Small-scale Matters for Large Water Masses in Labrador Sea

  • 28 October 2020
Small-scale Matters for Large Water Masses in Labrador Sea

The transport of heat, nutrients, and dissolved gases in the ocean depends on processes which occur at all scales. At the submesoscale, or small-scale, energetic ocean boundary layer currents flowing along steep slopes often generate vortices. These whirling masses of water can be sustained for long periods of time, over a year, and travel long distances away from their point of origin. Until now, there have been few studies which focus on how these small-scale vortices impact larger ocean transport processes. Researchers supported by CPO’s Climate Variability & Predictability (CVP) program studied how the Labrador Sea Water (LSW) is represented in a regional climate model at different resolutions, or the scale at which processes are defined, to understand how the inclusion of small-scale vortices impacts the formation of the LSW. Their findings are published in Nature Scientific Reports

The Labrador Sea, nestled between the eastern coast of Canada and Greenland, is one of two major sites in the North Atlantic where deep convection regularly occurs. As a result of convection mixing the surface water to great depths, a fresh, cold water mass known as the LSW is formed and spreads southward across the northwest Atlantic at mid-depths. Despite being a well-studied area, climate models continue to struggle to accurately simulate the LSW. In this study, researchers found surprisingly large differences in the model representation of the LSW formation depending on model resolution and determined that current climate models greatly overestimate the formation of the LSW. When small-scale processes are accounted for there was a more than 80% reduction in the modeled volume of convected waters. 

Their findings support a direct link between small-scale water mass instabilities and the Labrador Sea’s contribution to the global meridional overturning circulation. This has implications for understanding Earth’s climate trajectory and calls for developing Earth system models that account for the vortices generated by submesoscale instabilities in relevant regions. 

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