The decrease in snow cover has led to greater differences in both temperature and pressure systems between the Indian subcontinent and the Arabian Sea. The pressure differences generate monsoon winds that mix the ocean water in the Western Arabian Sea. This mixing leads to better growing conditions for tiny, free-floating ocean plants called phytoplankton.
Lead author of the study is Joaquim Goes. He is a senior researcher at the Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine. Goes and colleagues used satellite observations of ocean color to show phytoplankton concentrations in the Western Arabian Sea have increased by more than 350 percent over the past seven years. The study is in this week's SCIENCE magazine
When winter and spring snow cover is low over Eurasia, the amount of solar energy reflected back into the atmosphere is less. A decline in the amount of snow cover means less of the sun's energy goes towards melting of snow and evaporation of wet soil. As a result the land mass heats up more in summer creating a larger temperature difference between the water of the Arabian Sea and the Indian subcontinent landmass.
The temperature difference is responsible for a disparity in pressure over land and sea, creating a low pressure system over the Indian subcontinent and a high pressure system over the Arabian Sea. This difference in pressure causes winds to blow from the Southwest Arabian Sea bringing annual rainfall to the subcontinent from June to September. In the Western Arabian Sea, these winds also cause upwelling of cooler nutrient-rich water, creating ideal conditions for phytoplankton to bloom every year during summer.
Since 1997, a reduction in snow has led to wider temperature differences
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Source:NASA/Goddard Space Flight Center--EOS Project Science Office