The Atlantic Water entering the Arctic Ocean carries enough heat to melt all of the Arctic’s sea ice. Thanks to a cold and fresh layer right below the sea ice, it is insulated and protected from the heat stored in the Atlantic Water below. The relatively weak mixing processes in the present-day Arctic Ocean ensure the persistence of this vertical structure and hence the existence of Arctic sea ice. However, there is growing evidence that the ongoing decline of Arctic sea ice caused by global warming might lead to an increased generation of internal gravity waves, and, through their breaking, enhanced turbulent mixing in the interior Arctic Ocean. The interior mixing might then be sufficiently vigorous to erode the strong stratification and expose the sea ice to heating from the warm Atlantic Waters below, amplifying at possibly dramatic rates the loss of Arctic sea ice. The numerical models used to study the warming Arctic have so far applied a constant background diffusivity to represent the unresolved small-scale mixing processes associated with internal wave breaking in the Arctic. Since this constant is determined based on present-day observations, this approach can represent neither the spatial variability of Arctic wave-driven mixing nor past or future climate conditions. This calls for the development and application of energetically consistent parameterizations, which are based on the underlying physics alone and avoid model tuning to specific climate conditions. The Emmy-Noether group Artemics will for the first time apply an energetically consistent parameterization of wave-induced mixing, the IDEMIX closure, to robustly investigate the link between internal wave energetics, wave-induced mixing, and sea ice in the changing Arctic. IDEMIX is the only operational framework to consistently represent the mixing induced by different types of internal gravity waves and was shown to successfully represent internal wave effects in the global ocean. We will here adapt IDEMIX to the specific conditions of the Arctic Ocean, where different generation mechanisms and in particular the role of sea ice need to be taken into account. In a combination of observational and numerical analyses we will develop a representation of these interdependencies between waves and sea ice in IDEMIX that adjusts to the modeled climate conditions. The final goal is to apply this improved IDEMIX framework in transient climate change simulations to re-assess, if necessary, conclusions drawn from inconsistent mixing parameterizations and to answer many urgent open questions about the fate of Arctic Ocean dynamics, internal wave energetics, and sea ice in our warming world.
DFG Programme
Emmy Noether Independent Junior Research Groups
International Connection
USA
