A Lagrangian Method to Isolate the Impacts of Mixed Layer Subduction on the Meridional Overturning Circulation in a Numerical Model

Large differences in the Atlantic meridional overturning circulation (AMOC) exhibited between the available ocean models pose problems as to how they can be interpreted for climate policy. A novel Lagrangian methodology has been developed for use with ocean models that enables a decomposition of the...

Full description

Bibliographic Details
Published in:Journal of Climate
Main Authors: Thomas, Matthew, Treguier, Anne-marie, Blanke, Bruno, Deshayes, Julie, Voldoire, Aurore
Format: Article in Journal/Newspaper
Language:English
Published: Amer Meteorological Soc 2015
Subjects:
Circulation
Dynamics
Convection
Lagrangian circulation
transport
Meridional overturning circulation
Atm
Ocean Structure
Phenomena
Oceanic mixed layer
Models and modeling
General circulation models
Irminger Sea
Labrador Sea
Nordic Seas
Online Access:https://archimer.ifremer.fr/doc/00284/39523/38016.pdf
https://doi.org/10.1175/JCLI-D-14-00631.1
https://archimer.ifremer.fr/doc/00284/39523/
Description
Summary:Large differences in the Atlantic meridional overturning circulation (AMOC) exhibited between the available ocean models pose problems as to how they can be interpreted for climate policy. A novel Lagrangian methodology has been developed for use with ocean models that enables a decomposition of the AMOC according to its source waters of subduction from the mixed layer of different geographical regions. The method is described here and used to decompose the AMOC of the Centre National de Recherches Météorologiques (CNRM) ocean model, which is approximately 4.5 Sv (1 Sv = 106 m3 s−1) too weak at 26°N, compared to observations. Contributions from mixed layer subduction to the peak AMOC at 26°N in the model are dominated by the Labrador Sea, which contributes 7.51 Sv; but contributions from the Nordic seas, the Irminger Sea, and the Rockall basin are also important. These waters mostly originate where deep mixed layers border the topographic slopes of the Subpolar Gyre and Nordic seas. The too-weak model AMOC can be explained by weak model representations of the overflow and of Irminger Sea subduction. These are offset by the large Labrador Sea component, which is likely to be too strong as a result of unrealistically distributed and too-deep mixed layers near the shelf.

Similar Items