Dense bottom layers in the Scotia Sea, Southern Ocean: Creation, lifespan, and destruction
The lower limb of the Atlantic overturning circulation is
renewed by dense waters from the Southern Ocean, a
substantial portion of which flow through the Scotia Sea.
We report dense bottom layers here, with gradients in
temperature and salinity comparable to those seen near the
surface of the Southern Ocean. These are overlain by layers
with much weaker stratification, and are caused by episodic
overflows of dense waters across the South Scotia Ridge,
and topographic trapping within deep trenches. One such
layer was found to be at least 3–4 years older than the water immediately above. The estimated vertical diffusivity to which this layer was subject is substantially less than the strong basin-average deep mixing reported previously. We
conjecture that (a) vertical mixing in the Scotia Sea is
strongly spatially inhomogeneous, and (b) the flushing of
these layers, like their formation, is related to overflow
events, and hence also strongly episodic.
Authors: Meredith, Michael P., Brown, Peter J., Naveira Garabato, Alberto C., Jullion, Loïc, Venables, Hugh J., Messias, Marie-José