Coastal upwelling along the north coast of Papua New Guinea and El Nino events during 1981-2005

We investigate the relationship between sea surface temperature (SST) cooling and upwelling along Papua New Guinea's (PNG) north coast before the onset of El Nino events using a hindcast experiment with a high-resolution ocean general circulation model. Coastal upwelling and related SST cooling appear along PNG north coast during the boreal winter before the onsets of six El Nino events occurring during 1981-2005. Relatively cool SSTs appear along PNG north coast during that time, when anomalous northwesterly surface wind stress, which can cause coastal upwelling by offshore Ekman transport appearing over the region. In addition, anomalous cooling tendencies of SST are observed, accompanying anomalous upward velocities at the base of the mixed layer and shallow anomalies of 27 degrees C isotherm depth. It is also shown that entrainment cooling plays an important role in the cooling of the mixed layer temperature in this region.