Preprints
https://doi.org/10.5194/egusphere-2022-869
https://doi.org/10.5194/egusphere-2022-869
 
08 Sep 2022
08 Sep 2022

On the ocean's response to enhanced Greenland runoff in model experiments: relevance of mesoscale dynamics and atmospheric coupling

Torge Martin1 and Arne Biastoch1,2 Torge Martin and Arne Biastoch
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
  • 2Christian-Albrechts-Universität Kiel, Kiel, Germany

Abstract. Increasing Greenland Ice Sheet–melting is anticipated to impact watermass transformation in the subpolar North Atlantic and ultimately the meridional overturning circulation. Complex ocean and climate models are widely applied to predict magnitude and timing of related impacts under projected future climate. We discuss the role of the ocean mean state, subpolar gyre circulation, mesoscale eddies and atmospheric coupling in shaping the response of the subpolar North Atlantic Ocean to enhanced Greenland runoff. In a suite of eight dedicated 60 to 100-year long model experiments with and without atmospheric coupling, with eddy processes parameterized and explicitly simulated, with regular and significantly enlarged Greenland runoff, we find (1) a major impact by the interactive atmosphere in enabling a compensating temperature feedback, (2) a non-negligible influence by the ocean mean state biased towards greater stability in the coupled simulations, both of which making the Atlantic Merdional Overturning Circulation less susceptible to the freshwater perturbation applied, and (3) a more even spreading of the runoff tracer in the subpolar North Atlantic and enhanced inter-gyre exchange with the subtropics in the strongly eddying simulations. Overall, our experiments demonstrate the important role of mesoscale ocean dynamics and atmosphere feedbacks in projections of the climate system response to enhanced Greenland Ice Sheet–melting and hence underline the necessity to advance scale-aware eddy parameterizations for next-generation climate models.

Torge Martin and Arne Biastoch

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Amendment to code and data availability', Torge Martin, 09 Sep 2022
    • EC1: 'Reply on AC1', Karen J. Heywood, 09 Sep 2022
  • RC1: 'Review on : “On the ocean’s response to enhanced Greenland runoff in model experiments: relevance of mesoscale dynamics and atmospheric coupling”Comment on egusphere-2022-869', Anonymous Referee #1, 31 Oct 2022
    • AC2: 'Reply on RC1', Torge Martin, 02 Nov 2022
    • AC4: 'detailed response to RC1', Torge Martin, 09 Dec 2022
  • RC2: 'Comment on egusphere-2022-869', Anonymous Referee #2, 05 Nov 2022
    • AC3: 'Reply on RC2', Torge Martin, 11 Nov 2022
    • AC5: 'detailed response to RC2', Torge Martin, 09 Dec 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • AC1: 'Amendment to code and data availability', Torge Martin, 09 Sep 2022
    • EC1: 'Reply on AC1', Karen J. Heywood, 09 Sep 2022
  • RC1: 'Review on : “On the ocean’s response to enhanced Greenland runoff in model experiments: relevance of mesoscale dynamics and atmospheric coupling”Comment on egusphere-2022-869', Anonymous Referee #1, 31 Oct 2022
    • AC2: 'Reply on RC1', Torge Martin, 02 Nov 2022
    • AC4: 'detailed response to RC1', Torge Martin, 09 Dec 2022
  • RC2: 'Comment on egusphere-2022-869', Anonymous Referee #2, 05 Nov 2022
    • AC3: 'Reply on RC2', Torge Martin, 11 Nov 2022
    • AC5: 'detailed response to RC2', Torge Martin, 09 Dec 2022

Torge Martin and Arne Biastoch

Torge Martin and Arne Biastoch

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Increasing Greenland Ice Sheet--melting is anticipated to impact water mass transformation in the subpolar North Atlantic and ultimately the meridional overturning circulation. Greenland meltwater redistribution pathways in and impact on the subpolar North Atlantic and overturning circulation is currently among the most debated topics. The manuscript provides new insights to both physical oceanographic processes and climate modelling. Based on a systematic setup of model configurations the importance of atmospheric feedbacks and mesoscale dynamics for specific regions of the subpolar North Atlantic are emphasized. This reaches beyond aspects of model techniques and also addresses the need for continued and improved observations in critical locations of the subpolar North Atlantic gyre circulation.
Short summary
How is the ocean affected by continued Greenland ice sheet mass loss? We show in a systematic set of model experiments that atmospheric feedback needs to be accounted for as the large-scale ocean circulation is more than twice as sensitive to the meltwater otherwise. Coastal winds, boundary currents and ocean eddies play a key role in redistributing the meltwater. Eddy paramterization helps the coarse simulation to perform better in the Labrador Sea but not in the North Atlantic Current region.