Warming of Atlantic Waters in Fram Strait and Underneath the 79°N-Glacier

The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers around Greenland. A key region for the mass balance of the Greenland Ice Sheet is the Northeast Greenland Ice Stream. This large ice stream drains the second-largest basin of the Greenland Ice Sheet and feeds three outlet glaciers. The largest one is Nioghalvfjerdsfjorden (79°N-Glacier) featuring an 80 km long floating ice tongue. Observations showed that warm waters of Atlantic origin are present in the subglacial cavity and cause strong basal melt at the grounding line of the 79°N-Glacier.

In order to study the relevant processes of glacier-ocean interaction with respect to the North Atlantic warming, we combine observations and model work. In general the complex continental shelf bathymetry steers the flux of warm water of Atlantic origin from the open ocean onto the continental shelf and into the sub-glacial cavity of the 79°N-Glacier. Based on historic and recent hydrographic observations, we show that the warmest water observed in the cavity of the 79°N-Glacier originates from the south-eastern entry via Norske Trough, where modified Atlantic Water recirculated in Fram Strait enters the continental shelf area. We found that these Atlantic waters, both on the shelf and in the cavity, have become warmer by about 0.5°C during the last two decades. We propose that an increase in Atlantic Water temperatures in Fram Strait likely propagates onto the continental shelf and underneath the 79°N-Glacier, where it may cause increased basal melt. This is supported by first results based on model runs with a high-resolution configuration of the Finite Element Sea ice Ocean Model (FESOM).