Observed and simulated estimates of the meridional overturning circulation at 26.5° N in the Atlantic

[摘要] Daily timeseries of the meridional overturning circulation (MOC) estimatedfrom the UK/US RAPID/MOCHA array at 26.5° N in the Atlantic are usedto evaluate the MOC as simulated in two global circulation models: (I) an8-member ensemble of the coupled climate model ECHAM5/MPI-OM, and (II) theECCO-GODAE state estimate. In ECHAM5/MPI-OM, we find that the observed andsimulated MOC have a similar variability and time-mean within the 99%confidence interval. In ECCO-GODAE, we find that the observed and simulatedMOC show a significant correlation within the 99% confidence interval.To investigate the contribution of the different transport components, theMOC is decomposed into Florida Current, Ekman and mid-oceantransports. In both models, the mid-ocean transport is closely approximatedby the residual of the MOC minus Florida Current and Ekman transports. As themodels conserve volume by definition, future comparisons of the RAPID/MOCHAmid-ocean transport should be done against the residual transport in themodels. The similarity in the variance and the correlation between theRAPID/MOCHA, and respectively ECHAM5/MPI-OM and ECCO-GODAE MOC estimates at26.5° N is encouraging in the context of estimating (natural)variability in climate simulations and its use in climate changesignal-to-noise detection analyses. Enhanced confidence in simulatedhydrographic and transport variability will require longer observational timeseries.

[学科分类] 海洋学与技术