Investigating the variability and dynamics of the Beaufort Gyre from satellite observations and a high-resolution model

Heather Regan (visitor to the Sea Ice Modelling group)
LOPS, Ifremer, Brest, France
Seminar Date: 
19. November 2019 - 13:15 - 13:45
Lecture room, Ground Floor, NERSC

Authors: Heather Regan (LOPS, Ifremer, Brest, France), in collaboration with Camille Lique and Claude Talandier (LOPS), Thomas Armitage (JPL) and Gianluca Meneghello (MIT)

The Arctic freshwater system supplies freshwater to the North Atlantic and stores large quantities of freshwater within its interior. Studies suggest that variability in Arctic freshwater export has the potential to affect global thermohaline circulation, and therefore the wider climate system. The Beaufort Gyre, in the Canada Basin of the Arctic, is a significant reservoir of freshwater, and acts to modulate freshwater export to the North Atlantic. In recent decades, its freshwater content has increased. Despite the potential importance of this, the dynamics of the gyre are still not fully understood. In this presentation, I will first show results that use a satellite altimetry dataset that provides sea surface height (SSH) in ice-covered regions to characterize the spatial and temporal variability of the gyre over 2003-14. An expansion of the gyre was observed over this period, with a significant raise in SSH, and we investigate this ‘spin-up’ using a high-resolution simulation with NEMO. We focus on describing the total and eddy kinetic energy in the Canada Basin, and their response to this spin up of the gyre. On average and in contrast to the typical open ocean conditions, the levels of mean and eddy kinetic energy are of the same order of magnitude, and the eddy kinetic energy is only intensified along the boundary and in the subsurface. In response to a strong input of momentum at the surface in 2007-2008, the mean kinetic in the gyre increases by nearly an order of magnitude and this new state is sustained afterwards. In contrast, the eddy kinetic energy does not increase significantly, despite simple process models suggesting that eddy generation is the key mechanism of equilibrating the gyre. We will discuss the potential implications of our results for understanding the mechanisms at play for equilibrating the Beaufort Gyre and the variability and future changes of the Arctic freshwater system.