Long-term changes of temperature in the sea of oman and the western arabian sea

The NCEP-NCAR Reanalysis database (1948-2010), the Hadley Centre SST2 data (1850-2012), and historical data from 98 oceanographic expeditions (1950-2010) were used, in analyzing the long-term changes of temperature. In the western Arabian Sea in summer, the maximal gradient of temperature between the "oldest" mean vertical profile (1960-1970) and the newest one (2001-2010) was observed in the upper mixed layer. In winter, the gradient was located in the deepest layers sampled (150-300m). This points out that in summer warming of the water column comes from the upper mixed layer whereas in winter it comes from the deep; the Persian Gulf Water mass, situated at 200-300m is getting progressively warmer over the years. Historical data on salinity showed that this water mass is getting saltier (due to declining atmospheric precipitation in the region). The major heat for the upper layer comes with the solar radiation reaching its maximum in June. However, the summer-winter gradient of sea surface temperature is changing over the years, in a different way. During the past 60 years, the summer temperatures were increasing whereas the winter temperatures were relatively stable. Perhaps this seasonal difference has led to the strengthening of the vertical stratification of the water column over years. The spectral analysis of the sea surface temperature has evaluated an enhanced variability at 70 years, 9 years, 4 years, 1 year and 6 month periods. Also, these time series exhibited a positive trend in sea surface temperature anomalies covering the past 162 years. The role of the El-NiňoSouthern Oscillation, the Indian Ocean Dipole, and the Siberian High atmospheric pressure system in mediating temperature variability is discussed.