With increasing concern over unusual warming of oceans, melting ice sheets and glaciers gripping the world, the National Centre for Antarctic and Ocean Research (NCAOR) – an autonomous Research and Development Institute of India, in a bid to understand Climate change and predict Climate trends, has expanded its mission from the Antarctic region of the Southern Oceans to the Arctic region of the northern oceans and the Himalayan range. The NCAOR wants to study if rising temperatures is a natural phenomenon that is beyond our control or whether it is because of human contribution.
After its extensive research studies in the Antarctic region, the institution has begun to track weather patterns in the Arctic region and the Himalayas in order to see if the rising atmospheric temperatures can be predicted and if action can be taken to stop or at least retard the process. Besides, the researchers have been trying to understand why the Indian Ocean was warming twice as fast as the other oceans since 2004.
The NCAOR, which has been conducting sustained studies on the issue for the last few years, has pointed out that the Indian Ocean is warming much faster than all other oceans as it is landlocked on the Northern side by the Asian land mass. The atmospheric heat absorbed in the Indian Ocean water was stagnating and goes on building up, while in the Pacific Ocean and Atlantic Ocean, the heat captured over the Equator is pushed towards the Poles. The stagnating heat at the Indian Ocean’s surface releases energy into the atmosphere, increasing regional temperatures and largely influencing global weather patterns. The NCAOR relied on satellite observations and global network of floating buoys, which chart temperature, salinity, currents movement, and other internationally available data to arrive at the findings.
Marine Scientists and Researchers reckon sea levels primarily rise due to water expanding on account of atmospheric heat and, more water being added, from, for instance, melting of ice sheets and glaciers. While melting ice sheets and glaciers account for 70 per cent of the global rise in sea levels, expansion of water due to absorption of atmospheric heat was the biggest cause of rise in sea levels in the Indian Ocean. The present increase in sea levels is part of the decadal oscillation – now in an increasing phase. It is almost double the global sea levels rise. The atmospheric heat that is absorbed in the Indian Ocean is stagnating, and this is precisely one of the important reasons the extreme warming of the ocean and the consequent rise in sea levels is increasing at a much faster rate.
Researchers point out that wind flows, which welled warm water of the Indian Ocean surface, changed directions every decade and influenced sea level patterns. This inter-decadal trend is an extremely important factor, and underlines why we need to plan coastal management better.
According to researchers studying the seas around India, from 1993 to 2003 – the first decade when satellites started to consistently track the rise and fall of ocean heights and global temperatures soared – the North Indian Ocean (NIO) sea levels fell. The NIO consisted of the Arabian Sea, the Bay of Bengal and part of the Indian Ocean up till the 5 degree South Latitude. After 2004, sea levels began an unprecedented accelerated spike till 2014. This rise and fall was even as global temperatures steadily climbed and registered their largest two-decadal jump in more than a century.
Previous studies that had measured ocean heights based on traditional tide gauges, found that the NIO – like the rest of the world’s seas continued to rise between 1993 and 2004. Even the UN inter-governmental panel on Climate Change (IPCC) reports have concluded that while unabated greenhouse gas emissions into the atmosphere would cause oceans to rise every year, there would be years during which some seas could register a fall. Scientists associated with the study said that such a ‘decadal swing’ in the North Indian Ocean was unique and never observed either in the Pacific or Atlantic Oceans.
The NIO went down about 0.3mm a year, and from 2004 gained about 6mm annually. This was twice the global annual average of about 3mm. When temperature and sea level trends in the NIO were mathematically separated out from the other oceans, the fall was even more dramatic; nearly 3mm per year and the Arabian Sea cooling off rapidly at 4mm per year.
Unlike the Pacific and Atlantic, the NIO was hemmed in all sides, except for an outlet of the southern side. This influenced the rate at which atmospheric heat was absorbed and flushed out from within the system. According to the calculations by the researchers, heat was moving out slower from the Indian Ocean after 2004 than during the 1990s. Their work appears in the latest edition of the peer-reviewed ‘Climate Dynamics’.
Besides, rapid warming of the Indian Ocean in the last over a century has led to significant decrease in summer monsoon rainfall over the central east and northern regions of India, along the Ganges-Brahmaputra basins and the Himalayan foothills, says a study by an international team of researchers at the Indian Institute of Tropical Meteorology (IITM), Pune. In the study, the researchers reported that the reduction in summer rainfall in India during the past century is almost 10 to 20 per cent. The Gangetic plains of India, where agriculture is still largely rain-fed, hence a significant reduction in rainfall over the region can be detrimental to the socio-economic well-being of the people of this region as well as of other parts of the country.
(The writer is a freelance journalist)
