On the possibility of a long subglacial river under the north Greenland ice sheet

Abstract. Does a long subglacial river with a source deep in the interior of the Greenland ice sheet, drain into the sea at the Petermann Glacier grounding line? Basal topographic data shows a segmented valley extending from Petermann Fjordinto the centre of Greenland, however the locations of radar scan lines, used to create the bedrock topography data, indicate that valley discontinuity is due to data interpolation. Simulations where the valley is opened are used to investigate effects on basal water and ice sheetsliding. The simulations indicate that the opening of this valley results in an uninterrupted water pathway from the interior along the valley that alters ice sheetsliding in the Petermann catchment and in areas of west Greenland. Along its length, the path of the valley progresses gradually down an ice surface slope causing a lowering of ice overburden pressurethat could enable water flow along its path. The fact that the valley base appears to be relatively flat and follows a path along the interior ice dividethat intersects the east and west basal hydrological basins, is presented as evidence that its present day form developed as a consequence of the overlying ice sheetrather than prior to ice sheetinception. Though considerable uncertainty remains, the results are consistent with a present day active long subglacial river system. The results raise issues concerning the need to better observe, understand, and simulate the complicated basal hydrology of the Greenland and other ice sheets.