Joint Seminar: Tropical-extratropical exchange based on Argo profiles and ship/mooring observations

The tropical-extratropical exchange in the northwestern Pacific Ocean is studied using the absolute geostrophic currents based on Argo Profiles, which are calculated using the P-vector method for the period of 2004 through present.  The meridional transport of the geostrophic currents is compared with the Sverdrup theory and found to differ significantly in several locations.  Analyses have shown that errors of wind stress estimation cannot account for all of the differences.  The largest differences are found in the area, where nonlinear activities are vigorous.  It is, therefore, suggested that the linear dynamics of the Sverdrup theory is deficient in explaining the geostrophic transport of the tropical northwestern Pacific Ocean.

The simulated meridional volume transports of 11 coupled climate models that participate in the Coupled Model Intercomparison Project phase 5 (CMIP5) are evaluated based on the comparisons with the Argo geostrophic currents.  The comparisons show that the non-Sverdrup gyre circulation identified in the tropical northwestern Pacific Ocean was not reproduced by the CMIP5 models, suggesting model deficiencies.  The assessment is extended to the decadal variability simulations of the CMIP5 model in comparison with the pentadal (5-year) meridional geostrophic transports of the Global Ocean Heat and Salt Content Data.  The simulated meridional transport anomalies in the CMIP5 models are consistent with the Sverdrup theory at the decadal time scales, whereas the observed meridional transport variability differs from the Sverdrup theory in the tropical northwestern Pacific Ocean significantly.  The discrepancy suggests model deficiencies in simulating and predicting the decadal oscillations in the Pacific Ocean.

Using ocean observations from two cruises in the La Niña winter of 2010 and in a normal winter of 2012, the anomalies of the western boundary current transport are compared with the meridional transports in the interior of the North Pacific Ocean.  The results suggest variations during the 2010 La Niña opposite to the discharge-recharge theory of ENSO, which has neglected the role of the western boundary currents.

Date

10.08.2016

Time

13:30 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Dongliang Yuan, Key Laboratory of Ocean Circulation and Waves, and Institute of Oceanology Chinese Academy of Sciences

Organizers

Jochem Marotzke

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