Effects of Glacial Melting on the East Greenland Current Kevin Gaynor

Current Properties The East Greenland Current (EGC) flows southward along the eastern coast of Greenland from Fram Strait (79°N) to Cape Farewell (60°N) via the Greenland Sea, the Norwegian Sea, and the Denmark Strait. Its low-density water and the conservation of potential vorticity cause the EGC to remain geostrophically constrained to the Greenland Continental Margin Current supplies water to WGC and Labrador Current.

Water Properties Three major water masses can be found in the EGC: In the upper 150 m there is Polar Water with temperatures between 0°C and below the freezing point. This layer has a strong halocline, with salinity of 30 psu or less at surface. Under the Polar Water is the Atlantic Intermediate Water, which extends to approximately 800 m. Its temperature remains above 0°C, while its salinity increases with depth from about 34 psu to a value between 34.88 and 35 psu. It usually reaches this maximum value at about 400 m, a depth below which the salinity remains fairly constant. The final water mass, the Deep Water, is found below 800 m. Its temperature is less than 0°C, and its salinity is between 34.87 and 34.95 psu. The Polar Water of the EGC originates in the Arctic Ocean, while the deep water masses circulate cyclonically

Dynamics The general movement of the EGC is southward along the eastern Greenland continental margin. The currents are quite strong with annual averages of 6–12 cm/s in the upper part of the EGC (<500 m) with inter-annual maximums of 20–30 cm/s. Estimated that the transport of water southward ranged from 2–32 sverdrups.

Ice Transport It is a major pathway for sea ice to leave the Arctic. It is estimated that more than 90% of the Arctic Sea Ice exported from the Arctic takes place within the East Greenland Current The volume export ranges greatly from year to year. It can be as high as 5000 km3/year and as low as 1000 km3/year. Simulations of seasonal ice flux shows a max in October and smaller values from in February.

Low Salinity Two salinity processes in EGC: Cold, fresh water melts off the continent and enters the Greenland Sea and travels southward. Warm, salty water from the lower latitudes reaches the Arctic. Water then freezes and fresh water becomes ice sheets and eventually drifts southward. This allows high salinity water to sink to bottom, and eventually travel southward.

Effects on NAO/AO Atmospheric forcings also have a strong impact on Arctic Sea Ice export through the EGC. The North Atlantic Oscillation (NAO)/Arctic Oscillation (AO) has a profound impact on the wind field over the Arctic. During high NAO/AO indices the cyclonic wind field over the Arctic becomes very strong, this transports more ice out through Fram Strait and into the EGC. During low NAO/AO indices the cyclonic wind field is quite small and thus the transport out of the Fram Strait diminishes greatly.

Effects on NAO/AO Positive NAO/AO indices also increases melt rates on Greenland, increasing the amount of freshwater that enters the ocean, and decreases salinity. This low salinity water allows for more CO2 to enter the water which eventually causes ocean acidification and warmer temperatures. The low salinity water causes a positive feedback between the ocean, atmosphere, and land, so that the decrease in salinity causes warmer SST, which increases air temperature, and melts more ice.

Freshwater’s Effect The addition of freshwater to the East Greenland Current has had several lasting effects on the current. The amount of ice transported southward has increased as pieces of melting ice shelves off of Greenland and the Arctic ice cap has dislodged and entered the ocean. The increase in sea ice, allows for cold, freshwater to travel further south than it normally would have. The speed of the current has speed up in recent years as the water density has decreased. The depth of the surface layer has gotten larger as more freshwater has entered the ocean.

References Davenport, C., Haner, J., Buchanan, L., & Watkins, D. (2015). Greenland Is Melting Away. The New York Times. The New York Times. http://www.nytimes.com/interactive/2015/10/27/world/greenland-is-melting-away.html?_r=0 Rudels, B., Fahrbach, E., Meincke, J., Bude´us, G., and Eriksson, P. 2002. The East Greenland Current and its contribution to the Denmark Strait overflow. – ICES Journal of Marine Science, 59: 1133–1154. Foldvik, A., Aagaard, K., & Tørresen, T. (1988). On the velocity field of the East Greenland Current. Deep Sea Research Part A. Oceanographic Research Papers, 35(8), 1335–1354. doi:http://dx.doi.org/10.1016/0198-0149(88)90086-6 Gyory, J. The East Greenland Current. The East Greenland Current. http://oceancurrents.rsmas.miami.edu/atlantic/east-greenland.html Tsukernik, Maria; Deser, Clara; Alexander, Michael; Tomas, Robert (2009). "Atmospheric forcing of Fram Strait sea ice export: a closer look". Climate Dynamics 35 (7–8): 1349–1360. Bibcode:2010ClDy...35.1349T. doi:10.1007/s00382-009-0647-z