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In ice-free surfaces of King George Island (South Shetland Islands, Maritime Antarctica) themain formations along topographic chronosequences consist of weathered volcanic rockoutcrops, marine platforms, deposits of glacial materials such as moraines, andpresent day beaches. In relation with recent glacier retreat processes of sedimentredistribution in unstable paraglacial environments are highly active in the area. Togetherwith soil particles the mobilization of associated soil organic carbon (SOC) can befurther enhanced under conditions of climate change by melting snow and ice. InFebruary 2015 we conducted a selective sampling of reference sites on marineplatforms and moraines to be compared with surface sediments recently deposited inlakes on the platforms and in the proglacial environment of the Bellingshausen IceDome. During a 15 days field campaign funded by IAEA INT5153 project wecollected soil and sediment profiles and lake surface sediments to assess if there weredifferences between old marine platforms and contemporary moraines in their FRNs andSOC signatures, as both proxies have been found to be effective tracers of recentglacier retreat in other polar environments. The reference samples on the platformswere characterized by relatively slightly higher contents of sand (> 50%) thansilt fraction and low clay contents (< 5%) accompanied by SOC contents rangingbetween 1 and 3.5 % and FRNs values of 3.5 Bq kg−1for 137Cs and of 8 Bq kg−1for210Pbex. In contrast, on moraines the dominant grain size was silt (> 70 %), theSOC contents were below 0.5% and FRNs were much lower than in platforms soilswith activities of 137Cs below the detection limit and of 210Pbex less than 5 Bqkg−1. The surface sediments accumulated in the proglacial lakes were enrichedin sand (> 80 %) while in the platform lake they were mainly silt (> 70 %) andclay fractions reached up to 12 %. The sediments of the platform lake had highSOC contents (6.3 %) but the proglacial lakes had negligible values (< 0.1%).FRNs were not detected at the proglacial Upper Lake where the source materials aremoraine and fresh glacier materials. However, the low FRNs activities found at theLower Lake are because its headwaters also comprise soils developed on marineplatforms. Our results regarding contents of FRNs and SOC in the source areas and thesediments accumulated in the lakes, reflect a clear link on the provenance of sediments.The differences of grain size in lake sediments might suggest a relatively moreenergetic runoff in the proglacial lakes related to melting snow and ice directlyfrom glacier in comparison with that on platforms. These results are consistentwith a highly dynamic environment and in which soil and sediment particles areredistributed along the sediment cascade system in ice-free areas of Maritime Antarctica. [ABSTRACT FROM AUTHOR]

As in other regions of the world, glaciers in South America like in Torres del Paine NationalPark are shrinking. The trends of increasing temperatures would accelerate melting processthat will affect not only populations but also natural resources as water and soil that supportlife. Recent works in other polar and cold regions have shown the usefulness ofcombining fallout radionuclides and soil organic carbon (SOC) for tracking recentglacier retreat on glacial formations of proglacial environments. Such combinationof proxies is also useful for gaining information on the creation of new soils onrecently formed glacial landforms as well as to get insights on soil erosion anddeposition processes in paraglacial landscapes. In this study a survey of soils andglacial deposits of an area surrounding the Grey Lake and Glacier, located in ChileanPatagonia has been undertaken in the frame of the IAEA INT5153 project. During a15 days field campaign composite surface samples were collected on previouslyidentified main landforms in the eastern and western margins of the Grey Glacier Lake.The study proglacial landforms include glacio-fluvial terraces, moraines, swamps,colluvial and forest slopes. The different landforms generated at different stages fromLast Glacial Maximum (LMG) to Little Ice Age (LIA) and recent glacier retreatsuffer the impact of climate change. At present the retreat of the Grey Glacier ishighly active and entails the creation of new geomorphic elements along with activeerosion and deposition processes. Analyses of 137Cs, SOC and grain size alongwith standard soil properties were performed for characterizing the surface soil andsediment samples. The grain size of the study samples is medium coarse as indicatedby the general predominance of silt and sand fractions, pH values are acidic andsalinity and carbonate contents are low. The mass concentration of 137Cs activity(Bq kg−1) varied largely with highest mean values in soils on forest slopes (12Bq kg−1) and swamps (45 Bq kg−1) in coincidence with the highest mean SOCcontents of 7 and 17 % for forest slopes and swamps, respectively. On the mostrecently formed landforms, colluvial and glacio-fluvial terraces, the surface soils andsediments had the coarsest textures along with the lowest mean contents of SOC (< 1%) and of 137Cs mass activity (2 Bq kg−1), which are in accordance with morerecent processes of soil formation. Fallout 137Cs and SOC can provide valuableinformation on soil processes under rapidly changing environmental conditionsoccurring in the last decades in the area of the Grey Glacier Lake. Our results mighthelp in understanding the trends in the dynamic of formation of new soils fromrecently exposed surfaces related to the shrinking of glaciers with rising temperatures. [ABSTRACT FROM AUTHOR]