Variability and Trends of Sea Surface Temperature and Circulation in the Indian Ocean
Tropical Indian Ocean is warming at a faster rate compared to other tropical oceans. The warming trends show a basin-scale surface warming with peak warming in the central equatorial Indian Ocean. This warming is favourable for weakening the monsoon Hadle
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Variability and Trends of Sea Surface Temperature and Circulation in the Indian Ocean C. Gnanaseelan, M.K. Roxy and Aditi Deshpande
1 Observations in the Indian Ocean The history of the Indian Ocean observations stretches back approximately to the 1870s (Deser et al. 2010), and a large share of these measurements came from ships of opportunity, mostly linking Mediterranean through the Suez Canal to the maritime continent. Physical oceanographic expeditions were rare in the Indian Ocean until 1950s, with usually more than a couple of decades between two observations in the same region (Behrman 1981). It was only during 1959–1965 that a systematic recording of the Indian Ocean characteristics started with the International Indian Ocean Expedition (IIOE). This was later appended with large-scale sampling through regional programs such as MONEX, BOBMEX, JASMINE and ARMEX (Murakami 1979; Bhat et al. 2001; Webster et al. 2002; Shenoi et al. 2005) along with the use of Argo array profiling floats. Since the advent of satellite era, high-resolution satellite data at frequent intervals became available, helping scientists to decipher the spatiotemporal variability of the Indian Ocean even at finer scales (Bhat et al. 2004). Another major advancement in comprehending the Indian Ocean dynamics took place with the altimeter mission Topex/Poseidon. Understanding of the Indian Ocean sea surface temperature (SST) variability entered a new phase with the advent of microwave radiometer-based satellite observations from December 1997, especially during the cloudy period. Currently, the northern Indian Ocean has a reasonable observational coverage dating back to approximately 1870s (Deser et al. 2010) which supports a reliable analysis of Indian Ocean SST variability on both short and long timescales. The next section discusses the SST trends and variability over the tropical C. Gnanaseelan (&) M.K. Roxy A. Deshpande Indian Institute of Tropical Meteorology, Earth System Science Organization, Pune, India e-mail: [email protected] A. Deshpande Savitribai Phule Pune University, Pune, India © Springer Science+Business Media Singapore 2017 M.N. Rajeevan and S. Nayak (eds.), Observed Climate Variability and Change Over the Indian Region, Springer Geology, DOI 10.1007/978-981-10-2531-0_10
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Indian Ocean, at annual, interannual and intraseasonal timescales and their impact on regional climate. Section 3 discusses the variability and trends in the Indian Ocean circulation.
2 Sea Surface Temperature (SST) Variability in the Indian Ocean Among the tropical oceans, the Indian Ocean is the smallest and the warmest. The tropical Indian Ocean forms the major part of the largest warm pool (SST > 28 °C) among the global oceans. Tropical Indian Ocean SST plays a significant role in shaping climate as well as its variability on both regional (Chowdary et al. 2015) and global scales (Schott et al. 2009), and it is hence important to know the characteristics of Indian Ocean SST on spatial and temporal scales. Indi
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