Terrestrial biomarkers in sediments from the continental slope of Nordaustlandet, Svalbard reveal unprecedented subglacial meltwater drainage during the Last Termination

The subglacial environment and its characteristics are of primary importance for the behaviour and the stability of ice sheets; however, the mechanisms that take place beneath ice sheets still need to be accurately quantified. Here we present the results of a multi-proxy, biogeochemical analysis carried out on a marine sediment core (HH11-09GC) from the northern Svalbard continental slope, encompassing the last 30 ka. During Termination I, our results suggest a persistent polynya-like environment with significant input of terrigenous organic matter. Indeed, the amount of land-derived material during this period is comparable to that found in the immediate proximity of the major Siberian river mouths during modern times. Alkenone fingerprint suggests that the origin of the terrigenous material could be related to an as yet unidentified freshwater body located in the White Sea/Pechora Basin region, at the margin of the Svalbard Barents Sea Ice Sheet; therefore, the environmental conditions at the base of the ice sheet were suitable for the existence of a large subglacial water drainage. According to our data, this drainage network was able to carry huge amounts of water and sediments beneath the ice sheet and, subsequently, discharge them thousands of kilometres away from their origin. This could represent the first evidence of a pervasive, highly connected subglacial drainage network in the Barents Sea region. Our results may shed new insights on the magnitude of subglacial drainage systems, and thus have important implications with regards to ice sheet modelling.