The seasonal movement of the zero-degree isotherm across the Southern Ocean and Antarctic Peninsula drives major changes in the physical and biological processes around maritime Antarctica. These include spatial and temporal shifts in precipitation phase, snow accumulation and melt, thawing and freezing of the active layer of the permafrost, glacier mass balance variations, sea ice mass balance and changes in physiological processes of biodiversity. Here, we characterize the historical seasonal southward movement of the monthly near-surface zero-degree isotherm latitude (ZIL), and quantify the velocity of migration in the context of climate change using climate reanalyses and projections. From 1957 to 2020, the ZIL exhibited a significant southward shift of 16.8 km decade(-1) around Antarctica and of 23.8 km decade(-1) in the Antarctic Peninsula, substantially faster than the global mean velocity of temperature change of 4.2 km decade(-1), with only a small fraction being attributed to the Southern Annular Mode (SAM). CMIP6 models reproduce the trends observed from 1957 to 2014 and predict a further southward migration around Antarctica of 24 +/- 12 km decade(-1) and 50 +/- 19 km decade(-1) under the SSP2-4.5 and SSP5-8.5 scenarios, respectively. The southward migration of the ZIL is expected to have major impacts on the cryosphere, especially on the precipitation phase, snow accumulation and in peripheral glaciers of the Antarctic Peninsula, with more uncertain changes on permafrost, ice sheets and shelves, and sea ice. Longer periods of temperatures above 0 degrees C threshold will extend active biological periods in terrestrial ecosystems and will reduce the extent of oceanic ice cover, changing phenologies as well as areas of productivity in marine ecosystems, especially those located on the sea ice edge.

The knowledge of soil thermal properties is important for determining how a soil will behave under changing climate conditions, especially in the sensitive environment of permafrost affected soils. This paper represents the first complex study of the interplay between the different parameters affecting soil thermal conductivity of soils in Antarctica. Antarctic Peninsula is currently the most rapidly warming region of the whole Antarctica, with predictions of this warming to continue in the upcoming decades. This study focuses on James Ross Island, where the Abernethy Flats automatic weather station is located in a lowland area with semi-arid climate. Air and ground temperature, soil heat flux and soil moisture during the thawing season were monitored on this site from 2015 to 2023. Moreover, two approaches to determining soil thermal conductivity were compared - laboratory measurements and calculation from field data. During this period, mean annual temperatures have increased dramatically for both air (from-6.9 degrees C in 2015/2016 to-3.8 degrees C in 2022/2023) and ground (from-6.5 degrees C to-3.2 degrees C), same as active layer thickness (from 68 cm to 95 cm). Average soil thermal conductivity for the thawing period reached values between 0.49 and 0.74 W/m.K-1 based on field data. Statistically significant relationships were found between the seasonal means of volumetric water content and several other parameters - soil thermal conductivity (r = 0.91), thawing degree days (r = -0.87) and active layer thickness (r = - 0.88). Although wetter soils generally have a higher conductivity, the increase in temperature exhibits a much stronger control over the active layer thickening, also contributing to the overall drying of the upper part of the soil profile.

Climate change and its impacts on sensitive polar ecosystems are relatively little studied in Antarctic regions. Permafrost and active layer changes over time in periglacial regions of the world are important indicators of climate variability. These changes (e. g. permafrost degradation, increasing of the active layer thickness) can have a significant impact on Antarctic terrestrial ecosystems. The study site (AWS-JGM) is located on the Ulu Peninsula in the north of James Ross Island. Ground temperatures at depths of 5, 50, and 75 cm have been measured at the site since 2011, while air temperature began to be measured in 2004. The main objective is to evaluate the year-to-year variability of the reconstructed temperature of the top of the permafrost table and the active layer thickness (ALT) since 2004 based on air temperature data using TTOP and Stefan models, respectively. The models were verified against direct observations from a reference period 2011/12-2020/21 showing a strong correlation of 0.95 (RMSE = 0.52) and 0.84 (RMSE = 3.54) for TTOP and Stefan models, respectively. The reconstructed average temperature of the permafrost table for the period 2004/05-2020/21 was -5.8 degrees C with a trend of -0.1 degrees C/decade, while the average air temperature reached -6.6 degrees C with a trend of 0.6 degrees C/decade. Air temperatures did not have an increasing trend throughout the period, but in the first part of the period (2004/05-2010/11) showed a decreasing tendency (-1.3 degrees C/decade). In the period 2011/ 12-2020/21, it was a warming of 1.9 degrees C/decade. The average modelled ALT for the period 2004/05-2020/21 reached a value of 60cm with a trend of -1.6 cm/decade. Both models were found to provide reliable results, and thus they significantly expand the information about the permafrost and ALT, which is necessary for a better understanding of their spatiotemporal variability and the impact of climate change on the cryosphere.

Ice sheet serves as a crucial indicator for assessing climate change. Mass loss in recent remote sensing-based studies indicated that the Antarctic Peninsula has rapid rates of glacier retreat and speed up of surface velocity. However, observations of seasonal variability of ice speed are limited, and glacier-area changes require multi-temporal monitoring. This study investigated the changes in area and surface velocities of similar to 375 glaciers on the northern Antarctic Peninsula (NAP) utilizing satellite images acquired by the Sentinel 1 & 2 satellites during 2018 - 2022. The results indicate that the glacier area reduced by approximately 166.1 +/- 44.2 km(2) (-0.2% +/- 0.1% per year) during the study period, with an acceleration after 2020 (-0.4% +/- 0.3% per year), and the most dramatic reduction happened on the eastern NAP. The maximum annual ice speeds on the NAP generally exceeded 3500 m per year, while the ice speeds in 2021 were the highest (exceeded 4210 m per year). The ice speed variability in austral autumn was higher than in other seasons, meanwhile the summer ice speeds showed an increasing trend. The glacier G012158E47018N, McNeile Glacier, glacier G299637E64094S and Drygalski Glacier showed the most remarkable ice speed variations represented by high daily velocities and strong fluctuations on their termini. Our results demonstrated that the variations in glacier area and seasonal ice speed on the NAP were responsive to the ice - ocean - atmosphere processes. Therefore, seasonal velocity and area variations should be considered when conducting accurate mass balance calculations, model validations and change mechanism analyses under climate warming scenarios.

The timing of neoglacial advances in the Antarctic Peninsula (AP) is not yet well constrained. Accurate temporal reconstruction of Neoglaciation in the AP is needed to better understand past glacial responses and regional and global teleconnections during the Holocene. Here, we examine all available information about neoglacial advances in the South Shetland Islands (SSI) as well as in the broader geographical context of the AP region and Antarctic continent. In order to shed light on the contrasting chronologies existing for neoglacial advances in these regions, we focused on a case study where a detailed picture of the Holocene deglaciation was already available. Lake sediments revealed that Byers Peninsula, west of Livingston Island (SSI), was fully deglaciated during the Holocene Thermal Maximum. To complement this approach, we identified glacially polished bedrock surfaces, erratic boulders and a moraine ridge near the present front of the glacier in the SE corner. We applied cosmogenic ray exposure (CRE) dating using in situ Cl-36 for basalt rocks and Be-10 for granitic rocks in: (i) 8 samples from glacial erratic and ice-rafted boulders, (ii) 2 samples from moraine boulders, (iii) 2 samples from polished bedrock surfaces, and (iv) 1 sample from an erratic boulder deposited on one of these surfaces. The CRE dates indicate that the onset of deglaciation started around 9.9 +/- 1.2 ka, with two phases of glacier expansion during the Mid-Late Holocene forming moraines at similar to 4.1 +/- 0.5 and similar to 1.0 +/- 0.2 ka, respectively. The main neoglacial advances in the AP and the SSI were mostly synchronous and coincided with cold periods, as shown by other records (e.g. glacio-isostatic marine terraces, marine and lake sediments). In addition, these periods of glacial expansion show a similar timing to those recorded in the Arctic. These results suggest that Neoglaciation was driven by global climate forcing in both polar areas despite temporal variations at regional and local scale. (C) 2020 Elsevier Ltd. All rights reserved.

Wilhelm et al. (2015) employed the widely used Stefan and Kudryavtsev equations to predict the maximum active-layer thickness (ALT) on Amsler Island, Western Antarctic Peninsula. Their predictions far exceed the observations of ALT reported from other parts of the region. Here, I demonstrate that the values of ALT are significantly overestimated by the predictive equations because the authors incorrectly assumed that little or no latent heat of phase change is absorbed during thawing. Although the area is the warmest in the Antarctic Peninsula region, with a rapid increase in air temperature and permafrost temperatures close to 0 degrees C, the active layer is likely to be substantially thinner than values predicted by Wilhelm et al. (2015). Copyright (c) 2016 John Wiley & Sons, Ltd.

The Antarctic Peninsula (AP) is often described as a region with one of the largest warming trends on Earth since the 1950s, based on the temperature trend of 0.54 degrees C/decade during 1951-2011 recorded at Faraday/Vernadslcy station. Accordingly, most works describing the evolution of the natural systems in the AP region cite this extreme trend as the underlying cause of their observed changes. However, a recent analysis (Turner et al., 2016) has shown that the regionally stacked temperature record for the last three decades has shifted from a warming trend of 032 degrees C/decade during 1979-1997 to a cooling trend of -0.47 degrees C/decade during 1999-2014. While that study focuses on the period 1979-2014, averaging the data over the entire AP region, we here update and reassess the spatially-distributed temperature trends and inter-decadal variability from 1950 to 2015, using data from ten stations distributed across the AP region. We show that Faraday/Vernadsky warming trend is an extreme case, circa twice those of the long-term records from other parts of the northern AP. Our results also indicate that the cooling initiated in 1998/1999 has been most significant in the N and NE of the AP and the South Shetland Islands (>0.5 degrees C between the two last decadeS), modest in the Orkney Islands, and absent in the SW of the AP. This recent cooling has already impacted the cryosphere in the northern AP, including slow-down of glacier recession, a shift to surface mass gains of the peripheral glacier and a thinning of the active layer of permafrost in northern AP islands. (C) 2016 Elsevier B.V. All rights reserved.

The Western Antarctic Peninsula region is one of the hot spots of climate change and one of the most ecologically sensitive regions of Antarctica, where permafrost is near its climatic limits. The research was conducted in Deception Island, an active stratovolcano in the South Shetlands archipelago off the northern tip of the Antarctic Peninsula. The climate is polar oceanic, with high precipitation and mean annual air temperatures (MAAT) close to -3 degrees C. The soils are composed by ashes and pyroclasts with high porosity and high water content, with ice rich permafrost at -0.8 degrees C at the depth of zero annual amplitude, with an active layer of about 30 cm. Results from thaw depth, ground temperature and snow cover monitoring at the Crater Lake CALM-S site over the period 2006 to 2014 are analyzed. Thaw depth (TD) was measured by mechanical probing once per year in the end of January or early February in a 100 x 100 m with a 10 m spacing grid. The results show a trend for decreasing thaw depth from ci. 36 cm in 2006 to 23 cm in 2014, while MAAT, as well as ground temperatures at the base of the active layer, remained stable. However, the duration of the snow cover at the CALM-S site, measured through the Snow Pack Factor (SF) showed an increase from 2006 to 2014, especially with longer lasting snow cover in the spring and early summer. The negative correlation between SF and the thaw depth supports the significance of the influence of the increasing snow cover in thaw depth, even with no trend in the MAAT. The lack of observed ground cooling in the base of the active layer is probably linked to the high ice/water content at the transient layer. The pyroclastic soils of Deception Island, with high porosity, are key to the shallow active layer depths, when compared to other sites in the Western Antarctic Peninsula (WAP). These findings support the lack of linearity between atmospheric warming and permafrost warming and induce an extra complexity to the understanding of the effects of climate change in the ice-free areas of the WAP, especially in scenarios with increased precipitation as snow fall. (C) 2016 Elsevier B.V. All rights reserved.

The effects of climate change along the climatically sensitive Western Antarctic Peninsula (WAP) on active layer dynamics have just begun to be monitored. But extreme climates and difficult access make borehole installation here challenging. This study was designed to examine the ability of two commonly used, minimally intrusive techniques (the Stefan and Kudryavtsev equations) to predict active layer temperature dynamics and maximum active layer thickness (ALT) on Amsler Island, on the WAP. The ALT in soils and unconsolidated materials was predicted to be between 4.7 and 8.7 m, and between 11.9 and 18.6 m in bedrock, consistent with measurements made in a 14.6 m deep borehole. The thermal model HYDRUS accurately predicted temperature dynamics at several monitored borehole depths. The success of the HYDRUS method indicates that the model can be a useful tool in predicting active layer temperatures and approximating ALTs in regions that are too difficult to install monitoring boreholes. Copyright (c) 2015 John Wiley & Sons, Ltd.