This project investigates the processes that determine the ocean flow through Nares Strait, which is a narrow passage between northwest Greenland and Ellesmere Island.  Freshwater accumulates in the Arctic Ocean due to river inputs, precipitation and sea-ice melt. While most of this water leaves the Arctic on the eastern side of Greenland through Fram Strait, some also leaves through Nares Strait. Changes in this flow will affect how the density of the Arctic Ocean changes on seasonal and longer time scales. Furthermore, the water passing southward through Nares Strait can affect melting of glaciers in western Greenland and processes in the Labrador Sea that lead to formation of dense water.

Earth & Space Research (ESR) and Oregon State University (OSU) collaborated on this project, which uses a high-resolution numerical model to study flow in Nares Strait. OSU is the lead institution and conducted the modeling: the main role of ESR personnel was to assist with the modeling based on our previous long experience with polar oceanography and glaciology. The project also used several years of data collected in Nares Strait by Andreas Muenchow at the University of Delaware (UDel) to verify that the model was producing reasonable results.

ESR’s contribution to the intellectual merit of this work is documented in two papers and three conference presentations. One of the papers (Muenchow et al., 2014, in the Journal of Glaciology) reported a detailed study of the mass budget for Petermann Ice Shelf in Petermann Fjord in northwest Greenland. This ice shelf is the floating extension of Petermann Glacier (PG), which drains a portion of the northwest Greenland Ice Sheet into the ocean. The grounded part of PG includes a large area where the ice is grounded well below sea level: such ‘marine-based’ glaciers can retreat rapidly if the ice shelf disappears, with consequences for global sea level rise. Our paper looked for evidence of the processes that might cause ice-shelf loss and glacier retreat. We used airborne and satellite measurements to map the thinning of Petermann Ice Shelf prior to two large ice loss (iceberg ‘calving’) events in 2010 and 2012.  At the end of these two events, the ice shelf was shorter than it had ever been recorded since the first documented siting in 1879. This study found that Petermann Ice Shelf was thinning rapidly by ocean melting of its base before 2010, suggesting that this thinning might have helped set the scene for iceberg calving. Furthermore, occasional measurements of ocean temperature, inside Petermann Fjord near the ice shelf and outside the fjord in Nares Strait, suggest that warmer water coming southwards through the strait may have been responsible for the thinning of the ice shelf.  Therefore, if we could predict future changes in ocean temperature in Nares Strait, we might be able to predict ice loss from northwest Greenland and its contribution to sea level.

ESR personnel also contributed to Shroyer et al. (submitted to the Journal of Physical Oceanography). This modeling study looks at the processes that drive flow through Nares Strait. The strait is very narrow – less than 20 km in some places – so that the model needs to be very high resolution. The principal results from this model are that the flow is driven mainly by the difference in sea level pressure between the Arctic and northern Baffin Bay: winds over Nares Strait have only a small effect on flow. The distribution of currents in Nares Strait changes significantly between the short sea-ice-free summer and the winter period where much of the strait is covered by stationary sea ice. We suggest that the change in circulation, including the presence of current meanders and instabilities in summer, will affect the input of warm ocean water into adjacent fjords. If this is true, then reductions...

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