US Coast Guard Cutter Healy parked in an ice floe. (Photo: NASA/Kathryn Hansen)
Phytoplankton blooms discovered under sheets of Arctic ice
Monday, June 11, 2012, 23:50 (GMT + 9)
A National Aeronautics and Space Administration- (NASA) sponsored expedition has found waters richer in microscopic marine plants than any other ocean region on Earth. Scientists discovered a 100 km-stretch of phytoplankton blooming under 3ft of Arctic ice.
Researchers previously assumed that sea ice blocked the sunlight necessary for marine plants to thrive -- but four times more phytoplankton was found under the ice sheets than in ice-free waters close by.
The findings were published this week in the journal Science.
The expedition, called Impacts of Climate on EcoSystems and Chemistry of the Arctic Pacific Environment (ICESCAPE), explored Arctic waters in the Beaufort and Chukchi seas along Alaska's western and northern coasts onboard a US Coast Guard (USCG) icebreaker in the summers of 2010 and 2011. Via optical technologies, scientists studied the impacts of environmental variability and change in the Arctic on the ocean biology, ecology and biogeochemistry.
"Part of NASA's mission is pioneering scientific discovery, and this is like finding the Amazon rainforest in the middle of the Mojave Desert," said Paula Bontempi, NASA's ocean biology and biogeochemistry programme manager in Washington.
"We embarked on ICESCAPE to validate our satellite ocean-observing data in an area of the Earth that is very difficult to get to. We wound up making a discovery that hopefully will help researchers and resource managers better understand the Arctic," she continued.
|Holley Kelly, a teacher from Farragut High School, helped retrieve the CTD/Rosette ensemble from the Bering Strait, east of the Diomede Islands.(Photo: NASA/Kathryn Hansen)
Phytoplankton, the base of the marine food chain, were thought to grow in the Arctic Ocean only after sea ice had retreated for the summer. Scientists now believe the thinning Arctic ice is letting sunlight reach the waters under the ice and leading to new plant blooms.
"This discovery was a complete surprise,” said Kevin Arrigo of Stanford University in Stanford, California, leader of the ICESCAPE mission and lead author of the new study.
In July 2011, the researchers saw blooms beneath the ice that reached from the sea-ice edge to 72 mi into the ice pack. NASA’s ocean current data showed that these blooms formed under the ice had not drifted there from open water, where phytoplankton concentrations can be high.
The phytoplankton were doubling in number more than once a day – whereas blooms in open waters double in two to three days.
|Don Perovich, of Cold Regions Research and Engineering Laboratory, maneuvered through melt ponds collecting optical data along the way to get a sense of the amount of sunlight reflected from sea ice and melt ponds in the Chukchi Sea.(Photo: NASA/Kathryn Hansen)
"At this point we don't know whether these rich phytoplankton blooms have been happening in the Arctic for a long time and we just haven't observed them before," Arrigo said. "These blooms could become more widespread in the future, however, if the Arctic sea ice cover continues to thin."
Researchers estimate that phytoplankton production under the ice in some parts of the Arctic could be up to 10 times higher than in the nearby open ocean.
As fast-growing phytoplankton consume large amounts of carbon dioxide, the study concludes that scientists will have to reassess the amount of carbon dioxide entering the Arctic Ocean if the under-ice blooms turn out to be widespread.
By Natalia Real