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Role of the seasonal cycle in the subduction rates of upper-Southern Ocean waters

Citation

Kwon, EY and Downes, SM and Sarmiento, JL and Farneti, R and Deutsch, C, Role of the seasonal cycle in the subduction rates of upper-Southern Ocean waters, Journal of Physical Oceanography, 43, (6) pp. 1096-1113. ISSN 0022-3670 (2013) [Refereed Article]

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DOI: doi:10.1175/JPO-D-12-060.1

Abstract

A kinematic approach is used to diagnose the subduction rates of upper–Southern Ocean waters across seasonally migrating density outcrops at the base of the mixed layer. From an Eulerian viewpoint, the term representing the temporal change in the mixed layer depth (which is labeled as the temporal induction in this study; i.e., Stemp = ∂h/∂t where h is the mixed layer thickness, and t is time) vanishes over several annual cycles. Following seasonally migrating density outcrops, however, the temporal induction is attributed partly to the temporal change in the mixed layer thickness averaged over a density outcrop following its seasonally varying position and partly to the lateral movement of the outcrop position intersecting the sloping mixed layer base. Neither the temporal induction following an outcrop nor its integral over the outcrop area vanishes over several annual cycles. Instead, the seasonal eddy subduction, which arises primarily because of the subannual correlations between the seasonal cycles of the mixed layer depth and the outcrop area, explains the key mechanism by which mode waters are transferred from the mixed layer to the underlying pycnocline. The time-mean exchange rate of waters across the base of the mixed layer is substantially different from the exchange rate of waters across the fixed winter mixed layer base in mode water density classes. Nearly 40% of the newly formed Southern Ocean mode waters appear to be diapycnally transformed within the seasonal pycnocline before either being subducted into the main pycnocline or entrained back to the mixed layer through lighter density classes.

Item Details

Item Type:Refereed Article
Keywords:water mass subduction
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical Oceanography
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Climate Change Models
UTAS Author:Downes, SM (Dr Stephanie Downes)
ID Code:103129
Year Published:2013
Web of Science® Times Cited:7
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2015-09-22
Last Modified:2017-11-01
Downloads:0

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