Polar Transitions: The Arctic Ocean's Diffusive Staircase

The Arctic Ocean, and its reflective sea ice, is of key importance for global climate change. In the Arctic Ocean, warmer waters can underlie colder waters - thus, a reservoir of heat sits at depth. These warm, salty waters are sourced from the Atlantic and subduct below cooler, fresher waters in the Arctic Basin. One way this stored ocean heat is transported vertically is via diffusive convection, a process that may occur if ocean temperature and salinity gradients are both positive with depth. This diffusive-convective mixing mechanism is evidenced by distinctive ``staircase'' features, where approximately meter-thick layers are separated by cm-thick interfaces in temperature and salinity. These staircase features are found across the Arctic Ocean, most notably in the Beaufort Gyre, a region of the western Arctic. However, how these staircases form, and what ultimately governs staircase layer thicknesses is not well known. In this talk, I will describe how the thickness of these layers shows a sharp spatial transition across the Beaufort Gyre, using an observational data set. I will then relate this transition to the influx of a warm Atlantic water pulse as well as the background oceanographic circulation. This work describes how staircases propagate across the Arctic, and how staircase features may give insight into Arctic climate change.