Seasonality of freshwater in the East Greenland Current system from 2014 to 2016

TitleSeasonality of freshwater in the East Greenland Current system from 2014 to 2016
Publication TypeJournal Article
Year of Publication2018
AuthorsLe Bras I.AA, Straneo F, Holte J., Holliday N.P
JournalJournal of Geophysical Research-Oceans
Volume123
Pagination8828-8848
Date Published2018/12
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000456405900010
Keywordscirculation; coastal current; currents; fram strait; freshwater; heat; ice-sheet; labrador sea; north; ocean; oceanography; transport; variability; water masses
Abstract

The initial 2years of Overturning in the Subpolar North Atlantic Program mooring data (2014-2016) provide the first glimpse into the seasonality of freshwater in the complete East Greenland Current system. Using a set of eight moorings southeast of Greenland at 60 degrees N, we find two distinct, persistent velocity cores on the shelf and slope. These are the East Greenland Coastal Current, which carries cold, fresh water from the Arctic and Greenland along the shelf, and the East Greenland/Irminger Current over the slope, which is a combination of cold, fresh waters and warm, salty waters of Atlantic origin. Together, these currents carry 70% of the freshwater transport across the subpolar North Atlantic east of Greenland. The freshwater transport referenced to a salinity of 34.9 is approximately equipartitioned between the coastal current (East Greenland Coastal Current) and the fresh portion of the slope current (East Greenland Current), which carry 426 and 326mSv, respectively. The coastal and slope current freshwater transports have staggered seasonality during the observed period, peaking in December and March, respectively, suggesting that summer surveys have underestimated freshwater transport in this region. We find that the continental slope is freshest in the winter, when surface cooling mixes freshwater off the shelf. This previously unmeasured freshwater over the slope is likely to enter the Labrador Sea downstream, where it can impact deep convection. Plain Language Summary East of Greenland, the ocean has very low salinity, as fresh water and sea ice from the Arctic as well as Greenland melt and icebergs flows into it. This fresh water has the potential to alter the formation of dense water by cooling because it is very light due to its low salinity. This, in turn, is expected to affect global ocean circulation and climate. Despite these potential consequences, the pathways of freshwater around Greenland are uncertain, and measurements outside the summer months are scarce. Here we present the first year-round measurements of the complex current system on the continental shelf and slope southeast of Greenland. We find that the two currents (one on the shelf and one over the slope) have a maximum in freshwater transport in the late fall and winter, respectively. This implies that summer measurements have been underestimating the amount of freshwater these currents carry. We find a freshwater maximum over the slope in winter and present evidence that this freshwater has been mixed off the shelf by winter cooling. This is a novel pathway for freshwater that is likely to have consequences downstream.

DOI10.1029/2018jc014511
Short TitleJ Geophys Res-Oceans
Student Publication: 
No