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Integrated studies on the interplay between soils, periglacial geomorphology and plant communities are crucial for the understanding of climate change effects on terrestrial ecosystems of Maritime Antarctica, one of the most sensitive areas to global warming. Knowledge on physical environmental factors that influence plant communities can greatly benefit studies on monitoring climate change in Maritime Antarctica, where new ice-free areas are being constantly exposed, allowing plant growth and organic carbon inputs. The relationship between topography, plant communities and soils was investigated in Potter Peninsula, King George Island, Maritime Antarctica. We mapped the occurrence and distribution of plant communities and identified soil-landform-vegetation relationships. The vegetation map was obtained by classification of a Quickbird image, coupled with detailed landform and characterization of 18 soil profiles. The subformations were identified and classified, and we also determined the total elemental composition of lichens, mosses and grasses. Plant communities at Potter Peninsula occupy 23% of the ice-free area, at different landscape positions, showing decreasing diversity and biomass from the coastal zone to inland areas where sub-desert conditions prevail. There is a clear dependency between landform and vegetated soils. Soils with greater moisture or poorly drained, and acid to neutral pH, are favourable for mosses subformations. Saline, organic-matter rich ornithogenic soils of former penguin rookeries have greater biomass and diversity, with mixed associations of mosses and grasses, while stable felseenmeers and flat rocky cryoplanation surfaces are the preferred sites for Usnea and Himantormia lugubris lichens, at the highest surface. Lichens subformations cover the largest vegetated area, showing varying associations with mosses. [ABSTRACT FROM AUTHOR]

Global warming has become one of the most prominent global issues, and Antarctic ice sheet is one of the indicator of global climate change. Satellite imagery has become an important means of monitoring the changes in Antarctic ice sheet. Due to the high overlap of satellite imaging swaths, the existing Antarctica images have the disadvantages of long period of imagery acquisition, large temporal difference among the mosaic images, and low utilization of satellite resource. This paper proposes a satellite imaging mission planning method for fast Antarctica coverage. First, the imaging time window is forecasted within the specified imaging time range to obtain all the visible time windows of the imaging satellite to Antarctica. Then, taking the selection of each time window and the satellite swing angle in each time window as decision variables, and the satellite attitude maneuver ability as constraint, an imaging mission model including two objective functions with minimum number of imaging time windows and the maximum coverage rate is established. To solving the proposed multi-objective optimization model, an improved real-binary hybrid LMOCSO (large-scale multi-objective optimization based on a competitive swarm optimizer) is proposed in this paper. Finally, a simulation experiment was performed using Gaofen-3 satellite to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

As the climate warms, the grounded ice sheet and floating ice shelves surrounding Antarctica are melting and releasing additional freshwater into the Southern Ocean. Nonetheless, almost all existing coupled climate models have fixed ice sheets and lack the physics required to represent the dominant sources of Antarctic melt. These missing ice dynamics represent a key uncertainty that is typically unaccounted for in current global climate change projections. Previous modelling studies that have imposed additional Antarctic meltwater have demonstrated regional impacts on Southern Ocean stratification, circulation, and sea ice, as well as remote changes in atmospheric circulation, tropical precipitation, and global temperature. However, these previous studies have used widely varying rates of freshwater forcing, have been conducted using different climate models and configurations, and have reached differing conclusions on the magnitude of meltwater–climate feedbacks. The Southern Ocean Freshwater Input from Antarctica (SOFIA) initiative brings together a team of scientists to quantify the climate system response to Antarctic meltwater input along with key aspects of the uncertainty. In this paper, we summarize the state of knowledge on meltwater discharge from the Antarctic ice sheet and ice shelves to the Southern Ocean and explain the scientific objectives of our initiative. We propose a series of coupled and ocean–sea ice model experiments, including idealized meltwater experiments, historical experiments with observationally consistent meltwater input, and future scenarios driven by meltwater inputs derived from stand-alone ice sheet models. Through coordinating a multi-model ensemble of simulations using a common experimental design, open data archiving, and facilitating scientific collaboration, SOFIA aims to move the community toward better constraining our understanding of the climate system response to Antarctic melt. [ABSTRACT FROM AUTHOR]

The effect of global warming on the southern polar regions necessitates careful monitoring of glacier deformations and their movements, as well as an understanding of atmospheric physics. For this purpose, the yearly movements of UNAVCO stations-South Pole Station (AMU2) (winter-summer) and other stations in the South Pole region have been observed in this paper for about a fifteen-year period (2006–2021). In addition, the area differences of the Antarctic continent due to seasonal changes (winter-summer) between 1980 and 2021 were investigated in this study. Moreover, the height values of the stations on the Antarctic continent were observed seasonally. The subglacial lakes in the Antarctic continent cause the differences in the height values as a result of the seasonal changes. A decrease in sea ice of 0.91 million km² for the winter season and 0.55 million km² for the summer season during a 41-year period has been determined for four sectors of the Antarctic continent. The temperature changes on the Antarctic continent in the summer and winter seasons (2005–2022) were also evaluated in this paper. Air temperature increases was apparent especially in the Antarctic Peninsula, East Antarctic and West Antarctic coasts. The Weddell Sea and the Amundsen Sea regions have had the most sea ice loss, each with 1.24 million km². On the other hand, it can be observed that the East Antarctic sector has expanded by 0.32 million km². [ABSTRACT FROM AUTHOR]

As the climate warms, the grounded ice sheet and floating ice shelves surrounding Antarctica are losing mass at an increasing rate and injecting the resulting meltwater into the Southern Ocean. This freshwater input could feed back onto climate change, particularly since the Southern Ocean is a key contributor to global heat and carbon uptake. Nonetheless, almost all existing coupled climate models have fixed ice sheets, and lack the physics required to represent the dominant sources of Antarctic melt. These missing ice dynamics represent a key uncertainty that is unaccounted for in current global climate change projections. Previous studies have inserted additional Antarctic meltwater into models, demonstrating that it can alter Southern Ocean stratification, circulation, and sea ice, as well as influence remote atmospheric circulation, tropical precipitation, and global temperature. However, these previous studies have used widely varying rates of freshwater forcing, been conducted using different climate models and configurations, and have reached differing conclusions on the magnitude of meltwater-climate feedbacks. The Southern Ocean Freshwater release model experiments InitiAtive (SOFIA) brings together a team of scientists to quantify the climate system response to Antarctic meltwater input. In this paper, we summarize the state of knowledge on meltwater discharge from the Antarctic ice sheet and ice shelves to the Southern Ocean and explain the scientific objectives of our initiative. We propose a series of coupled and ocean/sea-ice model experiments, including idealized meltwater experiments, historical experiments with observationally consistent meltwater input, and future scenarios driven by meltwater inputs derived from stand-alone ice sheet models. Through coordinating a multi-model ensemble of simulations, with data housed in a common archive, SOFIA will be able to produce a consistent estimate of the climate system response to Antarctic meltwater, as well as the uncertainty of this response. [ABSTRACT FROM AUTHOR]

Like other international institutions, the Antarctic Treaty System (ATS) relies on the goodwill and self-binding commitment of its members. Legitimacy, understood as the belief in the 'rightfulness' of a governing arrangement by its stakeholders, lies at the heart of the ATS' success as a multilateral institution. Global warming and geopolitical power shifts are poised to challenge established forms of Antarctic legitimacy and effectiveness, with external calls for Antarctic democratisation and reform increasing. Using the concepts of input, output, and throughput legitimacy, this paper explores how the ATS has been legitimated as the only authoritative decision-making context for Antarctic matters, internally amongst Treaty Partners as well as externally towards the rest of the international community. It argues that the increase of input legitimacy through the inclusion of more consultative parties led to a perceived lack of output legitimacy for some especially environmental critics which illustrates the importance but also the limits of maintaining consensus about throughput legitimacy: the agreed upon processes and rules of decision-making. Finally, the analysis problematises the inhibiting centrality of nation states and the logic of sovereignty during times of global ecological and geopolitical change and asks how an ambitiously democratic future of Antarctic governance in the Anthropocene might look like. [ABSTRACT FROM AUTHOR]

Solid precipitation measurements in Antarctica are crucial as snowfall represents the main water input term for the polar cap, and its probable increase in the coming century can mitigate sea-level rise caused by global warming. This paper presents 7 years of Micro Rain Radar (Metek MRR-2) data at the Dumont d'Urville station in coastal Adélie Land, East Antarctica. Statistics are calculated on 3 radar variables (equivalent reflectivity, mean Doppler velocity and signal-to-noise ratio) to outline the main characteristics of the radar dataset. Seasonal and interannual variabilities are also investigated, but no significant temporal trends are detected except for the seasonal mean Doppler velocity which is higher in summer and lower in winter. We then use the snowfall rate (S) data from a colocated snow-gauge to estimate the MRR precipitation profile from the radar equivalent reflectivity (Ze) through a locally derived Ze-S relation. We find the relation Ze = 43.3 S0.88. The processing method used to obtain this relation, data quality and uncertainty considerations are discussed in the manuscript. In order to give an example of application of the dataset, a brief statistical comparison of the MRR precipitation rate along the vertical with model data from the ERA5 reanalysis and the LMDZ climate model is performed, and notably shows that models underestimate heavy precipitation events. [ABSTRACT FROM AUTHOR]

Abstract–A seismogenic-trigger mechanism is proposed for the activation of methane emission on the Arctic shelf in the late 1970s, which caused the onset of abrupt climate warming in the Arctic and a rapid disintegration of West Antarctica's ice sheet and ice shelves in the late 20th and early 21st centuries. This process is accompanied by the release of methane from the underlying hydrate-bearing sedimentary rocks and accelerated climate warming in Antarctica. The proposed mechanism is associated with the action of deformation tectonic waves in the lithosphere–asthenosphere system, caused by strong earthquakes occurring in the subduction zones closest to the polar regions: the Aleutian, located in the northern part of the Pacific Ocean, the Chilean and Kermadec-Macquarie, located in the southeastern and southwestern parts of the Pacific lithosphere. Disturbances of the lithosphere are transmitted at an average velocity of about 100 km/yr over distances as long as 2000–4000 km, and the associated additional stresses that come to the Arctic and Antarctica several decades after earthquakes lead to the destruction of metastable gas hydrates located in the frozen rocks of the Arctic shelf or in the subglacial sedimentary rocks of Antarctica, causing the greenhouse effect and climate warming. Moreover, transmission of additional stresses causes a decrease in the adhesion of the ice sheet to the underlying rocks, its accelerated sliding and the destruction of the ice shelves in Antarctica. The considered hypothesis leads to the conclusion that in the coming decades, the processes of glacier destruction and climate warming in Antarctica will increase due to an unprecedented increase in the number of strong earthquakes in the subduction zones of the South Pacific Ocean in the late 20th and early 21st centuries. [ABSTRACT FROM AUTHOR]

This paper quantifies the potential benefit of limiting the global warming to 1.5°C above the preindustrial level on the high‐latitude climate of the Southern Hemisphere compared to 2.0°C and above. A set of Coupled Model Intercomparison Project Phase 5 global climate model experiments is used in order to determine the mean projected changes in surface air temperature, sea level pressure, surface winds and sea ice distribution over and around Antarctica. Alongside, changes in selected variables related to extremes (such as the annual number of extremely cold mornings and extremely cold days) are also quantified as a function of the Representative Concentration Pathway (RCP) considered reaching the given warming threshold. Physical mechanisms for the projected variations in sea ice are proposed, including surface air temperature, changes in low‐level air temperature advection and meridional winds. Results show that there would be significant differences in the atmospheric and sea ice variable changes depending on the warming threshold and RCP considered, and that indeed keeping the global warming under 1.5°C could have a noticeable impact particularly on the distribution of sea ice over the Southern Ocean. [ABSTRACT FROM AUTHOR]

Over 40 years ago, the glaciologist John Mercer warned that parts of the West Antarctic Ice Sheet were at risk of collapse due to the CO2 greenhouse effect. Mercer recognised the unique vulnerability of ice sheets resting on beds far below sea level (marine-based ice sheets), where an initial warming signal can initiate irreversible retreat. In this paper, we review recent work on evidence for ice sheet collapse in warmer periods of the recent geological past, the current behaviour of the ice sheet, and computer models used to predict future ice-sheet response to global warming. Much of this work points in the same direction: warming climates can indeed trigger collapse of marine-based portions of the West Antarctic Ice Sheet, and retreat in response to recent warming has brought parts of the ice sheet to the threshold of instability. Further retreat appears to be inevitable, but the rate of collapse depends critically on future emissions. [ABSTRACT FROM AUTHOR]

A detailed understanding of how the Antarctic ice sheet (AIS) responds to a warming climate is needed because it will most likely increase the rate of global mean sea level rise. Time-variable satellite gravimetry, realized by the Gravity Recovery and Climate Experiment (GRACE) and Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) missions, is directly sensitive to AIS mass changes. However, gravimetric mass balances are subject to two major limitations. First, the usual correction of the glacial isostatic adjustment (GIA) effect by modelling results is a dominant source of uncertainty. Second, satellite gravimetry allows for a resolution of a few hundred kilometres only, which is insufficient to thoroughly explore causes of AIS imbalance. We have overcome both limitations by the first global inversion of data from GRACE and GRACE-FO, satellite altimetry (CryoSat-2), regional climate modelling (RACMO2), and firn densification modelling (IMAU-FDM). The inversion spatially resolves GIA in Antarctica independently from GIA modelling jointly with changes of ice mass and firn air content at 50 km resolution. We find an AIS mass balance of - 144 ± 27 Gt a -1 from January 2011 to December 2020. This estimate is the same, within uncertainties, as the statistical analysis of 23 different mass balances evaluated in the Ice sheet Mass Balance Inter-comparison Exercise (IMBIE ;). The co-estimated GIA corresponds to an integrated mass effect of 86 ± 21 Gt a -1 over Antarctica, and it fits better with global navigation satellite system (GNSS) results than other GIA predictions. From propagating covariances to integrals, we find a correlation coefficient of - 0.97 between the AIS mass balance and the GIA estimate. Sensitivity tests with alternative input data sets lead to results within assessed uncertainties. [ABSTRACT FROM AUTHOR]

The stability of contemporary ice shelves is under threat due to global warming, and the geological records in the Ross Sea offer such an opportunity to test the linkage between them. However, the absence of calcareous microfossils in the sediments of the Ross Sea results in uncertainties in establishing a precise chronology for studies. Hence, three sediment cores were collected and studied in terms of radiocarbon dating, magnetic susceptibility, and sediment grain size to reconstruct the environmental processes in the Ross Sea since the last glacial period. The main results are as follows: (1) two grain-size components were identified for the studied cores, which can be correlated to ice-shelf and sea-ice transport, respectively; (2) due to old-carbon contamination and an inconsistent carbon reservoir, the radiocarbon dates were generally underestimated, and as an alternative, changes in magnetic susceptibility of the studied cores can be tuned to the ice-core records to establish a reliable age–depth model and; (3) integrating sediment grain-size changes and comparisons with other paleoenvironmental proxies in the Antarctic, a process from a sub-ice sheet in the last glacial period to a sub-ice shelf in the glacial maximum, and, finally, to a glaciomarine state since the last deglacial period was identified in the western Ross Sea. Integrating these findings, the warming processes in the Antarctic were highlighted in the retreat processes of the Ross Ice Shelf in the past. [ABSTRACT FROM AUTHOR]

The ocean is the main heat reservoir in Earth's climate system, absorbing most of the top-of-the-atmosphere excess radiation. As the climate warms, anomalously warm and fresh ocean waters in the densest layers formed near Antarctica spread northward through the abyssal ocean, while successions of warming and cooling events are seen in the deep-ocean layers formed near Greenland. The abyssal warming and freshening expands the ocean volume and raises sea level. While temperature and salinity characteristics and large-scale circulation of upper 2000 m ocean waters are well monitored, the present ocean observing network is limited by sparse sampling of the deep ocean below 2000 m. Recently developed autonomous robotic platforms, Deep Argo floats, collect profiles from the surface to the seafloor. These instruments supplement satellite, Core Argo float, and ship-based observations to measure heat and freshwater content in the full ocean volume and close the sea level budget. Here, the value of Deep Argo and planned strategy to implement the global array are described. Additional objectives of Deep Argo may include dissolved oxygen measurements, and testing of ocean mixing and optical scattering sensors. The development of an emerging ocean bathymetry dataset using Deep Argo measurements is also described. [ABSTRACT FROM AUTHOR]

The Oligocene (33.9–23.03 Ma) was characterised by generally warm climates, with flattened meridional temperature gradients while Antarctica retained a significant cryosphere. This makes the Oligocene an imperfect analogue to long-term future climate states with unipolar icehouse conditions. Although local and regional climate and environmental reconstructions of Oligocene conditions are available, the community lacks synthesis of regional reconstructions. In order to provide a comprehensive overview of marine and terrestrial climate and environmental conditions in the Oligocene, as well as a reconstruction of trends through time, we here review marine and terrestrial proxy records and numerical climate model simulations of the Oligocene. Results display weaker temperature gradients during the Oligocene compared to modern times, with generally warm poles and colder-than-modern temperatures around the equator. Sea surface temperatures (SSTs) show similar trends to the land temperatures, with warm temperatures around the mid and high latitudes (~60–90°) of especially the Southern Hemisphere. Vegetation-based precipitation reconstructions of the Oligocene suggest drier conditions compared to modern times, in particular around the equator. When compared to proxy-based data, climate modelling approaches overestimate Oligocene precipitation in most areas, in particular the tropics. Temperature around the mid to high latitudes is generally underestimated in models compared to proxy data and tend to overestimate the warming in the tropics. In line with previous conclusions models underestimate polar amplification and the equator-to-pole heat distribution that prevailed during the Oligocene. Despite prevalent glaciation on Antarctica, the Oligocene "icehouse" experienced warm global average temperatures while still maintaining a unipolar icehouse state. [ABSTRACT FROM AUTHOR]

Inland Antarctic nunataks typically have simple physically weathered soils and limited ecosystem complexity. In this paper we present quantitative measurements of soil physical and chemical properties at one Antarctic nunatak. We measured pH, grain size, field capacity, soil organic carbon, phosphate, nitrate, ammonium and the cations magnesium, calcium and potassium along two transects. The data obtained indicated that very low levels of nutrients were present/available to biota, and that liquid water was absent, at least from the surface depths of soil, except during periods of active snow melt. Consequently, biological activity is severely limited. We conclude that, due to the climatic and microclimatic conditions at this location, the development of biological communities and soils is maintained in an extremely simple but still apparently stable ‘quasi climax’ state. Increased soil development and biological complexity can be expected if the contemporary rapid regional warming in the Antarctic Peninsula region continues. [ABSTRACT FROM AUTHOR]

We investigate feedbacks between subsurface continental shelf ocean temperatures and Antarctic glacial melt using a coupled climate model. The model was forced with SSP5‐8.5 and an uncoupled projection of basal melt and calving fluxes. SSP5‐8.5 forcing with fixed pre‐industrial glacial melt warms all continental shelves, such that historically "cool" and "fresh" shelves transition to "warm." Additional glacial melt, added at depth, cools the Eastern Ross, Amundsen, and Bellingshausen seas, suggesting a negative feedback on basal melt—a novel result for a coarse resolution coupled model. From the Weddell Sea, along East Antarctica, and into the western Ross Sea—where continental shelves transition to a "warm" state—additional glacial melt increases temperatures at the continental shelf sea floor, suggesting a positive feedback. The sign of the glacial melt–subsurface temperature feedback is critically dependent on continental shelf properties, climate state, and the vertical distribution of glacial melt inputs. Plain Language Summary: Antarctic ice shelves lose mass as freshwater—primarily from melting at their base and when icebergs break off. We know that the rate at which Antarctic ice shelves are losing mass is increasing and we expect this freshwater input into the ocean to increase further in a warmer world. Most climate models do not include a representation of this changing freshwater input, and its climatic impacts are uncertain. One particularly important climate impact is how the additional freshwater changes the subsurface ocean temperature. If freshwater warms/cools the coastal ocean it could increase/decrease melt in a positive/negative feedback loop. But existing studies disagree about this effect and even about the sign of the feedback. We added a timeseries of freshwater input to a climate model and ran experiments with strong climate warming to investigate this feedback. The sign of the feedback varies by region. Where climate change drives a cold coastal ocean to transition to a new warmer state, we find that freshwater causes a strong additional warming (a positive feedback). Where the coastal ocean is already warm in the present day and warms in future, freshwater reduces this warming (a negative feedback). To achieve the negative feedback freshwater must be added at depth. Key Points: A glacial melt projection is added to a 1° coupled climate model under SSP5‐8.5 to investigate ocean temperature feedbacksAdditional glacial melt cools the Eastern Ross, Amundsen, and Bellingshausen seas at depth, but warms elsewhereThe addition of glacial melt at depth is necessary to generate the cooling response [ABSTRACT FROM AUTHOR]

The Antarctic region has been experiencing some of the planet's strongest climatic changes, including an expected increase of the land temperature. The potential effects of this warming trend will lead ecosystems to a risk of losing biodiversity. Antarctic mosses and lichens host different microbial groups, microarthropods and meiofaunal organisms (e.g., tardigrades, rotifers). The eutardigrade Acutuncus antarcticus is considered a model animal to study the effect of increasing temperature due to global warming on Antarctic terrestrial communities. In this study, life history traits and fitness of this species are analyzed by rearing specimens at two different and increasing temperatures (5°C vs. 15°C). Moreover, the first transcriptome analysis on A. antarcticus is performed, exposing adult animals to a gradual increase of temperature (5°C, 10°C, 15°C, and 20°C) to find differentially expressed genes under short- (1 day) and long-term (15 days) heat stress. Acutuncus antarcticus specimens reared at 5°C live longer (maximum life span: 686 days), reach sexual maturity later, lay more eggs (which hatch in longer time and in lower percentage) compared with animals reared at 15°C. The fitness decreases in animals belonging to the second generation at both rearing temperatures. The short-term heat exposure leads to significant changes at transcriptomic level, with 67 differentially expressed genes. Of these, 23 upregulated genes suggest alterations of mitochondrial activity and oxido-reductive processes, and two intrinsically disordered protein genes confirm their role to cope with heat stress. The long-term exposure induces alterations limited to 14 genes, and only one annotated gene is upregulated in response to both heat stresses. The decline in transcriptomic response after a long-term exposure indicates that the changes observed in the short-term are likely due to an acclimation response. Therefore, A. antarcticus could be able to cope with increasing temperature over time, including the future conditions imposed by global climate change. [ABSTRACT FROM AUTHOR]

Surface melting is one of the primary drivers of ice shelf collapse in Antarctica and is expected to increase in the future as the global climate continues to warm because there is a statistically significant positive relationship between air temperature and melting. Enhanced surface melt will impact the mass balance of the Antarctic Ice Sheet (AIS) and, through dynamic feedbacks, induce changes in global mean sea level (GMSL). However, the current understanding of surface melt in Antarctica remains limited in terms of the uncertainties in quantifying surface melt and understanding the driving processes of surface melt in past, present and future contexts. Here, we construct a novel grid-cell-level spatially distributed positive degree-day (PDD) model, forced with 2 m air temperature reanalysis data and spatially parameterized by minimizing the error with respect to satellite estimates and surface energy balance (SEB) model outputs on each computing cell over the period 1979 to 2022. We evaluate the PDD model by performing a goodness-of-fit test and cross-validation. We assess the accuracy of our parameterization method, based on the performance of the PDD model when considering all computing cells as a whole, independently of the time window chosen for parameterization. We conduct a sensitivity experiment by adding ±10 % to the training data (satellite estimates and SEB model outputs) used for PDD parameterization and a sensitivity experiment by adding constant temperature perturbations (+1 , +2 , +3 , +4 and +5 ∘ C) to the 2 m air temperature field to force the PDD model. We find that the PDD melt extent and amounts change analogously to the variations in the training data with steady statistically significant correlations and that the PDD melt amounts increase nonlinearly with the temperature perturbations, demonstrating the consistency of our parameterization and the applicability of the PDD model to warmer climate scenarios. Within the limitations discussed, we suggest that an appropriately parameterized PDD model can be a valuable tool for exploring Antarctic surface melt beyond the satellite era. [ABSTRACT FROM AUTHOR]

Global warming intensifies atmospheric water vapor transport between ocean and land, which increases the likelihood of extreme precipitation and floods. However, accurate estimations of water vapor exchange between ocean and land are difficult due to the lack of available data and effective methods. This study developed a novel eight-direction-vector decomposition algorithm for calculating water vapor flux between ocean and land based on the ERA5 dataset, and the results showed that global water vapor exchange between ocean and land had significantly increased in the past 40 years, except for Antarctica. During 1980–2018, the average annual net water vapor inflow from ocean to land (Qnet) was 44.68 × 1015 kg yr−1, and Qnet increased at a rate of 1.48 × 1015 kg yr−1 decade−1. The intensified atmospheric water vapor exchange between ocean and land was directly caused by the increase of atmospheric water vapor content, which largely depended on the rising air temperature, and it was found that water vapor flux between ocean and land increased by over 8% K−1 with the increasing air temperature at the global average. This study also identified El Niño–Southern Oscillation (ENSO) as an important contributor to the global ocean–land water vapor exchange anomalies. A strong El Niño event (MEI = 1) can result in a 1.36 × 1015 kg yr−1 (3.03%) decrease in Qnet, and a strong La Niña event (MEI = −1) can increase Qnet by 1.38 × 1015 kg yr−1 (3.09%). The eight-direction-vector decomposition algorithm was effective in ocean–land water vapor flux estimations at different spatial and temporal scales, which could provide great insights into the mechanisms of extreme precipitation events. Significance Statement: This study developed a novel approach on water vapor flux estimation (i.e., the eight-direction-vector decomposition algorithm) and achieved a high-temporal–spatial-resolution estimation of water vapor flux between ocean and land. It was found that water vapor flux between ocean and land was intensified by increasing air temperature at a rate of 8% K−1, and El Niño yielded an anomaly low net water vapor input from ocean to land at the global scale. The algorithm developed in this study can be used for estimating water vapor fluxes at different spatial and temporal scales, which is crucial for evaluating the role of water vapor flux on formations for extreme weather (e.g., torrential rainstorms and heat waves) and climatic extremes (e.g., droughts and floods). [ABSTRACT FROM AUTHOR]

Soil moisture–atmosphere coupling (SA) amplifies greenhouse gas-driven global warming via changes in surface heat balance. The Scenario Model Intercomparison Project projects an acceleration in SA-driven warming due to the 'warmer climate – drier soil' feedback, which continuously warms the globe and thereby exerts an acceleration effect on global warming. The projection shows that SA-driven warming exceeds 0.5 °C over extratropical landmasses by the end of the 21st Century. The likelihood of extreme high temperatures will additionally increase by about 10% over the entire globe (excluding Antarctica) and more than 30% over large parts of North America and Europe under the high-emission scenario. This demonstrates the high sensitivity of SA to climate change, in which SA can exceed the natural range of climate variability and play a non-linear warming component role on the globe. Soil moisture–atmosphere coupling induces non-linear warming via the 'warmer climate – drier soil' feedback, which exerts an accelerating effect on global warming and on extremely high temperatures. [ABSTRACT FROM AUTHOR]

Few ice cores from the Amundsen Sea and Bellingshausen Sea sectors of the West Antarctic Ice Sheet (WAIS) extend back in time further than a few hundred years. The WAIS is believed to be susceptible to collapse as a result of anthropogenic climate change and may have at least partially collapsed during the Last Interglacial (LIG) period. Understanding the stability of the WAIS during warm periods such as the LIG and Holocene is important. As part of the WACSWAIN (WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial) project, the British Antarctic Survey's (BAS) Rapid Access Isotope Drill (RAID) was deployed in 2020 on Sherman Island in the Abbot Ice Shelf, West Antarctica. We drilled a 323 m deep borehole, with discrete samples of ice chippings collected that cover the entire depth range of the drilled ice. The samples were analysed for stable water isotope composition and major ion content at BAS from 2020–2022. Using annual layer counting of chemical records, volcanic horizon identification and ice modelling, an age scale for the record of 1724 discrete samples is presented. The Sherman Island ice record extends back to greater than 1240 years, providing the oldest, continuous ice-derived palaeoclimate records in the coastal Amundsen and Bellingshausen Sea sectors to date. We demonstrate the potential for recovery of a complete Holocene climate record from Sherman Island in the future and confidence in the ability of RAID samples to contain sufficiently resolved records for meaningful climatic interpretation. [ABSTRACT FROM AUTHOR]

Global warming has been accelerating the frequency and intensity of climate extremes, and has had an immense influence on the economy and society, but attention is seldom paid to future Antarctic temperature extremes. This study investigates five surface extreme temperature indices derived from the multimodel ensemble mean (MMEM) based on 14 models from phase 6 of the Coupled Model Intercomparison Project (CMIP6) under the shared socioeconomic pathways (SSPs) of SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5. In Antarctica, the variations in extreme temperature indices exhibit regional and seasonal differences. The diurnal temperature range (DTR) usually illustrates a downward trend, particularly for the Antarctic Peninsula and Antarctic coast, and the strongest change occurs in austral summer. In all cases, the annual highest minimum/maximum temperature (TNx/TXx) increases faster in inland Antarctica. Antarctic amplification of extreme temperature indices is detected and is strongest at the lowest maximum temperature (TXn). At the Antarctic Peninsula, TXx amplification only appears in winter. Great DTR amplification appears along the Antarctic coast and is strongest in summer and weakest in winter. The changes in extreme temperature indices indicate the accelerated Antarctic warming in future scenarios. [ABSTRACT FROM AUTHOR]

The oceanic forcing of basal melt under floating ice shelves in Greenland and Antarctica is one of the major sources of uncertainty in climate ice sheet modelling. We use a high-resolution, nonhydrostatic configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) to investigate basal melt rates and melt-driven circulation in the Sherard Osborn Fjord under the floating tongue of Ryder Glacier, northwestern Greenland. The control model configuration, based on the first-ever observational survey by Ryder 2019 Expedition, yielded melt rates consistent with independent satellite estimates. A protocol of model sensitivity experiments quantified the response to oceanic thermal forcing due to warming Atlantic Water and to the buoyancy input from the subglacial discharge of surface fresh water. We found that the average basal melt rates show a nonlinear response to oceanic forcing in the lower range of ocean temperatures, while the response becomes indistinguishable from linear for higher ocean temperatures, which unifies the results from previous modelling studies of other marine-terminating glaciers. The melt rate response to subglacial discharge is sublinear, consistent with other studies. The melt rates and circulation below the ice tongue exhibit a spatial pattern that is determined by the ambient density stratification. [ABSTRACT FROM AUTHOR]

With progressing global warming, snowfall in Antarctica is expected to increase, which could counteract or even temporarily overcompensate increased ice-sheet mass losses caused by increased ice discharge and melting. For sea-level projections it is therefore vital to understand the processes determining snowfall changes in Antarctica. Here we revisit the relationship between Antarctic temperature changes and precipitation changes, identifying and explaining regional differences and deviations from the theoretical approach based on the Clausius–Clapeyron relationship. Analysing the latest estimates from global (CMIP6, Coupled Model Intercomparison Project Phase 6) and regional (RACMO2.3) model projections, we find an average increase of 5.5 % in annual precipitation over Antarctica per degree of warming, with a minimum sensitivity of 2 % K -1 near Siple Coast and a maximum sensitivity of > 10 % K -1 at the East Antarctic plateau region. This large range can be explained by the prevailing climatic conditions, with local temperatures determining the Clausius–Clapeyron sensitivity that is counteracted in some regions by the prevalence of the coastal wind regime. We compare different approaches of deriving the sensitivity factor, which in some cases can lead to sensitivity changes of up to 7 percentage points for the same model. Importantly, local sensitivity factors are found to be strongly dependent on the warming level, suggesting that some ice-sheet models which base their precipitation estimates on parameterisations derived from these sensitivity factors might overestimate warming-induced snowfall changes, particularly in high-emission scenarios. This would have consequences for Antarctic sea-level projections for this century and beyond. [ABSTRACT FROM AUTHOR]

Deep-time palynological studies are necessary to evaluate plant and fungal distribution under warmer-than-present scenarios such as those of the Middle Miocene. Previous palynological studies from southern McMurdo Sound, Antarctica (SMS), have provided unique documentation for Neogene environments in the Ross Sea region during a time of pronounced global warming. The present study builds on these studies and provides a new climate reconstruction using the previously published SMS pollen and plant spore data. Additionally, 44 SMS samples were reanalyzed with a focus on the fungal fraction of the section to evaluate the fungal distribution under warmer than present conditions. The probability-based climate reconstruction technique (CREST) was applied to provide a new plant-based representation of regional paleoclimate for this Miocene Climatic Optimum (MCO) locality. CREST reconstructs a paleoclimate that is warmer and significantly wetter than present in SMS during the MCO, with mean annual precipitation reconstructed at 1147 mm yr -1 (95 % confidence range: 238–2611 mm yr -1) and a maximum mean annual temperature of 10.3 ∘ C (95 % confidence range: 2.0–20.2 ∘ C) for the warmest intervals of the MCO. The CREST reconstruction fits within the Cfb Köppen–Geiger climate class during the MCO of SMS. This new reconstruction agrees with previous reconstructions using various geochemical proxies. The fungal palynological analyses yielded surprising results, with only a single morphotype recovered, in low abundance, with concentrations ranging up to 199 fungi per gram of dried sediment. The taxa present belongs to the Apiosporaceae family and are known to be adapted to a wide range of climate and environmental conditions. As fungi are depauperate members of the SMS MCO palynofloras and because the one morphotype recovered is cosmopolitan, using the fungi record to confirm a narrow Köppen–Geiger climate class is impossible. Overall, the study demonstrates refinement of plant-based paleoclimatic reconstructions and sheds light on the limited presence of fungi during the MCO in Antarctica. [ABSTRACT FROM AUTHOR]

Keywords: Antarctica; global warming; Thwaites Glacier; sea level rise; climate crisis; ice melt EN Antarctica global warming Thwaites Glacier sea level rise climate crisis ice melt 121 128 8 05/12/20 20200501 NES 200501 On the Thwaites Glacier on Antarctica's western shelf, researchers are going all-out to learn what is happening deep under the surface of the ice, out of sight: How much is melting from below, where the ice comes into contact with warm ocean waters? B Davis b :My understanding is if the whole of the Thwaites Glacier were to collapse - and there's no indication that would occur - you would get somewhere between 50 centimeters (19.5 inches) and maybe 65-to-80 centimeters (25.5-to-31.5 inches) of sea level rise from this one glacier and the region of the ice sheet that it drains alone. B Davis b :The whole of the West Antarctic ice sheet, of which the Thwaites Glacier is a part, has the potential for two-to-three meters of sea level rise, if the whole of the ice sheet were to collapse. Antarctica, global warming, Thwaites Glacier, sea level rise, climate crisis, ice melt. [Extracted from the article]

Antarctica's continental margins pose an unknown submarine landslide-generated tsunami risk to Southern Hemisphere populations and infrastructure. Understanding the factors driving slope failure is essential to assessing future geohazards. Here, we present a multidisciplinary study of a major submarine landslide complex along the eastern Ross Sea continental slope (Antarctica) that identifies preconditioning factors and failure mechanisms. Weak layers, identified beneath three submarine landslides, consist of distinct packages of interbedded Miocene- to Pliocene-age diatom oozes and glaciomarine diamicts. The observed lithological differences, which arise from glacial to interglacial variations in biological productivity, ice proximity, and ocean circulation, caused changes in sediment deposition that inherently preconditioned slope failure. These recurrent Antarctic submarine landslides were likely triggered by seismicity associated with glacioisostatic readjustment, leading to failure within the preconditioned weak layers. Ongoing climate warming and ice retreat may increase regional glacioisostatic seismicity, triggering Antarctic submarine landslides. Changes in climate preconditioned large-scale, recurrent Miocene to Pleistocene Antarctic submarine landslides through variations in biological productivity, ice proximity and ocean circulation, posing tsunami risk to Southern Hemisphere populations. [ABSTRACT FROM AUTHOR]

Nonlinear trends (i.e. quadratic trends, usually defined as accelerations) in Antarctic ice mass loss due primarily to the complex climate warming forcing regimes have induced large uncertainty to future sea level projection. Here, we quantify the nonlinear and spatially varying mass losses in the Antarctic ice sheet during the last two decades using the satellite gravimetry data collected by Gravity Recovery And Climate Experiment (GRACE) and its successor GRACE Follow-On. We use a regional inversion methodology to generate the mass change time-series over Antarctica. Our findings reveal that seven regions have evidenced significant nonlinear mass change. These regions are all concentrated along the coast of Antarctica and show spatially heterogeneous mass balance nonlinear trend patterns. Among them, the Amundsen Sea Embayment (ASE) and the Dronning Maud Land (DML) are found to be particularly sensitive to short-term climate variability. The GRACE-inferred nonlinear mass balance signal can be confirmed by independent Global Positioning System (GPS) observations, and the difference between the nonlinear vertical deformation trends estimated by GRACE and GPS, especially in ASE, is likely due to the imperfect correction of the glacial isostatic adjustment (GIA) effect. For Antarctic ice sheet as a whole, GRACE satellite gravimetry indicates an ice mass loss of −101.3 ± 18.0 Gt yr−1, with an accelerated loss of −6.4 ± 1.3 Gt yr−2 during 2002–2021. [ABSTRACT FROM AUTHOR]

Understanding the influence of the Antarctic on the global climate is crucial for the prediction of global warming. However, due to very few observation sites, it is difficult to reconstruct the rational spatial pattern by filling in the missing values from the limited site observations. To tackle this challenge, regional spatial gap-filling methods, such as Kriging and inverse distance weighted (IDW), are regularly used in geoscience. Nevertheless, the reconstructing credibility of these methods is undesirable when the spatial structure has massive missing pieces. Inspired by image inpainting, we propose a novel deep learning method that demonstrates a good effect by embedding the physics-aware initialization of deep learning methods for rapid learning and capturing the spatial dependence for the high-fidelity imputation of missing areas. We create the benchmark dataset that artificially masks the Antarctic region with ratios of 30%, 50% and 70%. The reconstructing monthly mean surface temperature using the deep learning image inpainting method RFR (Recurrent Feature Reasoning) exhibits an average of 63% and 71% improvement of accuracy over Kriging and IDW under different missing rates. With regard to wind speed, there are still 36% and 50% improvements. In particular, the achieved improvement is even better for the larger missing ratio, such as under the 70% missing rate, where the accuracy of RFR is 68% and 74% higher than Kriging and IDW for temperature and also 38% and 46% higher for wind speed. In addition, the PI-RFR (Physics-Informed Recurrent Feature Reasoning) method we proposed is initialized using the spatial pattern data simulated by the numerical climate model instead of the unified average. Compared with RFR, PI-RFR has an average accuracy improvement of 10% for temperature and 9% for wind speed. When applied to reconstruct the spatial pattern based on the Antarctic site observations, where the missing rate is over 90%, the proposed method exhibits more spatial characteristics than Kriging and IDW. [ABSTRACT FROM AUTHOR]

We apply geologic evidence from ice-free areas in Antarctica to evaluate model simulations of ice sheet response to warm climates. This is important because such simulations are used to predict ice sheet behaviour in future warm climates, but geologic evidence of smaller-than-present past ice sheets is buried under the present ice sheet and therefore generally unavailable for model benchmarking. We leverage an alternative accessible geologic dataset for this purpose: cosmogenic-nuclide concentrations in bedrock surfaces of interior nunataks. These data produce a frequency distribution of ice thickness over multimillion-year periods, which is also simulated by ice sheet modelling. End-member transient models, parameterized with strong and weak marine ice sheet instability processes and ocean temperature forcings, simulate large and small sea-level impacts during warm periods and also predict contrasting and distinct frequency distributions of ice thickness. We identify regions of Antarctica where predicted frequency distributions reveal differences in end-member ice sheet behaviour. We then demonstrate that a single comprehensive dataset from one bedrock site in West Antarctica is sufficiently detailed to show that the data are consistent only with a weak marine ice sheet instability end-member, but other less extensive datasets are insufficient and/or ambiguous. Finally, we highlight locations where collecting additional data could constrain the amplitude of past and therefore future response to warm climates. [ABSTRACT FROM AUTHOR]

Global warming may result in increased polar amplification, but future temperature changes under different climate change scenarios have not been systematically investigated over Antarctica. An index of Antarctic amplification (AnA) is defined, and the annual and seasonal variations of Antarctic mean temperature are examined from projections of the Coupled Model Intercomparison Project Phase 6 (CMIP6) under scenarios SSP119, SSP126, SSP245, SSP370 and SSP585. AnA occurs under all scenarios, and is strongest in the austral summer and autumn, with an AnA index greater than 1.40. Although the warming over Antarctica accelerates with increased anthropogenic forcing, the magnitude of AnA is greatest in SSP126 instead of in SSP585, which may be affected by strong ocean heat uptake in high forcing scenario. Moreover, future AnA shows seasonal difference and regional difference. AnA is most conspicuous in the East Antarctic sector, with the amplification occurring under all scenarios and in all seasons, especially in austral summer when the AnA index is greater than 1.50, and the weakest signal appears in austral winter. Differently, the AnA over West Antarctica is strongest in austral autumn. Under SSP585, the temperature increase over the Antarctic Peninsula exceeds 0.5°C when the global average warming increases from 1.5°C to 2.0°C above pre-industrial levels, except in the austral summer, and the AnA index in this region is strong in the austral autumn and winter. The projections suggest that the warming rate under different scenarios might make a large difference to the future AnA. [ABSTRACT FROM AUTHOR]

The Southern Hemisphere westerly winds (SWW) play a critical role in global climate, yet their behavior on decadal to centennial timescales, and the mechanisms driving these changes during the preindustrial era, remain poorly understood. We present a decadally resolved record of dust compositions using strontium and neodymium isotope ratios in mineral dust from the Siple Dome ice core, Antarctica, to explore the potential that abrupt changes in SWW behavior occurred over the past millennium. The record spans portions of the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) intervals as defined in the Northern Hemisphere. We find evidence of an abrupt strengthening of atmospheric circulation during the MCA at ∼1125 CE (825 BP) that persisted for about 60 yr, indicating increased influence of Patagonia‐sourced dust. This occurs during an extended positive phase of Southern Annular Mode (SAM+)‐like conditions, characterized by high SWW velocities and a southerly shift of the main wind belt toward ∼60°S, suggesting that rapid changes in SWW strength could occur under the present SAM+ pattern. A second 20 yr long shift in dust compositions during the LIA at ∼1748 CE (200 BP) is coincident with higher dust delivery to Siple Dome, and may indicate increased dust emissions related to glacier activity in Patagonia. The new Siple Dome ice core data set demonstrates that Sr‐Nd isotopes can be used to trace shifts in atmospheric circulation on decadal timescales. Plain Language Summary: The prevailing winds that encircle Antarctica, blowing west to east, play an outsized role in global climate. Because they blow continuously over the ocean, they create ocean currents and cause upwelling. When deep ocean water comes to the surface, it releases carbon dioxide into the atmosphere, causing the climate to warm. Changes in wind strength and positioning modulate the release of carbon dioxide. Therefore, knowing how and why the winds shift is important for understanding how Earth's climate system operates. We use the composition of dust preserved in an Antarctic ice core to learn how the balance of dust sources changed during the past millennium. This allows us to track past shifts in the winds around Antarctica and to learn how they respond to climate changes on short timespans, such as decades to centuries. We observe an abrupt change in dust composition at ∼1125 CE lasting for about 60 yr, indicating a greater influence of dust sourced from Patagonia in South America. This dust shift occurred during a globally observed warm period, and corresponded with an interval of stronger westerly winds blowing closer to Antarctica. Our data show that decade‐scale changes can be superimposed on longer intervals of intensified wind strength. Key Points: An ice core dust provenance record from Siple Dome shows marked shifts at about 1125 CE (lasting ∼60 yr) and 1748 CE (∼20 yr)Sr‐Nd isotopes indicate changes in the relative deposition of dust from Patagonian and Antarctic sources driven by changes in windsData suggest decade‐scale changes can be superimposed on longer intervals of intensified westerly wind strength during SAM + ‐like phases [ABSTRACT FROM AUTHOR]

Aim: Until recently, complete information on global reptile distributions has not been widely available. Here, we provide the first comprehensive climate impact assessment for reptiles on a global scale. Location: Global, excluding Antarctica. Time period: 1995, 2050 and 2080. Major taxa studied: Reptiles. Methods: We modelled the distribution of 6296 reptile species and assessed potential global and realm‐specific changes in species richness, the change in global species richness across climate space, and species‐specific changes in range extent, overlap and position under future climate change. To assess the future climatic impact on 3768 range‐restricted species, which could not be modelled, we compared the future change in climatic conditions between both modelled and non‐modelled species. Results: Reptile richness was projected to decline significantly over time, globally but also for most zoogeographical realms, with the greatest decreases in Brazil, Australia and South Africa. Species richness was highest in warm and moist regions, with these regions being projected to shift further towards climate extremes in the future. Range extents were projected to decline considerably in the future, with a low overlap between current and future ranges. Shifts in range centroids differed among realms and taxa, with a dominant global poleward shift. Non‐modelled species were significantly stronger affected by projected climatic changes than modelled species. Main conclusions: With ongoing future climate change, reptile richness is likely to decrease significantly across most parts of the world. This effect, in addition to considerable impacts on species range extent, overlap and position, was visible across lizards, snakes and turtles alike. Together with other anthropogenic impacts, such as habitat loss and harvesting of species, this is a cause for concern. Given the historical lack of global reptile distributions, this calls for a re‐assessment of global reptile conservation efforts, with a specific focus on anticipated future climate change. [ABSTRACT FROM AUTHOR]

The Hunga Tonga‐Hunga Ha'apai (HTHH) eruption on 15 January 2022 was one of the most explosive volcanic events of the 21st century so far. According to satellite‐based measurements, 0.4 Tg of sulfur dioxide (SO2) was injected into the stratosphere during the eruption. By using observations and model simulations, here we investigate changes in the chemical compositions of the stratosphere 1 year after the HTHH eruption and examine the key physical and chemical processes that influence the ozone (O3) concentrations. Injected SO2 was oxidized into sulfate during the first 2 months, and transported from the tropics to the Antarctic by the Brewer‐Dobson circulation within 1 year. In mid‐to‐low latitudes, enhanced sulfate aerosol increased O3 concentrations in the middle stratosphere but declined in the lower stratosphere. In addition to the chemical processes, sulfate aerosols also reduced polar low‐stratospheric O3 concentrations through enhanced Antarctic upwelling anomalies. Plain Language Summary: The Hunga Tonga‐Hunga Ha'apai (HTHH) eruption on 15 January 2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention. Volcanic ash and gases entering the atmosphere could affect weather and climate processes. Recent studies have largely explored the effects on global warming of HTHH eruption, and have founded that its climate impact is not very strong. However, its impacts on ozone (O3) remains unclear. We used observations and models to analyze how HTHH eruption could influence O3. It confirms that stratospheric O3 can be affected when volcano‐induced aerosols are transported. We suggest that physical and chemical processes combine together to influence stratospheric O3 after HTHH eruption. Moreover, the effect on O3 of HTHH eruption is probably one of the reasons for the recent discovery of a larger O3 hole in Antarctica. Key Points: Volcano‐induced stratospheric sulfate aerosols are transported toward the South Pole and downwards by the Brewer‐Dobson circulationCatalytic nitrogen oxide ozone loss cycles and sulfate aerosols' radiative effects cause extra‐polar stratospheric ozone anomaliesVolcanic aerosol‐induced heterogeneous chemistry and enhanced upward transport causes polar stratospheric ozone anomalies [ABSTRACT FROM AUTHOR]

A seismogenic-trigger mechanism is proposed for the rapid activation of destruction of cover and shelf glaciers in West Antarctica at the end of the 20th and beginning of the 21st centuries, accompanied by release of methane from the underlying hydrate-bearing sedimentary rocks and consequent rapid climate warming. This mechanism is associated with the action of deformation waves in the lithosphere–asthenosphere system, resulting from large earthquakes occurring in the subduction zones surrounding Antarctica: Chile and Kermadec–Macquarie. Disturbances in the lithosphere are transmitted over long distances on the order of 3000 km, and their additional associated stresses, which reach Antarctica several decades after the earthquakes, leading to a decrease in the adhesion of glaciers to underlying rocks, accelerated sliding of glaciers and development of faults in them. This process, in turn, reduces pressure on the underlying gas-hydrate-bearing sedimentary layers, leading to methane emission and climate warming. This hypothesis leads to the conclusion that in the coming decades, glacier destruction and climate warming processes in Antarctica will speed up due to an unprecedented increase in the number of large earthquakes in South Pacific subduction zones in the late 20th and early 21st centuries. [ABSTRACT FROM AUTHOR]

Antarctic ice shelves play a key role in regulating the rate of ice flow in tributary ice streams. Temporal variations in the associated ice‐shelf buttressing stress are observed to impact ice flow in glaciers and ice streams. Ephemeral grounding induced by tides is an important mechanism for modulating the buttressing stress. Here, we develop an approach to inferring variations in 3‐D surface displacements at an ice‐shelf‐stream system that explicitly accounts for ephemeral grounding. Using a temporally dense nine‐month‐long synthetic‐aperture radar image acquisition campaign collected over Rutford Ice Stream, West Antarctica, by the 4‐satellite COSMO‐SkyMed constellation, we infer the ephemeral grounding zones and the spatiotemporal variation of the fortnightly ice‐flow variability. We find ephemeral grounding zones along the western ice‐shelf margin as well as a few prominent ephemeral grounding points in the central trunk and in the vicinity of the grounding zone. Our observations provide evidence for tide‐modulated buttressing stress and the temporally asymmetric response of ice‐shelf flow to tidal forcing. Long‐term oceanic warming and ice‐shelf thinning will cause the loss of ephemeral grounding and decrease in ice‐shelf buttressing stress. Plain Language Summary: Antarctic ice shelves, the floating extensions of the Antarctic Ice Sheet, play a key role in ice‐flow dynamics by providing buttressing forces that resist the seaward flow of ice. Temporal variations in buttressing forces have been observed at glaciers and ice streams to impact ice‐flow speed. The grounding of ice shelves on the seafloor during low ocean tides, which is referred to as ephemeral grounding, causes temporal variations in buttressing forces. Here, using satellite radar observations, we develop an approach to inferring the surface displacements of an ice‐shelf‐stream system that explicitly accounts for ephemeral grounding. Using satellite radar imagery collected over Rutford Ice Stream, West Antarctica, we infer ephemeral grounding zones and the associated variability in ice flow. Our study provides evidence for the temporal variation in buttressing forces and improves our understanding of the short‐term response of ice‐shelf flow to ocean tides. In a warming climate, ice‐shelf thinning will reduce the impact of identified zones of ephemeral grounding, thereby causing long‐term ice‐flow speed to increase. Key Points: We develop an approach to inferring tide‐induced ephemeral grounding of ice shelves from synthetic‐aperture radar observationsEphemeral grounding plays a key role in the asymmetric response of ice‐shelf flows to tidal forcingLong‐term oceanic warming and ice‐shelf thinning will cause the loss of ephemeral grounding and reduction in ice‐shelf buttressing stress [ABSTRACT FROM AUTHOR]

Several large‐scale components of the climate system may undergo a rapid transition as critical conditions are exceeded. These tipping elements are also dynamically coupled, allowing for a global domino effect under global warming. Here we focus on such cascading events involving the Greenland Ice Sheet (GIS), the West Antarctica Ice Sheet (WAIS) and the Atlantic Meridional Overturning Circulation (AMOC). Using a conceptual model, we study the combined tipping behavior due to three dominant feedbacks: the marine ice sheet instability for the WAIS, the height‐surface mass balance feedback for the GIS and the salt‐advection feedback for the AMOC. We show that, in a realistic parameter range of the model, a tipping of the WAIS can inhibit cascading events by preserving the AMOC stability. Plain Language Summary: In the climate system, the interaction of specific components known as tipping elements are thought to be able to induce a global domino effect, or cascading tipping. In this study, we present a conceptual model containing the most strongly interacting components, namely the Atlantic Meridional Overturning Circulation (AMOC), the Greenland Ice Sheet and the West Antarctica Ice Sheet. We find that the stability of this system as a whole is strongly modified when interactions are included. Especially, while a Greenland Ice Sheet collapse destabilizes the AMOC, the model shows that a collapse of the West Antarctica Ice Sheet might prevent a global cascading event by stabilizing the AMOC. Key Points: A conceptual model of interacting Atlantic Meridional Overturning Circulation (AMOC), Greenland Ice Sheet and West Antarctica Ice Sheet (WAIS) is presentedInteractions between these tipping elements strongly modifies the stability of the whole systemA collapse of the WAIS can prevent tipping of the AMOC [ABSTRACT FROM AUTHOR]

Climate models project that a reduction in the Antarctic sea-ice extent due to global warming in the future would exert an influential role on the climate system. However, due to the coupled nature of the climate system and various feedbacks present, the underlying mechanism is not well understood. The present study attempts to investigate the potential effects of the model projected Antarctic sea-ice loss on the climate system and understand the underlying mechanism causing such changes using coupled model simulations. The investigation suggests that the projected sea-ice loss will result in the localized surface warming accompanied with tropospheric warming that will be experienced globally. The surface evaporation will enhance, accompanied by an increase in the precipitation and cloud cover around Antarctica's coastal periphery, with marginal changes observed over the continent's interiors. The strength of the atmospheric circulation in the Southern Hemisphere will change significantly, resulting in an enhancement in the Polar cell and katabatic flow accompanied by a marginal reduction in the Ferrel and Hadley cells, causing an equatorial shift in the jet's position. The eddy transport will also significantly weaken, leading to an overall reduction in the poleward energy transport at higher latitudes. These atmospheric circulation changes are essentially driven by the radiative budget, with more absorbed short-wave radiation reducing the poleward transport requirements. Compared to the reported uncoupled simulations studies, the remote global influence of sea ice loss noted in these coupled simulations which extends up to the Arctic highlights the strong pole-to-pole connections in the climate system through atmospheric and oceanic circulations. [ABSTRACT FROM AUTHOR]

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Ocean warming around Antarctica has the potential to trigger marine ice‐sheet instabilities. It has been suggested that abrupt and irreversible cold‐to‐warm ocean tipping points may exist, with possible domino effect from ocean to ice‐sheet tipping points. A 1/4° ocean model configuration of the Amundsen Sea sector is used to investigate the existence of ocean tipping points, their drivers, and their potential impact on ice‐shelf basal melting. We apply idealized atmospheric perturbations of either heat, freshwater, or momentum fluxes, and we characterize the key physical processes at play in warm‐to‐cold and cold‐to‐warm climate transitions. Relatively weak perturbations of any of these fluxes are able to switch the Amundsen Sea to an intermittent or permanent cold state, that is, with ocean temperatures close to the surface freezing point and very low ice‐shelf melt rate. The transitions are reversible, that is, canceling the atmospheric perturbation brings the ocean system back to its unperturbed state within a few decades. All the transitions are primarily driven by changes in surface buoyancy fluxes resulting from the freshwater flux perturbation or from modified net sea‐ice production due to either heat flux or sea‐ice advection anomalies. These changes affect the vertical ocean stratification over the continental shelf and thereby the eastward undercurrent at the shelf break, which both impact ice‐shelf melting. As sea‐ice induced deep convection is already quite limited in present‐day conditions, surface buoyancy gain in a warmer climate has relatively little effect on deep ocean properties compared to colder climate conditions. Plain Language Summary: The West Antarctic Ice Sheet is under the threat of a partial collapse, which would induce rapid global sea level rise. This threat is partly related to the thinning of floating ice shelves, and the consequent retreat of the grounding line, which is a self‐sustained ice dynamics process. It is triggered by increased basal melting of the ice shelves, which results from enhanced flow of relatively warm waters onto the continental shelf. It has been suggested that self‐sustained ocean processes may lead to abrupt changes in the flow of warm water into ice‐shelf cavities, which could facilitate the tipping to a marine ice‐sheet instability. Here, we analyze whether such abrupt ocean changes can occur under cold‐to‐warm or warm‐to‐cold transitions in the Amundsen Sea, West Antarctica. We use a regional ocean model with a set of idealized local atmospheric perturbations to characterize the thresholds and reversibility of ocean abrupt changes.We find that the currently warm Amundsen Sea could switch intermittently or permanently to a cold state for relatively weak atmospheric perturbations and could be slightly warmer in the future. All transitions are reversible. The main mechanism involved on decadal scale is related to a change in the surface buoyancy fluxes. Key Points: The currently warm ice‐shelf cavities of the Amundsen sector could become or have been cold for slightly colder climatic conditionsThe transitions are reversible: canceling the atmospheric perturbation brings the ocean back to its unperturbed state within a few decadesAll the transitions are primarily driven, at multi‐decadal scale, by changes in surface buoyancy fluxes over the continental shelf [ABSTRACT FROM AUTHOR]

Sea level rise (SLR) is a long‐lasting consequence of climate change because global anthropogenic warming takes centuries to millennia to equilibrate for the deep ocean and ice sheets. SLR projections based on climate models support policy analysis, risk assessment and adaptation planning today, despite their large uncertainties. The central range of the SLR distribution is estimated by process‐based models. However, risk‐averse practitioners often require information about plausible future conditions that lie in the tails of the SLR distribution, which are poorly defined by existing models. Here, a community effort combining scientists and practitioners builds on a framework of discussing physical evidence to quantify high‐end global SLR for practitioners. The approach is complementary to the IPCC AR6 report and provides further physically plausible high‐end scenarios. High‐end estimates for the different SLR components are developed for two climate scenarios at two timescales. For global warming of +2°C in 2100 (RCP2.6/SSP1‐2.6) relative to pre‐industrial values our high‐end global SLR estimates are up to 0.9 m in 2100 and 2.5 m in 2300. Similarly, for a (RCP8.5/SSP5‐8.5), we estimate up to 1.6 m in 2100 and up to 10.4 m in 2300. The large and growing differences between the scenarios beyond 2100 emphasize the long‐term benefits of mitigation. However, even a modest 2°C warming may cause multi‐meter SLR on centennial time scales with profound consequences for coastal areas. Earlier high‐end assessments focused on instability mechanisms in Antarctica, while here we emphasize the importance of the timing of ice shelf collapse around Antarctica. This is highly uncertain due to low understanding of the driving processes. Hence both process understanding and emission scenario control high‐end SLR. Plain Language Summary: Taking a co‐production approach between scientists and practioners, we provide high‐end sea level rise (SLR) estimates for practitioner application based on an expert evaluation of physical evidence and approaches currently used in policy environments to understand high end risk. We do this for two global warming scenarios, a modest and a strong one, for two time slices 2100 and 2300. The large and growing differences between the scenarios beyond 2100 emphasize the long‐term benefits of mitigation. However, even a modest warming may cause multi‐meter SLR on centennial time scales with profound consequences for coastal areas. Earlier high‐end assessments focused on instability mechanisms in Antarctica, while here we emphasize the importance of the timing of ice shelf collapse around Antarctica as well as how practitioners use high end projections to frame risk. We stress that both emission scenario and limited physical understanding control the outcome. Key Points: A high‐end estimate of sea level rise in 2100 and 2300Decisionmaker/practitioner perspective on high‐endTiming of collapse of ice shelves critical [ABSTRACT FROM AUTHOR]

Despite global warming and Arctic sea-ice loss, on average the Antarctic sea-ice extent has not declined since 1979 when satellite data became available. In contrast, climate model simulations tend to exhibit strong negative sea-ice trends for the same period. This Antarctic sea-ice paradox leads to low confidence in 21st-century sea-ice projections. Here we present multi-resolution climate change projections that account for Southern Ocean mesoscale eddies. The high-resolution configuration simulates stable September Antarctic sea-ice extent that is not projected to decline until the mid-21st century. We argue that one reason for this finding is a more realistic ocean circulation that increases the equatorward heat transport response to global warming. As a result, the ocean becomes more efficient at moderating the anthropogenic warming around Antarctica and hence at delaying sea-ice decline. Our study suggests that explicitly simulating Southern Ocean eddies is necessary for providing Antarctic sea-ice projections with higher confidence. Delayed Antarctic sea-ice decline is linked to Southern Ocean eddies - and their explicit treatment in models is crucial. New multi-resolution climate change projections give a possible reason for low confidence in IPCC's current 21st-century Antarctic sea-ice projections. [ABSTRACT FROM AUTHOR]

Cold regions, including high-latitude and high-altitude landscapes, are experiencing profound environmental changes driven by global warming. With the advance of earth observation technology, remote sensing has become increasingly important for detecting, monitoring, and understanding environmental changes over vast and remote regions. This paper provides an overview of recent achievements, challenges, and opportunities for land remote sensing of cold regions by (a) summarizing the physical principles and methods in remote sensing of selected key variables related to ice, snow, permafrost, water bodies, and vegetation; (b) highlighting recent environmental nonstationarity occurring in the Arctic, Tibetan Plateau, and Antarctica as detected from satellite observations; (c) discussing the limits of available remote sensing data and approaches for regional monitoring; and (d) exploring new opportunities from next-generation satellite missions and emerging methods for accurate, timely, and multi-scale mapping of cold regions. [ABSTRACT FROM AUTHOR]

In the last three decades, several interdisciplinary studies investigated the marine ecosystems off the West Antarctic Peninsula (WAP), one of the most impacted areas of the Southern Ocean by the global warming. Although the extent of near-shore habitats along the WAP is wider than elsewhere in Antarctica, the coastal fish communities have been rarely studied. Complementing these previous studies, we provide new data on the species composition, population structure and relative abundance of the inshore fish community living off the Argentine Islands (Bellingshausen Sea). Fish samples were caught all the year round during four different periods spread over ten years (from 2006 to 2017). The fish fauna consisted of fourteen high-Antarctic and low-Antarctic species of notothenioids, most of them belonging to the Nototheniidae. Notothenia coriiceps was by far the most abundant species, followed in decreasing abundance by Chaenocephalus aceratus, Notothenia rossii, Trematomus newnesi and Trematomus bernacchii. Our findings provide context for future ecological studies as this area represents either a spawning and nursery area for multiple species in this study. More generally, the inshore waters off the Argentine Islands represent the southern limit of distribution for several low-Antarctic species, and our results provide critical baseline data for assessing possible disruptions in population dynamics driven by the ongoing climate change. [ABSTRACT FROM AUTHOR]

This study investigates the formation mechanism of the ocean surface warming pattern in response to a doubling CO2 with a focus on the role of ocean heat uptake (or ocean surface heat flux change, ΔQnet). We demonstrate that the transient patterns of surface warming and rainfall change simulated by the dynamic ocean–atmosphere coupled model (DOM) can be reproduced by the equilibrium solutions of the slab ocean–atmosphere coupled model (SOM) simulations when forced with the DOM ΔQnet distribution. The SOM is then used as a diagnostic inverse modeling tool to decompose the CO2-induced thermodynamic warming effect and the ΔQnet (ocean heat uptake)–induced cooling effect. As ΔQnet is largely positive (i.e., downward into the ocean) in the subpolar oceans and weakly negative at the equator, its cooling effect is strongly polar amplified and opposes the CO2 warming, reducing the net warming response especially over Antarctica. For the same reason, the ΔQnet-induced cooling effect contributes significantly to the equatorially enhanced warming in all three ocean basins, while the CO2 warming effect plays a role in the equatorial warming of the eastern Pacific. The spatially varying component of ΔQnet, although globally averaged to zero, can effectively rectify and lead to decreased global mean surface temperature of a comparable magnitude as the global mean ΔQnet effect under transient climate change. Our study highlights the importance of air–sea interaction in the surface warming pattern formation and the key role of ocean heat uptake pattern. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula is one of the fastest-warming places on Earth. Elevated sea water temperatures cause glacier and sea ice melting. When icebergs melt into the ocean, it "freshens" the saltwater around them, reducing its salinity. The oceans absorb excess anthropogenic carbon dioxide (CO2) causing decline in ocean pH, a process known as ocean acidification. Many marine organisms are specifically affected by ocean warming, freshening and acidification. Due to the sensitivity of Antarctica to global warming, using biomarkers is the best way for scientists to predict more accurately future climate change and provide useful information or ecological risk assessments. The 70-kilodalton (kDa) heat shock protein (HSP70) chaperones have been used as biomarkers of stress in temperate and tropical environments. The induction of the HSP70 genes (Hsp70) that alter intracellular proteins in living organisms is a signal triggered by environmental temperature changes. Induction of Hsp70 has been observed both in eukaryotes and in prokaryotes as response to environmental stressors including increased and decreased temperature, salinity, pH and the combined effects of changes in temperature, acidification and salinity stress. Generally, HSP70s play critical roles in numerous complex processes of metabolism; their synthesis can usually be increased or decreased during stressful conditions. However, there is a question as to whether HSP70s may serve as excellent biomarkers in the Antarctic considering the long residence time of Antarctic organisms in a cold polar environment which appears to have greatly modified the response of heat responding transcriptional systems. This review provides insight into the vital roles of HSP70 that make them ideal candidates as biomarkers for identifying resistance and resilience in response to abiotic stressors associated with climate change, which are the effects of ocean warming, freshening and acidification in Antarctic organisms. [ABSTRACT FROM AUTHOR]

Future projection of temperature extremes in the "Earth's three poles" (the Arctic, Antarctica, and Third Pole‐Tibetan Plateau [TP]) is of importance to risk assessment and policymaking owing to the high sensitivity to climate change in these regions. In this study, future projections of four extreme temperature indices were constructed after the application of a bias correction method in models of Phase 6 of the Coupled Model Intercomparison Project (CMIP6). The reduced intensification of temperature extremes in the Earth's three poles if warming can be limited to 1.5°C instead of 2°C above the pre‐industrial level was examined. Results showed that all the extreme temperature indices show significant increasing trends under both the SSP2–4.5 and SSP5–8.5 scenarios over the Earth's three poles (SSP: Shared Socioeconomic Pathway). For the coldest night (TNn), warmest night (TNx), and warmest day (TXx), the greatest increase by the end of the 21st century under SSP5–8.5 occurs in the Arctic, followed by the TP and finally Antarctica. For the coldest day (TXn), the greatest increase occurs in the Arctic, followed by Antarctica and finally the TP. If global warming can be limited to 1.5°C rather than 2°C, the intensification of TNn, TNx, TXn, and TXx in the Arctic (Antarctica/TP) under SSP5–8.5 is projected to reduce by 66% (21.7%/44.26%), 50.31% (54.79%/60.52%), 71.58% (12.91%/65.81%), and 41.73% (81.3%/57.34%), respectively, and the results are similar for SSP2–4.5. Therefore, keeping a lower warming target is essential for reducing the risk of extreme events in the Earth's three poles. Plain Language Summary: Efforts to understand and project climate change over the Earth's three poles (the Arctic, Antarctica, and Third Pole‐Tibetan Plateau) under global warming scenarios are crucial for risk assessment and policymaking aimed at coping with future climate change. This study reports the future change of four extreme temperature indices over the Earth's three poles based on the observational data sets and outputs from models of Phase 6 of the Coupled Model Intercomparison Project with bias correction. We find that global warming will lead to substantial changes in extreme temperature indices over the Earth's three poles. All the four extreme temperature indices with bias correction show consistent increasing trends under both Shared Socioeconomic Pathway (SSP)2–4.5 and SSP5–8.5 over the Earth's three poles. Although the future changes in extreme temperature indices under a 1.5°C or 2°C warming world are not uniform in space, the risk of temperature extremes over the Earth's three poles is likely to decrease when global warming is limited to 1.5°C instead of 2°C under both SSP2–4.5 and SSP5–8.5. This means that a lower warming target is necessary for reducing the risks of extreme temperature over the three poles. Key Points: All the four extreme temperature indices show consistent increasing trends under both Shared Socioeconomic Pathway (SSP)2–4.5 and SSP5–8.5 in the Earth's three polesThe increase of four extreme temperature indices in the Earth's three poles with global mean temperature is linearA lower warming target is necessary for reducing the risks of extreme temperature over the three poles [ABSTRACT FROM AUTHOR]

Global warming is causing significant losses of marine ice around the polar regions. In Antarctica, the retreat of tidewater glaciers is opening up novel, low‐energy habitats (fjords) that have the potential to provide a negative feedback loop to climate change. These fjords are being colonized by organisms on and within the sediment and act as a sink for particulate matter. So far, blue carbon potential in Antarctic habitats has mainly been estimated using epifaunal megazoobenthos (although some studies have also considered macrozoobenthos). We investigated two further pathways of carbon storage and potential sequestration by measuring the concentration of carbon of infaunal macrozoobenthos and total organic carbon (TOC) deposited in the sediment. We took samples along a temporal gradient since time of last glacier ice cover (1–1000 years) at three fjords along the West Antarctic Peninsula. We tested the hypothesis that seabed carbon standing stock would be mainly driven by time since last glacier covered. However, results showed this to be much more complex. Infauna were highly variable over this temporal gradient and showed similar total mass of carbon standing stock per m2 as literature estimates of Antarctic epifauna. TOC mass in the sediment, however, was an order of magnitude greater than stocks of infaunal and epifaunal carbon and increased with time since last ice cover. Thus, blue carbon stocks and recent gains around Antarctica are likely much higher than previously estimated as is their negative feedback on climate change. [ABSTRACT FROM AUTHOR]

Abstract: Since the Discovery Investigations of the 1920s and 1930s, seawater temperatures have increased in the Atlantic sector by ∼1°C; greater than the global mean rise. The aims of this paper were first to rescue the Discovery macrozooplankton data, second to provide quantitative “baseline” distribution maps, relating these to indices of temperature and food. Our third aim was to use the relationships we derived between abundance and temperature to project the potential affect of a 1°C warming on the Discovery era distribution patterns. Based on the 1m ringnet data retrieved from 615 stations (Nov–March), four taxa comprised >90% of the Antarctic macrozooplankton abundance: Rhincalanus gigas, Thysanoessa spp., Euphausia superba, and Chaetognaths. Most of the taxa, especially the more abundant ones, were warm water species penetrating into Antarctica and thus total macrozooplankton abundance decreased about 100-fold from 50°S to 70°S. While temperature correlated best with distribution at this large scale, food availability (proxied by a present-day satellite-based Chlorophyll a climatology) had a secondary effect, with the major euphausiids Euphausia superba and Thysanoessa spp. concentrated in high chl a areas. A modelled uniform 1°C temperature rise produced a poleward shift for all taxa, but the Antarctic continent blocked this re-adjustment for the high latitude species, constricting their predicted range. More widespread polar/sub-polar species were predicted to increase their penetration into Antarctica by 4–12° in latitude, whereas the poleward shift in potential range of sub-Antarctic taxa were limited by the steep temperature gradient across the Antarctic Polar Front (APF). However, within the Scotia Sea the relatively warm temperatures of the northern Antarctic Zone, abundant food due to iron fertilisation and intense eddy activity provide a “gateway” for northern species to penetrate south of the APF. Our model predictions, based on measured distributional ranges and observed temperature increases, provide a yardstick with which to compare modern day data compilations and assess the potential effects of future temperature increases. [Copyright &y& Elsevier]

There is no consensus on how quickly the earth's ice sheets are melting due to global warming, nor on the ramifications to sea level rise. Due to its potential effects on coastal populations and global economies, sea level rise is a grave concern, making ice melt rates an important area of study. The ice‐sheet science community consists of two groups that perform related but distinct kinds of research: a data community, and a model building community. The data community characterizes past and current states of the ice sheets by assembling data from field and satellite observations. The modeling community forecasts the rate of ice‐sheet decline with computational models validated against observations. Although observational data and models depend on one another, these two groups are not well integrated. Better coordination between data collection efforts and modeling efforts is imperative if we are to improve our understanding of ice sheet loss rates. We present a new science gateway, GHub, a collaboration space for ice sheet scientists. This web‐accessible gateway will host datasets and modeling workflows, and provide access to codes that enable tool building by the ice sheet science community. Using GHub, we will collect and centralize existing datasets, creating data products that more completely catalog the ice sheets of Greenland and Antarctica. We will build workflows for model validation and uncertainty quantification, extending existing ice sheet models. Finally, we will host existing community codes, enabling scientists to build new tools utilizing them. With this new cyberinfrastructure, ice sheet scientists will gain integrated tools to quantify the rate and extent of sea level rise, benefitting human societies around the globe. [ABSTRACT FROM AUTHOR]