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Modelled Variations of Deep Convection in the Irminger Sea during 2003–10

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  • 1 Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada
  • | 2 Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
  • | 3 Meteorological Service of Canada, Dorval, Québec, Canada
  • | 4 Mercator-Océan, Ramonville-Saint-Agne, France
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Abstract

Results from a high-resolution ice–ocean model are analyzed to understand the physical processes responsible for the interannual variability of ocean convection over the Irminger Sea. The modeled convection in the open Irminger Sea for the winters of 2007/08 and 2008/09 is in good agreement with observations. Deep convection is caused by strong atmospheric forcing that increases the ocean heat loss through latent and sensible heat fluxes. Greenland tip jets are found to be the only strong wind events that directly affect the deep convection area and explain up to 53% of the total turbulent heat loss during active convection years. Deep convection is modeled where there is favorable preconditioning of the water column due to isopycnal doming inside the semienclosed Irminger Gyre. The region of deep convection is also characterized by weak eddy kinetic energy. Finally, an estimation of the surface-forced water mass transformation confirms the Irminger Sea as a region of intermittent production of Labrador Sea Water, with annual averages between 0.9 and 1.9 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of water denser than 27.7 kg m−3 for years of active convection.

Corresponding author address: Jean-Philippe Paquin, Department of Oceanography, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, NS B3H 4R2, Canada. E-mail: paquin.jeanphilippe@gmail.com

Abstract

Results from a high-resolution ice–ocean model are analyzed to understand the physical processes responsible for the interannual variability of ocean convection over the Irminger Sea. The modeled convection in the open Irminger Sea for the winters of 2007/08 and 2008/09 is in good agreement with observations. Deep convection is caused by strong atmospheric forcing that increases the ocean heat loss through latent and sensible heat fluxes. Greenland tip jets are found to be the only strong wind events that directly affect the deep convection area and explain up to 53% of the total turbulent heat loss during active convection years. Deep convection is modeled where there is favorable preconditioning of the water column due to isopycnal doming inside the semienclosed Irminger Gyre. The region of deep convection is also characterized by weak eddy kinetic energy. Finally, an estimation of the surface-forced water mass transformation confirms the Irminger Sea as a region of intermittent production of Labrador Sea Water, with annual averages between 0.9 and 1.9 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of water denser than 27.7 kg m−3 for years of active convection.

Corresponding author address: Jean-Philippe Paquin, Department of Oceanography, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, NS B3H 4R2, Canada. E-mail: paquin.jeanphilippe@gmail.com
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