This study investigates the transient snowline (TSL) altitude for summer 2020, as well as glacial area loss in King George Island Icefields since 1988 using Sentinel-1 and 2 and Landsat Thematic Mapper (TM) imagery. Trends and anomalies in atmospheric temperature, U-wind, and V-wind were examined using ERA5 solutions. Results show the wet-snow zone corresponds to values of ≤ -13dB, and 44.3% of the glacial area is located above the TSL (≥ 300 m). Glacial area for 2020 is 999.95 km², and losses in the period represent 104.9 km² (error <1%) – a retreat of 3.17 km² / year. Glaciers in Keller Peninsula and Bellingshausen Dome lost the most area (28% and 17%, respectively) and did not have a TSL in 2020; followed by Warszawa (15%), Kraków (13%), and Eastern (10%), where the TSL was verified. Percentage area loss values increased with decreases in dimensions, area above TSL, and maximum elevation. Calving glaciers with ice-flow toward deeper and steeper submarine sectors (Bransfield Strait) exhibited greater glacier variations. The trend in warming atmospheric temperature was greater in the Bransfield Strait than in the Drake Passage. TSL and retreat difference between glaciers were influenced by climatic and ocean input, as well as multiple environmental factors.

O objetivo deste trabalho é identificar as feições deposicionais de mesoescala marginais ao gelo e os processos geomorfológicos relacionados aos ambientes proglaciais das geleiras Ecology, Sphinx, Baranowski, Tower e Windy, localizadas na margem leste do campo de gelo Warszawa na Ilha Rei George, Antártica (62°12’0” S - 58°30’0” W). A análise geomorfométrica, através do TANDEM-X de resolução espacial de 8 m, possibilitou verificar que há o predomínio das classes de elevação entre 100 e 200m na área total de estudo, as áreas livres de gelo correspondentes as geleiras Tower e Sphinx possuem os maiores valores de declividade. O mapeamento geomorfológico das áreas livres de gelo foi obtido através da análise visual em imagens Sentinel-2 (verão 2018) e WorldView-2 (verão 2014). A retração das geleiras tem levado a formação de ambientes proglaciais dinâmicos, com exposição de geoformas, como morainas laterais, frontais de recessão, latero-frontais, eskers, além de corpos hídricos como lagos e lagunas, canais de drenagem entrelaçados ou não. As formas de relevo deposicionais glaciais estão sob influência da alta atividade paraglacial. O ambiente proglacial apresenta uma completa transição paraglacial, há predomínio conforme se distancia das margens frontais das geleiras (ambientes proglaciais II e III), pois a influência glacial é predominante na paisagem na margem das geleiras (ambiente proglacial I). As geleiras Tower e Sphinx possuem os ambientes I de menores dimensões, devido ao perfil mais íngreme. As feições mapeadas resultaram na reconstrução glacial e a descontinuidade da moraina latero-frontal mais externa evidenciaram condições de término marinho para todas as geleiras.

This study investigated the terrestrial and submarine geomorphology and glacial landform records in the Martel inlet (King George Island) using a multi-resolution topobathymetric data based on seismic, multibeam surveys and terrestrial satellite datasets (REMA DEM). Geomorphometric analysis provided glacial landforms and sedimentary processes interpretation. The submarine sector has a mean depth of 143 m, a maximum depth of 398 m, and most of it has a low slope (0°-16°). Steep slopes (>30°) are found along the mid-outer sectors transition area. The continental shelf was divided into inner fjord (49 m depth), middle fjord (119 m), and outer fjord (259 m), based on depth, elevation and slope. The topobathymetric digital model provides evidence of geomorphological contrasts between these zones in the fjord's seafloor and subaerial environments. A prominent morainal bank in the transition between the inner and middle parts marks the limit of a past stationary stage of the Dobrowolski-Goetel ice margin. Streamlined glacial lineations demonstrate an NE-SW past ice flow direction and a wet-based thermal regime. The combined analysis of submarine and subaerial landforms enable the understanding of the former glacier configuration and its deglaciation history.

O artigo investiga alterações nos sistemas paraglaciais e interconexões com a retração glacial em setores da ilha Rei George, Antártica Marítima. Foi analisado o ambiente proglacial, resultado da deglaciação recente, e identificados os tipos de formas de relevo em suas diferentes escalas. Estes registros são úteis para a reconstrução de estágios sucessivos evolutivos no sistema paraglacial. Os resultados demonstraram que o ambiente marginal às geleiras e sistemas paraglaciais estão evoluindo na ilha Rei George e há novas paisagens. Algumas geleiras apresentaram uma mudança importante entre 2000 e 2019, onde sua classificação mudou de geleira de terminação marinha para geleira de terminação terrestre (não-marinha). Atualmente há 21 geleiras com término em terra na ilha Rei George (correspondendo a 31% das geleiras) e 11 destas estão localizadas na Baía do Almirantado. 25% destas geleiras eram marinhas em 2000. Os novos ambientes paraglaciais (desde 2000) têm 1,7 km2 ao total de área. Os ambientes marginais às geleiras (como as geleiras Ecology, Wanda, Windy, Anna Sul e Baranowski) mostraram formas de gênese não glacial, como planície de lavagem, depositos de tálus, ravinas e canais fluviais no sistema paraglacial recente. O mapeamento geomorfológico evidencia que os processos paraglaciais se diferenciam entre os ambientes marginais ao gelo das geleiras, não são padronizados. Palavras-chave: processos geomorfológicos glaciais, áreas livres de gelo, mudanças climáticas.

The paper aims to reconstruct the fluctuations of Dobrowolski Glacier, a tidewater glacier located in the inner position of the Admiralty Bay (King George Island, Antarctica), from the Little Ice Age (1400-1700) until the present. Measurements of the glacier’s area and length were based on multitemporal satellite imagery and submarine glacial landforms. The glacier surface area variations between the Little Ice Age and 2014 A.D were estimated. Morainic banks and paleoglacial reconstructions provided evidence of fluctuations in the surface area of the glacier between PIG and 2014 AD. Therefore, four stages of analysis were established: Stage I (Part I) (1400 to 1700), Stage I (Part II) (1700 until the mid-20th century), Stage II (mid-20th century until the 1980s), Stage III (1980 to 2000), and Stage IV (2000 to 2020). The climate during the Little Ice Age triggered the last major glacial advance, and their grounding line position was recorded by an external and prominent morainic bank. After the major glacial advance position of the grounding line, the ice-margin has undergone higher retreat rates (stage I) as response to the warming trend and the loss of anchoring point. The stage II (Unit B) is recorded by distal and discontinuous morainal ridges and glacial lineations formed in the context of an active ice flow at a deeper point in the fjord. During stage III (Unit C) glacial lineations and steep slopes occur, while landforms are less preserved, revealing a fast shrinkage phase. Stage IV is characterized by discontinuous morainic ridges (Unit D), when the glacier presents the highest annual glacial area loss. Currently, the accelerated shrinkage may be linked to the loss of anchorage on seamounts (serving as pinning points) and increased warming. The U-shaped valley geometry has also influenced the glacier shrinkage processes and the redirection of glacial paleoflow during the last 300 years. The retreat rate to mid-20th century-2020 period is higher than Little Ice Age- mid-20th century period.