Hydrology and biogeochemistry of subglacial environment of Greenland ice sheet

Abstract

<p>The Greenland ice sheet surface melt has increased substantially in intensity and spatial extent over the recent decades. The rapid migration of melt towards upstream areas of Greenland ice sheet is expected to incur major changes in hydrological behaviour of the ice sheet and outlet glaciers along with changes in export fluxes of carbon, methane, and other nutrient fluxes, which, in turn, will further affect the downstream ecosystem of rivers, fjords and oceans. Subglacial environments are emerging as ecological hotspots, urging detailed understanding of interaction between subglacial hydrology and biogeochemistry. However, due to their inaccessibility, the hydrology and geochemistry of subglacial environment thus far lacks a detailed understanding. As such this area is now the focus of many major projects in Greenland and Antarctica. </p><p> </p><p>Under the NuttI (<strong>Nut</strong>rient fac<strong>t</strong>ories under the <strong>I</strong>ce) project, we aim to develop a hydrological-biogeochemical model framework to investigate seasonal and inter-annual evolution of subglacial hydrology system and quantify carbon and nutrient export from subglacial environments to proglacial rivers. We use the subglacial hydrology model GlaDS (Glacier Drainage System model) to simulate seasonal and interannual evolution of distributed and channelized subglacial water flow while calculating subglacial water storage, residence time, water flux and effective pressure. A subglacial erosion scheme is coupled to the model to calculate physical weathering occurring especially in early melt and peak melt season due to glacier sliding and higher water flow, respectively. All these parameters are used in a geochemical model to quantify subglacial chemical weathering fluxes. The meltwater becomes chemically enriched subglacially and reaches the glacier outlet through subglacial channels. We also intend to further develop the model to investigate processes such as subglacial cycling of silica and production of methane.</p><p> </p><p>We primarily use the coupled model to simulate Leverett glacier, a land-terminating outlet glacier in southwest Greenland which has been well studied with different geophysical measurements and long-term monitoring. The model output is validated with the in-situ measurement of discharge and export fluxes in the proglacial river of the land-terminating glacier. </p>