Title: Observations of cross-shelf exchange and mixing at Narsaq Trough, Greenland

Abstract:

Greenland’s continental shelf is incised by submarine troughs of varying sizes, orientations, and geometries. These troughs have the potential to deflect the coastal currents that circulate around Greenland, where the nearshore cold, fresh Polar Water abuts the warm, salty Atlantic Water offshore. However, the role they play in driving vertical or horizontal exchange of waters is largely unknown despite implications for export of freshwater into the convective basins and warm water access to the Greenland Ice Sheet.

In this talk I will present results from a ship-based survey of Narsaq trough – a large, branched trough in southwest Greenland. We use CTD-oxygen measurements, nutrient samples, and shipboard ADCP to describe the water mass properties and flow field upstream, midstream, and downstream of the trough and investigate whether water mass modification occurs. A key result is that the sub-surface waters in Narsaq trough are colder, fresher and more oxygen rich than waters at the same depth offshore, suggesting that surface waters are entrained downwards. I also show that these modified trough waters are at times exported from the trough, possibly resulting in freshening, cooling, and oxygenation of the West Greenland Current.