North Atlantic Ocean climate in the recent decade

Description

North Atlantic marine climate in recent decades

In this presentation of the marine climate in the North Atlantic Ocean, the focus is on the Subpolar Gyre, the Greenland-Scotland Ridge and the Norwegian Sea areas. In the recent decade, two events dominated the marine climate in the Subpolar Gyre. In the winter 2014/15, extreme cooling occurred in the Irminger Sea, resulting in very low temperature anomalies over large areas of the Subpolar Gyre. This event was termed “The Cold Blob”. In 2015, stronger atmospheric forcing over the Subpolar region in form of stronger winds and increased heat loss, mainly over the Irminger Sea, resulted in a stronger Subpolar Gyre, which expanded eastward. The atmospheric forcing also led to a stronger freshwater flux from the New Foundland shelf into the Subpolar Gyre and increased precipitation. Together these events resulted in an extreme freshening in the eastern part of the Gyre with exceptionally fresh water in the Iceland Basin. Despite the increased cooling, the temperature of the Atlantic Water crossing the Greenland-Scotland Ridge remained relatively high and a de-coupling between temperature and salinity thus occurred. This de-coupling is also evident in the Norwegian Sea where the upper layers have experienced a warming and freshening trend since 2011. In the Norwegian Basin, more than 60% of the warming is explained by reduced ocean heat loss to the atmosphere, while the freshening mainly is due to inflow of fresher Atlantic Water. We might speculate, if the de-coupling between temperature and salinity might affect the deep water formation in and downstream of the Norwegian Sea, but hitherto the exchanges of Atlantic Water and Overflow Water across the Greenland-Scotland Ridge have remained stable. The Norwegian Sea also receives inflow of Modified East Icelandic Water (MEIW) from the East Icelandic Current, but this inflow apparently was low during 2005-2017. In recent years the presence of MEIW in the southern part of the Norwegian basin seems to have increased and this might impact the marine climate in the Norwegian Sea in the coming years. Both MEIW and Subpolar Gyre waters are rich in nutrients and are therefore important for the marine ecosystems downstream and on nearby shelves. On the other hand, silicate concentrations in Arctic Waters entering the Subpolar region have been declining for several years and this trend is expected to impact the phytoplankton growth and composition in marine ecosystems in the region.

Period	20 Jun 2022
Held at	International Council for Exploration of the Seas, Denmark
Degree of Recognition	International