Trends and Interannual Variability of Winds and Turbulent Heat Flux in the Indian Ocean Sector of Southern Ocean during 2000-2009

Using satellite-based wind and sea surface temperature (SST) observations, linear trend and interannual variability of wind stress, turbulent heat flux (Q) and wind stress curl are addressed for the Indian Ocean sector of the Southern Ocean (ISO, 0 ̊E 155 ̊E) for the period 2000-2009. The analysis reveals that spatial mean of Q varies between 70 and 73 Wm−2 in the austral summer and winter, respectively, while the mean wind stress is nearly same at 0.22 Nm−2 for both seasons. The anticyclonic curl dominates the ISO, which increases from 0.15 × 10−7 to 0.35 × 10−7 Nm−3 during the austral summer. The detrended box-mean time series of Q, wind stress, and wind stress curl exhibits a decreasing trend of –6.3 ± 1.6 Wm−2∙decade−1, −0.012 ± 0.004 Nm−2∙decade−1 and −0.48 ± 0.6 × 10−8 Nm−3∙decade−1, respectively. The Empirical Orthogonal Function (EOF) analysis was carried out to study interannual variability. EOF-1 of Q captures 25% of the total variance, which mimics the austral summer pattern; its time coefficient is highly and negatively correlated with a 2-month lagged Nino3.4 SST index (r = −0.8 at 95% confidence). EOF-1 of wind stress accounts for 35% of the total variance and its time coefficient is strongly correlated with the Antarctic Oscillation (r = 0.86 at 95% confidence). EOF-1 of wind stress curl captures 15% of the total variance; its time coefficient is correlated to the Nino3.4 SST index (r = 0.65 at 95% confidence) with the former lagging the latter by two years. The repercussions of the weakening trends of the climatic parameters on the air-sea interaction and ocean circulation are highlighted.