Heat, salt and volume transports by eddies in the vicinity of the Luzon Strait

The heat, salt and volume transports by oceanic meso-scale eddies generated near the Luzon Strait and moving into the South China Sea (SCS) are estimated by combining satellite altimetry and sea surface temperature (SST) data with hydrographic data. By establishing a statistical relationship among steric height, SST and subsurface temperature, together with a multi-grid 3D-Var assimilation method, an eddy-resolving temperature/salinity dataset from 1993 to 2008 is reconstructed from the altimetry sea surface height (SSH) anomaly, remote sensing SST and historical temperature/salinity profiles in the SCS. Using two cases of eddies in the reconstructed temperature/salinity dataset, we show that a cyclonic eddy can carry negative heat anomaly with −6.7±2.5×1018 J, which contributes to the heat balance of the region where it travels through, and freshwater of 0.0005±0.0002 Sv into the SCS, and that an anti-cyclonic eddy can transport positive heat anomaly with 4.6±1.8×1018 J, which might have affected the inteannual variation of heat in the upper layer of the SCS and bring freshwater of 0.0004±0.0001 Sv into the SCS on top of the 26.5σθ isopycnal surface. The 16-year averaged heat, salt and volume transports by meso-scale eddies near the Luzon Strait are estimated as 0.00003±0.00001 PW, 0.004 ± 0.001 × 10 6 kg s − 1 and 0.3 Sv into the SCS on top of the 25.0σθ isopycnal surface. During the 16-year period, these transports show significant interannual variations. Generally, the heat transport is positive during summers of El Niño, while it is negative or weakly positive during summers of La Niña.