At Earth's polar ends, scientists are studying the telling fingerprints of past climate trapped in ice for hundreds
if not thousands of years, to compare the atmospheric composition of long ago with present day. They want to know if
the well-documented warming trend is a mere blip in the cyclical climate record, or part of a larger, long-term
NSF plays a leadership role in climate research at both ends of the Earth.
The Arctic Ocean is a perpetually ice-covered sea encompassed by the continental landmasses of Europe and North
America. The area above the Arctic is home to the world's largest ice sheet.
As part of a large-scale climate investigation, researchers at ice station SHEBA (Surface Heat Budget of the Arctic
Ocean), took a year-long look at Arctic climate. The idea was to study all aspects of the ocean-ice-atmosphere system
that contribute to improving climate models of a critical but little understood part of the world. An icebreaker
purposely frozen into the ocean pack ice hundreds of miles north of Alaska served as home base.
Elsewhere, NSF convened a group of more than 400 scientists to map out an international strategy for studying
environmental change in the Arctic. Known as the Study of Environmental Arctic Change, or SEARCH, the project is a
broad, federal-interagency initiative to analyze and understand trends in Arctic climate. Scientists attending the
meeting came away with a plan based on four large-scale ideas:
- Arctic environmental change is related to change in the atmospheric polar vortex, a large-scale cyclonic
circulation in the atmosphere centered generally over the North Pole.
Arctic environmental change is a component of a more widespread change in climate.
Feedback between the ocean, the land and the atmosphere are critical to the change process.
Such physical changes have large impacts on the Arctic ecosystems and societies.
To complement SEARCH studies, NSF supports the North Pole
Environmental Observatory (NPEO), a multi-year project to observe conditions in the Arctic Ocean that could affect
the oceans and atmosphere around the globe.
Arctic warming, for example, has apparently begun to thaw the soils of the Arctic tundra, that until recently,
were permanently frozen. That has allowed carbon to escape into the atmosphere in the form of the major greenhouse gas,
carbon dioxide. Another NSF-funded study indicates that an ancient reservoir of the gas currently locked into peat bogs
is adding to the mix and contributing to the Arctic warming trend.
During a 35-day snowmobile trek across Alaska, the six-member Snow Science Traverse - Alaska Region, or SnowSTAR
2002, expedition, sampled snow at more than 75 locations in the roughly 700 miles from Nome to Barrow. The traverse was
part of an ongoing larger project known as the Arctic Transitions in the Land Atmosphere System, or ATLAS. The amount
and characteristics of snow cover play an important role in the climate balance of the Arctic by stabilizing Earth's
At the opposite end of the globe, scientists in Antarctica are providing clues from a variety of experiments to show
how the Earth may react to changing temperatures.
As in the Arctic, scientific observations now indicate that warming temperatures may already be affecting the
Antarctic ice sheets. For instance, the Antarctic Peninsula, which juts northwards toward Chile, has warmed rapidly in
recent years. And in 2002, a massive ice shelf on the peninsula known as the Larsen B, crumbled to the sea and washed
away. According to scientists, a preliminary study of sediment cores from the area suggests the ice shelf's collapse
may be unprecedented in the roughly 12,000 years since the last Ice Age.
And, as in the Arctic, long cores extracted from deep in the ice sheet reveal the chemistry of the atmosphere as it
was when that ice fell as snow hundreds to thousands of years ago. A comparison of the chemical composition of the ice
with the composition of the current atmosphere can tell scientists how the atmosphere has changed over time.
Correlating today's atmosphere chemistry with known climatic conditions and records from the past can help show how
atmospheric chemistry-then and now-affects temperatures.
In 2003, for example, scientists crossed the Antarctic
ice sheet by tractor train, taking samples of ice that fell as snow over the past 200 years. Locked into that ice
are clues to how the chemical composition of the atmosphere may have changed during the relatively recent Industrial
It is no small wonder the dry, yet very icy, Antarctica is also full of apparent contradictions. Despite
well-documented warming on the Antarctic Peninsula, NSF-supported researchers based at the Long Term Ecological
Research station in McMurdo, have shown that, overall, Antarctica has actually cooled during the past 35 years.
Biologists also play a role in unlocking the mysteries of Antarctic climate change.
The Victoria Land coast of Antarctic's Ross Sea region is now home to thriving colonies of Adelie penguins. But not
always. Researchers recently discovered that thousands of the birds abandoned their colonies beginning about 2,000
years ago, when a long cooling trend caused an ice build-up large enough to block the birds' access to open water.
Nesting penguins need ready ocean access to acquire food for themselves and their young. Apparently unable to obtain
food, the penguins slowly abandoned the area for locations more hospitable to raising young.
Using radiocarbon analyses of nests from abandoned colonies on Ross Island, scientists believe the modern, warmer,
ice-free conditions that once again allow the birds to come and go developed in the region within the past 1,000 years.
Because thick sea ice prevented them from reaching the area sooner, the Adelie colonies now living on Ross Island are
likely no more than 500 years old.
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