Sea Surface Warming and its Implications for Harmful Algal Blooms off Oman

Abstract

The analysis of the sea surface temperature (SST) data for the period from 1961 to 2010, showed the SST regime changes off Oman on different temporal scales. A rapid warming phase is conspicuous in the SST off Muscat and off Masirah along Oman after 1984. The shifts in the SST occurred several times on shorter time scales prior to 1984 but a notable shift in the SST occurred after 1984 when the mean annual SST increased by 0.53℃ off Masirah and by 0.32℃ off Muscat. The amplitude and period of heating/cooling are smaller and shorter off Muscat compared to Masirah with increasing summer warming and decreasing winter cooling. The multivariate ENSO index (MEI) and the annual mean SST at the study locations showed better correlation (R 2 =0.3) with April-May MEI compared to the other months. The highs and lows of SST at both the locations responded with stronger El Nino and La Nina events respectively. The frequency of harmful algal bloom (HAB) events off Oman closely followed the warming and cooling patterns of the sea surface. The frequency of HAB events increased with increasing SST during present decade (2001~2010). The increase in toxic or potentially harmful HAB events may be the consequence of upper ocean stratification forced by increasing SST.