A NASA funded study has found a decline in winter and spring snow cover over Southwest Asia and the Himalayan mountain range is creating conditions for more widespread blooms of ocean plants in the Arabian Sea.
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.

Chlorophyll concentration (Courtesy: NASA)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.
While large blooms of phytoplankton can enhance fisheries, exceptionally large blooms could be detrimental to the ecosystem. Increases in phytoplankton amounts can lead to oxygen depletion in the water column and eventually to a decline in fish populations.
All this can start a downward spiral in the health of the marine ecosystem; as fish die, larger fish and mammals die, and this decreases the oxygen content further, since the decomposing bacteria start flourishing. It might take a while for the ocean systems to recover from such a downward trend, and in the meantime, economies around the world might take a beating.
Happy Earth Day, everyone ;)