Schröter, Jens

Staneva, J.

Wenzel, Manfred

English

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SEA LEVEL CHANGE IN THE LAST DECADE-WHAT DO WE UNDERSTAND?Jens Schröter, Joanna Staneva, Manfred WenzelAlfred Wegener Institute for Polar and Marine Research, Bremerhavensea level change 1993-2001• Model: LSG (2° x 2 ° in the horizontal, 23 vertical layers)• Method: 4D VAR data assimilation• As control parameters we use  the model initial state and the model forcing (heat flux, P-E, wind-stress)• Nine years (1993-2001)  T/P data, Reynolds SST are assimilated        into the model• Additionally Levitus climatology, transports of heat and  freshwater are used to constrained the model trajectory (but with low weights)RMS difference of SSA (model v.s. T/P data)SLA correlation (1993-2001)heat and freshwater fluxeslocal sea level changes due to:• freshwater flux• divergence• sub grid gravity waves• thermosteric• halostericdzStS pTH ∂∂∂∂+ ∫− ,1ζ ααEPt−=∂∂ ζ∫−∇+ζHdzv.ζ∆+ hAdzTtT pSH ∂∂∂∂+ ∫− ,1ζ ααdivergence (almost) compensates P-Esea level trendssteric sea level trendsfull depth   upper 512 msteric sea level trends512 m-2250 m   2250 m-bottommodel regionsNorth Pacific and AtlanticNorthern and Western PacificTropical PacificTropical Indian and AtlanticSouth Indian and AtlanticSouth Pacifictemporal evolution of area mean sea levelGlobal heat contentconclusions• We obtained an optimal dynamic ocean evolution for 1993 to 2001 using 4D-VAR data assimilation.• The correlation between the model and T/P SSA is significantly  improved in the constrained model.• The analysis reveals a large regional variability of the local sea level trends. • The model trend is a combination of steric sea level rise (mostly in the upper layers) and eustatic sea level fall.• The warming seems very strong, additional data are needed to constrain the total ocean mass.( such as OAM, J2, GRACE etc.)J2 variationsGood News

Sea level change in the last decade - what do we understand? (solicited)

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