Freshwater runoff on the east Greenland shelf

Abstract

The Greenland Ice Sheet releases fresh water from ice melt, tundra snow melt, and solid ice at an increasing rate during recent decades resulting in an increasing amount of freshwater runoff into the ocean. As a result, freshwater runoff is changing the continental shelf circulation by increasing the amount of fresher water on the shelf that may then enter the deep ocean. Observational studies show that dense water does traverse the east Greenland shelf near the ocean bottom but it is unclear to what extent the transport of near surface fresh water, as a result of runoff, reaches deeper water and enters the Irminger Basin. Using 4 km resolution nested numerical model simulations with and without freshwater runoff, we show freshwater runoff increases salinity variability with increased baroclinicity. While higher salinity variability and baroclinicity suggest a greater potential for water mass exchange across the East Greenland Current, most freshwater runoff along east Greenland remains on the shelf. From freshwater runoff alone, salinity and salt mass decreases by 0.22% on the continental shelf compared to a 0.01% in the rest of the Nordic Seas. There is a 0.05% reduction in salt mass on the Greenland shelf region that makes up 8% of the simulation domain, suggesting little water exits the shelf along the east coast of Greenland. The largest reduction in salt mass occurs around Iceland, where substantial freshwater runoff exists. A calculation of baroclinic conversion rate suggests likely pathways for runoff to exit the continental shelf and enter deep water in the Denmark Strait and over the Greenland/Scottland ridge east of Iceland. Most of the fresh water, however, released along the east coast of Greenland continues towards Cape Farewell, outside our modeling domain, and into the Labrador Sea.