Antarctica’s Ross Sea is
one of the few Polar Regions where summer sea-ice coverage has increased during
the last few decades, bucking a global trend of drastic declines in summer sea
ice across the Arctic Ocean and in two adjacent embayments of the Southern
Ocean around Antarctica. But now, a modeling study led
by Professor Walker Smith of the Virginia Institute of Marine Science suggests
that the Ross Sea’s recent observed increase in summer sea-ice cover is likely
short-lived, with the area projected to lose more than half its summer sea ice
by 2050 and more than three quarters by 2100.
ADVERTISEMENT
These changes, says Smith,
will significantly impact marine life in what is one of the world’s most
productive and unspoiled marine ecosystems, where rich blooms of phytoplankton
feed krill, fish, and higher predators such as whales, penguins, and seals.
Smith, who has been
conducting ship-based fieldwork in the Ross Sea since the 1980s, collaborated
on the study with colleagues at Old Dominion University. Their paper, “The
effects of changing winds and temperatures on the oceanography of the Ross Sea
in the 21st century,” appears in the Feb. 26 issue of Geophysical Research
Letters. Smith’s co-authors are Mike Dinniman, Eileen Hofmann, and John Klinck.
Smith says “The Ross Sea is
critically important in regulating the production of Antarctica’s sea ice
overall and is biologically very productive, which makes changes in its physical
environment of global concern. Our study predicts that it will soon reverse its
present trend and experience major drops in ice cover in summer, which, along
with decreased mixing of the vertical column, will extend the season of
phytoplankton growth. These changes will substantially alter the area’s
pristine food web.”
Researchers attribute the
observed increase in summertime sea ice in the Ross Sea—where the number of
days with ice cover has grown by more two months over the past three decades—to
a complex interplay of factors, including changes in wind speed, precipitation,
salinity, ocean currents, and air and water temperature.
Sea ice covers a large part
of the Ross Sea in this summer 2007 photo. A large opening in the ice cover, or
polynya, extends to the east. Photo courtesy of NASA. But global climate models
agree that air temperatures in Antarctica will increase substantially in the
coming decades, with corresponding changes in the speed and direction of winds
and ocean currents. When Smith and his colleagues fed these global projections
into a high-resolution computer model of air-sea-ice dynamics in the Ross Sea,
they saw a drastic reduction in the extent and duration of summer sea ice.
Read more at ENN affiliate Click
Green.
Iceberg
at Ross Sea image via Shutterstock.