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Using an optical band index generated from Landsat 8 OLI data, an inventory of Antarctic supraglacial lakes (size >0.01 km2) during 2014-2023 is presented. Shaded snow, cloud and rock shadow were removed by using a band-based filter. Over the north Antarctica, we identified 639 lakes covering an area of 520.79 km2, 1025 lakes covering 272.82 km2 over the East Antarctica, and 1045 lakes covering 93 km2 over south Antarctica. The influence of air temperature, 10-m zonal/meridional wind components and climate indices on surface melt were investigated. Over the north Antarctica, air temperature promoted melt, while Föhn and katabatic winds warmed adiabatically along the leeward side of the elevated features and initiated melt in south Antarctica. Nearly all areas have exhibited a decrease in melt over the past few years, and the number of melt cases dropped after 2020. Negative SAM index favoured melt over the north Antarctica. This study identified new SGLs, which will be a benchmark for further studies. The undulating terrain posed a difficulty for collecting and interpreting satellite data, which should be addressed using advanced technologies and algorithms. [ABSTRACT FROM AUTHOR]

A main source of regional climate change uncertainty is the large disparity across models in simulating the atmospheric circulation response to global warming. Using the latest suite of global climate models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), a storyline approach is adopted to derive physically plausible scenarios of Antarctic climate change for 2070–99, according to Shared Socioeconomic Pathway SSP5-8.5. These storylines correspond to differences in the simulated amount of seasonal sea ice loss and either (i) the delay in the summertime stratospheric polar vortex (SPV) breakdown or (ii) wintertime SPV strengthening, which together constitute robust drivers of the response pattern to future climate change. Such changes combined are known to exert a strong control over the Southern Hemisphere midlatitude jet stream, which we quantify as collectively explaining up to 70% of the variance in jet response in summer and 35% in winter. For summer, the expected strengthening and displacement of the tropospheric jet stream varies between a ∼1 and 2 m s−1 increase and ∼2°–4° poleward shift, respectively, across storylines. In both seasons, a larger strengthening of the jet is correlated with less Antarctic warming. By contrast, the response in precipitation is more consistent but still strongly attenuated by large-scale dynamics. We find that an increase in high-latitude precipitation around Antarctica is more pronounced for storylines characterized by a greater poleward jet shift, particularly in summer. Our results highlight the usefulness of the storyline approach in illustrating model uncertainty and understanding the processes that determine the spread in projected Antarctic regional climate response. Significance Statement: Uncertainty in future climate predictions for the Antarctic is dominated by the unknown response of the large-scale (global) atmospheric circulation. In characterizing such uncertainty, plausible outcomes of climate response (storylines) are generated from the organization of model projections according to the amount of simulated seasonal sea ice loss and the delay in summertime breakdown/winter strengthening of the stratospheric westerly circulation (polar vortex). The intensity and location of the tropospheric jet stream is strongly dependent on both factors, which strongly influences the near-surface climate response over Antarctica. We find that the simulated amount that Antarctic air temperatures increase by in the future (to the end of the century) is intrinsically related to the projected intensification of the Southern Hemisphere tropospheric jet, varying by a factor of 2 or more across storylines for summer. Storylines with greater jet strengthening are associated with less Antarctic warming (reduced poleward advection of air masses from lower latitudes). Similar differences are found for changes in jet position, which we note has a much stronger control on mid- to high-latitude precipitation response. This includes both an enhanced wetting response around Antarctica and drying response farther equatorward, for storylines characterized by a greater poleward jet shift. [ABSTRACT FROM AUTHOR]

Temperature analysis is of special interest in polar areas because temperature is an essential variable in the energy exchange between the Earth's surface and atmosphere. Although land surface temperature (LST) obtained using satellites and air temperature (Ta) have different physical meanings and are measured with different techniques, LST has often been successfully employed to estimate Ta. For this reason, in this work, we estimated Ta from LST MODIS collection 6 (C6) and used other predictor variables. Daily mean Ta was calculated from Spanish State Meteorological Agency (AEMET) stations data on the Livingston and Deception Islands, and from the PERMASNOW project stations on Livingston Island; both islands being part of the South Shetland Islands (SSI) archipelago. In relation to our previous work carried out in the study area with collection 5 (C5) data, we obtained higher R2 values (R2CV = 0.8, in the unique model with Terra daytime data) and lower errors (RMSECV = 2.2 °C, MAECV = 1.6 °C). We corroborated significant improvements in MODIS C6 LST data. We analyzed emissivity as a possible factor of discrepancies between C5 and C6, but we did not find conclusive results, therefore we could not affirm that emissivity is the factor that causes differences between one collection and another. The results obtained with the applied filters indicated that MODIS data can be used to study Ta in the area, as these filters contribute to the reduction of uncertainties in the modeling of Ta from satellites. [ABSTRACT FROM AUTHOR]

The year 2023 marked a turning point for the Antarctic region as the Southern Hemisphere experienced a significant reduction in its sea ice extent, with a record-breaking sea ice minimum in July 2023 of approximately 2.4 million square kilometers below the long-term average. This study highlights the drivers behind this exceptional event by combining observational, satellite, and reanalysis data, with a special focus on the large-scale atmospheric circulation. Throughout the year, the Antarctic Sea ice extent broke record after record, ranking as the lowest sea ice on record from January to October, except for March and April. The exceptionally low sea ice extent from May to August was mainly driven by the prevalence of a zonal wave number 3 pattern, characterized by alternating surface high- and low-pressure systems, which favored the advection of heat and moisture, especially over the Ross Sea (RS), Weddell Sea (WS), and Indian Ocean (IO). The anomalous large-scale circulation was accompanied by record-high sea surface and subsurface temperatures over the regions with reduced sea ice extent. In addition to the air and ocean temperature, record-breaking heat, moisture, and sensible heat fluxes have been observed, especially over the WS, RS, and IO, which further amplified the reduction in the sea ice extent over these areas. Notably, over the Weddell Sea, we observed air temperature anomalies reaching up to 8°C and sea surface temperature anomalies of up to 3°C from May to July. Similar temperature anomalies were recorded over the Ross Sea, particularly in July and August. A change point analysis indicates that a regime shift in the Antarctic Sea ice, as well as in the average mean air temperature and (sub)surface ocean temperature over the Weddell Sea, started around 2015. The low sea ice extent in Antarctica in 2023 was a stark reminder of the ongoing changes in the polar regions. Thus, understanding the underlying mechanisms of these extreme events provides crucial insights into the changing dynamics of Antarctic Sea ice and its broader climatic significance. [ABSTRACT FROM AUTHOR]

The ERA5 climate reanalysis dataset plays an important role in applications such as monitoring and modeling climate system changes in polar regions, so the calibration of the reanalysis to ground observations is of great relevance. Here, we compare the 2 m air temperature time series of the ERA5 reanalysis and the near-surface bias-corrected reanalysis to the near-ground air temperature measured at 17 automatic weather stations (AWSs) in the McMurdo Dry Valleys, Antarctica. We find that the reanalysis data have biases that change with the season of the year and do not clearly correlate with elevation. Our results show that future work should rely on secondary observations to calibrate when using the ERA5 reanalysis in polar regions. [ABSTRACT FROM AUTHOR]

We simulated the seasonal temperature evolution in the atmosphere of Antarctica and the Arctic focusing on infrared processes. Contributions by other processes were parametrized and kept fixed throughout the simulations. The model was run for current CO2 and CH4 and for doubled concentrations. For doubling CH4 the warming in Antarctica is restricted to the lowest few hundred meters above the surface while in the Arctic we find a warming in the whole troposphere. We find that the amount of water is the main driver for the differences between both polar regions. When increasing both, CO2 and CH4 from pre‐industrial values to current concentrations, and averaged over the whole troposphere, we find a warming of 0.42 K for the Arctic and a slight cooling of 0.01 K for Antarctica. Our results contribute to the understanding of the lack of warming seen in Antarctica throughout the last decades. Plain Language Summary: In 2015 we have initiated a discussion on a fundamental property of the radiation in the atmosphere over Antarctica: The negative greenhouse effect (Schmithüsen et al., 2015, https://doi.org/10.1002/2015GL066749). A negative greenhouse effect means, the atmosphere emits more radiation to space than it receives from the surface. This results in a cooling somewhere in the Antarctic atmosphere during some months of the year, when increasing CO2. We now simulate how the Antarctic atmospheric temperature responds in all altitude levels to CO2 and CH4 increases, and show this is different from the temperature response in the Arctic. We show for example, that an increase in CH4 cools nearly the whole troposphere, although the response for CH4 is much lower in amplitude than for CO2. We find that the amount of water is the main driver for the differences between both polar regions. Since the amount of water vapor strongly depends on temperature, the colder Antarctic atmosphere responds differently to the Arctic when greenhouse gases increase. Our studies could be one important factor when understanding the lack of warming in Antarctica throughout the last decades. Key Points: We simulate the temperature development in both polar regions in the infrared and find that doubling CO2 and CH4 lead to opposing forcingsThe different amount of water vapor shows to be responsible for the differences in warming/cooling in both polar regionsIn Antarctica doubling CH4 leads to a cooling of almost the whole troposphere, a future increase in H2O could invert this [ABSTRACT FROM AUTHOR]

The results of sensing of East Antarctica and the adjoining areas of the Southern Ocean by MTVZA-GYа microwave satellite radiometers at frequency ν = 10–190 GHz and AMSR2 at ν = 6–89 GHz in conditions of warm and humid air (an atmospheric river (AR)) invasion from the area of Tasmania area in March 2022 are presented. The surface air warming caused by AR was recorded by the Automatic Weather Station at the coast and at the Vostok, Concordia, and Dome CII stations in East Antarctica. The variability of atmospheric characteristics above Antarctica was studied using readings of radiosondes launched from the Casey station at the coast and Concordia station at a height of 3230 m and time series of brightness temperatures averaged over a circular area 200 km in diameter with the center at a distance of ~200 km from the Concordia station. The influence of air and surface temperature and atmospheric water-vapor content variations on brightness temperature Tb(ν) variations was estimated from the results of modeling of microwave radiation transfer in the atmosphere–firn system using radiosonde profiles from the Concordia station. It was shown that the increase in Tb(ν) at frequencies of 89–92 GHz of a large part of East Antarctica was caused mainly by an increase in the firn temperature. The increase at frequencies of ∼176–190 GHz in the area of the water vapor absorption line was caused by an increase of both the firn temperature and air temperature and humidity. Based on measurements of brightness temperature Tb(ν) over the open ocean at frequencies in the atmospheric-transparency windows of ∼6–48 and 88–92 GHz, wind speed W, cloud liquid-water content Q, and atmospheric water-vapor content V were determined and the temporal variability of parameters in the AR area was studied. [ABSTRACT FROM AUTHOR]

The Greenland Climate Network (GC-Net) consists of 31 automatic weather stations (AWSs) at 30 sites across the Greenland Ice Sheet. The first site was initiated in 1990, and the project has operated almost continuously since 1995 under the leadership of the late Konrad Steffen. The GC-Net AWS measured air temperature, relative humidity, wind speed, atmospheric pressure, downward and reflected shortwave irradiance, net radiation, and ice and firn temperatures. The majority of the GC-Net sites were located in the ice sheet accumulation area (17 AWSs), while 11 AWSs were located in the ablation area, and two sites (three AWSs) were located close to the equilibrium line altitude. Additionally, three AWSs of similar design to the GC-Net AWS were installed by Konrad Steffen's team on the Larsen C ice shelf, Antarctica. After more than 3 decades of operation, the GC-Net AWSs are being decommissioned and replaced by new AWSs operated by the Geological Survey of Denmark and Greenland (GEUS). Therefore, making a reassessment of the historical GC-Net AWS data is necessary. We present a full reprocessing of the historical GC-Net AWS dataset with increased attention to the filtering of erroneous measurements, data correction and derivation of additional variables: continuous surface height, instrument heights, surface albedo, turbulent heat fluxes, and 10 m ice and firn temperatures. This new augmented GC-Net level-1 (L1) AWS dataset is now available at 10.22008/FK2/VVXGUT (Steffen et al., 2023) and will continue to be refined. The processing scripts, latest data and a data user forum are available at https://github.com/GEUS-Glaciology-and-Climate/GC-Net-level-1-data-processing (last access: 30 November 2023). In addition to the AWS data, a comprehensive compilation of valuable metadata is provided: maintenance reports, yearly pictures of the stations and the station positions through time. This unique dataset provides more than 320 station years of high-quality atmospheric data and is available following FAIR (findable, accessible, interoperable, reusable) data and code practices. [ABSTRACT FROM AUTHOR]

Cloud remains one of the largest uncertainties in weather and climate research due to the lack of fine-resolution observations of cloud vertical structure (CVS) on a large scale. In this study, near-global CVS is characterized by high-vertical-resolution twice-daily radiosonde observations from 374 stations over land, which are distributed in Europe, North America, East Asia, Australia, the Pacific Ocean, and Antarctica. To this end, we initially develop a novel method to determine CVS, by combining both the vertical gradients of air temperature and relative humidity (RH) and the altitude-dependent thresholds of RH. It is found that the cloud base heights (CBHs) from radiosondes have a higher correlation coefficient (R= 0.91) with the CBHs from a millimeter-wave cloud radar than those from the ERA5 reanalysis (R= 0.49). Overall, cloudy skies occur 65.3 % (69.5 %) of the time, of which 55.4 % (53.8 %) are one-layer clouds at 00:00 (12:00) UTC. Most multi-layer clouds are two-layer clouds, accounting for 62.2 % (61.1 %) among multi-layer clouds at 00:00 (12:00) UTC. Geographically, one-layer clouds tend to occur over arid regions, whereas two-layer clouds do not show any clear spatial preference. The cloud bases and tops over arid regions are higher compared with humid regions albeit with smaller cloud thickness (CT). Clouds tend to have lower bases and thinner layer thicknesses as the number of cloud layer increases. The global-mean CT, CBH, and cloud top height (CTH) are 4.89 ± 1.36 (5.37 ± 1.58), 3.15 ± 1.15 (3.07 ± 1.06), and 8.04 ± 1.60 (8.44 ± 1.52) km above ground level (a.g.l.) at 00:00 (12:00) UTC, respectively. The occurrence frequency of clouds is bimodal, with lower peaks between 0.5 and 3 km a.g.l. and upper peaks between 6 and 10 km a.g.l. The CBH, CTH, and CT undergo almost the same seasonality; namely, their magnitudes in boreal summer are greater than in boreal winter. As expected, the occurrence frequencies of clouds exhibit pronounced diurnal cycles in different seasons. In boreal summer, clouds tend to form as the sun rises and the occurrence frequencies increase from morning to late afternoon, with the peak in the early afternoon at the altitude of 6–12 km a.g.l., while in boreal winter, clouds have peak occurrence frequencies in the morning. The relations between surface meteorological variables and moisture with CBH are investigated as well, showing that CBHs are generally more significantly correlated with 2 m relative humidity (RH2m) and 2 m air temperature (T2m) than with surface pressure and 10 m wind speed. Larger T2m and smaller RH2m always correspond to higher CBH. In most cases CBHs are negatively correlated to soil water content. The near-global CVS obtained from high-vertical-resolution radiosondes in this study can provide key data support for improving the accuracy of cloud radiative forcing simulation in climate models. [ABSTRACT FROM AUTHOR]

Knowledge about local air temperature variations and extremes in Antarctica is of large interest to many polar disciplines such as climatology, glaciology, hydrology, and ecology and it is a key variable to understand climate change. Due to the remote and harsh conditions of Antarctica's environment, the distribution of air temperature observations from Automatic Weather Stations is notably sparse across the region. Previous studies have shown that satellite-derived land and ice surface temperatures can be used as a suitable proxy for air temperature. Here, we developed a daily near-surface air temperature dataset, AntAir ICE for terrestrial Antarctica and the surrounding ice shelves by modelling air temperature from MODIS skin temperature for the period 2003 to 2021 using a linear model. AntAir ICE has a daily temporal resolution and a gridded spatial resolution of 1 km2. AntAir ICE has a higher accuracy in reproducing in-situ measured air temperature when compared with the well-established climate re-analysis model ERA5 and a higher spatial resolution which highlights its potential for monitoring temperature patterns in Antarctica. [ABSTRACT FROM AUTHOR]

The annular structure of Antarctic oscillation (AAO) is a research hotpot, but its asymmetry receives less attention. In this paper, the self‐organizing map method is employed to cluster the AAO patterns into symmetric and asymmetric modes in austral autumn. The asymmetry is mainly reflected in the Pacific‐Atlantic sector, and the AAO evolves toward asymmetric positive polarity, with the most pronounced asymmetry in May. Originating from near Australia, the asymmetry indicates a zonal wave train in the Pacific‐Atlantic sector. Both modeled and observed results demonstrate that the sea surface temperature anomaly in the equatorial western Pacific stimulates a local meridional circulation anomaly and induces anomalous Rossby wave sources near Australia subsequently. An anomalous wave train propagating toward the Antarctic Peninsula is formed, and the associated geopotential anomaly enhances the asymmetry of AAO. Asymmetric AAO is conducive to the Antarctic dipole, which modulates the air temperature and sea ice anomalies around Antarctica. Plain Language Summary: The zonal symmetry of the Antarctic oscillation (AAO; also named southern annular mode) is well known to researchers, while the zonal asymmetry has received less attention. We use a clustering method to cluster the AAO modes in austral autumn into symmetric modes and asymmetric modes. The asymmetry of AAO is mainly reflected in the Pacific‐Atlantic sector. The results show that the AAO mode evolves to a positive asymmetric mode, and the asymmetry is most obvious in May. Both simulations and observations suggest that this asymmetry stems from sea surface temperature anomaly in the equatorial western Pacific that stimulates an anomalous local meridional circulation near Australia, and in turn triggers an anomalous wave train propagating toward the Antarctic Peninsula. The associated geopotential anomalies enhance the asymmetry of AAO. The asymmetric AAO favors the Antarctic dipole, regulating the air temperature and sea ice anomalies around Antarctica. Key Points: Via a cluster method, we obtained the zonal asymmetric Antarctic oscillation (AAO) mode, and analyzed its trend and preferred monthThe source of its asymmetry is from the sea surface temperature anomaly in the tropical western PacificThe asymmetric AAO mode has a vital influence on the Antarctic dipole [ABSTRACT FROM AUTHOR]

During the second half of the twentieth century, the Antarctic Surface Air Temperature (SAT) trends are characterized by fast warming over West Antarctica but mild cooling over East Antarctica. However, after 2000, the warming over several stations in the Antarctic Peninsula slowed down, whereas the South Pole experienced fast warming. These reversed SAT trends show strong regionality and seasonality, together with large uncertainty and disagreement among different observational and reanalysis datasets, which makes it difficult to achieve a comprehensive understanding of the multi-decadal Antarctic SAT trend and its reversal. In this study, we use the Combined Maximum Covariance Analysis (CMCA) method to extract the most coherent modes of the Antarctic SAT trends among six reanalysis datasets and 26 station-based observations. Further analysis shows that the reversals of the SAT trends before and after 2000, especially for austral spring and summer, are mainly attributed to the reversed trends of the leading CMCA modes and their related atmospheric circulation and thermal advection patterns over Antarctica. For austral spring, the reversal of the west-warming-east-cooling pattern over Antarctica is closely related to the changes of thermal advection induced by the anomalous circulation center over the Antarctic Peninsula–Weddell Sea region. For summer, the post-2000 reversal of the Antarctic Peninsula-warming-East Antarctic-cooling is attributed to the stratospheric ozone recovery over the Antarctic, and the associated adjustment of the southern annular mode. The CMCA decomposition better combines the information from different measurements, clarifying the long-term SAT trend and its reversal for different seasons. [ABSTRACT FROM AUTHOR]

We introduce Version 2 of our widely used 1-km Köppen-Geiger climate classification maps for historical and future climate conditions. The historical maps (encompassing 1901–1930, 1931–1960, 1961–1990, and 1991–2020) are based on high-resolution, observation-based climatologies, while the future maps (encompassing 2041–2070 and 2071–2099) are based on downscaled and bias-corrected climate projections for seven shared socio-economic pathways (SSPs). We evaluated 67 climate models from the Coupled Model Intercomparison Project phase 6 (CMIP6) and kept a subset of 42 with the most plausible CO2-induced warming rates. We estimate that from 1901–1930 to 1991–2020, approximately 5% of the global land surface (excluding Antarctica) transitioned to a different major Köppen-Geiger class. Furthermore, we project that from 1991–2020 to 2071–2099, 5% of the land surface will transition to a different major class under the low-emissions SSP1-2.6 scenario, 8% under the middle-of-the-road SSP2-4.5 scenario, and 13% under the high-emissions SSP5-8.5 scenario. The Köppen-Geiger maps, along with associated confidence estimates, underlying monthly air temperature and precipitation data, and sensitivity metrics for the CMIP6 models, can be accessed at www.gloh2o.org/koppen. [ABSTRACT FROM AUTHOR]

This study examines the process of water-column stratification breakdown in Antarctic coastal polynyas adjacent to an ice shelf with a cavity underneath. This first part of a two-part sequence seeks to quantify the influence of offshore katabatic winds, alongshore winds, air temperature, and initial ambient stratification on the time scales of polynya destratification through combining process-oriented numerical simulations and analytical scaling. In particular, the often-neglected influence of wind-driven circulation on the lateral transport of the water formed at the polynya surface—which we call Polynya Source Water (PSW)—is systematically examined here. First, an ice shelf–sea ice–ocean coupled numerical model is adapted to simulate the process of PSW formation in polynyas of various configurations. The simulations highlight that (i) before reaching the bottom, majority of the PSW is actually carried away from the polynya by katabatic wind–induced offshore outflow, diminishing water-column mixing in the polynya and intrusion of the PSW into the neighboring ice shelf cavity, and (ii) alongshore coastal easterly winds, through inducing onshore Ekman transport, reduce offshore loss of the PSW and enhance polynya mixing and PSW intrusion into the cavity. Second, an analytical scaling of the destratification time scale is derived based on fundamental physical principles to quantitatively synthesize the influence of the physical factors, which is then verified by independent numerical sensitivity simulations. This work provides insights into the mechanisms that drive temporal and cross-polynya variations in stratification and PSW formation in Antarctic coastal polynyas, and establishes a framework for studying differences among the polynyas in the ocean. [ABSTRACT FROM AUTHOR]

Antarctic firn presents an exotic seismological environment in which the behaviors of propagating waves can be significantly at odds with those in other Earth media. We present a condensed view of the nascent field of ambient noise seismology in Antarctic firn-covered media, and highlight multiple unusual and information-rich observations framed through the lens of the firn's important role as a buffer for air temperature anomalies and a complex contributor to ice mass balance. We summarize key results from several recent papers depicting novel wind-excited firn resonances and point to the plethora of ways these observations could facilitate imaging and monitoring of glacial systems at single, isolated seismometers. Finally, we propose significant instrumental and computational objectives necessary to constrain resonance excitation mechanisms and broadly apply these observations as useful monitoring tools in Antarctica. [ABSTRACT FROM AUTHOR]

Numerical simulations employing prognostic stable water isotopes can not only facilitate our understanding of hydrological processes and climate change but also allow for a direct comparison between isotope signals obtained from models and various archives. In the current work, we describe the performance and explore the potential of a new version of the Earth system model AWI-ESM (Alfred Wegener Institute Earth System Model), labeled AWI-ESM-2.1-wiso, in which we incorporated three isotope tracers into all relevant components of the water cycle. We present here the results of pre-industrial (PI) and mid-Holocene (MH) simulations. The model reproduces the observed PI isotope compositions in both precipitation and seawater well and captures their major differences from the MH conditions. The simulated relationship between the isotope composition in precipitation (δ18 O p) and surface air temperature is very similar between the PI and MH conditions, and it is largely consistent with modern observations despite some regional model biases. The ratio of the MH–PI difference in δ18 O p to the MH–PI difference in surface air temperature is comparable to proxy records over Greenland and Antarctica only when summertime air temperature is considered. An amount effect is evident over the North African monsoon domain, where a negative correlation between δ18 O p and the amount of precipitation is simulated. As an example of model applications, we studied the onset and withdrawal date of the MH West African summer monsoon (WASM) using daily variables. We find that defining the WASM onset based on precipitation alone may yield erroneous results due to the substantial daily variations in precipitation, which may obscure the distinction between pre-monsoon and monsoon seasons. Combining precipitation and isotope indicators, we suggest in this work a novel method for identifying the commencement of the WASM. Moreover, we do not find an obvious difference between the MH and PI periods in terms of the mean onset of the WASM. However, an advancement in the WASM withdrawal is found in the MH compared to the PI period due to an earlier decline in insolation over the northern location of Intertropical Convergence Zone (ITCZ). [ABSTRACT FROM AUTHOR]

Using data from three automatic weather stations (LGB69, Eagle and Dome A) from distinctly different climatological zones along the CHINARE (Chinese National Antarctic Research Expedition) traverse route from Zhongshan Station to Dome A, we investigated the characteristics of meteorological conditions and subsurface heat conduction. Spatial analysis indicated decreasing trends in air temperature, relative humidity and wind speed from the coastal katabatic wind zone to the inland plateau region, and air temperatures clearly showed a strong daily variability in winter, suggesting the effect from the fluctuation in the Antarctic atmospheric system. We also analyzed the optimal response time of the 1 and 3 m depth snow temperatures to the 0.1 m depth snow temperature for each site under clear/overcast and day/night situations. This showed an important enhancement to the heat transfer from shortwave radiation penetration. Using an iterative optimization method, we estimated the subsurface heat conduction variations along the transect. This was ~3–5 W m–2. Multiple maxima in daily mean subsurface fluxes were found in winter, with a typical value above 2 W m–2, while a single minimum value under –2 W m–2 was found in summer. On an annual scale, a larger mean loss of subsurface heat conduction was observed in the inland plateau compared to in the coastal katabatic area. Finally, we discussed the possible influences of turbulent and radiant transport on the vertical heat response and confirmed the wind enhancement on the growth of thermal conductivity. This preliminary study provides a brief perspective and an important reference for studying subsurface heat conduction in inland areas of Antarctica. [ABSTRACT FROM AUTHOR]

Warming has been and is being enhanced at high latitudes or high elevations, whereas the quantitative estimation for warming from altitude and latitude effects has not been systematically investigated over Antarctic Ice Sheet, which covers more than 27 degrees of latitude and 4000 m altitude ranges. Based on the monthly surface air temperature data (1958–2020) from ERA5 reanalysis, this work aims to explore whether elevation-dependent warming (EDW) and latitude-dependent warming (LDW) exist. Results show that both EDW and LDW have the cooperative effect on Antarctic warming, and the magnitude of EDW is stronger than LDW. The negative EDW appears between 250 m and 2500 m except winter, and is strongest in autumn. The negative LDW occurs between 83 °S and 90 °S except in summer. Moreover, the surface downward long-wave radiation that related to the specific humidity, total cloud cover and cloud base height is a major contributor to the EDW over Antarctica. Further research on EDW and LDW should be anticipated to explore the future Antarctic amplification under different emission scenarios. [ABSTRACT FROM AUTHOR]

Increasing temperatures in Antarctica have resulted in the enlargement of proglacial regions on the Antarctic Peninsula, following glacier melt. This melt has increased river activity yet direct runoff measurements remain scarce in Antarctica, despite it acting as a proxy for glacial ablation. Here, we present discharge and water temperature data from 2013 for three streams on Vega Island and discuss their relationship with air temperature. The average discharge at the largest stream was 0.523 m3s−1 with a maximum of 5.510 m3s−1 – among the highest recorded in Antarctica. The rivers continued to flow even when temperatures dropped to −7°C, indicating that a large proportion of the total runoff originated sub-glacially. This is supported by the one-day time lag between air and water temperatures. Using river discharge as a proxy, we measured 124.5 ± 14.4 mm w.e. of ablation. This indirect measurement proved an effective tool to complement classic glaciological observations. [ABSTRACT FROM AUTHOR]

West Antarctica exhibits a pronounced sea ice variability in interannual timescale, and 20%–30% of the total variance can be explained by the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) during austral spring. The sea ice variation is primarily linked with anomalous atmospheric circulation in the Amundsen‐Bellingshausen Sea (ABS) that modulates poleward atmospheric temperature advection and radiative forcing. With a co‐varying relationship between ENSO and IOD, isolating their remote impacts on Antarctica has been limited in observations. An idealized experiment using the atmospheric model with a dry dynamical core suggests that the anticyclonic circulation anomaly in the ABS is primarily contributed by the ENSO in the Pacific Ocean, while the contribution of the IOD in the Indian Ocean is only one‐third large. This study implies that atmospheric teleconnection through the southern Pacific Ocean is crucial for understanding the West Antarctic sea ice concentration variability. Plain Language Summary: Antarctic sea ice, which affects the Earth's climate system, has gained considerable attention in recent years. Previous studies have shown that the El Nino‐Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) in the tropics affect the sea ice variation in West Antarctica through atmospheric teleconnections at interannual timescale. Unfortunately, due to the high positive correlation between these two climate modes, it is unclear how each phenomenon contributes to the West Antarctic sea ice variation. Therefore, this study investigates the underlying mechanisms related to the sea ice changes caused by ENSO and IOD during austral spring and quantifies the effect of each phenomenon on the West Antarctic sea ice through an idealized model experiment. It is found that the ENSO and the IOD account for 20%–30% of sea ice variance during austral spring, which is primarily contributed by the dynamic and thermodynamic mechanisms associated with atmospheric circulation in the Amundsen‐Bellingshausen Sea (ABS). In addition, we confirm through the model experiments that the effect of ENSO in the Pacific Ocean on the atmospheric circulation patterns of ABS is about three times stronger than that of IOD in the Indian Ocean. Key Points: El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) account for 20%–30% of the variability in total sea ice concentration in austral springThe tropical variability affects circulation anomalies in the Amundsen‐Bellingshausen Sea, leading to sea ice variations in West AntarcticaAn idealized atmospheric model experiment suggests the ENSO effect on the West Antarctic circulation is much stronger than the IOD [ABSTRACT FROM AUTHOR]

Numerical simulations employing prognostic stable water isotopes can not only facilitate our understanding of hydrological processes and climate change but also allow for a straightforward comparison between isotope signals obtained from models and various archives. In the current work, we describe the performance and explore the potential of a new version of the Earth system model AWI-ESM, labeled AWI-ESM-wiso, in which we incorporated three isotope tracers into all relevant components of the water cycle. We present here the results of pre-industrial (PI) and mid-Holocene (MH) simulations. The model well reproduces the observed PI isotope compositions in both precipitation and sea water, and captures their major differences from the MH condition. The simulated relationship between the isotope composition in precipitation (δ18Op) and surface air temperature is very similar between the PI and MH conditions, and largely consistent with modern observations despite some regional model biases. The ratio of the MH-PI difference in δ18Op to the MH-PI difference in surface air temperature is reasonable over Greenland and Antarctica only when summertime air temperature is considered. An amount effect is evident over the North Africa monsoon domain, where a negative correlation between δ18Op and the amount of precipitation is simulated. As an example of model applications, we studied the onset date of MH West Africa summer monsoon (WASM) using daily variables. We find that defining the WASM onset based on precipitation alone may yield erroneous results due to the substantial daily variations of precipitation, which may obscure the distinction between pre-monsoon and monsoon seasons. Combining precipitation and isotope indicators, we suggest in this work a novel method for identifying the commencement of the WASM. Moreover, we do not find obvious difference between the MH and PI in terms of the mean onset date of WASM. [ABSTRACT FROM AUTHOR]

We calculate a regional surface "melt potential" index (MPI) over Antarctic ice shelves that describes the frequency (MPI-freq; %) and intensity (MPI-int; K) of daily maximum summer temperatures exceeding a melt threshold of 273.15 K. This is used to determine which ice shelves are vulnerable to melt-induced hydrofracture and is calculated using near-surface temperature output for each summer from 1979/80 to 2018/19 from two high-resolution regional atmospheric model hindcasts (using the MetUM and HIRHAM5). MPI is highest for Antarctic Peninsula ice shelves (MPI-freq 23%-35%, MPI-int 1.2-2.1 K), lowest (2%-3%, 0 K) for the Ronne-Filchner and Ross ice shelves, and around 10%-24% and 0.6-1.7 K for the other West and East Antarctic ice shelves. Hotspots of MPI are apparent over many ice shelves, and they also show a decreasing trend in MPI-freq. The regional circulation patterns associated with high MPI values over West and East Antarctic ice shelves are remarkably consistent for their respective region but tied to different large-scale climate forcings. The West Antarctic circulation resembles the central Pacific El Niño pattern with a stationary Rossby wave and a strong anticyclone over the high-latitude South Pacific. By contrast, the East Antarctic circulation comprises a zonally symmetric negative Southern Annular Mode pattern with a strong regional anticyclone on the plateau and enhanced coastal easterlies/weakened Southern Ocean westerlies. Values of MPI are 3-4 times larger for a lower temperature/melt threshold of 271.15 K used in a sensitivity test, as melting can occur at temperatures lower than 273.15 K depending on snowpack properties. [ABSTRACT FROM AUTHOR]

Coastal polynyas around the Antarctic continent are regions of very strong ocean–atmosphere heat and moisture exchange that are important for local and regional weather, sea ice production, and water mass formation. Due to extreme atmospheric conditions (very strong offshore winds, low air temperature, as well as humidity) the surface ocean layer in polynyas is highly turbulent, with mixing due to combined Langmuir, wind-induced, and buoyancy-driven turbulence. One of the visible signs of complex interactions between the mixed-layer dynamics and the forming sea ice are frazil streaks, elongated patches of high ice concentration separated by areas of open water. In spite of their ubiquity, observational and modelling analyses of frazil streaks have been very limited largely due to the fact that their significance for heat flux and ice production is only just becoming apparent. In this study, the first comprehensive analysis of the spatial variability of surface frazil concentration is performed for the Terra Nova Bay Polynya (TNBP). Frazil streaks are identified in high-resolution (pixel size 10–15 m) visible satellite imagery, and their properties (surface area, width, spacing, and orientation) are linked to the meteorological forcing (wind speed and air temperature). This provides a simple statistical tool for estimating the extent and ice coverage of the region of high ice production under given meteorological conditions. It is also shown that the orientation of narrow streaks tends to agree with the wind direction, suggesting the dominating role of the local wind forcing in their formation. Very wide streaks, in turn, deviate from that pattern, as they are presumably influenced by several additional factors, including local water circulation and the associated convergence zones. An analysis of peak wavelengths and directions determined from the images, compared to analogous open-water wavelengths computed with a spectral wave model, demonstrates a significant slow-down in the observed wave growth in TNBP. This suggests an important role of frazil streaks in modifying wind-wave growth and/or dissipation in polynyas. [ABSTRACT FROM AUTHOR]

The reconstruction of past sea-ice distribution in the Southern Ocean is crucial for an improved understanding of ice–ocean–atmosphere feedbacks and the evaluation of Earth system and Antarctic ice sheet models. The Antarctic Peninsula (AP) has been experiencing a warming since the start of regular monitoring of the atmospheric temperature in the 1950s. The associated decrease in sea-ice cover contrasts the trend of growing sea-ice extent in East Antarctica. To reveal the long-term sea-ice history at the northern Antarctic Peninsula (NAP) under changing climate conditions, we examined a marine sediment core from the eastern basin of the Bransfield Strait covering the last Deglacial and the Holocene. For sea-ice reconstructions, we focused on the specific sea-ice biomarker lipid IPSO 25 , a highly branched isoprenoid (HBI), and sea-ice diatoms, whereas a phytoplankton-derived HBI triene (C 25:3) and warmer open-ocean diatom assemblages reflect predominantly ice-free conditions. We further reconstruct ocean temperatures using glycerol dialkyl glycerol tetraethers (GDGTs) and diatom assemblages and compare our sea-ice and temperature records with published marine sediment and ice core data. A maximum ice cover is observed during the Antarctic Cold Reversal 13 800–13 000 years before present (13.8–13 ka), while seasonally ice-free conditions permitting (summer) phytoplankton productivity are reconstructed for the late Deglacial and the Early Holocene from 13 to 8.3 ka. An overall decreasing sea-ice trend throughout the Middle Holocene coincides with summer ocean warming and increasing phytoplankton productivity. The Late Holocene is characterized by highly variable winter sea-ice concentrations and a sustained decline in the duration and/or concentration of spring sea ice. Overall diverging trends in GDGT-based TEX 86L and RI-OH' subsurface ocean temperatures (SOTs) are found to be linked to opposing spring and summer insolation trends, respectively. [ABSTRACT FROM AUTHOR]

In coastal West Antarctic Peninsula (WAP) waters, large phytoplankton blooms in late austral spring fuel a highly productive marine ecosystem. However, WAP atmospheric and oceanic temperatures are rising, winter sea ice extent and duration are decreasing, and summer phytoplankton biomass in the northern WAP has decreased and shifted toward smaller cells. To better understand these relationships, an Imaging FlowCytobot was used to characterize seasonal (spring to autumn) phytoplankton community composition and cell size during a low (2017–2018) and high (2018–2019) chlorophyll a year in relation to physical drivers (e.g., sea ice and meteoric water) at Palmer Station, Antarctica. A shorter sea ice season with early rapid retreat resulted in low phytoplankton biomass with a low proportion of diatoms (2017–2018), while a longer sea ice season with late protracted retreat resulted in the opposite (2018–2019). Despite these differences, phytoplankton seasonal succession was similar in both years: (1) a large‐celled centric diatom bloom during spring sea ice retreat; (2) a peak summer phase comprised of mixotrophic cryptophytes with increases in light and postbloom organic matter; and (3) a late summer phase comprised of small (< 20 μm) diatoms and mixed flagellates with increases in wind‐driven nutrient resuspension. In addition, cell diameter decreased from November to April with increases in meteoric water in both years. The tight coupling between sea ice, meltwater, and phytoplankton species composition suggests that continued warming in the WAP will affect phytoplankton seasonal dynamics, and subsequently seasonal food web dynamics. [ABSTRACT FROM AUTHOR]

Antarctic surface air temperature (SAT) variability is characterized by strong seasonality and regionality, which are associated with the tropical–polar teleconnections and the radiative forcing caused by the concentration changes in ozone and other greenhouse gases. Nevertheless, the sparse in situ observations and the strong disagreement between different reanalysis datasets hinder coherent conclusions about Antarctic SAT variability. In this study, we use a newly developed statistical method, combined maximum covariance analysis (CMCA), to retrieve coherent SAT modes from six reanalysis datasets and 26 station observations. The results show that the Antarctic SAT variability may be dominated by a continental-wide warming/cooling mode, an East–West Antarctic seesaw mode, and a dipole SAT mode around West Antarctica. These SAT modes are strongly associated with three principal modes of Antarctic atmospheric circulation. Furthermore, all six reanalyses can represent these SAT modes well, compared with the observations, despite a clear deviation over the Antarctic Peninsula associated with the biases in the Foehn wind, which may not be clearly reproduced in a low-resolution reanalysis. This study provides an effective means by which to extract coherent signals from all reanalyses and observations to represent the Antarctic SAT variability, and to improve its predictability and projection. [ABSTRACT FROM AUTHOR]

Based on the analysis of the frequency of anomalous anatomical structures in the wood of Siberian larch and Siberian spruce (frost rings, light rings, and false rings, as well as missing and narrow rings), we reconstructed a timeline of climatic extremes (summer frosts, sharp multiday decreases in air temperature during the growing season, and low average summer temperatures) in Yamal (Western Siberia) over the last 4500 years. In total, 229 years were determined to have experienced extreme events. The most significant temperature extremes were recorded in 2053, 1935, 1647, 1626, 1553, 1538, 1410, 1401, 982, 919, 883 BCE, 143, 404, 543, 640, 1209, 1440, 1453, 1466, 1481, 1601 and 1818 CE. These dates with extrema observed in Yamal corrobarated with tree ring data from other regions and revealed several coincidences. That is, in these years, the observed extremes appeared to have been on a global rather than a regional scale. Moreover, these dates coincided with traces of large volcanic eruptions found in ice cores from Greenland and Antarctica, dated to approximately the same years. Therefore, the cause of the extreme summer cooling on a global scale, in most cases, can be linked to large volcanic eruptions. [ABSTRACT FROM AUTHOR]

Climate during the last glacial period was marked by abrupt instability on millennial timescales that included large swings of temperature in and around Greenland (Daansgard–Oeschger events) and smaller, more gradual changes in Antarctica (AIM events). Less is known about the existence and nature of similar variability during older glacial periods, especially during the early Pleistocene when glacial cycles were dominantly occurring at 41 kyr intervals compared to the much longer and deeper glaciations of the more recent period. Here, we report a continuous millennially resolved record of stable isotopes of planktic and benthic foraminifera at IODP Site U1385 (the "Shackleton Site") from the southwestern Iberian margin for the last 1.5 million years, which includes the Middle Pleistocene Transition (MPT). Our results demonstrate that millennial climate variability (MCV) was a persistent feature of glacial climate, both before and after the MPT. Prior to 1.2 Ma in the early Pleistocene, the amplitude of MCV was modulated by the 41 kyr obliquity cycle and increased when axial tilt dropped below 23.5 ∘ and benthic δ18O exceeded ∼3.8 ‰ (corrected to Uvigerina), indicating a threshold response to orbital forcing. Afterwards, MCV became focused mainly on the transitions into and out of glacial states (i.e. inceptions and terminations) and during times of intermediate ice volume. After 1.2 Ma, obliquity continued to play a role in modulating the amplitude of MCV, especially during times of glacial inceptions, which are always associated with declining obliquity. A non-linear role for obliquity is also indicated by the appearance of multiples (82, 123 kyr) and combination tones (28 kyr) of the 41 kyr cycle. Near the end of the MPT (∼0.65 Ma), obliquity modulation of MCV amplitude wanes as quasi-periodic 100 kyr and precession power increase, coinciding with the growth of oversized ice sheets on North America and the appearance of Heinrich layers in North Atlantic sediments. Whereas the planktic δ18O of Site U1385 shows a strong resemblance to Greenland temperature and atmospheric methane (i.e. Northern Hemisphere climate), millennial changes in benthic δ18O closely follow the temperature history of Antarctica for the past 800 kyr. The phasing of millennial planktic and benthic δ18O variation is similar to that observed for MIS 3 throughout much of the record, which has been suggested to mimic the signature of the bipolar seesaw – i.e. an interhemispheric asymmetry between the timing of cooling in Antarctica and warming in Greenland. The Iberian margin isotopic record suggests that bipolar asymmetry was a robust feature of interhemispheric glacial climate variations for at least the past 1.5 Ma despite changing glacial boundary conditions. A strong correlation exists between millennial increases in planktic δ18O (cooling) and decreases in benthic δ13C , indicating that millennial variations in North Atlantic surface temperature are mirrored by changes in deep-water circulation and remineralization of carbon in the abyssal ocean. We find strong evidence that climate variability on millennial and orbital scales is coupled across different timescales and interacts in both directions, which may be important for linking internal climate dynamics and external astronomical forcing. [ABSTRACT FROM AUTHOR]

Polar amplification has been a research focus in climate research in recent decades. However, little attention has been paid to Antarctic amplification (AnA). We have examined the variations in annual and seasonal temperature over the Antarctic Ice Sheet and its amplification based on reconstruction covering the period 2002–2018. The results show the occurrence of annual and seasonal AnA, with an AnA index greater than 1.39 with seasonal differences, and that AnA is strong in the austral winter and spring. Moreover, AnA displays regional differences, with the greatest amplification occurring in East Antarctica, with an AnA index greater than 1.51, followed by West Antarctica. AnA is always absent in the Antarctic Peninsula. In addition, amplification in East Antarctica is most conspicuous in spring, which corresponds to the obvious warming in this season; and the spring amplification signal is weakest for West Antarctica. When considering the influence of the ocean, the AnA becomes obvious, compared to when only the land is considered. Southern Annular Mode (SAM), surface pressure and westerlies work together to affect the temperature change over Antarctica and AnA; and SAM and surface pressure are highly correlated with the temperature change over East Antarctica. The picture reflects the accelerated changes in Antarctic temperature. [ABSTRACT FROM AUTHOR]

The Eocene‐Oligocene transition (EOT) marks the shift from greenhouse to icehouse conditions at 34 Ma, when a permanent ice sheet developed on Antarctica. Climate modeling studies have recently assessed the drivers of the transition globally. Here we revisit those experiments for a detailed study of the southern high latitudes in comparison to the growing number of mean annual sea surface temperature (SST) and mean air temperature (MAT) proxy reconstructions, allowing us to assess proxy‐model temperature agreement and refine estimates for the magnitude of the pCO2 forcing of the EOT. We compile and update published proxy temperature records on and around Antarctica for the late Eocene (38–34 Ma) and early Oligocene (34–30 Ma). Compiled SST proxies cool by up to 3°C and MAT by up to 4°C between the timeslices. Proxy data were compared to previous climate model simulations representing pre‐ and post‐EOT, typically forced with a halving of pCO2. We scaled the model outputs to identify the magnitude of pCO2 change needed to drive a commensurate change in temperature to best fit the temperature proxies. The multi‐model ensemble needs a 30 or 33% decrease in pCO2, to best fit MAT or SST proxies respectively. These proxy‐model intercomparisons identify declining pCO2 as the primary forcing of EOT cooling, with a magnitude (200 or 243 ppmv) approaching that of the pCO2 proxies (150 ppmv). However individual model estimates span a decrease of 66–375 ppmv, thus proxy‐model uncertainties are dominated by model divergence. Plain Language Summary: Antarctica was once a continent with little to no ice on it. Around 34 million years ago Antarctica developed its first permanent ice sheet as temperatures cooled. To evaluate how much cooling occurred on and around Antarctica, we compiled evidence from the molecules left behind by ancient organisms, that carry information about temperature, as reported previously in the literature. We then compared the ancient evidence to climate model experiments which allows us to test cause and effect. Cooling is thought to be caused by a drop in carbon dioxide concentrations in the atmosphere, and we tested how much carbon dioxide levels would need to drop to explain the cooling found. Our estimates are similar to independent evidence from marine organisms for carbon dioxide concentrations. Key Points: Air temperatures at the margins of the Antarctic continent dropped by 0°C–4°C across the Eocene‐Oligocene transition (EOT)Southern high latitude sea surface temperatures cooled by 0°C–3°CBest fit to the proxy surface air temperatures from CO2‐only runs suggest a 30% decrease in pCO2 across the EOT [ABSTRACT FROM AUTHOR]

A new meteorological dataset derived from records of Antarctic automatic weather stations (here called the AntAWS dataset) at 3 h, daily and monthly resolutions including quality control information is presented here. This dataset integrates the measurements of air temperature, air pressure, relative humidity, and wind speed and direction from 267 Antarctic AWSs obtained from 1980 to 2021. The AWS spatial distribution remains heterogeneous, with the majority of instruments located in near-coastal areas and only a few inland on the East Antarctic Plateau. Among these 267 AWSs, 63 have been operating for more than 20 years and 27 of them in excess of more than 30 years. Of the five meteorological parameters, the measurements of air temperature have the best continuity and the highest data integrity. The overarching aim of this comprehensive compilation of AWS observations is to make these data easily and widely accessible for efficient use in local, regional and continental studies; it may be accessed at 10.48567/key7-ch19 (Wang et al., 2022). This dataset is invaluable for improved characterization of the surface climatology across the Antarctic continent, to improve our understanding of Antarctic surface snow–atmosphere interactions including precipitation events associated with atmospheric rivers and to evaluate regional climate models or meteorological reanalysis products. [ABSTRACT FROM AUTHOR]

There are nine year-round and 11 seasonal scientific stations in the South Shetland Islands, an area often visited by cruise ships and sailing yachts. Although this is the warmest part of Antarctica, the weather conditions may be demanding for humans. We analysed the variability of biothermal conditions near Henryk Arctowski Station Polish Antarctic Station, on King George Island, during the period 2013–2021, using the wind chill index (WCI), which combines air temperature and wind speed, to determine thermal sensation. WCI values were interpreted using two cold sensation categorisations. Hourly WCI values were assigned to thermal sensation classes that ranged from “comfortable” to “frosty.” The most favourable biothermal conditions occurred from December to February. The “cold” sensation was dominant in all months, its average occurrence frequency ranging from 56.4% (in January) to 84.4% (in July). From November to March, there was no risk of frostbite to uncovered body parts. Such conditions occurred only from April to October, with a frequency of 0.2–6.8%; biothermal conditions were also the most variable in this period. Maximal WCI hourly values show that dangerous weather conditions may occur throughout the day in June and for most of the day from July to September. An abrupt change in biothermal conditions was more often caused by wind speed change than by air temperature change. The most marked WCI changes occurred from April to September, on average five times per year. Our results indicate that biothermal conditions in the vicinity of Arctowski Station are predominantly favourable for outdoor work only if a person wears proper winter clothing. [ABSTRACT FROM AUTHOR]

Early reanalyses are less than optimal for investigating the regional effects of ozone depletion on Southern Hemisphere (SH) high-latitude climate because the availability of satellite sounder data from 1979 significantly improved their accuracy in data sparse regions, leading to a coincident inhomogeneity. To determine whether current reanalyses are better at SH high-latitudes in the pre-satellite era, here we examine the capabilities of the European Centre for Medium-range Weather Forecasts (ECMWF) fifth generation reanalysis (ERA5), the Twentieth Century Reanalysis version 3 (20CRv3), and the Japanese Meteorological Agency (JMA) 55-year reanalysis (JRA-55) to reproduce and help explain the pronounced change in the relationship between the Southern Annular Mode (SAM) and Antarctic near-surface air temperatures (SAT) between 1950 and 1979 (EARLY period) and 1980–2020 (LATE period). We find that ERA5 best reproduces Antarctic SAT in the EARLY period and is also the most homogeneous reanalysis across the EARLY and LATE periods. ERA5 and 20CRv3 provide a good representation of SAM in both periods with JRA-55 only similarly skilful in the LATE period. Nevertheless, all three reanalyses show the marked change in Antarctic SAM-SAT relationships between the two periods. In particular, ERA5 and 20CRv3 demonstrate the observed switch in the sign of the SAM-SAT relationship in the Antarctic Peninsula: analysis of changes in SAM structure and associated meridional wind anomalies reveal that in these reanalyses positive SAM is linked to cold southerly winds during the EARLY period and warm northerly winds in the LATE period, thus providing a simple explanation for the regional SAM-SAT relationship reversal. [ABSTRACT FROM AUTHOR]

There is growing interest in the international scientific community in characterizing climate variability in Antarctica because of the continent's fundamental role in regulating the world's climate. Researchers have intensively studied the Antarctic Peninsula since the warming that began in the mid‐1950s. This was followed by a subsequent cooling period over the last decades. For this paper, using the available data, we analysed the variability in surface air temperatures at five meteorological stations located on King George Island (KGI) (a subantarctic island that is part of the South Shetland Islands); we also investigated the relationships between the air temperatures and large‐scale atmospheric patterns from 1968 to 2019. In this study we found that summer temperatures are above 0°C from December to March and close to melting temperatures (extreme values) in spring and autumn; consequently, a small increase in temperature can have a significant impact on the cryosphere. The statistical analysis of the mean temperatures confirmed a trend toward cooling during the summer and in the mean monthly maximum temperatures over the 1990s at most of the weather stations whose data we analysed. Analysing the teleconnection patterns showed that the Southern Annular Mode (SAM) had strong, direct, and positive correlations during the autumn and less strong connections in spring, winter, and on an annual scale. Furthermore, we observed a lesser influence of El Niño‐Southern Oscillation (ENSO). [ABSTRACT FROM AUTHOR]

Clouds and blowing snow (BLSN) occur frequently over Antarctica, where it is critical to understand their feedbacks to surface and atmospheric boundary layer processes. Dome C, an elevated East Antarctic station, dominated by lengthy periods of surface longwave (LW) radiative cooling, is selected to reveal cloud and BLSN impacts within a largely stable environment. The sky condition is classified as clear, cloudy, or BLSN, using 3 years of Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations satellite data. Co‐located and contemporaneous in situ observations are used to investigate the relationship of sky condition with surface and atmospheric boundary layer thermal structure, focusing on seasonal variability. Results show that increased downwelling LW radiation from clouds abate surface radiative cooling losses, contributing to warming during all seasons. An increase of 3°C in the mean surface air temperature is observed during spring, whereas, a more dramatic rise (around 10°C), due to accompanying large‐scale subsidence, is observed during fall and winter in association with clouds. For all seasons, the wind speed and wind speed shear are strongest during BLSN events, and the surface‐based inversion is weakened by cooling which peaks in a shallow above‐surface turbulent layer. The stronger background stability during fall and winter seasons, restricts turbulence and BLSN depths generally to the lowest tens of meters. The Earth's cryosphere is among the most rapidly evolving yet least well‐observed regions, and knowledge of clouds and BLSN interactions with the typical stable atmospheric boundary layer can help further understand energy and moisture exchanges. Plain Language Summary: The sky‐condition over Antarctica can be cloudy, clear, or characterized by blowing snow (BLSN) which is a phenomenon where snow is lifted, sometimes up to few hundreds of meters, and transported across the continent by winds. Knowing the impact of clouds and BLSN on the surface and the atmospheric boundary layer, which is the lower portion of the atmosphere that is directly linked to the surface, is crucial for understanding Antarctic climate. Dome C, an elevated dome‐shaped peak in East Antarctica, is chosen to study these impacts. In this location, an investigation covering a 3 year period using satellite observations and in situ measurements reveals that clouds can warm the surface and atmospheric boundary layer by increasing the downwelling longwave radiation. BLSN is accompanied by relatively stronger winds, and the wind‐driven atmospheric turbulence tends to weaken the strong positive temperature gradient in the atmospheric boundary layer, which is known as the temperature inversion. Temperature inversions are common at Dome C, and are most intense in the fall and winter seasons during which time they seemingly restrict the atmospheric turbulence and BLSN layer depth to a few tens to several tens of meters. Key Points: Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations and co‐located in situ observations allow study of cloud and blowing snow (BLSN) impacts on Antarctic atmosphereAt Dome C, clouds abate surface longwave radiative cooling losses, causing warming in all seasonsBLSN, accompanied by intense winds, weakens the temperature inversion, and is vertically restricted by strong background stability [ABSTRACT FROM AUTHOR]

This paper introduces a unique multiyear dataset and the monitoring capability of the PANDA automatic weather station network, which includes 11 automatic weather stations (AWSs) across the Prydz Bay–Amery Ice Shelf–Dome A area from the coast to the summit of the East Antarctic Ice Sheet. The ∼ 1460 km transect from Zhongshan to Panda S follows roughly along ∼ 77 ∘ E longitude and covers all geographic units of East Antarctica. Initial inland observations, near the coast, started in the 1996/97 austral summer. All AWSs in this network measure air temperature, relative humidity, air pressure, wind speed and wind direction at 1 h intervals, and some of them can also measure firn temperature and shortwave/longwave radiation. Data are relayed in near real time via the Argos system. The data quality is generally very reliable, and the data have been used widely. In this paper, we firstly present a detailed overview of the AWSs, including the sensor characteristics, installation procedure, data quality control protocol and the basic analysis of each variable. We then give an example of a short-term atmospheric event that shows the monitoring capacity of the PANDA AWS network. This dataset, which is publicly available, is planned to be updated on a near-real-time basis and should be valuable for climate change estimation, extreme weather events diagnosis, data assimilation, weather forecasting, etc. The dataset is available at 10.11888/Atmos.tpdc.272721 (Ding et al., 2022b). [ABSTRACT FROM AUTHOR]

The polar amplification (PA) has become the focus of climate change. However, there are seldom comparisons of amplification among Earth's three poles of Arctic (latitude higher than 60 °N), Antarctica (Antarctic Ice Sheet) and the Third Pole (the High Mountain Asia with the elevation higher than 4000 m) under different socioeconomic scenarios. Based on CMIP6 multi-model ensemble, two types of PA index (PAI) have been defined to quantify the PA intensity and variations, and PAI1/PAI2 is defined as the ratio of the absolute value of surface air temperature linear trend over Earth's three poles and that for global mean/over other regions except Earth's three poles. Arctic warms fastest in winter and weakest in summer, followed by the Third Pole, and Antarctica warms least. The similar phenomenon proceeds when global warming of 1.5–2.0 °C, and 2.0–3.0 °C above pre-industrial levels. After removing the Earth's three poles self-influence, all the PAI2s increase much more obviously relative to the PAI1s, especially the Antarctic PAI. Earth's three poles warm faster than the other regions. With the forcing increasing, PA accelerates much more over Antarctica and the Third Pole, but becomes weaker over Arctic. This demonstrates that future warming rate might make a large difference among Earth's three poles under different scenarios. [ABSTRACT FROM AUTHOR]

MODIS (Moderate Resolution Imaging Spectroradiometer) land surface temperature measurements in combination with in situ air temperature records from 119 meteorological stations are used to reconstruct a monthly near-surface air temperature product over the Antarctic Ice Sheet (AIS) by means of a neural network model. The product is generated on a regular grid of 0.05° 3 0.05°, spanning from 2001 to 2018. Comparison with independent in situ air temperature measurements shows low uncertainty, with a mean bias of 0.098C, a mean absolute error of 2.23°C, and a correlation coefficient of 97%. Furthermore, the performance of the reconstruction is better than ERA5 (the fifth-generation ECMWF reanalysis model) against in situ measurements. For the 2001-18 period, the MODIS-based near-surface air temperature product yields annual warming in the East Antarctica, but cooling in the Antarctic Peninsula and West Antarctica. However, they are not statistically significant. This product can also be used to investigate the impact of the Southern Hemisphere annual mode (SAM) on year-to-year variability of air temperature. The enhanced positive phase of SAMin recent decades in austral summer has a cooling effect on East andWest Antarctica. In addition, the dataset has the potential application for climate model validation and data assimilation due to the independence of the input of a numerical weather prediction model. [ABSTRACT FROM AUTHOR]

Regional climate models (RCMs) and reanalysis datasets provide valuable information for assessing the vulnerability of ice shelves to collapse over Antarctica, which is important for future global sea level rise estimates. Within this context, this paper examines variability in snowfall, near-surface air temperature and melt across products from the Met Office Unified Model (MetUM), Regional Atmospheric Climate Model (RACMO) and Modèle Atmosphérique Régional (MAR) RCMs, as well as the ERA-Interim and ERA5 reanalysis datasets. Seasonal and trend decomposition using LOESS (STL) is applied to split the monthly time series at each model grid cell into trend, seasonal and residual components. Significant systematic differences between outputs are shown for all variables in the mean and in the seasonal and residual standard deviations, occurring at both large and fine spatial scales across Antarctica. Results imply that differences in the atmospheric dynamics, parametrisation, tuning and surface schemes between models together contribute more significantly to large-scale variability than differences in the driving data, resolution, domain specification, ice sheet mask, digital elevation model and boundary conditions. Despite significant systematic differences, high temporal correlations are found for snowfall and near-surface air temperature across all products at fine spatial scales. For melt, only moderate correlation exists at fine spatial scales between different RCMs and low correlation between RCM and reanalysis outputs. Root mean square deviations (RMSDs) between all outputs in the monthly time series for each variable are shown to be significant at fine spatial scales relative to the magnitude of annual deviations. Correcting for systematic differences results in significant reductions in RMSDs, suggesting the importance of observations and further development of bias-correction techniques. [ABSTRACT FROM AUTHOR]

In this article marking the 40th anniversary of the US National Science Foundation's Long Term Ecological Research (LTER) Network, we describe how a long-term ecological research perspective facilitates insights into an ecosystem's response to climate change. At all 28 LTER sites, from the Arctic to Antarctica, air temperature and moisture variability have increased since 1930, with increased disturbance frequency and severity and unprecedented disturbance types. LTER research documents the responses to these changes, including altered primary production, enhanced cycling of organic and inorganic matter, and changes in populations and communities. Although some responses are shared among diverse ecosystems, most are unique, involving region-specific drivers of change, interactions among multiple climate change drivers, and interactions with other human activities. Ecosystem responses to climate change are just beginning to emerge, and as climate change accelerates, long-term ecological research is crucial to understand, mitigate, and adapt to ecosystem responses to climate change. [ABSTRACT FROM AUTHOR]

McMurdo Station, Antarctica, serves as a major scientific and support operations hub for the US Antarctic Program (USAP). Winter Quarters Bay (WQB) is adjacent to the Station, where vessels dock at the southernmost port to unload cargo and fuel. The ice pier at McMurdo is vital to ensure this once-annual vessel resupply. The use of the ice pier requires the deployment of a Bailey bridge, which creates an operating bottleneck for resupply. The occasional breakup of the ice pier, during or immediately after vessel operations, demonstrates a potential point for failure. The feasibility of artificial freezing of seawater using thermopiles (TP; a passive cooling technology) to grow the existing WQB bottomfast ice edge to a point where ships could dock directly will be investigated in this study. The timing to freeze an ice dock depends on the air temperature, TP fin size, the distance between TPs, and the number of TP rows that are engaged simultaneously. The results indicated that to complete a bottomfast ice edge 40 m seaward and 100 m long that was parallel to the shore and adequate for ship docking and offload, it would take from 255 to 820 days. This study shows that TPs could successfully be used to generate a direct docking bottomfast ice wharf at McMurdo and similar locations. [ABSTRACT FROM AUTHOR]

Antarctic firn presents an exotic seismological environment in which the behaviors of propagating waves can be significantly at odds with those in other Earth media. We present a condensed view of the nascent field of ambient noise seismology in Antarctic firn-covered media, and highlight multiple unusual and information-rich observations framed through the lens of the firn's important role as a buffer for air temperature anomalies and a complex contributor to ice mass balance. We summarize key results from several recent papers depicting novel wind-excited firn resonances and point to the plethora of ways these observations could facilitate imaging and monitoring of glacial systems at single, isolated seismometers. Finally, we propose significant instrumental and computational objectives necessary to constrain resonance excitation mechanisms and broadly apply these observations as useful monitoring tools in Antarctica. [ABSTRACT FROM AUTHOR]

Terrestrial climate records for Antarctica, beyond the age limit of ice cores, are restricted to the few unglaciated areas with exposed rock outcrops. Marine sediments on Antarctica's continental shelves contain records of past oceanic and terrestrial environments that can provide important insights into Antarctic climate evolution. The SHALDRIL II (Shallow Drilling on the Antarctic Continental Margin) expedition recovered sedimentary sequences from the eastern side of the Antarctic Peninsula of late Eocene, Oligocene, middle Miocene, and early Pliocene age that provides insights into Cenozoic Antarctic climate and ice sheet development. Here, we use biomarker data to assess atmospheric and oceanic temperatures and glacial reworking from the late Eocene to the early Pliocene. Analyses of hopanes and n‐alkanes indicate increased erosion of mature (thermally altered) soil biomarker components reworked by glacial erosion. Branched glycerol dialkyl glycerol tetraethers from soil bacteria suggest similar air temperatures of 12°C ± 1°C (1σ, n = 46) for months above freezing for Eocene, Oligocene, and Miocene timeslices but much colder (and likely shorter) periods of thaw during the Pliocene (5°C ± 1°C, n = 4) on the Antarctic Peninsula. TEX86‐based (Tetraether index of 86 carbons) sea surface temperature estimates indicate ocean cooling from 7°C ± 3°C (n = 10) in the Miocene to 3°C ± 1°C (n = 3) in the Pliocene, consistent with deep ocean cooling. Resulting temperature records provide useful constraints for ice sheet and climate model simulations seeking to improve understanding of ice sheet response under a range of climate conditions. Plain Language Summary: Records of past climate and ice sheet evolution are preserved in sediment deposited on Antarctica's continental shelves. Using marine sediments allow glimpses of those past conditions in Antarctica. We bring new approaches to revisit the evidence in those sediments. Reworked pollen and soil components show increasing glacial erosion of degraded sediments from land. Soil bacteria grow when soils thaw recording warm season temperatures of 11°C–12°C in the older sections, but much colder (and likely shorter) summers when there is ice cover. Ocean temperatures cool from 11.5°C to 2.8°C from the oldest section (36 Myr ago) to the youngest section (roughly 5 Myr ago). Key Points: Marine sediments provide snapshots of Cenozoic climate conditions on the Antarctic PeninsulaTerrestrial biomarkers indicate increased reworking of old carbon as cooling and glaciation proceededSoil biomarkers reveal that from the Oligocene to Pliocene, austral summer air temperatures cooled by 7°C, while oceans cooled by 10°C [ABSTRACT FROM AUTHOR]

This study aims to quantify the areal variation of glacial lakes in the coastal ice-free areas of King George Island (KGI) and Nelson Island (NI) from 1986 to 2020. Glacial lake and glacial area fluctuations are estimated using spaceborne remote sensing data and annual mean near-surface air temperature data from station observations and ERA-Interim reanalysis were analyzed. The area of glacial lakes expanded 732%, from 0.18 km2 in the 1980s to 1.39 km2 in 2020. For the 1988–2000/2003 and 2000/2003–2020 periods, the increase in NI lake area is estimated to be 190% and 86%, respectively. Meanwhile, on KGI, the increase is estimated to be 316% for the 1988–2000/2003 period and 103% for the 2000/2003–2020 period. The majority of lakes and higher lake expansions occurred at the glacier fronts and can be attributed to the melting of glacier fronts and the subsequent glacial retreat in recent decades. [ABSTRACT FROM AUTHOR]

A new dataset of meteorological records from Antarctic automatic weather stations (here called AntAWS dataset) at 3-hourly, daily and monthly resolutions is constructed with quality control. This dataset compiles the measurements of air temperature, air pressure, relative humidity, and wind speed and direction from 216 AWSs available during 1980-2021. Their spatial distribution remains heterogeneous, with a majority of instrumented sites located on the coastal areas, and less at the inland East Antarctic Plateau. Among the 216 AWSs, 55 of them have the records spanning more than 20 years, and 25 of them spanning more than 30 years. Among the five meteorological parameters, the air temperature measurement data have the best continuity and the highest data integrity. The comprehensive compilation of AWS observations has the main aim to make them easy and time-saving to be used for local, regional and continental studies, which can be accessed at https://doi.org/10.48567/key7-ch19 (Wang et al., 2022). This dataset will be valuable for better characterizing surface climatology throughout the continent of Antarctica, improving our understanding of Antarctic surface snow-atmosphere interactions, and estimating regional climate models or meteorological reanalysis products. [ABSTRACT FROM AUTHOR]

This paper introduces a unique multiyear dataset and the monitoring capability of the PANDA automatic weather station network which includes eleven automatic weather stations (AWS) across Prydz Bay-Amery Ice Shelf-dome area from the coast to the summit of the East Antarctica ice sheet. The ~1460 km transect from Zhongshan to Panda S station follows roughly along ~77° E longitude and covers all geographic and climatic units of East Antarctica. Initial inland observation, near the coast, started in the 1996/1997 austral summer. All AWSs in this network measure air temperature, relative humidity, air pressure, wind speed and wind direction at 1-hour intervals, and some of them can also measure firn temperature and shortwave/longwave radiation. Data are relayed in near real-time via the ARGOS system. Data quality is generally very reliable and the data have been used widely. In this paper, we firstly present a detailed overview of the AWSs, including the sensor characteristics, installation procedure, data quality control protocol, and the basic analysis of each variable. We then give an example of a short-term atmospheric event that shows the monitoring capacity of the network. This dataset, which is publicly available, is planned to be updated on a near-real time and should be valuable for climate change estimation, extreme weather events diagnosis, data assimilation, weather forecasting, etc. The dataset is available at https://doi.org/10.11888/Atmos.tpdc.272721 (Ding et al., 2022). [ABSTRACT FROM AUTHOR]

The Southern Ocean is supposed to play a crucial role in influencing atmospheric CO2 concentrations. However, the dynamic relationships among the rate of Southern Ocean upwelling, atmospheric CO2 concentration, and Antarctic climate at millennial timescales remain unclear. Here, we present high‐resolution color reflectance component b* and natural gamma radiation from the southern Scotia Sea sector of the Southern Ocean to reconstruct productivity over the past 160 ka. We find that these two independent productivity proxies, reflecting the signal of nutrient supply in this region, captured millennial‐scale upwelling that covaried in timing with Heinrich Stadials and Antarctic warming events, supporting the bipolar seesaw mechanism. The one‐to‐one coupling of variability between productivity and atmospheric CO2 concentrations reveals that the upwelling is closely linked to atmospheric CO2 and climate change. Plain Language Summary: The Southern Ocean's physical and associated biogeochemical processes play important roles in influencing atmospheric CO2 and climate change. In this study, we investigate temporal changes in productivity in the Antarctic Zone of the Southern Ocean by color reflectance component b* and natural gamma radiation data over the past 160 ka. We find that millennial‐scale productivity variability, which reflects the rate of upwelling in this region, corresponds to millennial‐scale variations in Antarctic temperature and atmospheric CO2 concentration over the past 160 ka. These tight couplings could imply that Southern Ocean upwelling is involved in atmospheric CO2 fluctuation and climate change. Key Points: Change in productivity at Site U1537 reflects the degree of upwelling in the Antarctic Zone of the Southern OceanThe millennial‐scale productivity peaks correspond to the Antarctic Isotope Maximum events that coincided with the Heinrich Stadials or Dansgaard‐Oeschger events in GreenlandThe rate of upwelling and atmospheric CO2 concentrations are positively correlated during the Heinrich Stadials [ABSTRACT FROM AUTHOR]

Antarctic sea ice is projected to decrease in response to increasing greenhouse gas concentrations. Limited studies so far have examined the coupled atmosphere–ocean response to Antarctic sea ice loss. Here, we isolate the response to Antarctic sea ice loss in the atmosphere and ocean using bespoke sea ice albedo perturbation experiments with HadGEM3-GC3.1-LL, provide the first detailed examination of the global ocean response, and quantify the importance of atmosphere–ocean coupling, through comparison to uncoupled experiments with prescribed Antarctic sea ice loss. Lower-tropospheric warming and moistening over regions of sea ice loss and the nearby Southern Ocean are simulated in both coupled and uncoupled configurations but are of greater magnitude in the coupled model. A weakening and equatorward shift of the tropospheric westerly jet are simulated in both configurations, but are also larger in the coupled model. Ocean coupling allows the warming response to spread northward, and by poleward atmospheric energy transport, back to the Antarctic interior. Warmer tropical sea surface temperatures enhance atmospheric convection, driving upper-tropospheric warming and triggering atmospheric teleconnections to the extratropics, including a weakened Aleutian low. A 20% reduction in Antarctic Circumpolar Current transport and a weakening of the shallow tropical convergence cell are simulated. Surface waters warm and freshen globally, becoming more stratified and stable in the Southern Ocean, with similar changes, but of lesser magnitude, in the Arctic Ocean, where sea ice declines. Our results suggest that the climate effects of Antarctic sea ice loss stretch from pole to pole and from the heights of the tropical troposphere to the depths of the Southern Ocean. [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]

In this article, we present empirical models for estimating daily mean air temperature (Ta) in the Hurd Peninsula of Livingston Island (Antarctica) using Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) data and spatiotemporal variables. The models were obtained and validated using the daily mean Ta from three Spanish in situ meteorological stations (AEMET stations), Juan Carlos I (JCI), Johnsons Glacier (JG), and Hurd Glacier (HG), and three stations in our team's monitoring sites, Incinerador (INC), Reina Sofía (SOF), and Collado Ramos (CR), as well as daytime and nighttime Terra-MODIS LST and Aqua-MODIS LST data between 2000 and 2016. Two types of multiple linear regression (MLR) models were obtained: models for each individual station (for JCI, INC, SOF, and CR—not for JG and HG due to a lack of data) and global models using all stations. In the study period, the JCI and INC stations were relocated, so we analyzed the data from both locations separately (JCI1 and JCI2; INC1 and INC2). In general, the best individual Ta models were obtained using daytime Terra LST data, the best results for CR being followed by JCI2, SOF, and INC2 (R2 = 0.5–0.7 and RSE = 2 °C). Model cross validation (CV) yielded results similar to those of the models (for the daytime Terra LST data: R2CV = 0.4–0.6, RMSECV = 2.5–2.7 °C, and bias = −0.1 to 0.1 °C). The best global Ta model was also obtained using daytime Terra LST data (R2 = 0.6 and RSE = 2 °C; in its validation: R2CV = 0.5, RMSECV = 3, and bias = −0.03), along with the significant (p < 0.05) variables: linear time (t) and two time harmonics (sine-cosine), distance to the coast (d), slope (s), curvature (c), and hour of LST observation (H). Ta and LST data were carefully corrected and filtered, respectively, prior to its analysis and comparison. The analysis of the Ta time series revealed different cooling/warming trends in the locations, indicating a complex climatic variability at a spatial scale in the Hurd Peninsula. The variation of Ta in each station was obtained by the Locally Weighted Regression (LOESS) method. LST data that was not "good quality" usually underestimated Ta and were filtered, which drastically reduced the LST data (<5% of the studied days). Despite the shortage of "good" MODIS LST data in these cold environments, all months were represented in the final dataset, demonstrating that the MODIS LST data, through the models obtained in this article, are useful for estimating long-term trends in Ta and generating mean Ta maps at a global level (1 km2 spatial resolution) in the Hurd Peninsula of Livingston Island. [ABSTRACT FROM AUTHOR]