Location Schirmacher Hills, located in the Central Queen Maud Land of East Antarctica, is an ice free area, bounded by a continental ice sheet on the south and the Fimbul ice-shelf on the north. The region is 17 km in length, 2-3 km wide and lies 100 km from the East Antarctic ice-sheet. Constituted by low lying hills that run East-West, the area varies widely in terms of elevation above sea level. The southern portion of the area is overlain by continental ice-sheet with recessional moraines and ice sheets descending onto bare rock. In contrast, the northern area exhibits steep escarpments all along its length in contact with the ice-shelf, an area often containing epishelf or tidal freshwater lakes similar to those that occur in the Bunger Hills. There are over 100 lakes and ponds of varying depths and melt-water streams in the area.
Formation and diversity The Schirmacher Hills contains several freshwater lakes formed by ice erosion and relict saline lakes formed as a result of the isolation of sea inlets and lagoons. The lakes are fed by melt water from snow beds and ice slopes during the summer.
Lakes Verkhneye, Pomornik, Glubokoye, and Stancionnoye lie in the eastern portion of the Shirmacher Hills and originate from glacial icescour. These lakes range in depth from 3 to 35 m. Lakes Untersee and Obersee are the two most studied lakes in the region and lie at elevations between 650 and 800 m. Lake Untersee (11.4 km2) is a perennially ice-covered (—3 m ice cover), ultra-oligotrophic lake with a maximum depth of 169 m. About 2% of the incident sunlight reaches 145 m, making Lake Untersee one of the most transparent water bodies in the world. The water column throughout the majority of the lake is well mixed; however, there is a trough in the south-eastern portion of the lake that is physically and chemically stratified. The surface waters are supersaturated with oxygen, while water below 80 m is anoxic. High pH values (10-11) occur above 75 m, but decrease to —7 at 100 m. Methanogenesis, methane oxidation, and sulphate reduction have all recently been measured in the deeper waters of this lake. Although smaller, Lake Obersee (3.4 km2) shares many of the same physiochemical features (i.e., high pH, oxygen supersaturation, and high transparency of ice) with Lake Untersee.
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