Causes and Consequences

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Step by step, Goés and his team traced their way backward from what they thought was a mistake to a surprising discovery of how complexly connected Earth’s land surface, oceans, atmosphere and living creatures are—declining snow cover and a hotter Eurasian land mass; greater temperature difference between land and ocean; stronger monsoon winds across the Arabian Sea; greater upwelling of deep, nutrient-rich water; and bigger blooms of phytoplankton. The intricacy is amazing.

According to Goés, more than one link in that chain of climate cause-and-effect could make problems for people. On the one hand, increasing phytoplankton populations might help fisheries. But too much phytoplankton can have a down side, especially in the Arabian Sea. When phytoplankton die, bacteria decompose them, using up oxygen in the water. “The Arabian Sea already has a large zone of oxygen-poor water because it is landlocked to the north,” explains Goés. It doesn’t benefit from large-scale ocean circulation patterns that disperse oxygen-depleted water. In this already oxygen-poor environment, Goés suspects that such huge increases in phytoplankton could be catastrophic.

“Just recently [October 2005] we have received messages from our colleagues in Oman saying there are reports of massive fish deaths in the area. In many cases, these deaths have been preceded by mass strandings of fish and other marine animals closely following major blooms,” Goés said. One reasonable hypothesis, he says, is that the animals are tying to escape suffocation in the oxygen-depleted waters that result from such massive phytoplankton blooms and their resulting decay.

Oxygen-poor waters are a problem for a second reason: they create more habitat for a kind of bacteria that metabolizes nitrate in the water and produces nitrous oxide—laughing gas—in the process. Unfortunately, there is nothing funny about possible increases of nitrous oxide. Nitrous oxide is a powerful greenhouse gas; its heat-trapping potential is about 300 times greater than carbon dioxide. According to measurements published by scientists in the journal Nature in 2000, the amount of nitrous oxide coming from the western Indian Ocean has been increasing as the sea’s low-oxygen zone increases.

Goés is also concerned about the impact of an intensifying monsoon on regional rainfall. “This past summer,” said Goés, whose family is originally from the state of Goa in southwestern India, “the city of Mumbai, on India’s western coast, experienced its worst flood disaster on record.” At least a thousand people died, and much of the city was underwater for days. “We speculate that the runaway decline in Eurasian snow cover since 1997 may be strengthening Southwest monsoon rainfall in regions where the rains are strongly tied to the Arabian Sea winds, such as along the western coast of India,” said Goés. This could mean more intense rain and more frequent floods in Southwest Asia.

  Photograph of relief workers after Mumbai floods in 2005.

The most immediate threat of course, is the snow cover decline itself. “Many people in India, Pakistan, and China depend on snow melt for water, and it [snow] is in decline. If glaciers continue to melt at the present rate, many high-altitude lakes could start overflowing,” Goés explained. The melting of glaciers and warming of the ground can destabilize mountain slopes and trigger dangerous landslides. Eventually drought could prevail in regions where snow and glaciers are unable to persist.


Stronger summer monsoons may mean more rain for parts of India—perhaps much more rain. On July 26, 2005, the coastal city of Mumbai endured a record 24-hour rainfall of 94.4 centimeters (37.2 inches). In this photograph, people lift bottled water over a flooded street. (Photograph copyright Soumik Kar)

  Photograph of glaciers in the Karakorum

As a remote-sensing oceanographer, this study was particularly satisfying to Goés. He hopes it will inspire others to look for ways to use satellite observations to help predict how climate change like global warming will be felt at a regional level. “This study is a concrete example of what satellite data can do to help predict regional climate change. Without satellite data, we probably never would have been able to establish these relationships and trends,” said Goés. “But because we were able to cross-check so many different types of data, we can be much more certain these connections are real.”


Declining snow cover and retreating glaciers in the Himalaya may reduce fresh water supplies in India, Pakistan, and Tibet. Mountain glaciers will likely continue to retreat, and their loss could destabilize mountain slopes. This photograph shows summer melt ponds on the Vigne Glacier in the Concordia region of Pakistan. (Photograph copyright Kelly Cheng)