Freshwater Export in the East Greenland Current Freshens the North Atlantic

Abstract

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 km3, representing a significant external source of freshwater to the North Atlantic.

Role of Greenland Freshwater Anomaly in the Recent Freshening of the Subpolar North Atlantic

“…The freshwater transport estimates that include the shelf mooring observation are used for this study. These estimates have much higher mean freshwater transport than the time series without the shelf mooring observations (for detail, see De Steur et al, ). The time series covers the time period from September 2003 through August 2015.…”

“…The time series covers the time period from September 2003 through August 2015. Anomalies of freshwater transport in Fram Strait are calculated relative to the mean transport over 2004–2009, the time period during which the freshwater transport did not exhibit a significant trend (De Steur et al, ). Values of FWC in the Beaufort Gyre are estimated from the Beaufort Gyre Observing System hydrographic observations (Proshutinsky et al, ).…”

“…Importantly, there is no indication of any decrease in the FWC in this region before 2010 that could be attributed to the freshening of the 2010s in the SPNA. Along with the increasing Arctic FWC, no increasing trend in the liquid freshwater export to the SPNA was observed in the Davis Strait and Fram Strait during the 2000s until 2009 (Curry et al, ; De Steur et al, ; Haine et al, ). No significant change in the sea ice volume export through Fram Strait was observed during 2003–2008 (Spreen et al, ).…”

“…Although the timing of this increased freshwater transport matches the time of the observed freshening in the Labrador Sea and Fylla Bank (around 2007), the volume of this surplus freshwater flux would be insufficient to cause the freshening of observed magnitude. Since 2009, mooring observations in the Fram Strait (De Steur et al, ) reveal a rapid increase of freshwater flux from the Arctic Ocean (Figure a). In two years (2010 and 2011), the surplus freshwater export through Fram Strait contributed ~2,150 km 3 of freshwater to the SPNA totaling 3,260 km 3 by the end of 2015 (Figure b).…”

A Framework for the Development, Design and Implementation of a Sustained Arctic Ocean Observing System

“…There are many broad and important efforts underway regionally and topically. These include, for example, observing systems characterizing Arctic gateways (Fram Strait, e.g., Soltwedel et al, 2013;Hansen et al, 2013;Rabe et al, 2013;Sagen et al, 2016;de Steur et al, 2018;Bering Strait, e.g., Woodgate,. 2018; Davis Strait, e.g., Curry et al, 2014), a network of distributed, drifting Ice Tethered Profilers (e.g., Toole et al, 2011) and observing systems under the PAG, such as the DBO (see Moore and Grebmeier, 2018).…”