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Arctic Ocean freshwater content increased in the 2000s. Since variations in freshwater input into the North Atlantic Ocean can modify its properties, monitoring the freshwater export from the Arctic Ocean to southern latitudes is critical. The Arctic Outflow Observatory in Fram Strait has collected continuous ocean measurements from moored platforms since 1997. Here new and improved records of freshwater transport from the mooring array are presented until 2015, showing that, since the last documented record in 2009, the freshwater export was substantially larger from 2010 to 2013. The increase was mostly due to increased southward flow, and secondly due to low salinities. While sea level pressure gradient across the strait explains seasonal variability, it does not explain the observed freshwater anomaly. The cumulative freshwater anomaly between 2010 and 2014 amounted to 3,684 km(3), representing a significant external source of freshwater to the North Atlantic.

Plain Language Summary The Arctic Ocean contains a large amount of freshwater due to river input from Siberian rivers and fresh inflow from the Pacific Ocean. Earlier studies have shown that the freshwater content in the Arctic had increased significantly from the 1990s to the 2000s. Large export of this freshwater to lower latitudes is expected to have an impact on the ocean circulation in the North Atlantic Ocean by changing surface properties. In this study we have analyzed current velocity and salinity data from the East Greenland Current obtained by a mooring array in Fram Strait from 1997 to 2015. Our results show that from 2010 to 2013 a freshwater anomaly was exported from the Arctic Ocean. This was due to large southward velocities from 2010 to 2013 and low salinities in 2011 and 2012. By 2014, the anomaly amounted to a total volume of 3,684 km(3). Comparison with data from Denmark Strait suggests that this has been transported to the North Atlantic Ocean. The freshwater input was larger than the contribution from the Greenland Ice Sheet in the same period and hence should be considered as an important addition of freshwater which may have consequences for the North Atlantic Ocean.