Abstract
Abstract. Subglacial lakes in Antarctica influence to a large extent the flow of the ice sheet. In this study we use an idealised lake geometry to study this impact. We employ a) an improved three-dimensional full-Stokes ice flow model with a nonlinear rheology, b) a three-dimensional fluid dynamics model with eddy diffusion to simulate the basal mass balance at the lake-ice interface, and c) a newly developed coupler to exchange boundary conditions between the two individual models. Different boundary conditions are applied over grounded ice and floating ice. This results in significantly increased temperatures within the ice on top of the lake, compared to ice at the same depth outside the lake area. Basal melting of the ice sheet increases this lateral temperature gradient. Upstream the ice flow converges towards the lake and accelerates by about 10% whenever basal melting at the ice-lake boundary is present. Above and downstream of the lake, where the ice flow diverges, a velocity decrease of about 10% is simulated.
Highlights
During the last decades our knowledge on subglacial lake systems has greatly increased
Thoma been nurtured by microorganisms discovered in ice core samples (Karl et al, 1999; Lavire et al, 2006)
Discussions about the origin and history of the lake (Duxbury et al, 2001; Siegert, 2004; Pattyn, 2004; Siegert, 2005) are still ongoing. It is still unknown whether Subglacial Lake Vostok existed prior to the Antarctic glaciation and if it could have survived glaciation, or whether it formed subglacially after the onset of glaciation
Summary
Research assumed that subglacial lakes were isolated systems, while only recently Gray et al (2005), Wingham et al (2006) and Fricker et al (2007) found evidence that Antarctic subglacial lakes are connected, forming an extensive subglacial hydrological network. The exchange of latent heat associated with melting and freezing dominates heat conduction, but the latter process has be accounted for in subglacial lake modelling (Thoma et al, 2008b). Melting and freezing is closely related to the ice draft which varies spatially over subglacial lakes (Siegert et al, 2000; Studinger et al, 2004; Tikku et al, 2005; Thoma et al, 2007, 2008a, 2009a). The ice draft, and the water circulation within the lake, is maintained by the ice flow across lakes. In order to get an insight in the complex interaction processes between the Antarctic ice sheet and subglacial lakes, this study for the first time couples a numerical ice-flow and a lake-flow model with a simple asynchronous time-stepping scheme to overcome the problem of different adjustment time scales. The newly developed RIMBAY–ROMBAX–coupler RIROCO is introduced in Sect. 4, where we discuss the impact of a coupled icelake system on the ice flow and lake geometry
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