TY - JOUR
T1 - Dynamics of downwelling in an eddying marginal sea
T2 - Contrasting the eulerian and the isopycnal perspective
AU - Brüggemann, Nils
AU - Katsman, Caroline A.
PY - 2019
Y1 - 2019
N2 - In this study, we explore the downward branch of the Atlantic meridional overturning circulation (AMOC) from a perspective in depth space (Eulerian downwelling) as well as from a perspective in density space (diapycnal downwelling). Using an idealized model, we focus on the role of eddying marginal seas, where dense water is formed by deep convection due to an intense surface heat loss. We assess where diapycnal mass fluxes take place, investigate the pathways of dense water masses, and elucidate the role of eddies. We find that there are fundamental differences between the Eulerian and diapycnal downwelling: the strong Eulerian near-boundary downwelling is not associated with substantial diapycnal downwelling; the latter takes place in the interior and elsewhere in the boundary current. We show that the diapycnal downwelling appears to be more appropriate to describe the pathways of water masses. In our model, dense water masses are exported along two routes: those formed in the upper part of the boundary current are exported directly; those formed in the interior move toward the boundary along isopycnals due to eddy stirring and are then exported. This study thus reveals a complex three-dimensional view of the overturning in a marginal sea, with possible implications for our understanding of the AMOC.
AB - In this study, we explore the downward branch of the Atlantic meridional overturning circulation (AMOC) from a perspective in depth space (Eulerian downwelling) as well as from a perspective in density space (diapycnal downwelling). Using an idealized model, we focus on the role of eddying marginal seas, where dense water is formed by deep convection due to an intense surface heat loss. We assess where diapycnal mass fluxes take place, investigate the pathways of dense water masses, and elucidate the role of eddies. We find that there are fundamental differences between the Eulerian and diapycnal downwelling: the strong Eulerian near-boundary downwelling is not associated with substantial diapycnal downwelling; the latter takes place in the interior and elsewhere in the boundary current. We show that the diapycnal downwelling appears to be more appropriate to describe the pathways of water masses. In our model, dense water masses are exported along two routes: those formed in the upper part of the boundary current are exported directly; those formed in the interior move toward the boundary along isopycnals due to eddy stirring and are then exported. This study thus reveals a complex three-dimensional view of the overturning in a marginal sea, with possible implications for our understanding of the AMOC.
KW - Anticyclones
KW - Deep convection
KW - Diapycnal mixing
KW - Eddies
KW - Meridional overturning circulation
KW - Upwelling
KW - downwelling
UR - http://www.scopus.com/inward/record.url?scp=85073885350&partnerID=8YFLogxK
U2 - 10.1175/JPO-D-19-0090.1
DO - 10.1175/JPO-D-19-0090.1
M3 - Article
AN - SCOPUS:85073885350
SN - 0022-3670
VL - 49
SP - 3017
EP - 3035
JO - Journal of Physical Oceanography
JF - Journal of Physical Oceanography
IS - 11
ER -