Emmy Noether Junior Research Group Artemics
Does the ongoing sea ice decline in the Arctic lead to stronger internal wave generation and thereby to increased interior ocean mixing? Does this in turn increase upward heat fluxes from the warm Atlantic Water and cause even further sea ice melt? And how can we include this process in climate models?
These are the overarching questions of the Emmy-Noether group “Arctic internal wave energetics, mixing, and their interdependence with sea ice in changing climate conditions” (Artemics). We will combine state-of-the-art ocean models, internal wave theory, and observations to resolve the role of internal waves in the warming Arctic and to provide a physics-based representation of their effect in climate models.
Background
Internal waves form in the interior of stratified fluids, like the ocean or the atmosphere. Similar to the surface waves we observe at the beach, they can break and thus mix the surrounding waters. Internal waves play a key role in the climate system, because this mixing contributes to driving the large-scale overturning circulation in the ocean, which transports vasts amount of heat around the globe.
In the Arctic, the role of internal waves is less clear. This far north and under a strong sea ice cover, only few internal waves are generated. Due to global warming, however, the latter point is no longer given. This offers the potential for increased internal wave generation and hence increased wave-driven mixing in the
warming Arctic. The current, relatively weak mixing processes in the interior Arctic Ocean are the life insurance for its sea ice: The waters entering the Arctic Ocean from the Atlantic are a huge heat reservoir. But they are also relatively salty, which means that they are too dense to stay near the surface and instead sink down. A cold and fresh layer of water is located between the sea ice and the warm Atlantic Water and
insulates the sea ice from the heat below. As long as interior mixing processes are weak, this vertical structure persists and the sea ice is protected. The potential for a dramatic feedback loop arises: As global warming continues to drive sea ice decline, internal wave generation and mixing could increase such that enough heat from the Atlantic Water is fluxed toward the surface that even more sea ice melts.
Mission
We aim to shed light on the various feedback processes between Arctic internal waves and sea ice and the ramifications for ocean dynamics in the Arctic and beyond. Climate models do not resolve the small and intermittent mixing processes and so far, wave-driven mixing is not represented in a physics-based way in the Arctic. We will close this research gap and thereby contribute to improving climate projections.
