Salinity Budget In The Fresh Water Pool Of West Pacific Warm Pool Estimated By A Global GCM

The mixed layer salinity budget in the fresh pool of Western Pacific is evaluatedusing18years (1993-2010) data of a global general circulation model. WOA09, Argo,OAFlux and GPCP are used to evaluate the model’s results. Its spatial distribution,seasonal cycle and annual variability are investigated. The relationship betweensalinity budget and ENSO, barrier layer thickness (BLT), salinity front and heatbudget are analyzed emphatically.Results demonstrate that the salinity budget in this region is a balance betweensurface external forcing (SEF) and ocean dynamic processes (ODY). The mixingeffect, especially the turbulent diffusion is the dominant component of ODY，playingthe key role in the dissipation of fresh water in this region.The seasonal cycle of salinity budget is relatively weak compared withmid-latitude regions. SEF and ODY are balanced with each other so that [S]/tcanmaintain as a small value. Turbulent diffusion is the most significant component ofODY, advection and other components are much smaller than it. ODY is positivelycorrelated with salinity front (SF) while the latter one has a little time lag. Theseasonal cycle of turbulent diffusion is very significant and it is negatively correlatedwith the BLT.The annual cycle of fresh pool mixed layer salinity (MLS) has strong ENSOsignal and is highly correlated with advection and diffusion. The correlation betweenMLS and SEF is not obvious. The annual cycle of [S]/tis strong while its meanvalue is small. It is positively correlated with SEF and ODY. And it seems that thecombined effort of the two components has amplified the signal of [S]/t. Notingthat both of turbulent diffusion and advection have strong ENSO signal and they arenegatively correlated with each other (-0.89). The amplitude of the signal of advectionis as strong as turbulent diffusion but with the opposite phase.The annual cycles of SF and BLT have also been discussed and they also havestrong ENSO signal. It is worth noting that SF is positively correlated with BLT and advection, and negatively correlated with turbulent diffusion. It means whenadvection is enhanced (weaken), SF moving westward (eastward) and diffusion getsweaker (stronger), while BLT becomes thicker (thinner). It can be explained asfollows: when advection is enhanced (weaken), SF moving westward (eastward),more (less) high salinity water subducted under the warm pool mixed layer. At thesame time, diffusion gets weaker (stronger). At last, BLT is enhanced (weaken) by thecombined efforts of the enhanced subduction and weaken turbulent diffusion.The heat budget of the same area is evaluated using the same method. Resultsshowing that the ocean dynamics of heat budget is closely related with that of salinitybudget. Noting that diffusion of heat budget has a5month time lag compared withdiffusion of salinity budget which is suspect can be attribute to the specialtemperature-salinity structure of fresh pool.