Date: 2016-09-07

Title: Sea surface signature of the ocean overturning circulation
Supervisors: Fabien Roquet and Leon Chafik
E-mail: roquet@misu.su.se

Project description:

The sea surface height of the ocean is a key dynamical property, whose gradient determines the intensity and direction of surface geostrophic currents. Since the advent of satellite altimetry in the early 90’s, it has become possible to measure both its temporal and spatial variability with sufficient accuracy, revealing all the richness of the eddy turbulence and the complexity of major current systems (e.g., Wunsch and Stammer 1998).

Knowledge of sea surface height not only gives precious information on the near-surface ocean circulation, but it can also tell a lot about the deeper ocean circulation if carefully analyzed. In particular, the variability of the Atlantic meridional overturning circulation (AMOC), which carries surface waters northward across the Atlantic and deeper waters southward, should have a specific sea surface height signature or fingerprint (Zhang 2008).

In this project, we propose to investigate how the variability of the Gulf Stream position as detected from sea-surface heights (Pérez-Hernández and Joyce, 2013) is linked to changes in the AMOC. The analysis will be carried out on the ECCO state estimate (Forget et al., 2014), an advanced product that optimally combines state-of-the-art ocean general circulation models with the nearly complete global ocean data sets for 1992 to present.

References/links:

Pérez-Hernández, M. D. and Joyce, T. M., 2013. Two Modes of Gulf Stream Variability Revealed in the Last Two Decades of Satellite Altimeter Data. Journal of Physical Oceanography, 44:149-163.

Roquet F., Wunsch C., and G. Madec, 2011. On the Patterns of Wind-Power Input to the Ocean Circulation. J. Phys. Oc., 41:2328-2342. doi: 10.1175/JPO-D-11-024.1

Wunsch, C. and Stammer, D., 1998. Satellite altimetry, the marine geoid, and the oceanic general circulation, Annual review of earth and planetary sciences, 26:219-53.

Zhang (2008), Coherent surface-subsurface fingerprint of the Atlantic meridional overturning circulation, doi:10.1029/2008GL035463.