MASS AND HEAT BUDGETS IN THE EAST AUSTRALIAN CURRENT - A DIRECT APPROACH

We present a technique which uses the large set of expendable bathythe rmograph data that are available in the waters off Eastern Australia t o correct sampling errors in the mass transport function calculated fr om the much more limited number of deep hydrology stations. This techn ique utilizes the close correlation between temperature at a single de pth and subsurface steric height, found in these waters, to perform th e correction. After corrections are applied, it is found that a mass t ransport function for the top 2000 dbar can be used to estimate the ne t geostrophic outflows from the Tasman and Coral seas; it balances Ekm an inflows to within -0.4 +/-2.0 Sv (1 Sv = 1.0 x 10(6) m3 s-1). The m ass transport closure allows a much improved determination of the dist ribution of individual transport components into the region to be obta ined including a robust estimate of the net southward transport throug h the whole width of the Tasman Sea (including the East Australian Cur rent (EAC)) of 9.4 Sv, through a section at 28-degrees-S between the c oast and 171-degrees-E. A more direct determination of this Tasman Sea transport, which uses annual mean alongshore currents on the shelf to infer mass transport on the slope, provides an independent confirmati on. Mass budgets between density surfaces are also examined; for the d eeper layers we find a closure of the mass budget within 10% of the ne t inflow (a maximum misclosure of 0.9 Sv), suggesting little diapycnal mixing. The geostrophic inflow upwells as it flows south in the EAC a t a rate of about 3 Sv at a 250 m depth. The net transport balance alo ng the path also allows the first determination of the heat transport associated with the mean mass transport into the Tasman and Coral seas to be obtained (we have not considered any contributions from eddy he at transport). There is a small net inflow of heat transport to the re gion of 0.13 x 10(15) W, With more heat entering the Tasman Sea than t he (oral Sea. The net upward heat flux of 24 W m-2 (heat loss to the a tmosphere) is consistent with values given in climatologies obtained f rom direct surface flux calculations. The results from a Sverdrup-Munk model agree broadly with the the observed pattern of the mass transpo rt function, particularly the location of the boundary currents, altho ugh the model transports are generally higher.