Analytical evidence for deep ocean warming trend in tropical Indian Ocean

Abstract

Abstract The present climate change has a warming impact on the Earth’s climate system, hence called as global warming. Study about oceans is relevant to the current scenario of changing climate and many studies show significant warming trends in the Sea Surface Temperature (SST) in the ocean during the past several decades. Extensive warming is found in deeper layers of oceans too. In this study, the monthly mean deep ocean temperature data which was spatially averaged over the tropical Indian Ocean (IO) during the period 1950 to 2012 was subjected to a statistical EMD analysis to estimate the impact of warming to deeper IO. The temperature signal is decomposed into components called as Intrinsic Mode Functions (IMFs) along with a residual part. The IMFs represent the temperature fluctuations resulting from inter-annual oscillations such as ENSO (El-Nino Southern Oscillation) and the residual part can be considered as the long-term trend. The IMFs obtained at each depth showed variabilities in QBO, ENSO and tidal frequencies. Residual part of the signal too had significant magnitudes, indicating the impact of global warming signals at deeper oceans.