Friday, April 22, 2005

Earth science experts studying ocean currents and their relationship to snow melts have discovered that an unusual heating of the ground in one place on our planet can choke off sea life over a thousand miles away.

In a new NASA funded study, they have found that 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.

The senior researcher and lead author of the study is Joaquim Goes, from the Bigelow Laboratory for Ocean Sciences, West Boothbay Harbor, Maine. Goes and his colleagues used observations from satellite imagery of the ocean’s colors to show unusual blooms, or growth, of phytoplankton concentrations in the Western Arabian Sea. His work shows an increase of more than 350 percent over the past seven years.

Since 1997, a reduction in snow has led to wider temperature differences between the land and ocean during summer. As a consequence, sea surface winds over the Arabian Sea have strengthened leading to more intense upwelling and more widespread blooms of phytoplankton along the coasts of Somalia, Yemen and Oman.

According to Goes, 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.

The study is in this week’s SCIENCE magazine.