For the second time in 26 months, a massive iceberg has clogged a large portion of Antarctica's Ross Sea, causing what could turn out to be a devastating loss of penguins and other marine life, according to a NASA-funded study by Stanford scientists.
Using satellite data, geophysicists Kevin Arrigo and Gert L. van Dijken monitored the movements of a giant iceberg named "C-19," which calved off the western face of the Ross Ice Shelf in May 2002. C-19 is one of the largest icebergs ever recorded -- 19.2 miles wide and 124 miles long, or nearly twice as big as Rhode Island.
Arrigo is an assistant professor of geophysics, and van Dijken is a science and engineering associate in the department. In a study published in the American Geophysical Union's Geophysical Research Letters, the authors described how C-19 drifted northward from May until November 2002, when it apparently ran aground. By January 2003, the iceberg had become trapped against a shallow bank, eventually forming a perpendicular barrier that prevented sea ice from moving out of the southwestern Ross Sea for the next three months -- a crucial time of year when tons of microscopic marine algae, called phytoplankton, normally bloom in open water.
Phytoplankton are a major food source for krill, which in turn are consumed by fish, seals, penguins and whales. Without massive amounts of phytoplankton, the entire food chain in the Ross Sea can collapse.
Like plants, phytoplankton grow through the process of photosynthesis, using chlorophyll to convert sunlight into food. But unusually high levels of sea ice will block sunshine, preventing phytoplankton from growing.
To determine phytoplankton production levels in the Ross Sea, the researchers examined data from SeaWIFS -- the Sea-viewing Wide Field-of-view Sensor aboard NASA's SeaStar satellite.
"SeaWIFS measures the amount of light coming out of the ocean at different wavelengths," noted ArrigPage: 1 2 3 Related biology news :1
Contact: Mark Shwartz
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