Defrosting the Arctic Ocean layer cake

Dramatic sea ice loss (e.g. Polyakov et al., 2023) - a "defrosting" of the Arctic has occurred as it warms 4 times faster than elsewhere (Rantanen et al, Nature, 2022). This and other rapid Arctic changes, such as a freshwater release from the Beaufort Gyre (BG) that can disrupt the overturning circulation in the North Atlantic (Zhang et al., Nature Comms. 2021), may have global consequences.

Yet processes contributing to Arctic change are complex, with unresolved ocean-cryosphere-atmosphere feedbacks; e.g. sunlight better absorbed by the dark ice-free water can, in turn, accelerate icemelt (Curry et al., J. Clim. 1995). Heat loss to the atmosphere and evaporation occurring over expanding open water areas has coincided with an intensification of Arctic storms (Valkonen et al, 2021).

Storms inject more of their energy directly into the ocean, potentially mixing up heat stored in deep ocean. But fresh surface meltwater offsets mixing by insulating sea ice from the warm ocean below, stabilizing the Arctic Ocean stratification or "layering" (e.g. Lincoln et al., 2016).

Mixing and stratification thus compete to set sea surface temperatures critical to climate feedbacks here.

Despite total vertical mixing estimates show no discernable long-term trends (Dosser et al., GRL, 2021), the Eurasian Arctic has lost stratification and sea ice as it succumbs to "Atlantification" by ever-warming inflows from the North Atlantic. In contrast, BG stratification, enhanced by a steady freshwater accumulation over several decades, is now at risk of being released into the North Atlantic (Li et al, 2023).

This project will use observations and models to quantify trends in Arctic stratification and individual mixing processes (both vertical and lateral) to assess the role of ocean and atmospheric drivers of change, and identify potentially critical ice-ocean-atmosphere feedbacks, so as to evaluate the increasing risks of rapid Arctic and global climate change.