Significant groundwater contribution to Antarctic ice streams hydrologic budget

Abstract

Satellite observations have revealed active hydrologic systems beneath Antarctic ice streams, but sources and sinks of water within these systems are uncertain. Here we use numerical simulations of ice streams to estimate the generation, flux, and budget of water beneath five ice streams on the Siple Coast. We estimate that 47% of the total hydrologic input (0.98 km 3 yr À1 ) to Whillans (WIS), Mercer (MIS), and Kamb (KIS) ice streams comes from the ice sheet interior and that only 8% forms by local basal melting. The remaining 45% comes from a groundwater reservoir, an overlooked source in which depletion significantly exceeds recharge. Of the total input to Bindschadler (BIS) and MacAyeal (MacIS) ice streams (0.56 km 3 yr À1), 72% comes from the interior, 19% from groundwater, and 9% from local melting. This contrasting hydrologic setting modulates the ice streams flow and has important implications for the search for life in subglacial lakes.

Antarctic subglacial groundwater: a concept paper on its measurement and potential influence on ice flow

“…We are unaware of whether permafrost in sedimentary basins in the Antarctic -process (iii) -has been examined before. By analogy, because the WAIS has reduced in size and extent since its last maximum configuration, groundwater release from subglacial sedimentary reservoirs is expected -and, indeed, agrees with modelled groundwater flows into the modern-day interfacial water system beneath Siple Coast ice streams (Christoffersen et al 2014). The spatial and temporal distributions of subglacial water volumes, till deformation, and thus the magnitudes and timings of basal lubrication of ice flow will therefore be likely to differ significantly between models of interfacial ( Fig.…”

“…The hydrological balance of ice streams has so far been considered to include, as water sources, melt from geothermal heating and basal friction, as well as inflow from upstream and, as water sinks, basal freezing and flow downstream (Christoffersen et al 2014;Bougamont et al 2015) (Figs 1 & 2). The flow of subglacial water from sources to sinks has traditionally been restricted to an interfacial hydrological system between ice above and a presumed impermeable sedimentary basin below (Fig.…”

“…Numerical simulations of coupled ice flow and hydrology now suggest, however, that groundwater reservoirs in subglacial sedimentary basins may contribute up to half of all water affecting the basal lubrication of ice streams at the WAIS's Siple Coast (Christoffersen et al 2014). This notable flow of water into and out of a porous groundwater system contradicts the common assumption of impermeable subglacial sedimentary basins in ice-flow modelsbringing current models and forecasts of mass loss from the WAIS into question, as key hydrological processes may be unaccounted for.…”

“…'Interfacial' water system (Fig. 1a) of the Siple Coast in West Antarctica, constructed by Christoffersen et al (2014) with the CISM-2 model. Major water-flow pathways connect subglacial lakes (in black) within a large-scale distributed system of subglacial till layers and linked cavities.…”

Modelling water flow under glaciers and ice sheets

“…Models would ultimately benefit from internally consistent and coupled treatment of water flow from the surface to the subsurface, taking advantage of progress in modelling supraglacial [216], englacial [17,18,217,218] and groundwater drainage [80]. Any model striving for broad applicability will have to treat polythermal bed conditions [188,206,214], a complication often neglected but potentially important for both drainage and ice dynamics [219,220].…”