increase was especially high amongst female respondents. [ABSTRACT FROM AUTHOR]

Due to its involvement in numerous feedbacks, sea ice plays a crucial role not only for polar climate but also at global scale. We analyse state-of-the-art observed, reconstructed, and modelled sea-ice concentration (SIC) together with sea surface temperature (SST) to disentangle the influence of different forcing factors on the variability of these coupled fields. Canonical Correlation Analysis provides distinct pairs of coupled Arctic SIC–Atlantic SST variability which are linked to prominent oceanic and atmospheric modes of variability over the period 1854–2017. The first pair captures the behaviour of the Atlantic meridional overturning circulation (AMOC) while the third and can be associated with the North Atlantic Oscillation (NAO) in a physically consistent manner. The dominant global SIC–Atlantic SST coupled mode highlights the contrast between the responses of Arctic and Antarctic sea ice to changes in AMOC over the 1959–2021 period. Model results indicate that coupled SST–SIC patterns can be associated with changes in ocean circulation. We conclude that a correct representation of AMOC-induced coupled SST–SIC variability in climate models is essential to understand the past, present and future sea-ice evolution. [ABSTRACT FROM AUTHOR]

During the recent four decades since 1980, a series of modern climate satellites were launched, allowing for the measurement and record-keeping of multiple climate parameters, especially over the polar regions where traditional observations are difficult to obtain. China has been actively engaging in polar expeditions. Many observations were conducted during this period, accompanied by improved Earth climate models, leading to a series of insightful understandings concerning Arctic and Antarctic climate changes. Here, we review the recent progress China has made concerning Arctic and Antarctic climate change research over the past decade. The Arctic temperature increase is much higher than the global-mean warming rate, associated with a rapid decline in sea ice, a phenomenon called the Arctic Amplification. The Antarctic climate changes showed a zonally asymmetric pattern over the past four decades, with most of the fastest changes occurring over West Antarctica and the Antarctic Peninsula. The Arctic and Antarctic climate changes were driven by anthropogenic greenhouse gas emissions and ozone loss, while tropical-polar teleconnections play important roles in driving the regional climate changes and extreme events over the polar regions. Polar climate changes may also feedback to the entire Earth climate system. The adjustment of the circulation in both the troposphere and the stratosphere contributed to the interactions between the polar climate changes and lower latitudes. Climate change has also driven rapid Arctic and Southern ocean acidification. Chinese researchers have made a series of advances in understanding these processes, as reviewed in this paper. [ABSTRACT FROM AUTHOR]

Polar-orbiting satellite observations are of fundamental importance to explore the main scientific challenges in the Arctic Ocean, as they provide information on bio-geo-physical variables with a denser spatial and temporal coverage than in-situ instruments in such a harsh and inaccessible environment. However, they are limited by the lack of coverage near the North Pole (Polar gap), the polar night, and frequent cloud cover or haze over the ocean and sea ice, which prevent the use of optical satellite instruments, as well as by the limited availability of external validation data. The satellite sensors' coverage and repeat cycles may also have limitations in properly identifying and resolving the dominant spatial and temporal scales of atmospheric, ocean, cryosphere and land variability and their interactive processes and feedback mechanisms. In this paper, we provide a state of the art of contribution of satellite observations to the understanding of the polar environment and climate scientific challenges tackled within the Arktalas Hoavva project funded by the European Space Agency. We identify the current limitations to the wider use of polar orbiting remote sensing data, as well as the observational gaps of the existing satellite missions. A comprehensive overview of all satellite missions and applications is given provided with a primary focus on the European satellites. Finally, we assess the expected capability of the approved future satellite missions to answer today's scientific challenges in the Arctic Ocean. [ABSTRACT FROM AUTHOR]

Pollen analysis is still a manual task and an experienced pollen analyst may analyse two to four samples per day when a regular pollen sum of 300 pollen grains is used. Long continental pollen records (LCPRs) form a remarkable aspect of palynological research. The pollen analytical work Since 1988, efforts to analyse pollen grains automatically have been published regularly (Konert et al. [22]; Witte [34]; France et al. [9]; Marcos et al. [25]; Olsson et al. [28]) however, pollen analysis still is a manual procedure. [Extracted from the article]

McMurdo Station, located in Antarctica, experiences extreme weather conditions due to its proximity to the Southern Ocean and the surrounding features such as the Ross Sea, the Ross Ice Shelf, and the Transantarctic Mountains. The station is known for its cold temperatures and powerful katabatic winds, which are gravity-driven winds that accelerate dense, cold air downslope. These winds, along with the complex topography, create localized weather patterns and storms, including intense snowstorms called "Herbies." The area also includes the McMurdo Dry Valleys, which are the largest ice-free land area in Antarctica and some of the driest places in the world. McMurdo Station serves as a hub for scientific research and is administered by the United States National Science Foundation. [Extracted from the article]

In situ meteorological data are essential to better understand ongoing environmental changes in the Arctic. Here, we present a dataset of quality-controlled meteorological observations by two automatic weather stations in northwest Greenland from July 2012 to the end of August 2020. The stations were installed in an accumulation area on the Greenland Ice Sheet (SIGMA-A site, 1490 m a.s.l.) and near the equilibrium line of the Qaanaaq Ice Cap (SIGMA-B site, 944 m a.s.l.). We describe the two-step sequence of quality-control procedures that we used to create increasingly reliable datasets by masking erroneous data records. We analyzed the resulting 2012-2020 time series of air temperature, positive degree-days, snow height, surface albedo, and histograms of longwave radiation (a proxy of cloud formation frequency). We found that snow height increased and albedo remained steady at the SIGMA-A site, whereas high air temperatures and clear-sky conditions prevailed while snow height and albedo decreased in the summers of 2015, 2019, and 2020 at the SIGMA-B site. Therefore, it appears that these weather conditions led to notable snow height degradation at the SIGMA-B site but not at the SIGMA-A site. We anticipate that this quality-control method and these datasets will aid in climate studies of northwest Greenland as well as contribute to the advancement of broader polar climate studies. [ABSTRACT FROM AUTHOR]

The Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) will fill a gap in our understanding of polar processes and the polar climate by offering widespread, spectrally resolved measurements through the far-infrared (FIR) with two identical CubeSat spacecraft. While the polar regions are typically difficult for skillful cloud identification due to cold surface temperatures, the reflection by bright surfaces, and frequent temperature inversions, the inclusion of the FIR may offer increased spectral sensitivity, allowing for the detection of even thin ice clouds. This study assesses the potential skill, as well as limitations, of a neural network (NN)-based cloud mask using simulated spectra mimicking what the PREFIRE mission will capture. Analysis focuses on the polar regions. Clouds are found to be detected approximately 90% of time using the derived neural network. The NN's assigned confidence for whether a scene is "clear" or "cloudy" proves to be a skillful way in which quality flags can be attached to predictions. Clouds with higher cloud-top heights are typically more easily detected. Low-altitude clouds over polar surfaces, which are the most difficult for the NN to detect, are still detected over 80% of the time. The FIR portion of the spectrum is found to increase the detection of clear scenes and increase mid- to high-altitude cloud detection. Cloud detection skill improves through the use of the overlapping fields of view produced by the PREFIRE instrument's sampling strategy. Overlapping fields of view increase accuracy relative to the baseline NN while simultaneously predicting on a sub-FOV scale. Significance Statement: Clouds play an important role in defining the Arctic and Antarctic climates. The purpose of this study is to explore the potential of never-before systematically measured radiative properties of the atmosphere to aid in the detection of polar clouds, which are traditionally difficult to detect. Satellite measurements of emitted radiation at wavelengths longer than 15 μm, combined with complex machine learning methods, may allow us to better understand the occurrence of various cloud types at both poles. The occurrence of these clouds can determine whether the surface warms or cools, influencing surface temperatures and the rate at which ice melts or refreezes. Understanding the frequencies of these various clouds is increasingly important within the context of our rapidly changing climate. [ABSTRACT FROM AUTHOR]

Global warming can lead to a more frequent occurrence of hot days and heat waves and fewer cold days and cold waves. In this paper, the daily mean temperature (TM) was divided into 7 range categories (TM < − 15 °C, − 15 °C ≤ TM < − 5 °C, ... TM ≥ 35 °C). Then, the temperature days (TDs) were obtained and expressed as TD1, TD2, ..., TD6, and TD7, which correspond well to climate zones. The changes in future TDs are obvious, especially for TD1 and TD6. Under the Representative Concentration Pathway (RCP) 8.5 scenario, TD1 will decrease the most in the polar climate zone, from 162 to 102, while TD6 in warm tropical countries and regions, such as Brazil, Nigeria, and Congo, will increase by more than 70 days, reaching at least 300 days per year after 2066. By summarizing the anomalies of TD1, TD2, TD6, and TD7 in combination into 12 templates, the changes in TD1 and TD2 were determined to be more pronounced than those in TD6 and TD7. Although carbon dioxide emissions will remain basically stable from 2066 to 2095 under the RCP4.5 scenario, both TD1 and TD2 will decrease in central Antarctica, Eastern Europe, and northern Russia, and the melting of ice and snow will be irreversible. Countries such as Saudi Arabia and Australia will still face a continuous increase in both TD6 and TD7. Temperature range changes also affect the humidity of the climate: in the projected future, humid climate areas will decrease, while arid climate areas will increase. The boreal drylands in the middle and high latitudes will be replaced by temperate drylands. [ABSTRACT FROM AUTHOR]

In specific areas of the Arctic and Antarctic regions, air temperatures are expanding at rates more than two times the international average; additionally, there are other direct human impacts on polar regions. A quick change in climate impacting the polar regions will similarly have huge physical and biological consequences for the last existing parts of the planet since the ice-engulfed Arctic Ocean, the Antarctic landform, and the worldwide eminent Antarctic Circumpolar Current (ACC) serve a basic job in managing the Earth's current circumstance and ocean systems. Polar biodiversity is presently responding to this rapid climate change and more massive impacts will happen in this era. Intensifying the danger to polar biodiversity is the certainty that numerous polar environments have restricted functional redundancy; in case of the disappearance of a solitary keystone species, they may possibly be exposed to descending impacts and complete biological system rebuilding. This study focussed on the contributing factors of ecological change, the effects of natural change on the Antarctic environment, next to the effects of environmental change on the types of Antarctic biodiversity. The most rapidly changing biological agenda on our planet are arranged in the polar regions. This issue is picked to research the effects of natural change on a particular region's biodiversity. [ABSTRACT FROM AUTHOR]

Arctic sea ice change is one of the critical factors affecting the global climate environment; hence, it is crucial to obtain sea ice thickness with high accuracy while studying polar and global climate change. In the process of using altimetry data to estimate sea ice thickness, the mean sea surface height will bring greater uncertainty to the extraction of sea ice freeboard, which will affect the accuracy of sea ice thickness. Also, the influence of snow cover on radar signal penetration will bring greater uncertainty to sea ice thickness. In this paper, we present a processing chain for sea ice thickness estimation. First, we compare the effect of four different MSS models on the freeboard estimation. Then, considering the incomplete penetration of radar signals and the different speeds of radar signals penetrating the snow layer and the vacuum, the traditional sea ice thickness model is optimized to obtain the sea ice thickness. Compared with the Operation IceBridge (OIB) sea ice thickness, the accuracy of sea ice thickness obtained by the optimized model is better than 0.350 m, with a root mean square error of 0.260 m and a mean bias of 0.048 m. The comparison results show that the combination of the latest DTU18 MSS model and sea ice thickness optimization model effectively improve the accuracy of sea ice thickness. [ABSTRACT FROM AUTHOR]

Sea ice in the polar regions can move several tens of kilometers per day under the actions of winds, ocean currents, and internal stresses. Long-term observations of the rate and patterns of this motion are needed to characterize the full response of the polar environment to climate change. Here, we introduce a new climate data record (CDR) of year-round, global, daily sea-ice drift vectors covering 1991-2020. The motion vectors are computed from series of passive microwave imagery in the 5 winter months, and from a parametric free-drift model in the summer months. An evaluation against on-ice buoy trajectories reveals that the RMSEs of the sea-ice drift CDR are small and vary with hemisphere and seasons (2.1 km for Arctic winters, 2.6 km for Arctic summer, 3 to 4 km for the Antarctic sea ice). The CDR is un-biased for Arctic winter conditions. The bias is larger for Antarctic and for summer sea ice motion. The CDR consists of daily product files holding the dX and dY components of the drift vectors on an EASE2 grid with 75 km spacing, as well as associated uncertainties and flags. [ABSTRACT FROM AUTHOR]

Accurate monitoring of the spatiotemporal dynamics of snow and ice is essential for under-standing and predicting the impacts of climate change on Arctic ecosystems and their feedback on global climate. Traditional optical and Synthetic Aperture Radar (SAR) remote sensing still have limitations in the long-time series observation of polar regions. Although several studies have demonstrated the potential of moonlight remote sensing for mapping polar snow/ice covers, systematic evaluation on applying moonlight remote sensing to monitoring spatiotemporal dynamics of polar snow/ice covers, especially during polar night periods is highly demanded. Here we present a systematic assessment in Svalbard, Norway and using data taken from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) Day/Night Band (DNB) sensor to monitor the spatiotemporal dynamics of snow/ice covers during dark Arctic winters when no solar illumination available for months. We successfully revealed the spatiotemporal dynamics of snow/ice covers from 2012 to 2022 during polar night/winter periods, using the VIIRS/DNB time series data and the object-oriented Random Forests (RF) algorithm, achieving the average accuracy and kappa coefficient of 96.27% and 0.93, respectively. Our findings indicate that the polar snow/ice covers show seasonal and inter-seasonal dynamics, thus requiring more frequent observations. Our results confirm and realize the potential of moonlight remote sensing for continuous monitoring of snow/ice in the Arctic region and together with other types of remote sensing data, moonlight remote sensing will be a very useful tool for polar studies and climate change. [ABSTRACT FROM AUTHOR]

As the highest and most extensive plateau in the world, the Tibetan Plateau (TP) has remarkable effects on global climate. Through coupled model sensitivity experiments with and without the TP, we show that the TP can affect the Arctic directly via orography-forced stationary waves, and influence the Antarctic indirectly via stationary waves forced by sea surface temperature (SST) in the Indian Ocean. These far-reaching impacts occur mainly in wintertime. The fast atmospheric processes play an important role; particularly, the midlatitude westerly flow, which is stronger and closer to the equator in winter, provides a favorable condition for the eastward and poleward energy propagation of the forced waves. In the Northern Hemisphere, removing the TP causes a wave train traveling from the Asian continent to the North America–Atlantic Ocean region, resulting in intensified westerlies and thus an enhancement of stratospheric polar vortex and Arctic cooling. The pathways are northeastward directly in the upper level due to the background westerlies, while they are eastward and then northeastward in the lower level, modulated by the winter monsoon. To the south, the TP perturbation causes an anomalous cross-equatorial flow, leading to an anomalous SST dipole pattern in the Indian Ocean in the austral winter; this generates stationary waves propagating energy southeastward from the tropical Indian Ocean to the Antarctic, resulting in a Rossby wave train circulating around the Antarctic. Our study identifies the seasonality and pathways of the TP affecting the polar regions, which may help to understand the role of the TP in the future climate changes in polar regions. [ABSTRACT FROM AUTHOR]

The main energy input to the polar regions in winter is the advection of warm, moist air from lower latitudes. This makes the polar climate sensitive to the temperature and moisture of extrapolar air. Here, we study this sensitivity from an air-mass transformation perspective. We perform simulations of an idealized maritime air mass brought into contact with sea ice employing a three-dimensional large-eddy simulation model coupled to a one-dimensional multilayer sea ice model. We study the response of cloud dynamics and surface warming during the air-mass transformation process to varying initial temperature and humidity conditions of the air mass. We find in all cases that a mixed-phase cloud is formed, initially near the surface but rising continuously with time. Surface warming of the sea ice is driven by downward longwave surface fluxes, which are largely controlled by the temperature and optical depth of the cloud. Cloud temperature, in turn, is robustly constrained by the initial dewpoint temperature of the air mass. Since dewpoint only depends on moisture, the overall result is that surface warming depends almost exclusively on initial humidity and is largely independent of initial temperature. We discuss possible climate implications of this result}in particular, for polar amplification of surface warming and the role played by atmospheric energy transports. [ABSTRACT FROM AUTHOR]

A new, simple parameterization scheme for scalar (heat and moisture) exchange over sea ice and the marginal ice zone is tested in a numerical weather and climate prediction model. This new "Blended A87" scheme accounts for the influence of aerodynamic roughness on the relationship between momentum and scalar exchange over consolidated sea ice, in line with long‐standing theory and recent field observations, and in contrast to the crude schemes currently operational in most models. Using aircraft observations and Met Office Unified Model simulations of cold‐air outbreak (CAO) conditions over aerodynamically rough sea ice, we demonstrate striking improvements in model performance when the Blended A87 scheme replaces the model's operational treatment for surface scalar exchange, provided that the aerodynamic roughness over consolidated ice is appropriately prescribed. The mean biases in surface sensible heat flux, surface latent heat flux, near‐surface air temperature, and surface temperature reduce from 25 to 11 W m−2, 22 to 12 W m−2, 0.8 to 0.0 K, and 1.4 to 0.8 K, respectively. We demonstrate that such impacts on surface exchange over sea ice can have a marked impact on the evolution of the atmospheric boundary layer across hundreds of kilometres downwind of the sea ice during CAO conditions in the model. Our results highlight the importance of spatiotemporal variability in the topography of consolidated sea ice for both momentum and scalar exchange over sea ice; accounting for which remains a key challenge for modeling polar weather and climate. Plain Language Summary: A new algorithm for the turbulent exchange of heat and moisture between the atmosphere and the ice‐covered oceans of the polar regions is tested in a state‐of‐the‐art weather and climate model. The algorithm is applicable both over consolidated sea ice and in regions characterized by a mixture of open seawater and ice. It accounts for the influence of aerodynamic roughness (a function of wind speed and the fine‐scale topographic roughness of the surface), in line with long‐standing theory and recent field observations, and in contrast to the crude schemes currently operational in most models. Using low‐altitude aircraft observations from over the Arctic Ocean and Nordic Seas, we demonstrate striking improvements in model performance when the new algorithm replaces the model's operational treatment for surface scalar exchange, provided that the aerodynamic roughness over consolidated ice is appropriately prescribed. The mean biases in surface sensible heat flux, surface latent heat flux, near‐surface air temperature and surface temperature reduce from 25 to 11 W m−2, 22 to 12 W m−2, 0.8 to 0.0 K, and 1.4 to 0.8 K, respectively. We demonstrate that such impacts on surface exchange over sea ice can have a significant impact on model prediction of high‐latitude weather. Key Points: The model reproduction of scalar fluxes over sea ice is improved with a new parameterization that accounts for aerodynamic roughnessThe properties and structure of the polar atmospheric boundary layer are sensitive to the implementation of this new parameterizationThe benefit of the parameterization accounting for aerodynamic roughness hinges on the appropriate prescription of sea‐ice topography [ABSTRACT FROM AUTHOR]

Glacier and ice sheet surfaces host diverse communities of microorganisms whose activity (or inactivity) influences biogeochemical cycles and ice melting. Supraglacial microbes endure various environmental extremes including resource scarcity, frequent temperature fluctuations above and below the freezing point of water, and high UV irradiance during summer followed by months of total darkness during winter. One strategy that enables microbial life to persist through environmental extremes is dormancy, which despite being prevalent among microbial communities in natural settings, has not been directly measured and quantified in glacier surface ecosystems. Here, we use a combination of metabarcoding and metatranscriptomic analyses, as well as cell‐specific activity (BONCAT) incubations to assess the diversity and activity of microbial communities from glacial surfaces in Iceland and Greenland. We also present a new ecological model for glacier microorganisms and simulate physiological state‐changes in the glacial microbial community under idealized (i) freezing, (ii) thawing, and (iii) freeze–thaw conditions. We show that a high proportion (>50%) of bacterial cells are translationally active in‐situ on snow and ice surfaces, with Actinomycetota, Pseudomonadota, and Planctomycetota dominating the total and active community compositions, and that glacier microorganisms, even when frozen, could resume translational activity within 24 h after thawing. Our data suggest that glacial microorganisms respond rapidly to dynamic and changing conditions typical of their natural environment. We deduce that the biology and biogeochemistry of glacier surfaces are shaped by processes occurring over short (i.e., daily) timescales, and thus are susceptible to change following the expected alterations to the melt‐regime of glaciers driven by climate change. A better understanding of the activity of microorganisms on glacier surfaces is critical in addressing the growing concern of climate change in Polar regions, as well as for their use as analogues to life in potentially habitable icy worlds. [ABSTRACT FROM AUTHOR]

Water storage capacity in the layers of canopy, litter, and soil of forest ecosystems has not yet been thoroughly investigated on a global scale. We estimated the global pattern of water storage capacity of forest ecosystems related to water regulation services (WSCFE) in the above three layers based on 1,288 observations and analyzed their 22 controlling environmental factors. The results show that the global mean WSCFE per unit area is 456.7 mm, and the total volume of WSCFE is 22,662.5 km3. Climatic variables are the leading factors contributing to the variations of WSCFE, followed by forest attributes, terrain factors, soil properties, and litter characteristics. This study advances the understanding of the large‐scale variation mechanisms of WSCFE in different forest types and climate zones and provides scientific evidence for ecological protection according to local conditions. Plain Language Summary: Forest ecosystem plays a vital role in the earth's hydrological process, and water storage capacity of forest ecosystems related to water regulation service (WSCFE) is of vital importance for human well‐being. Water can be intercepted by forest canopy, be held by litter, and be stored in soils, which accounts for more than a quarter of the water volumes in the terrestrial hydrologic cycle. The WSCFE is affected by many factors and its global pattern has not been well understood. In this study, based on the observed data from literature, we provided a robust global pattern of the WSCFE in canopy layer, litter layer, and soil layer. The results show that the WSCFE in the canopy and soil layer decrease gradually from tropical climate zone to polar climate zone, while the maximum WSCFE in the litter layer appears in polar and cold climate zone. The main controlling factors have different impacts on the WSCFE in the three layers. These should be considered in the developing protection policies for important ecological functional areas. Key Points: Forest water storage capacity related to water regulation decreases from equator to pole, from coast to inland, and from mountains to plainsAmong the controlling factors, climatic factors have the largest and most positive influence on water storage capacityThe quantification of three important water storages provides a basis to delineate global water regulation zones [ABSTRACT FROM AUTHOR]

Much of the salty, high oxygen North Atlantic Deep Water (NADW) leaving the Atlantic flows through the Argentine Basin, where it is diluted by fresher, low oxygen Circumpolar Deep Water (CDW). This mixing of deep water masses is often overlooked in the zonally averaged description of the overturning circulation. Here, we show that intense mixing occurs along the western boundary: (a) extreme, isolated oxygen/temperature anomalies recorded by three autonomous biogeochemical floats suggest that subsurface eddies can inject relatively unmodified CDW far into the northwestern Argentine Basin, and (b) moderate, numerous temperature/salinity anomalies indicate a mixing zone from Rio Grande Rise to the Malvinas Current. This western eddy pathway shortcuts the gyre‐scale cyclonic route for CDW inferred from most previous studies. Significantly, CDW dilution of NADW affects the properties of deep waters that upwell in the Southern Ocean, and hence the connection between Northern and Southern Hemisphere polar climates. Plain Language Summary: Water, heat, and carbon are transported around the global ocean by the meridional overturning circulation, which helps regulate the climate system. In the Atlantic Ocean, the overturning circulation is characterized by net southward flow in the deep water layers, which transports water from the northern North Atlantic (North Atlantic Deep Water; NADW) all the way to the Southern Ocean. Often neglected in this picture is the modification of these deep waters as they flow south toward the Antarctic. Specifically, they become colder, fresher and less oxygenated due to mixing with much older deep water from the South Pacific, which enters the Atlantic below South America and joins the Circumpolar Deep Water (CDW) flowing northward into the Argentine Basin. Here, using autonomous float measurements, we investigate the mixing between NADW and CDW in the Argentine Basin. We show that isolated boluses of CDW with properties from the Malvinas are found far to the north on the western side of the basin, suggesting transport by isolated subsurface eddies. Understanding these pathways is important because they influence the properties of the water that rises to the surface in the Southern Ocean; dilution of NADW by CDW damps the transmission of Northern Hemisphere climate change to the Southern Ocean. Key Points: Pacific/Circumpolar Deep Water (CDW) with low oxygen, salinity, and pH dilutes North Atlantic Deep Water (NADW) in the South Atlantic's Argentine BasinIsolated low oxygen anomalies in the northwest Argentine Basin indicate a direct path of CDW northward via the MalvinasStrong isopycnic temperature variability along the western boundary identifies this as a mixing hotspot for these two deep water masses [ABSTRACT FROM AUTHOR]

Background: The international community has shown increasing interest in the Arctic and Antarctic due to the value polar regions have in terms of environmental research, natural resources, and national defense. The US Government maintains several permanent research and military facilities in polar regions. Medical evacuation (MEDEVAC) from these facilities can be limited for prolonged periods of time due to their extreme climates. Published data regarding MEDEVACs from these facilities is extremely limited. Methods: Evacuations on military aircraft registered in the Transportation Command Regulation and Command and Control Evacuation System (TRAC2ES) database in a previously de-identified dataset were queried for events from McMurdo, Antarctica. The data was analyzed to determine the number of evacuations, reasons for evacuation, and additional demographic data. Results: There were 31 evacuations from McMurdo Station and Scott Amundsen South Pole Station for 29 unique patients recorded in the available TRAC2ES dataset. Reasons for evacuation included traumatic brain/ head injury, behavioral health concerns, extremity injuries, pregnancy, and various other medical/surgical concerns. Conclusions: MEDEVAC was typically required for advanced diagnostic/treatment modalities or if a patient could no longer fulfill his/her duties. Most evacuations were not directly related to environmental exposure. Given the climate in polar regions can preclude timely evacuation for large periods of time, the need for evacuation must be anticipated and mitigated whenever possible. Better data is needed to guide staffing and mission planning in this remote location. [ABSTRACT FROM AUTHOR]

Polar lows (PLs) are intense maritime mesocyclones that typically develop during marine cold-air outbreak events over the high latitudes. The impacts posed by these systems to humans and the broader environment demand a robust understanding of the environmental factors that promote PL formation and, in turn, skillful prediction of PL activity. We hypothesize that the variability of PL activity is associated with some key large-scale climate variables skewed toward "extreme" values, which can provide predictable information on PL activity beyond the synoptic time scale. A PL genesis potential index (PGI) is developed that relates the climatological spatial distribution of PL genesis frequency and key climate variables in a Poisson regression framework. The optimal set of predictors consists of a static stability parameter and an environmental baroclinicity parameter. The optimal predictor categories are shown to be robust across different reanalyses and PL track datasets. The observed spatial distribution and seasonal cycle of PL genesis frequency are represented well by the PGI, and the interannual variability of PL activity is captured skillfully. The effects of the Arctic Oscillation (AO), El Niño–Southern Oscillation (ENSO), and a few other climate modes on the interannual variability of PL activity are explored. Overall, our results suggest that the PGI may be used to inform skillful subseasonal to seasonal prediction of PL activity. Significance Statement: Polar lows are intense mesocyclones over high-latitude oceans, and they have destructive impacts on coastal and island communities, and maritime and air operations. However, skillful prediction of polar lows on the subseasonal and longer time scales remains challenging. This study links polar low activity to large-scale environmental conditions in the Arctic through a statistical modeling approach. This work is based on the hypothesis that a shared statistical relationship exists between the large-scale climate variables and polar low activity across the Arctic, which enables a geographical unification of the controlling factors on polar low activity. Our results reveal two dominant factors, one related to the lower-tropospheric stratification and the other to the hydrodynamic instability of the lower-tropospheric flow. This statistical framework has potential applications to climate prediction and projection of polar low activity. [ABSTRACT FROM AUTHOR]

Marginal ice zones (MIZs) are qualitatively distinct sea-ice-covered areas that play a critical role in the interaction between the polar oceans and the broader Earth system. MIZ regions have high spatial and temporal variability in oceanic, atmospheric and ecological conditions. The salient qualitative feature of MIZs is their composition as a mosaic of individual floes that range in horizontal extent from centimetres to tens of kilometres. Thus the floe size distribution (FSD) can be used to quantitatively identify and describe them. Here, the history of FSD observations and theory, and the processes (particularly the impact of ocean waves) that determine floe sizes and size distribution, are reviewed. Coupled wave-FSD feedbacks are explored using a stochastic model for thermodynamic wave-sea-ice interactions in the MIZ, and some of the key open questions in this rapidly growing field are discussed. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

Despite enormous scientific and technological progress in numerical weather and climate prediction, sea ice still remains unreliably predicted by models, both in short-term forecasting and climate projection applications. The total ice extent in both hemispheres is tied to the location of the ice edge, and consequently to what happens in the portion of the ice cover immediately adjacent to the open ocean that is called the marginal ice zone (MIZ). There is mounting evidence that processes occurring in the MIZ might play an important role in the polar climate of both hemispheres, yet some key physical processes are still missing in models. As sea ice models developed for climate studies are increasingly used for operational forecasting, the missing physics also impede short-term sea ice prediction skills. This paper is a mini-review that provides a historical perspective on how MIZ research has progressed since the 1970s, with a focus on the fundamental importance of the interactions between sea ice and surface gravity waves on sea ice dynamics. Completeness is not achieved, as the body of literature is huge, scattered and rapidly growing, but the intention is to inform future collaborative research efforts to improve our understanding and predictive capabilities of sea ice dynamics in the MIZ. This article is part of the theme issue 'Theory, modelling and observations of marginal ice zone dynamics: multidisciplinary perspectives and outlooks'. [ABSTRACT FROM AUTHOR]

For this reason, climate refugia and climate-informed ecosystem-based management are both vital to maximize the resilience of species and ecosystem processes in these cold, polar habitats (Chown et al., 2022; Constable, 2022). In the Arctic terrestrial sphere, warming, permafrost thaw and snowfall decrease have led to profound landscape, ecosystem structure and hydrological changes (Fujii et al., 2022). Polar landscapes and their unique biodiversity are threatened by climate change. [Extracted from the article]

As changes to Earth's polar climate accelerate, the need for robust, long–term sea ice thickness observation datasets for monitoring those changes and for verification of global climate models is clear. By linking an algorithm for retrieving snow–ice interface temperature from passive microwave satellite data to a thermodynamic sea ice energy balance relation known as Stefan's law, we have developed a retrieval method for estimating thermodynamic sea ice thickness growth from space: Stefan's Law Integrated Conducted Energy (SLICE). With an initial condition at the beginning of the sea ice growth season, the method can model basin-wide absolute sea ice thickness by combining the one-dimensional SLICE retrieval with an ice motion dataset. The advantages of the SLICE retrieval method include daily basin-wide coverage, lack of atmospheric reanalysis product input requirement, and a potential for use beginning in 1987. Validation of the retrieval against measurements from 10 ice mass balance buoys shows a mean correlation of 0.89 and a mean bias of 0.06 m over the course of an entire sea ice growth season. Despite its simplifications and assumptions relative to models like the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS), basin-wide SLICE performs nearly as well as PIOMAS when compared against CryoSat-2 and Operation IceBridge using a linear correlation between collocated points. [ABSTRACT FROM AUTHOR]

Sea ice concentration (SIC) is the main variable for quantifying the sea ice change in the polar regions. Continuous SIC data is very important for the studies of climate and polar marine environments. This study generates a new SIC product covering the Arctic and Antarctic from November 2010 to December 2019. It is the first long-term SIC product derived from the Microwave Radiation Imager (MWRI) sensors onboard the Chinese FengYun-3B, -3C, and -3D satellites, after a recent re-calibration of brightness temperature. We also modified the preliminary dynamic tie points Arctic Radiation and Turbulence Interaction Study Sea Ice (ASI) algorithm mainly through input TB and initial tie points. The MWRI-ASI SIC was compared to the existing ASI SIC products and validated using ship-based SIC observations. Results show that the MWRI-ASI SIC mostly coincides with the ASI SIC obtained from the Special Sensor Microwave Imager series sensors, with overall biases of -1.4 ± 1.8% in the Arctic and 0.5 ± 2.2% in the Antarctic, respectively. The overall mean absolute deviation between the MWRI-ASI SIC and ship-based SIC is 16.1% and 17.1% in the Arctic and Antarctic, respectively, which is close to the existing ASI SIC products. The trend of sea ice extent (SIE) derived from MWRI-ASI SIC closely agrees with those of the Sea Ice Index SIEs provided by OSI-SAF and NSIDC. Therefore, the MWRI-ASI SIC is comparable with other SIC products and is qualified to be integrated into long-term sea ice records. The MWRI-ASI SIC dataset is available at https://doi.pangaea.de/10.1594/PANGAEA.945188 (Chen et al., 2022). [ABSTRACT FROM AUTHOR]

In this study, the damage caused by solutions with different salt contents, which are actively used in combating snow and ice in winter climate conditions, on asphalt concrete roads in different periods was investigated experimentally. Hot mix asphalt concrete (HMA) prepared within the framework of the standards for the wear layer directly affected by snow and ice were subjected to freeze-thaw at different periods (7, 14, 21, 28 cycles) and two different thawing environments were prepared for each thaw. For this reason, two different sodium chloride (NaCl) solutions, 1 mol (M) and 4 mol (M), were prepared and the frozen HMA samples were thawed in 1M or 4M solution environments at the end of each cycle. Thus, the effects of salt on the damage to the HMA surface were investigated. While the Marshall Stability (MS) value of the reference sample that was not exposed to freezing and thawing was 985 kg, the MS values of the samples exposed to freezing and thawing cycles for 7, 14, 21 and 28 days in 1M solutions were found to be 971 kg, 938.5 kg, 889.5 kg and 910 kg, respectively. On the other hand, the MS values of the samples exposed to freezing and thawing cycles for 7, 14, 21 and 28 days in 4M solution were obtained as 914 kg, 814 kg, 790 kg and 765 kg, respectively. In this study, it was observed that the freeze-thaw cycle caused a decrease in the stability of asphalt concrete. [ABSTRACT FROM AUTHOR]

Although these impacts were not explicitly discussed in this workshop, they can still be quantified using the standard output from regional climate models and do not require separate impacts models or additional effort from the regional climate modelers. Keywords: Climate models; Decision making; Regional models; Societal impacts EN Climate models Decision making Regional models Societal impacts E1866 E1874 9 09/27/22 20220801 NES 220801 Toward Effective Collaborations between Polar Regional Climate and Impacts Modelers What: The aim of this workshop was to discuss the needs and challenges in using high-resolution climate model outputs for impacts-relevant modeling. Outlook and future meeting suggestion The main outcome of this workshop was the identification of the importance of co-designing high-resolution regional climate projections by both the impact modelers (downstream users) and regional climate modelers, to ensure that regional climate simulations (including atmosphere-only, ocean-only, and coupled simulations) are useful for modeling and assessing impacts of change in the polar regions. The main objective of this workshop was to initiate and build close collaboration between groups developing and running the next generation of high-resolution regional climate models and impacts modelers to deliver more impacts-relevant climate projections for the polar regions. [Extracted from the article]

The absorption properties of snow and ice particles containing impurities such as black carbon (BC) and mineral dust (DS) were investigated using the geometrical optics approximation method (GOM). This study focuses on analyzing the single scattering co-albedo (SSCA) characteristics of non-spherical particles, aiming to enhance the interpretation of radiation observations in snow and ice regions. Particle sizes were varied ( r va = 50 , 200 and 500 μ m) and two types of inclusions (1 ppmw of BC and 100 ppmw DS) were considered. Significant differences in SSCA, ranging from one to two orders of magnitude were observed at λ = 0. 5 μ m between the "homogeneous model" with effective medium approximation method (EMA) and the "inhomogeneous model" with 50 BC inclusions. Similarly, differences of a factor of 2 to 4 were found for DS with 100 ppmw at λ = 0. 5 μ m and BC with 1 ppmw at λ = 0. 875 μ m. To bridge intermediate SSCA values between these models, we propose an "inhomogeneous model with EMA", introducing two parameters to account for impurity concentration and inclusion aggregation. Our findings highlight the importance of selecting appropriate single scattering calculation methods in the analysis of observation data, particularly when dealing with BC impurity with significant absorption characteristics. This research contributes to a deeper understanding of solar radiation absorption in snow and ice regions, with potential implications for the optical remote sensing of snow and ice and climate modeling studies. • The absorption of ice particles is studied in terms of the mixing state of inclusions • The "inhomogeneous model" is compared with the "homogeneous model with EMA" • An appropriate particle model is needed to analyze observations with inclusions [ABSTRACT FROM AUTHOR]

Lentic waterbodies provide terrestrial sedimentary archives of palaeoenvironmental change in deglaciated areas of the Antarctic. Knowledge of the long-term evolution of Antarctic palaeoenvironments affords important context to the current marked impacts of climate change in the Polar regions. Here, we present a comprehensively dated, multi-proxy sedimentary record from Monolith Lake, a distal proglacial lake in one of the largest ice-free areas of the Antarctic Peninsula region. Of the two defined sedimentary units in the cores studied, the lower Unit 1 exhibits a homogeneous composition and unvarying proxy data profiles, suggesting rapid clastic deposition under uniform, ice-proximal conditions with a sedimentation rate of ∼1 mm yr−1. 14C and optically stimulated luminescence (OSL) dating bracket the deposition interval to 1.5–2.5 ka BP, with the older age being more probable when compared to independent dating of the local deglaciation. The uppermost 11 cm of the record spans the last ∼2.2 ka BP (maximum age), suggesting a markedly decreased sedimentation rate of ∼0.05 mm yr−1 within Unit 2. Whereas Unit 1 shows only scarce evidence of biological activity, Unit 2 provides an uninterrupted record of diatoms (with 29 species recorded) and faunal subfossils, including the fairy shrimp Branchinecta gaini. Concentrations of organically-derived elements, as well as diatoms and faunal remains, are consistent, implying a gradual increase in lake productivity. These results provide an example of long-term Antarctic 'greening' (i.e. increasing organic productivity in terrestrial habitats) from a palaeolimnological perspective. The boundary between Units 1 and 2, therefore, marks the timing of local deglaciation at the final stages of a period of negative glacier mass balance, i.e. the Mid-Late Holocene Hypsithermal. Subsequent Neoglacial cooling is evidenced by the abated influence of glacial meltwater streams and turbidity decline linked to reduced glacier runoff, although most proxy responses mirror the natural proglacial lake ontogeny. • Antarctic lake sediments record rapid deglaciation ∼2.5 ka ago and subsequent lake ontogeny. • Portable optically stimulated luminescence (pOSL) enhanced absolute OSL and 14C dating. • For the last ∼2.2 ka, biodiversity hotspot persisted despite the Neoglacial cooling. • Fairy shrimp Branchinecta gaini did not become extinct on James Ross Island. • We present an example of long-term Antarctic greening from a palaeolimnological perspective. [ABSTRACT FROM AUTHOR]

Numerous studies have suggested that the North Atlantic subpolar gyre (SPG), Atlantic Meridional Overturning Circulation (AMOC), and Arctic sea ice impact the polar and global climate. Here, we use a fully linked atmosphere-ocean-sea ice Earth system model to investigate the North Atlantic subpolar ocean dynamics over the last 21 thousand years before the present (ka). We found that the SPG strength, net ocean surface heat flux, and mixed layer depth in the North Atlantic deep convection sites declined during the Heinrich 1 (H1; ∼19–17 ka) and Younger Dryas (YD; ∼12.9–11.3 ka) cold events. Consequently, the deep convection and AMOC strength declined, reducing the northward meridional heat transport and causing the expansion of Atlantic sea ice coverage. We also found that the North Atlantic subpolar net ocean surface heat flux varied coherently with AMOC strength throughout the past 21 ka. Subsequently, we observed a sea ice-capping mechanism wherein an increase (decrease) in Atlantic sea ice coverage during H1/YD (Bølling-Allerød (BA; ∼17–14.35 ka)) reduces (increases) net ocean surface heat flux and deep convection, thereby influencing the AMOC strength. Meanwhile, the SPG and AMOC strengths have been in-phase throughout the past 21 ka, except during the abrupt termination and input of freshwater flux during the BA and Meltwater Pulse 1 A (∼14.4–13.9 ka) events, respectively. In conclusion, our study suggests that a sudden shift in freshwater discharge into the subpolar North Atlantic may disturb the polar ocean dynamics. • The subpolar gyre and AMOC strength are in-phase, except during Bølling-Allerød and Meltwater Pulse 1A events. • The North Atlantic subpolar net ocean surface heat flux varied coherently with AMOC for the past 21ka. • Atlantic sea ice variability affects net ocean surface heat flux which influences AMOC strength. [ABSTRACT FROM AUTHOR]

Satellite sea-ice thickness observations are shown to be key to improving seasonal predictions of summer Arctic sea-ice concentration. The decrease in high-latitude surface albedo caused by the vanishing Arctic sea ice has a distinct signature on the Earth's radiative balance (Pistone I et al i ., [6]). The study shows that I in situ i observations play a critical role in initializing numerical weather forecasts during the winter season, while satellite microwave sounders are crucial during the summer season. [Extracted from the article]

As the second generation of Chinese polar-orbiting meteorological satellite missions, the Fengyun (FY)-3D satellite provides the latest multi-frequency brightness temperature (TB) of FY-3 series satellites. The microwave radiation imager (MWRI) boarded on FY-3D has similar sensor configuration as Advanced Microwave Scanning Radiometer 2 (AMSR2), and thus the intercalibration of these two sensors can make their TB data more consistent and continuous to facilitate their joint applications. In this study, the FY-3D H-pol and V-pol TB at five frequencies from 10.7 to 89 GHz during 2019 to 2020 were calibrated against AMSR2 TB over land. Two categories of intercalibration methods were compared, including global intercalibration method, i.e., global linear regression, and per-pixel-based intercalibration methods, i.e., per-pixel linear regression joint global linear regression, per-pixel linear regression joint inverse distance interpolation, per-pixel linear regression joint nearest neighbor interpolation, and global per-pixel linear regression. Furthermore, the effects of diverse environmental variables (i.e., land cover and its heterogeneity, climate types, water body fraction, terrain and its complexity, soil texture, and vegetation coverage) on FY-3D calibration accuracy were fully investigated. The results indicate that all five approaches can reduce the bias between FY-3D and AMSR2 TB, and the root-mean-square difference (RMSD) also reduces accordingly. Among them, the global per-pixel linear regression method performs the best with the lowest averaged RMSD of 2.93 K (at ascending overpass) and 2.34 K (at descending overpass), followed by the per-pixel linear regression joint inverse distance interpolation. The global linear regression method performs the worst with the largest RMSD of 4.69 and 3.82 K at ascending and descending overpass, respectively. The RMSD is relatively larger in temperate and polar climate zones, as well as in grasslands and croplands than in other climate and land cover types. The calibration errors generally decrease as the altitude increases, while they increase with the increase in land cover heterogeneity. The water body fraction exerts the greatest impact on the calibration accuracy, and the RMSD reaches 3 K when the water body fraction is greater than 15%. Soil texture, terrain complexity, and vegetation coverage generally have little influence on the calibration accuracy. These findings can provide a good reference for the intercalibration of satellites with similar configuration to generate long-term climate data records. [ABSTRACT FROM AUTHOR]