Dynamically consistent estimates of sea level change contributions from observations --1993-2004 (ECCO)

Type: Presentation

Venue: AGU Fall Meeting, San Francisco


Wunsch, C., P. Heimbach, and R.M. Ponte, 2006. Dynamically consistent estimates of sea level change contributions from observations --1993-2004 (ECCO), AGU Fall Meeting, San Francisco, December 2006, invited.

Resource Link: http://adsabs.harvard.edu/abs/2006AGUFMOS41D..02W

A dynamically consistent ocean state estimate is made by combining a general circulation model with 100 million oceanographic measurements plus 4xdaily meteorological forcing estimates in a least-squares formulation using Lagrange multipliers (adjoint method), and the heat and freshwater contributions to sea level change are examined in the solution. To understand the implications of in situ measurements of temperature and salinity over the period 1993-2004, the global-mean trends in the altimetric data are removed so that global average temperature and salinity trends are a direct requirement of the remaining data. Regional sea level changes are quite large (magnitudes over 2cm/year) in some regions with very large spatial variations in temporal variance. Because of the variance structure, the global average trend over the model domain (+/-80 degrees of latitude) is dependent upon the precise method used for its computation, and is thus fragile. Current best estimates are roughly consistent with those previously published, but are about 1/3 of the estimates from altimetry alone, focussing attention on the reliability of the latter. Contributions below 1000m, extending to the seafloor, are significant but not dominant, and can be expected to grow with elapsed time, if present near-surface perturbations are allowed to penetrate into the deep ocean.