A limnological survey of the Ablation Point area, Alexander Island, Antarctica

Abstract

The ice-free area around Ablation Point (70° 49' S, 68° 25' W) is of particular limnological interest. Numerous ponds and pools lie on coastal moraines and large, permanently ice-covered lakes lie in the valleys. Two of the lakes are unusual in that they are in contact with seawater from George VI Sound which is covered by an ice shelf, 100-500 m thick, and which separates Alexander Island from the Antarctic mainland. Evidence for the existence of a marine biome, 100 km from the open sea, was obtained from one lake. Freshwater biological samples added new genera to Antarctic lists, extended the known range of species, and illustrated the important role of isolation in the determination of antarctic biocoeneses.

Dynamic response of an Arctic epishelf lake to seasonal and long-term forcing: implications for ice shelf thickness

“…Excess freshwater inflow is then assumed to be exported below the base of the ice shelf to the open ocean. Where low tidal action and perennial ice cover limit mixing between the freshwater and saltwater layers, the halocline can be unusually sharp (with reported vertical salinity gradients of ∼ 40 ppt m −1 ; Heywood, 1977) and stable. The strong physical and chemical stratification creates a rare ecosystem where freshwater, brackish water, and saltwater biota can exist within a single water column (Laybourn-Parry et al, 2006;Veillette et al, 2011a).…”

“…Epishelf lakes are numerous in Antarctica and are distributed around the margins of the continental ice sheet (Heywood, 1977;Gibson and Andersen, 2002;Laybourn-Parry et al, 2006;Smith et al, 2006) and were once relatively numerous along the northern coast…”

“…The physical properties of epishelf lakes vary depending largely on the connection to the ocean below the ice shelf. At one extreme are those where the freshwater layer floats directly on seawater -such as Ablation Lake, West Antarctica (Heywood, 1977); Beaver Lake, East Antarctica (Wand et al, 2011); and Disraeli Fiord in the Canadian Arctic (Vincent et al, 2001) -while at the other extreme are epishelf lakes that are entirely fresh but have a restricted hydraulic connection to the ocean below the ice shelf (e.g., Schirmacher Oasis, East Antarctica; Bormann and Fritzsche, 1995), with lakes of varying degrees of stratification in between (e.g., southern Bunger Hills, East Antarctica; Gibson and Andersen, 2002). For epishelf lakes where freshwater floats directly on seawater, the focus of this paper, snow and ice meltwater from the surrounding catchment is thought to accumulate until the thickness of the freshwater layer is equal to the minimum draft of the ice shelf (Hattersley-Smith, 1973;Jeffries and Krouse, 1984;Gibson and Andersen, 2002;Mueller et al, 2003).…”

Range extension of Boeckella bergi Richard, 1897 (Crustacea: Copepoda: Centropagidae), with comments on the taxonomy of the species

“…The South American species of the genus Boeckella are endemic to this continent with exception of B. poppei (Mrázek 1901), which appears in the Malvinas Islands (Ekman 1905), several circumantarctic islands (Poppe & Mrá zek 1895;Ringuelet 1958;Pezzani-Herná ndez 1973;Weller 1977;Paggi 1983;Janiec 1988) and also in both East and West Antarctica (Ekman 1905;Harding 1941;Heywood 1977;Bayly & Burton 1993). This distribution pattern would thus indicate a speciation process within the South American continent after the Gondwana splitting.…”

Structure and sedimentology of George VI Ice Shelf, Antarctic Peninsula: implications for ice-sheet dynamics and landform development

“…The marginal zone in the vicinity of Ablation Lake and Moutonnée Lake (Heywood 1977), which is the subject of this investigation, was described by Stephenson & Fleming (1940) as an area of 'pressure ice' extending about 2 km from land, disposed in a series of parallel ridges. These ridges are associated with an ice-shelf moraine, which Sugden & Clapperton (1981) interpreted as the product of thrusting.…”