The Southern Annular Mode (SAM) represents the dominant pattern of climate variability in the extratropical Southern Hemisphere. However, its signature in coastal East Antarctic ice core records is unclear. A daily synoptic typing data set for the southern Indian Ocean constructed using self-organizing maps on 500 hPa daily geopotential height anomalies was used to investigate the relationship between the SAM and ice core records from Law Dome and Mount Brown South. Results indicate that synoptic weather regimes can either enhance or suppress the signature of the SAM on surface weather and ice core records. Weather regimes that are more likely during negative SAM and are associated with positive temperature anomalies over East Antarctica support the observed relationship between the SAM and the Law Dome delta 18O record since 1979. In contrast, weather regimes that describe meridional moisture flux toward Antarctica explain more snowfall accumulation variability at the ice core sites compared to the SAM, which contributes to suppressing the SAM signal in snowfall accumulation records. Results highlight the importance of considering the synoptic-scale dynamics on the relationship and stationarity of the SAM influence on surface weather and interpretation of ice core records. Given the limited robust relationships between the SAM and the ice core records investigated, caution should be taken before using these records to reconstruct past SAM variability. Instead, the coastal East Antarctic ice core records provide insight into the occurrence of meridional weather regimes, which are often associated with extreme temperature and precipitation conditions.

Rain-on-snow (ROS) events in the Arctic can lead to major impacts on the snow cover, cryosphere and environment. During the last decades, these events have significantly increased, mostly due to climate change. Here, we use outputs from the regional climate model MAR (version 3.14) driven by the ERA5 reanalysis at 10-km resolution over Greenland, in the period 1940-2023. MAR is used to simulate the climatological properties of summertime ROS events over Greenland, and their long-term changes over the period. The analyses also focused on the years after 1979, when reanalyses are more reliable. We found that both the spatial extension, the frequency, and rainfall amounts associated with ROS events all strongly increased, especially along the West and East coasts of Greenland. These changes either appeared, or strongly accelerated, during the last 40 yrs. We also analyzed the synoptic configurations conducive to major ROS events (the top 10% in terms of size and amounts). Poleward advection of moisture and heat generally prevails but shows non-negligible variability in their location, direction and strength of associated centers of action. About 10%-20% of those major ROS events correspond to atmospheric rivers, events that occur 1%-2% of the time but increase the probability of rainfall over Greenland by a factor 10 to nearly 40 locally, with respect to the climatology. Plain Language Summary The Arctic and Greenland are among the regions warming fastest on Earth. In summer, an increasing proportion of precipitation is liquid (rainfall), which causes snow to melt and leave ice unprotected. Here, we show that rain-on-snow events dramatically increased in frequency, size, and rainfall amounts. This increase is partly due to warming, turning snow to rain. Atmospheric circulations conducive to large rainfall amounts generally consist of southerly wind anomalies transporting moisture and heat polewards, among which 10%-20% correspond to "atmospheric rivers," corridors of particularly intense poleward transport. These results could help better understand the surface mass balance of the Greenland ice sheet.

This study conducts the first regional mapping exercise of landscape dynamics of the Kerguelen Archipelago; a remote sub-Antarctic archipelago located in the southern Indian Ocean. It is based on an original adaptation of the radiometric landscape methodology applied to the long time series of MODIS NDVI data covering the period 2003-2022, allowing the temporal dimension to be explicitly integrated into the regional-scale landscape mapping. The aim is to provide a comprehensive framework for analyzing the structure, dynamics, and evolutionary trajectories of the landscapes of this sub-Antarctic archipelago, which remain largely unknown yet essential for understanding ecosystem functioning in isolated environments. The adopted approach is based on three complementary steps. First, synthetic variables were extracted from the NASA's MODIS NDVI product to summarize seasonal and interannual information. Next, spatial segmentation was used to group pixels into radiometrically homogeneous objects, constituting basic units of the landscape. Finally, unsupervised clustering was applied to classify these units and produce a coherent landscape typology. This original data-driven approach overcomes the limitations of supervised classifications based on predefined criteria by distinguishing landscapes that may appear similar at a given moment but have divergent NDVI value trajectories over two decades. The analysis led to the identification of five major landscape units, revealing different dynamics at the regional scale. The integration of outputs from the MAR regional climate model and the NASADEM digital elevation model made it possible to place these landscape units in their environmental and topographical context. The results show that landscape stratification follows a marked altitudinal gradient, which strongly influences the distribution and evolution of radiometric landscape units. Beyond producing unprecedented mapping, this approach constitutes the first regional, remote sensing data-driven geographical partitioning of a sub-Antarctic archipelago based on long-term vegetation trajectories. It provides a foundational environmental framework that can serve as a baseline for future field-based investigations, comparative analyses between/within the five identified landscape units, and multi-scale ecological studies focusing on specific environments. By capturing the specific values and evolutionary trajectories of vegetation, this methodology makes it possible to establishes an initial typology of the archipelago's landscapes, while providing insights to better understand the interactions between climate, relief, and vegetation. Our approach contributes to improving the knowledge and monitoring of landscapes in remote sub-Antarctic environments. As a territory managed by the Terres Australes et Antarctiques Fran & ccedil;aises (TAAF), the Kerguelen Archipelago constitutes a sentinel of environmental change in the Southern Hemisphere. The proposed methodology provides regional and national decision-makers with a robust tool for long-term ecosystem and landscape monitoring, supporting management and conservation strategies adapted to these particularly fragile environments that are highly vulnerable to climate change.

From 19 to 23 December 2018, an atmospheric river sourced in the Atlantic hit the French-Italian Concordia station, located at Dome C, East Antarctic Plateau, 3233 m above sea level (a.s.l.). It induced a significant surface warming (+18 degrees C in 3 d), combined with high specific humidity (3-fold increase in 3 d) and a strong isotopic anomaly in water vapour (+17 parts per thousand for delta 18O). The isotopic composition of water vapour monitored during the event may be explained by the isotopic signature of long-range water transport, and by local moisture uptake during the event. In this study, we used continuous meteorological and isotopic water vapour observations, together with the atmospheric general circulation model LMDZ6iso, to describe this event and quantify the influence of each of these processes. The presence of mixed-phase clouds during the event induced a significant increase in downward long wave radiation, leading to high surface temperature and resulting in high turbulent mixing in the boundary layer. Although surface fluxes are underestimated in LMDZ6iso, near-surface temperature and specific humidity are well represented. The surface vapour delta 18O is accurately simulated during the event, despite an overestimated amplitude in the diurnal cycle outside of the event. Using the LMDZ6iso simulation, we perform a surface water vapour mass budget by decomposing total specific humidity into contributions from individual processes. Our analysis demonstrates that surface sublimation, which becomes significantly stronger during the event compared to typical diurnal cycles, emerges as the dominant driver of the vapour delta 18O signal at the peak of the event, accounting for approximately 70 % of the total contribution. The second largest contribution comes from moisture input via large-scale advection associated with the atmospheric river, accounting for approximately 30 % of the total. Consequently, our results reveal that the isotopic signal monitored in water vapour during this atmospheric river event reflects both long-range moisture advection and interactions between the boundary layer and the snowpack. Only specific meteorological conditions driven by a pronounced moisture intrusion can explain these strong interactions. Given the marked imprint of air-snow exchanges on the vapour isotopic signal, improving the representation of local processes in climate models could substantially improve the simulation of the isotopic signal over Antarctica and provide valuable insight into moisture uptake processes.

Water isotopes serve as tracers of hydrological processes and as proxies for past climates archived in ice cores. The isotopic signal is acquired throughout the hydrological cycle—through evaporation over the oceans, precipitation, which occurs as moisture is transported from lower to higher latitudes, and during post-depositional processes in which isotopic exchange between snow and atmospheric moisture occurs. Owing to these multiple influences, the relationship between isotope ratios in ice and local temperature varies across Antarctica, and distinct relationships are found when evaluating isotope ratios and temperature across space (for example, in surface snow) compared with temporal correlations at the same site (for example, in precipitation). Here we report measurements of water vapour isotopic compositions from a traverse across East Antarctica, as well as at two fixed sites: the coastal station Dumont D’Urville and Dome C on the plateau. Combining snow and vapour isotopic data, we demonstrate that the temporal and spatial isotope–temperature relationships are distinct because of differences in how the rainout fraction varies across time and space. Our findings support a shift from thinking about the isotope–temperature relationship in terms of distinct temporal and spatial slopes to recognizing that the relationship varies along a continuum based on known dependencies between circulation dynamics and mean climate state. By distilling moisture along moist isentropic transport paths, we can predict the isotope–temperature relationship across either time or space using a physical understanding of large-scale moisture transport under different climatic conditions. Atmospheric circulation patterns and mean climate conditions lead to heterogeneity in water isotope–temperature relationships across Antarctica, and accounting for these effects allows for more robust interpretation of temperature proxy records from ice cores.

Abstract. Three recent downscalings of CESM with MAR, RACMO, and HIRHAM under SSP5-8.5 produce consistent contemporary Antarctic surface mass balance (SMB), but diverge strongly by 2100, especially over ice shelves. HIRHAM simulates a large SMB decline driven by strong runoff increases, MAR a moderate decrease, while RACMO maintains near balance. These differences mainly reflect contrasting melt–albedo feedbacks, present-day melt and refreezing levels, and a persistent 1–2 °C temperature offset between MAR and RACMO. CESM shows a decline similar in magnitude to MAR, with high melt partly compensated by extensive refreezing. Over grounded ice, all models project increased SMB from higher snowfall, though runoff still drives their spread. Despite shared boundary conditions and similar contemporary SMB, model behavior diverges, and CESM’s integrated results resemble MAR's despite its coarse resolution. Performance differences in present-day melt suggest that uncertainty estimates should account for model skill, motivating Bayesian treatment of multi-model ensembles.

Atmospheric rivers (ARs) represent the main intrusions of moisture and heat into Antarctica, exerting a major influence on the continent's surface mass balance. Yet, due to geometric and directional constraints, existing detection algorithms often fail to track their evolution inland after landfall or in regions where abrupt directional changes occur. We introduce DARK (Detecting ARs using their Kurvature), a new Antarctic AR detection framework designed to overcome these limitations. DARK applies a strict 98th-percentile threshold to total integrated vapor transport and computes AR length along the curved axis to evaluate the 2000 km AR criterion. This enables the continuous detection of ARs with complex geometries, including those that curve, overturn, or extend across the South Pole. An additional AR-children module identifies smaller but still intense moisture remnants that detach from parent ARs after landfall yet continue to transport vapor and heat inland. The resulting climatology shows that DARK ARs account for about 18 % of total Antarctic precipitation and are linked to roughly half of top 1 % daily precipitation anomalies, 60 % of top 1 % daily maximum temperature anomalies, and 80 % of compound warm-and-wet events. DARK provides a more detailed assessment of AR-related precipitation and temperature impacts in the South Pole region. Despite slightly higher occurrence, risk ratio analysis shows that DARK ARs more effectively capture the most intense events than earlier Antarctic schemes. Including AR-children further strengthens these associations, especially over Victoria Land, where they contribute to about one third of AR-related precipitation.

Water stable isotope signals recorded in shallowfirn cores are essential to constrain the variations of climateand atmospheric water cycle over the past decades to cen-turies. However, deposition and post-deposition effects addadditional signal, often referred to as stratigraphic noise, tothe isotopic signal. One way to reduce the local stratigraphicnoise is to combine several firn cores at the same location.Here, we study the water isotopic composition and chemicalrecords from 9 firn cores (20 to 40 m depth) drilled in 2016 at3 sites (D47, Stop5 and Stop0) with high accumulation rates(similar to 200 mm w.e. yr(-1)) along a transect between the coast andthe plateau in Ad & eacute;lie Land in Antarctica (100 to 385 km fromthe coastal station Dumont d'Urville). Each core covers atleast the period from 1979 to 2016 and the high-resolutionmeasurements permit to capture the seasonal variations inboth chemical and isotopic records. At each site, similaritiesin the nssSO(4)and delta O-18 variations between the different coreswere used to combine the three isotopic records into a singlestacked isotopic curve, thereby enhancing the signal-to-noiseratio. At two sites, we find a good agreement when com-paring the water isotopic profiles recovered from the stackedrecords to those obtained as modeling output from virtual firncores calculated using the two isotope-enabled atmosphericgeneral circulation models, ECHAM6-wiso and LMDZ6iso over the period 1979-2016 which supports the good perfor-mances of the two models for the Ad & eacute;lie Land region. At thevery windy site of D47, building a coherent signal from the3 individual cores is not possible because the isotopic andimpurities signals are much more affected by stratigraphicnoise. This study confirms that, even if the benefit of stack-ing is limited at very windy sites, combining several cores isof primary importance to faithfully reconstruct water isotopevariability at one site. We also show that the stacked recordpermits to identify some strong climate signals recorded inthe water isotope profiles.

Abstract. Intense warming events (IWE) and intense precipitation events (IPE) and their impacts on ice bodies remain overlooked. Using in situ observations, a high-resolution regional circulation model and catalogue of atmospheric river (AR) occurrences, we investigate concurrent IWE over the Patagonian Icefields and IPE over the Antarctic Peninsula Ice Sheet associated with landfalling ARs. Our study focuses on summers (November–March) from 1980 to 2022. We identified 127 compound events linked to a dipole circulation pattern characterized by a ridge over southern South America and a low-pressure system over the Bellingshausen Sea. Both regions experience pronounced surface warming and enhanced melt leading to a negative Surface Mass Balance over the Patagonian Icefields, while positive anomalies still prevailed over the Antarctic Peninsula Ice Sheet were related with increased snowfall associated with AR activity. Surface Energy Balance anomalies were mainly driven by enhanced incoming shortwave radiation over Patagonia but increased longwave radiation over the Antarctic Peninsula, whereas sensible heat flux positively contributed in both regions. These findings highlight the interconnected influence of intense events and AR-driven dipole circulation patterns on the Southern Hemisphere cryosphere, even though individual events exhibit substantial thermodynamic variability and distinct life-cycle characteristics.

Atmospheric blocking is a key driver of persistent circulation anomalies and associated extreme events in the Southern Hemisphere, yet its characteristics around Antarctica remain poorly understood due to methodological diversity and the absence of a consolidated, long-term dataset. This study presents a new multi-method Antarctic atmospheric blocking dataset covering the period 1979–2024, derived from ERA5 reanalysis and constructed using multiple blocking detection approaches applied consistently across the Southern Hemisphere (25–90° S). The dataset integrates diagnostics based on 500 hPa geopotential height and vertically integrated potential vorticity within a unified framework for spatial filtering, event definition, and temporal tracking. It provides instantaneous blocking masks, spatiotemporally tracked event catalogs, time series, and aggregated climatologies that are directly comparable across methods. The results reveal only weak large-scale similarities in Antarctic blocking across detection approaches, mainly related to high-latitude occurrence and seasonal modulation. In contrast, pronounced method-dependent diversity is evident in blocking frequency, spatial extent, the number of detected blocking events, and persistence. Geopotential height-based methods identify a broader spectrum of anticyclonic flow regimes, including events extending into the Antarctic interior, whereas potential vorticity-based methods isolate fewer, more spatially confined events that emphasize dynamically coherent upper-level disturbances near the polar vortex. Event-based diagnostics further reveal systematic trade-offs between event frequency and duration, illustrating how different methodological choices preferentially capture either shorter-lived circulation anomalies or more persistent blocking structures. These contrasts arise from the diverse dynamical expressions of blocking at high southern latitudes, indicating that no single diagnostic fully captures Antarctic blocking behavior. Key uncertainties relate to threshold sensitivity, spatial filtering, and diagnostic formulation, which should be considered when interpreting blocking statistics and inter-method differences. By providing a consistent and openly accessible resource, archived on Zenodo at https://doi.org/10.5281/zenodo.18329806 (Bozkurt et al., 2026), this dataset allows direct intercomparison of blocking definitions, supports evaluation of climate models over Antarctica, and provides a foundation for future studies of blocking-related circulation variability and extreme events.

This study analyzes the interrelationship between atmospheric rivers (ARs) and weather types (WTs) on the Kerguelen Islands, in the southern Indian Ocean, over the last 40 years. Their respective characteristics and impacts as well as their influence on precipitation and temperature are investigated using ERA5 reanalyses and in situ data. Results show that, even though they can occur throughout the year, ARs are mostly associated with four WTs, which have a strong influence on preferential AR direction and landfalling location. These WTs correspond to those favoring northerly or northwesterly anomalies promoting moisture export from the subtropical latitudes. Weather type influence on daily precipitation and temperature is highly variable with the relationship depending on their co-occurrence, or lack thereof, with AR events. Depending on their orientation, ARs have different impacts on the local climate and are responsible for a majority of the strongest east-west precipitation gradients.

In many regions, extreme temperatures increase faster than background global warming due to complex atmospheric circulation changes. This has been overlooked in Antarctica. Here, we examine extreme temperatures recorded at 16 weather stations since 1950, and identify their changes and drivers. Over the Antarctic Peninsula and the South Pole, 10-year return level temperatures increased by up to 1.19°C per decade since 1980, outpacing mean temperature trends. Most extreme events, including statistically implausible or black swan events, were driven by intense atmospheric rivers linked to Rossby wave trains forced by tropical Pacific convection. In contrast, 10-year return level temperature decreased over most of East Antarctica, despite increasing atmospheric river activity, as the mean cooling muted the impacts of warm intrusion until recently. Our results highlight how the entire continent could become vulnerable in a warmer climate or enhanced tropical convective activity, as illustrated by the March 2022 heatwave.

Water stable isotopes signals recorded in snow, firn and ice cores were successfully used to investigate past temperatures on glacial/interglacial scales. However, many uncertainties hampered the interpretation of water isotope records at sub-annual to decadal resolution as a proxy of past temperature variations only. Condensation, sublimation and/or redistribution of snow triggered by strong katabatic winds as well as diffusion within firn lessen the representativeness of a single isotopic profile to reconstruct past temperature in this region. In order to mitigate the non-representativeness of a single isotopic profile, a solution consists of averaging several records to increase signal to noise ratios. In this study, we present an analysis of 3 stacked δ18O temporal series from the coast-to-plateau transition in Adélie land. Each of these stacks was built from three shallow firn cores (~20 m-long) drilled at 3 locations (so called D47, Stop5 and Stop0) with high accumulation rates (~200 mm w.eq ·yr-1) during the ASUMA campaign in December 2016 - January 2017. The sites feature different elevations (from 1516 m to 2416 m above sea level) and katabatic winds influence. We present a comparison of each of these stacks with virtual firn cores produced from the outputs of two atmospheric general circulation models including isotopes, ECHAM6wiso and LMDZ6iso for the period 1979 - 2016. In particular, we show how much of the climatic information we can retrieve from our δ18O stacked series.

Sea ice is a fundamental, highly variable element of the polar environments. Its variability deeply affects, not only the local climate- and ecosystem but also the global Earth system. Until recently Arctic sea ice experienced a general retreat as expected under global warming whilst Antarctic sea ice extent increased up to 2014. However, Antarctic sea-ice extent at maximum annual cover shifted from a record high (2014) to a record minimum extent (2023), begging to explore the relationship between sea ice and ocean/atmospheric forcing. In this work, we pinpoint some extreme atmospheric events, specifically, atmospheric rivers (ARs) to analyse their influence on sea ice and snow properties. ARs can have a direct impact on the nature of oceanic surface gravity waves. Increasing wind speed causes an increase in wave height and energy, leading to greater repercussions on snow and sea ice. The sea ice area most affected by this forcing is the one that separates the pack ice from the open oceans, known as the marginal ice zone (MIZ). Our analysis aims to understand wave-sea ice interaction and its effect on accelerating snow melt or changing sea ice morphology. To accomplish this we focus on the influence of wave overwash on sea ice surfaces during the spring season in the Weddell Sea. The MIZ is identified by posing the limits of sea ice concentration (SIC) ranging from 15% to 80%. ARs events are identified using ERA5 reanalysis data, estimating their integrated water vapour transport (IWV) and vertically integrated vapour transport (vIVT) values, which are considered extreme if they exceed 95% of historical norms for the same location and time of year over a time interval that spreads from 1980 to 2022. Data obtained from AMSRE, AMSR2 & SMOS passive microwave sensors are used to generate time series and local maps of brightness temperature. These microwave signatures serve in the analysis of the possible spatial and temporal correlation between ARs events and sea ice and snow characteristics. Initial findings suggest that ARs and their subsequent gravity waves may significantly affect the wetting of sea ice and of the snow on it leading to increased melting of the MIZ. This study will improve the methods to inform models used to forecast the impact that extreme atmospheric events can have on sea ice and snow, offering new directions to investigate the coupled ocean-sea ice-atmosphere system in a changing climate.

The recent two years have been marked by many regional climate-state extremes particularly over the southern polar region including record-high surface melt over the Antarctic Peninsula in February 2022 (Gorodetskaya et al., 2023; Zou et al., 2023), the strongest heatwave ever recorded over East Antarctica bringing extreme inland snowfall and coastal surface melt in March 2022 (Wille et al., 2024), and an extremely low Antarctic sea ice area observed in winter 2022 outpaced by the lowest record in winter 2023 (Purich and Doddridge, 2023). Increased magnitude and probability of occurrence of extreme events, along with their high impacts on the Antarctic surface mass balance require detailed understanding of the underlying large-scale, regional and local drivers, using comprehensive and high-resolution observations and modeling. Here we will present analysis of extreme surface melt events and their drivers based on targeted observations conducted during 2022-2023 over the northern Antarctic Peninsula, including two austral summer campaigns and the winter Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) enhanced observational period. Cloud and precipitation profiles using radar and lidar measurements are analyzed together with thermodynamic state of the troposphere from radiosonde observations and surface radiative fluxes with a specific focus on the extreme warm events characterized by surface melt and/or rainfall. In particular, the February 2022 extreme warm event showed very high downwelling longwave flux (up to 350 W/m2) due to the low warm-base liquid-containing clouds. Frequent occurrence of supercooled liquid water with low and warm cloud-bases is characteristic of the site during both summer and winter seasons and plays an important role in surface melt events. Another key factor during warm events is the transition from snowfall to rainfall (both with height in the vertical column, indicated by melt layer height derived from the precipitation radar measurements, and with time over the course of the event). Using radiosonde profiling, we identify layers of maximum moisture and heat transport into the Antarctic Peninsula, which showed an outstanding magnitude during the hot spell in February 2022 associated with an intense atmospheric river and which we further compare to other observed warm events. Significant differences are found for cloud and precipitation properties between ground-based measurements and ERA5 reanalysis, prompting the use of state-of-art high-resolution observations to improve representation of relevant processes in the models particularly during surface melt events.Funding acknowledgements: Portuguese Polar Program projects APMAR/TULIP/APMAR2; FCT projects MAPS and ATLACE; ANR project ARCA; KOPRI; NSF awards 2127632 and 2229392.References:Gorodetskaya et al. (2023): Record-high Antarctic Peninsula temperatures and surface melt in February 2022: a compound event with an intense atmospheric river. npj Clim Atmos Sci, https://doi.org/10.1038/s41612-023-00529-6Purich and Doddridge (2023): Record low Antarctic sea ice coverage indicates a new sea ice state. Commun Earth Environ, https://doi.org/10.1038/s43247-023-00961-9Wille et al (2024): The Extraordinary March 2022 East Antarctica “Heat” Wave. Part I: Observations and Meteorological Drivers. J. Climate, https://doi.org/10.1175/JCLI-D-23-0175.1.Zou et al (2023): Strong warming over the Antarctic Peninsula during combined atmospheric River and foehn events: Contribution of shortwave radiation and turbulence. J. Geophys. Res. Atmos., https://doi. org/10.1029/2022JD038138

Antarctic atmospheric rivers (ARs) are a form of extreme weather that transport heat and moisture from the Southern Hemisphere subtropics and/or mid-latitudes to the Antarctic continent. Present-day AR events generally have a positive influence on the Antarctic ice-sheet mass balance by producing heavy snowfall, yet they also cause melt of sea ice and coastal ice sheet areas, as well as ice shelf destabilization. In this Review, we explore the atmospheric dynamics and impacts of Antarctic ARs over their life cycle to better understand their net contributions to ice-sheet mass balance. ARs occur in high-amplitude pressure couplets, and those strong enough to reach the Antarctic are often formed within Rossby waves initiated by tropical convection. Antarctic ARs are rare events (~3 days per year per location) but have been responsible for 50–70% of extreme snowfall events in East Antarctica since the 1980s. However, they can also trigger extensive surface melting events, such as the final ice shelf collapse of Larsen A in 1995 and Larsen B in 2002. Climate change will likely cause stronger ARs as anthropogenic warming increases atmospheric water vapour. Future research must determine how these climate change impacts will alter the relationship among Antarctic ARs, net ice-sheet mass balance and future sea-level rise. Atmospheric rivers provide the majority of water vapour transport to the high latitudes. This Review summarizes Antarctic atmospheric river dynamics and climatology and discusses their impacts on the mass balance of the Antarctic ice sheet.

Although rare, atmospheric rivers (ARs) substantially influence the interannual variability of Antarctic surface mass balance. We identify characteristics unique to AR environments by comparing (1) AR, (2) Analog (environments that feature high-low pressure couplets, similar to AR environments, but no AR), and (3) Top AR (high-precipitation AR timesteps) during 1980–2019 around Antarctica. We find significant differences between AR and Analog environments including more intense and poleward-shifted mid-tropospheric geopotential height couplets as well as larger atmospheric moisture anomalies. We find similar significant enhancement in synoptic-scale dynamic drivers of Top ARs compared to AR environments, but no significant difference in local integrated water vapor anomalies. Instead, our results highlight the importance of large-scale dynamic drivers of Top AR timesteps, including connections between high-precipitation ARs and Rossby waves excited by tropical convection. This deeper understanding of Antarctic AR environments provides context for interpreting future changes to the Antarctic surface mass balance.

Water stable isotopes signals recorded in snow, firn and ice cores were successfully used to investigate past temperatures on glacial/interglacial scales (Jouzel and Masson-Delmotte 2010, Dansgaard, 1964). However, as evidenced by Goursaud et al. (2018) in coastal Adélie Land, many uncertainties hampered the interpretation of water isotope records at sub-annual to decadal resolution as a proxy of past temperature variations only (Goursaud et al. 2018). Condensation, sublimation and/or redistribution of snow triggered by strong katabatic winds as well as precipitation intermittencies, origin of moist air masses bringing precipitation and diffusion within firn lessen the representativity of a single isotopic profile to reconstruct past temperature in this region (Grazioli et al. 2017, Khale et al. 2018, Picard et al. 2019, Casado et al. 2020, Hirsch et al. 2023). In order to mitigate the non-representativity of a single isotopic profile, a solution consists in averaging several records to increase signal to noise ratios. However, to do so, it is necessary to provide a good correspondence between the different cores of interest.In this study, we make good use of water stable isotopes and major chemistry records from 9 firn core (20 to 40m deep) drilled at 3 sites (so called D47, Stop5 and Stop0) during the ASUMA campaign. These sites display a high mean accumulation rate of about 250 mm.weq/year and a wide range of environmental conditions with elevation ranging from 1550m to 2460m, distance from coast ranging from 103km to 423km and different katabatic winds influence. In particular, we use the Paleochrono probabilistic model with water stable isotopes signal and major chemistry records coupled with beta-gamma and RADAR data to obtain the best correspondence between the different cores. We then quantify to what extent the stacking of several cores enable to increase the signal to noise ratio at the different sites and can provide a faithful record to document variations of the temperature and/or atmospheric water cycle over the last decades in this region.