Sensitivity of abyssal water masses to overflow parameterisations

Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW) control the abyssal limb of theglobal overturning circulation and play a major role in oceanic heat uptake and carbon storage. However,current general circulation models are unable to resolve the observed AABW and NADW formation andt...

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Bibliographic Details
Published in:Ocean Modelling
Main Authors: Snow, K, Hogg, AM, Downes, SM, Sloyan, BM, Bates, ML, Griffies, SM
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier Sci Ltd 2015
Subjects:
Earth Sciences
Oceanography
Physical oceanography
Antarctic
Antarc*
NADW
North Atlantic Deep Water
North Atlantic
Sea ice
Online Access:https://doi.org/10.1016/j.ocemod.2015.03.004
http://ecite.utas.edu.au/103135
Description
Summary:Antarctic Bottom Water (AABW) and North Atlantic Deep Water (NADW) control the abyssal limb of theglobal overturning circulation and play a major role in oceanic heat uptake and carbon storage. However,current general circulation models are unable to resolve the observed AABW and NADW formation andtransport processes. One key process, that of overflows, motivates the application of overflow parameterisations.We present a sensitivity study of both AABW and NADW properties to three current parameterisationsusing a z * -coordinate ocean-sea ice model within a realistic-topography sector of the AtlanticOcean. Overflow parameterisations that affect only tracer equations are compared to a fully dynamicalLagrangian point particle method. An overflow parameterisation involving partial convective mixing oftracers is most efficient at transporting dense NADW water downslope. This parameterisation leads toa maximum mean increase in density in the north of 0.027 kg m -3 and a decrease in age of 525 years(53%). The relative change in density and age in the south is less than 30% of that in the north for all overflowparameterisations. The reduced response in the south may result from the differing dense water formationand overflow characteristics of AABW compared to NADW. Alternative approaches may benecessary to improve AABW representation in z * -coordinate ocean climate models.

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