SEMINAR: MPO Seminar:Dr. Rym Msadek, TODAY, at 3:00 p.m., in the Slab Seminar room, S/A 103

[Sandrine Apelbaum <sapelbaum@rsmas.miami.edu>]

MPO Seminar

Dr. Rym Msadek

GFDL/NOAA

Princeton University

"Comparing the MOC/MHT relationship at 26.5ºN in RAPID data 

and in GFDL and NCAR climate models"

Room: Slab seminar room, S/A 103

Date: Wednesday, February 8, at 3:00 p.m. 

Abstract:

The link at 26.5ºN between the Atlantic meridional heat transport (MHT) and the Atlantic meridional overturning circulation (MOC) is investigated in two coupled climate models, GFDL CM2.1 and NCAR CCSM4, and compared with the latest observational estimates from the RAPID-MOCHA array. Despite a stronger than observed MOC magnitude, both models underestimate the mean MHT at 26.5ºN due to an overly diffuse thermocline. Biases result from errors in both overturning and gyre components of the MHT. We show that the observed linear relationship between MHT and MOC at 26.5ºN is realistically simulated by the two models but with a too small sensitivity. CCSM4, which has a parameterization of Nordic Sea overflows and thus a more realistic North Atlantic Deep Water (NADW) penetration shows smaller biases than CM2.1 due to NADW transports at colder depths. The horizontal gyre heat transport and its sensitivity to the MOC are poorly represented in both models. The wind-driven gyre heat transport is weakly southward in both CM2.1 and CCSM4 while it is northward in observations. This leads to a decrease of the total mean MHT in the models. This bias results from errors in temperature and velocity particularly at the western boundary. Our results indicate that both better physics and resolution are required to realistically simulate the MHT and its link with the MOC at 26.5ºN.

 

Sandrine Apelbaum

Meteorology and Physical Oceanography 
Rosenstiel School of Marine and Atmospheric Science
University of Miami
4600 Rickenbacker Causeway
Miami, FL 33149-1098
Tel     (305) 421-4057
Fax     (305) 421-4696

sapelbaum@rsmas.miami.edu