Signy Island
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An unexpectedly rapid warming of lakes on a desolate
Antarctic island is evidence of global warming, according to a
20-year study by British and Canadian scientists. They say
that dramatic changes have taken place in Signy Island?s
lakes caused by a 1.8-degree Fahrenheit rise in air
temperature.
This increase has triggered a series of changes in the lakes
on the island, which is located 435 miles northeast of the
Antarctic Peninsula. The scientists consider polar lakes to be
early detectors of change due to global warming.
?This is almost a beacon going off saying, ?Look, we've gone
through this threshold at this point on the planet, and it?s an
indicator that the environment is changing rapidly,?? says
Lloyd Peck of the British Antarctic Survey. ?The main finding
of our work is that the ecology and the ecosystem in the
lakes that we?ve looked at have changed really dramatically
fast. ...What we?re seeing is an amplification of the larger-
scale environmental change signal.?
Peck and his team published their study just two weeks after
other researchers reported in the journal Nature that
temperatures in Antarctica had dropped since the mid-1980s,
in the area?s arid desert valleys, making Antarctica an
exception to the global warming taking place on the rest of
the Earth. Peck says his team?s contradictory results show
that regional variations exist in the midst of global warming.
Signy Island is about four miles long and three miles wide.
There is permanent ice covering a large part of the island,
but in summer, extensive areas of moss and some grasses are
exposed, and there are numerous freshwater pools and lakes.
Peck and his team found that the increase in winter lake
temperatures was three times higher than the increase in
local air temperatures. The amount of time during a given
year that the lakes were completely frozen over declined by
more than four weeks. This decline allowed the lake water
and sediments to absorb solar energy that normally would be
reflected away by the ice. Nutrient levels in the lakes rose,
most likely because streams ran over thawed ground rather
than ice. Algae and phytoplankton in the lakes also increased.
The island?s isolated location allowed the researchers to come
up with measurements that were not affected by local
pollution or heating associated with cities. ?In the Northern
Hemisphere, where they?re seeing fast changes in lakes,
they?ve often been associated with large human centers of
population,? Peck says. ?So it?s hard to say whether it?s a
global change ...or whether it?s something to do with extra
heating and pollution from big cities, like Chicago and the
Great Lakes. Whereas here, we?re in an island that is several
thousand [miles] away from the nearest big city.?
He also noted that the Dry Valleys where cooler temperatures
were found are about 4,000 miles away from Signy
Island. ?You would not expect to get the same message from
every point on the planet of warming, or whatever, during a
changing environmental scenario. It just doesn?t work that
way,? he says.
John Turner, also of the British Antarctic Survey, says a
complex picture is emerging of temperature change over the
whole Antarctic continent. While the Antarctic Peninsula
region experienced one of the largest temperature increases
on Earth over the last 50 years, the South Pole has
experienced a modest cooling. He says, ?However, what we
can say with certainty is that Antarctica is extremely
sensitive to environmental change.?
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