Decreasing intensity of open-ocean convection in the Greenland and Iceland seas

A combination of retreating sea ice and different rates of warming in the Greenland and Iceland seas is reducing winter air–sea heat fluxes. These fluxes drive ocean convection and are projected to decrease further. The air–sea transfer of heat and fresh water plays a critical role in the global cli...

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Bibliographic Details
Published in:Nature climate change 2015-09, Vol.5 (9), p.877-882
Main Authors: Moore, G. W. K., Våge, K., Pickart, R. S., Renfrew, I. A.
Format: Article
Language:English
Subjects:
704/106/125
704/106/694/2786
704/106/829/2737
Atmospheric forcing
Climate Change
Climate Change/Climate Change Impacts
Climate system
Climate variability
Environment
Environmental Law/Policy/Ecojustice
Global climate
letter
Marine
Oceanic convection
Overflow
Sea ice
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Summary:A combination of retreating sea ice and different rates of warming in the Greenland and Iceland seas is reducing winter air–sea heat fluxes. These fluxes drive ocean convection and are projected to decrease further. The air–sea transfer of heat and fresh water plays a critical role in the global climate system 1 . This is particularly true for the Greenland and Iceland seas, where these fluxes drive ocean convection that contributes to Denmark Strait overflow water, the densest component of the lower limb of the Atlantic Meridional Overturning Circulation (AMOC; ref.  2 ). Here we show that the wintertime retreat of sea ice in the region, combined with different rates of warming for the atmosphere and sea surface of the Greenland and Iceland seas, has resulted in statistically significant reductions of approximately 20% in the magnitude of the winter air–sea heat fluxes since 1979. We also show that modes of climate variability other than the North Atlantic Oscillation (NAO; refs  3 , 4 , 5 , 6 , 7 ) are required to fully characterize the regional air–sea interaction. Mixed-layer model simulations imply that further decreases in atmospheric forcing will exceed a threshold for the Greenland Sea whereby convection will become depth limited, reducing the ventilation of mid-depth waters in the Nordic seas. In the Iceland Sea, further reductions have the potential to decrease the supply of the densest overflow waters to the AMOC (ref.  8 ).
ISSN:1758-678X
1758-6798
DOI:10.1038/nclimate2688