Morfologia de feições geomorfológicas Periglaciais e Proglaciais da Península Fildes

A medida que uma geleira retrai expõe feições do terreno que são retrabalhadas pela ação intempérica, e por processos glacio fluviais e glacio marinhos. Dessa forma, é objetivo dessa pesquisa identificar feições decorrentes da retração da geleira Collins na península Fildes, Antártica. Foram realizados dois trabalhos de campo em 2015 e 2016, onde as feições foram fotografadas e tomado o ponto de GPS. Para as feições proglaciais foram coletadas amostras sedimentares para análise granulométrica e morfoscópica. No setor ao sul e central na península encaixam-se vales esculpidos por fluxos de gelo que se divergiam de acordo com a topografia local. No setor norte há um cordão morâinico de avanço, da Pequena Idade do Gelo, flutings e morainas supraglaciais sujeitas a ablação sazonal que indicam uma fase de retração recente da frente da geleira Collins. As feições identificadas servirão para interpretação e mapeamento geomorfológico de detalhe de toda península

Evidências Geomorfológicas de Mudanças Ambientais na Baía Esperança, Península Antártica

A geomorphological interpretation of the glacial geomorphology of the proglacial environments of the Buenos Aires, Kenney and Flora glaciers in Hope Bay, Antarctica, between the coordinates 63° 23'S and 63° 26'S latitude and 56° 8'W and 57° 4'W longitude. Sedimentary, granulometric and morphological analyzes were carried out on 15 samples collected in 2017 for the identification of depositional geomorphological features and subsequent geomorphological mapping. The glacier fronts were delineated from Sentinel-2 and Quickbird images of 1988, 2008 and 2017 using the ArcGIS® software to identify the landforms chronology of the shapes. The higher number of coarse grains, low selection, and high values of C40 in all samples indicate modification by erosive processes in supraglacial environment and/or transport distance after substrate quarrying process and grain fracturing by post-depositional physical weathering. The reconstruction of the Hope Bay’s Holocene landscape of indicates glaciers with tens of meters of advance compared to the current front during the Little Ice Age (LIA). The geomorphological mapping and sedimentary analyzes showed recent environmental changes in the proglacial system, with formation of hummocky moraines indicating the retreat/stabilization of the glaciers in the LIA. Furthermore, they set evidences of recent recession moraines, which prevail in the Buenos Aires Glacier predominate in the 2008-2017 phase, on the Flora Glacier in 1988-2008 period and the Kenney Glacier in the 2008-2017 period.The objective of this paper is to understand the glacial geomorphology of the proglacial environments of the Buenos Aires, Kenney and Flora glaciers in Hope Bay, Antarctica, between the coordinates 63° 23'S and 63° 26'S latitude and 56° 8'W and 57° 4'W longitude. Sedimentary, granulometric and morphological analyzes were carried out on 15 samples collected in 2017 for the identification of depositional geomorphological features and subsequent geomorphological mapping. The glacier fronts were delineated from Sentinel-2 and Quickbird images of 1988, 2008 and 2017 using the ARC GIS to identify the chronology of the shapes. The predominance of coarse grains, low selection, and high values ​​of C40 in all samples indicate modification by erosive processes in supraglacial environment and/or transport distance after substrate peeling and grain fracturing by post-depositional physical weathering . The reconstruction of the holocene landscape of Hope Bay indicates glaciers with tens of meters of advance compared to the current front during the Little Ice Age (LIA). The geomorphological mapping and performed analyzes show recent environmental changes in the proglacial system, with formation of Hummocky moraines indicating the retraction/stabilization of the glaciers in the LIA, and recent recession moraines, which in the Buenos Aires glacier predominate in the 2008-2017 phase, on the Flora glacier in the period 1988-2008 and the Kenney Glacier in the 2008-2017 period

Cambios climáticos y aumento de la vegetación en la Península Fildes, Antártica

The objective of the article is to evaluate the variation of area and location of mosses in the Fildes Peninsula, Antarctica, using the NDVI technique and LANDSAT images, for the period 1986-2016, in the face of climate change scenarios. The NDVI technique was applied on 7 LANDSAT images and the products were evaluated by the Kappa index. The vegetation area increased from 1.5 to 2.7 km² in the period. The Kappa index results indicatevariations with 0,81 to 0,93 accuracy, more than 70% of the mapped area were indicated above 0.1 (most likely vegetation area). The largest mosses fields (83% of the larger ones) are located in the part facing the Drake Passage and are associated to the moisture and wind coming from the ocean. The greatest amount of organic matter and floodwaters occur in the “U” valleys facing the Drake, contributing to the vegetation fixation. The mosses fields will continue to increase in the face of scenarios point to increasing mean air temperature and retraction of the local Collins glacier and, consequently, an increase in the availability of liquid water and sediments in the proglacial and periglacial environment.O objetivo do artigo é avaliar a variação de área e localização dos campos de musgos na Península Fildes, Antártica, utilizando a técnica de NDVI e imagens LANDSAT, para o período 1986 - 2016, frente a cenários de mudanças climáticas. A técnica de NDVI foi aplicada em 7 datas de imagens LANDSAT e os produtos foram avaliados pelo índice Kappa. A área de vegetação aumentou de 1,5 para 2,7 km² no período. Os resultados do índice Kappa indicam a variação entre 0,81 a 0,93 de acurácia, com mais de 70% das áreas mapeadas indicadas acima de 0,1 (área muito provável de vegetação). Os maiores campos de musgos (83% daqueles de maior dimensão) se localizam na porção orientada para o estreito de Drake e estão associados à umidade e vento proveniente do oceano. Há maior quantidade de matéria orgânica e formação de alagados nos paleovales em “U” voltados para o Drake, contribuindo para a fixação da vegetação. Os campos de musgos continuarão a aumentar ou haverá modificação da sua localização diante de cenários de retração da geleira local Collins e o consequente aumento da disponibilidade de água líquida e sedimentos no ambiente proglacial e periglacial

Soil and landform interplay in the dry valley of Edson Hills, Ellsworth Mountains, continental Antarctica

The main relief units from the dry valley of Edson Hills, Ellsworth Mountains, Antarctica (79°49′12.4″/83°40′16.1″), were assessed, emphasizing the analysis of soil and landform interplay. Soil morphological, physical, and chemical properties; salinity; surface boulder weathering (frequency and feature); classification; and weathering stages were analyzed. Three distinct landforms summarize the geomorphology of the dry valley of Edson Hills, Ellsworth Mountains: (i) periglacial features like slightly creeping debris-mantled slopes, steep debris-mantled slopes, patterned grounds, and thermokarst; (ii) glacial features like hummocky moraines, lateral moraines (supraglacial), lakes, kettle hole (proglacial), cirques infill (subglacial), horn, and arête (erosional glacial); and (iii) nonglacial features like scree slopes and talus deposits. All these glacial and periglacial features are related to the West Antarctica ice sheet variations. Soils in the dry valley of Edson Hills are pedologically poorly developed. However, the degree of development in soils associated with patterned ground and moraine systems is remarkable. All soils present desert pavement owing to the action of severe aeolian erosion. In addition, soils accumulate salts depending on the local drainage conditions. The most expressive soil classes among the studied soils were Typic Haploturbel and Typic Anhyorthel, especially because of: (i) a general trend of ice-cemented permafrost occurrence in lower portions of the landscape, particularly in the patterned ground area and in the hummocky moraine; and (ii) the presence of dry permafrost in higher positions of the landscape, in relief units such as in debris-mantled slopes and talus deposits. Thus, a close relationship among soil characteristics and landforms were observed in the dry valley of Edson Hills