Ocean convection linked to the recent ice edge retreat along east Greenland

• Published in: Nature communications Vol. 9; no. 1; pp. 1287 - 8
• Main Authors: Våge, Kjetil, Papritz, Lukas, Håvik, Lisbeth, Spall, Michael A., Moore, G. W. K.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29.03.2018; Nature Publishing Group; Nature Portfolio
• Subjects: 704/106/125; 704/106/35/823; 704/829/2737; Climate system; Convection; Gliders; Heat loss; Humanities and Social Sciences; multidisciplinary; Ocean circulation; Oceanic convection; Science; Science (multidisciplinary); Sea ice; Surface water; Ventilation; Winter; Greenland
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-03468-6

Warm subtropical-origin Atlantic water flows northward across the Greenland-Scotland Ridge into the Nordic Seas, where it relinquishes heat to the atmosphere and gradually transforms into dense Atlantic-origin water. Returning southward along east Greenland, this water mass is situated beneath a layer of cold, fresh surface water and sea ice. Here we show, using measurements from autonomous ocean gliders, that the Atlantic-origin water was re-ventilated while transiting the western Iceland Sea during winter. This re-ventilation is a recent phenomenon made possible by the retreat of the ice edge toward Greenland. The fresh surface layer that characterises this region in summer is diverted onto the Greenland shelf by enhanced onshore Ekman transport induced by stronger northerly winds in fall and winter. Severe heat loss from the ocean offshore of the ice edge subsequently triggers convection, which further transforms the Atlantic-origin water. This re-ventilation is a counterintuitive occurrence in a warming climate, and highlights the difficulties inherent in predicting the behaviour of the complex coupled climate system. Warm Atlantic water circulates cyclonically around the Nordic Seas while gradually cooling. Here, the authors show that the retreat of the ice edge toward Greenland has led to further transformation of this water mass, which is no longer situated underneath sea ice when transiting the western Iceland Sea in winter.