Reactivation of Kamb Ice Stream tributaries triggers century‐scale reorganization of Siple Coast ice flow in West Antarctica

Abstract

Ongoing, centennial‐scale flow variability within the Ross ice streams of West Antarctica suggests that the present‐day positive mass balance in this region may reverse in the future. Here we use a three‐dimensional ice sheet model to simulate ice flow in this region over 250 years. The flow responds to changing basal properties, as a subglacial till layer interacts with water transported in an active subglacial hydrological system. We show that a persistent weak bed beneath the tributaries of the dormant Kamb Ice Stream is a source of internal ice flow instability, which reorganizes all ice streams in this region, leading to a reduced (positive) mass balance within decades and a net loss of ice within two centuries. This hitherto unaccounted for flow variability could raise sea level by 5 mm this century. Better constraints on future sea level change from this region will require improved estimates of geothermal heat flux and subglacial water transport.

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

“…6). There are two main reasons why this so-called seismoelectric conversion is of particular interest (Kulessa et al 2006a, b), namely exceptional sensitivity to: (i) till permeability (Thompson & Gist 1993;Garambois & Dietrich 2002), a fundamental parameter in ice-sheet modelling (Christoffersen et al 2014;Bougamont et al 2011Bougamont et al , 2015 that cannot be measured with existing methods; and (ii) thin deformable till horizons (Haines & Pride 2006), which are the primary control of an Antarctic ice-stream's basal slip but are difficult to resolve in seismic data (Booth et al 2012). In contrast to seismoelectric conversions, coseismic energy is generated by small charge displacements inside seismic waves when they propagate by elastic deformation.…”

“…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.…”

Tremor during ice-stream stick slip

“…Since most ice flux in Antarctica occurs through ice streams (Whillans et al, 1987;Rignot et al, 2011), understanding the conditions that cause ice-stream stagnation is of basic importance in constraining the continent's contribution to future sea level rise. Although recent progress has been made in describing the relationship between basal conditions and ice stream motion (Bougamont et al, 2011(Bougamont et al, , 2015Robel et al, 2013;Kyrke-Smith et al, 2014, direct observation of the temporal variation in subglacial conditions during ice-stream stagnation has remained elusive.…”

Stochastic ice stream dynamics

“…If, instead, ice is in direct contact with bedrock, the lubrication provided by water at the ice−rock interface controls the rate at which ice slips over the bed (25). Water transport and ponding along ice stream beds have been also observed (30)(31)(32)(33), and model studies (34)(35)(36)(37)(38)(39)) also point to the subglacial drainage system as a control on the spatial and temporal dynamics of ice streams.…”