TY - JOUR
T1 - Sinking of Dense North Atlantic Waters in a Global Ocean Model
T2 - Location and Controls
AU - Katsman, C. A.
AU - Drijfhout, S. S.
AU - Dijkstra, H. A.
AU - Spall, M. A.
PY - 2018
Y1 - 2018
N2 - We investigate the characteristics of the sinking of dense waters in the North Atlantic Ocean that constitute the downwelling limb of the Atlantic Meridional Overturning Circulation (AMOC) as simulated by two global ocean models: an eddy-permitting model at 1/4° resolution and its coarser 1° counterpart. In line with simple geostrophic considerations, it is shown that the sinking predominantly occurs in a narrow region close to the continental boundary in both model simulations. That is, the regions where convection is deepest do not coincide with regions where most dense waters sink. The amount of near-boundary sinking that occurs varies regionally. For the 1/4° resolution model, these variations are in quantitative agreement with a relation based on geostrophy and a thermodynamic balance between buoyancy loss and alongshore advection of density, which links the amount of sinking to changes in density along the edge of the North Atlantic Ocean. In the 1° model, the amount and location of sinking appears not to be governed by this simple relation, possibly due to the large impact of overflows and nonnegligible cross-shore density advection. If this poor representation of the processes governing the sinking of dense waters in the North Atlantic Ocean is a generic feature of such low-resolution models, the response of the AMOC to changes in climate simulated by this type of models needs to be evaluated with care.
AB - We investigate the characteristics of the sinking of dense waters in the North Atlantic Ocean that constitute the downwelling limb of the Atlantic Meridional Overturning Circulation (AMOC) as simulated by two global ocean models: an eddy-permitting model at 1/4° resolution and its coarser 1° counterpart. In line with simple geostrophic considerations, it is shown that the sinking predominantly occurs in a narrow region close to the continental boundary in both model simulations. That is, the regions where convection is deepest do not coincide with regions where most dense waters sink. The amount of near-boundary sinking that occurs varies regionally. For the 1/4° resolution model, these variations are in quantitative agreement with a relation based on geostrophy and a thermodynamic balance between buoyancy loss and alongshore advection of density, which links the amount of sinking to changes in density along the edge of the North Atlantic Ocean. In the 1° model, the amount and location of sinking appears not to be governed by this simple relation, possibly due to the large impact of overflows and nonnegligible cross-shore density advection. If this poor representation of the processes governing the sinking of dense waters in the North Atlantic Ocean is a generic feature of such low-resolution models, the response of the AMOC to changes in climate simulated by this type of models needs to be evaluated with care.
KW - Climate
KW - Ocean circulation
UR - http://www.scopus.com/inward/record.url?scp=85047467150&partnerID=8YFLogxK
UR - http://resolver.tudelft.nl/uuid:a72cefd3-b910-4dba-beb3-c85a105d27d5
U2 - 10.1029/2017JC013329
DO - 10.1029/2017JC013329
M3 - Article
AN - SCOPUS:85047467150
SN - 2169-9275
VL - 123
SP - 3563
EP - 3576
JO - Journal of Geophysical Research: Oceans
JF - Journal of Geophysical Research: Oceans
IS - 5
ER -