Warming Polar Water and increased presence of Atlantic Water impact sea ice along the east coast of Greenland

The East Greenland Current in Fram Strait connects the Arctic and Subpolar North Atlantic as it transports Polar Water and sea ice to lower latitudes. In the past decade we have started to observe upper ocean warming and sea ice reduction, which further reduces the sea ice cover along Greenland.
Warming Polar Water and increased presence of Atlantic Water impact sea ice along the east coast of Greenland

The export of cold and fresh Polar Water and sea ice from the Arctic Ocean through the Fram Strait is one of the major sources of freshwater to the Nordic Seas and North Atlantic. Most of this transport occurs within the East Greenland Current, a large conveyor extending along the whole east coast of Greenland. Variations in the southward export of these less dense water masses have an influence on the upper ocean stratification within the East Greenland Current and further downstream. These have the potential to impact the production of denser waters and hence the overall intensity of the overturning in the North Atlantic. While added freshwater and heat to the system can reduce overturning, reduced sea ice cover can allow for an increase in overturning or dense water formation in winter. A change between these processes may influence the AMOC, i.e. the Atlantic Meridional Overturning Circulation. The East Greenland Current  at approximately 79°N  in the western Fram Strait has been monitored by The Fram Strait Arctic Outflow Observatory  since the 1990s. This observatory in the western Fram Strait is maintained by the Norwegian Polar Institute (NPI) , and demonstrates the value of long-term observations of ocean climate which are rare at these high latitudes.

The observing system in the western Fram Strait is maintained by the Norwegian Polar Institute (NPI) while the eastern part is maintained by the Alfred Wegener Institute (AWI). Cartoon by the Norwegian Polar Institute.

Our observations in the western Fram Strait show that the ongoing ocean warming and sea ice reduction in the Arctic Ocean is now clearly impacting its outflow in the East Greenland Current. In addition, warmer Atlantic water that enters the Arctic through Fram Strait can have a significant effect in winter since the sea ice that is now much thinner than 15 years ago and is thus easier to melt. When sea ice disappears in summer, solar radiation warms up the ocean surface, delays sea ice growth in autumn, and leads to less sea ice in the following winter. Increased presence of warm Atlantic Water in the Fram Strait in some years has a direct impact on the sea ice cover in winter by melting it from below and by providing heat that prevents sea ice growth. Both observed changes in the Fram Strait have shown to have an impact on the sea ice cover in the East Greenland Current as far south as the Denmark Strait between Greenland and Iceland. The increase in summer heat and summer ice melt will increase stratification there in summer, while wintertime sea-ice loss can allow for more cooling, mixing and overturning of watermasses near the ice edge. Hence, these processes combined can lead to an amplified seasonal cycle in the upper water column  and hence contribute to changes in regional ecosystems along the east coast of Greenland in particular in spring and late summer.

Despite interannual variations, these trends are as projected in climate models: Arctic amplification will further accelerate warming (atmosphere and ocean) and sea ice reduction. While observing the ocean is expensive, dedicated efforts to sustain long-term observations in the Arctic Gateways are indispensable to monitor the impact of changing Arctic on the subpolar seas and to identify the impact of anthropogenic climate change versus natural variability. 

Sea ice in western Fram Strait in September 2019. Photo: Lawrence Hislop (Norwegian Polar Institute).

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