Arctic Environment Changes Cause Swings in Global Weather

(Arctic critical "collection bed" for world's excess energy, NASA says)

Significant changes in the Arctic environment, especially those over the
past decade, could lead to dramatic swings in weather and climate patterns
across the rest of the globe, with potentially far-reaching consequences
for ecosystems and human populations.

According to a January 24 NASA press release, ground-based surface
temperature data show that the rate of warming in the Arctic from 1981 to
2001 is eight times greater than the rate of Arctic warming over the last
100 years. Arctic spring, summer and autumn have each warmed, lengthening
the seasons when sea ice melts from 10 to 17 days per decade.

A research study led by atmospheric scientist Jiping Liu of the Georgia
Institute of Technology showed that the total extent and area of Arctic
sea ice decreased, respectively, by 30,848 square kilometers and 35,372
square kilometers between 1978 and 2002, using ice data derived from NASA
and Defense Department meteorological satellites.

"If the current trends continue,・Liu said, 鄭rctic sea ice will become
much thinner in winter and almost non-existent in the summer, in keeping
with increased greenhouse loading in the atmosphere."

The Arctic is important to the world's climate because it acts as a
"collection bed" for the world's excess energy, according to the release.
To balance energy across the Earth's surface, heat is constantly
transported through atmospheric circulations and ocean currents from the
equator to the poles, where it is released into space.

However, if the climate continues to warm faster in the Arctic than at
lower latitudes, this transfer of heat will slow down, weakening overall
atmospheric circulation.

Weakening circulation would alter storm tracks and their intensity, but
the most profound impact would be on temperature. Oceans can hold a
tremendous amount of heat and moisture, which, when transferred through
its surface to the atmosphere, can significantly alter temperature and
pressure patterns.

Some scientists speculate that as low-latitude surface waters warm,
forces like the El Ni-Southern Oscillation (ENSO) will strengthen and
become even bigger players in the world's climate.

El Ni (EN) is signaled by a warming of the ocean surface off the west
coast of South America that occurs every 4-12 years when cold,
nutrient-rich water does not come up from the ocean bottom. EN causes
die-offs of plankton and fish and affects Pacific jet-stream winds,
altering storm tracks and creating unusual weather patterns.

Southern Oscillation (SO) refers to a seesaw of high and low pressure
that varies between Tahiti and Darwin, Australia.

Other researchers believe another cyclical atmospheric pressure system,
the Arctic Oscillation might also be responsible for declining Arctic sea
ice. This oscillation refers to a pattern of low- and high-pressure
systems between the Arctic and the mid-latitudes.

When the oscillation is in its positive phase, as it has generally been
over the last 20 years, air pressure tends to be low over the Arctic
Ocean. Some scientists theorize that a general warming of the Earth could
be pushing the oscillation toward a phase that warms the Arctic.

Although Liu's study showed that AO and ENSO trends cannot explain
recent regional sea ice trends, his research found they do influence the
Arctic sea ice to some degree on time scales from year to year.

Liu also says more study is needed to better understand how regional ice
trends might respond to a warmer climate, including less understood
large-scale processes such as the Pacific Decadal Oscillation (a
long-lived, El Ni-like pattern of Pacific climate variability) and other
influences, like river discharge into the Arctic Basin from Russia and
Canada and glacier discharge from Greenland.

Full text and images are available at
http://www.nasa.gov/centers/goddard/earthandsun/arctic_changes.html

Text of the NASA press release follows:

(begin text)

NASA Goddard Space Flight Center

Press release, January 24, 2005

[Greenbelt, Maryland]

Changes in the Arctic: Consequences for the World

Observations and computer models have long proven that the Arctic plays
an important role in maintaining a stable climate on Earth. However,
significant changes in the Arctic environment, especially those over the
past decade, could lead to dramatic swings in weather and climate patterns
across the rest of the globe, with potentially far-reaching consequences
for ecosystems and human populations. Societies that have adapted to their
current climates may be faced with highly disruptive changes over
relatively short time periods.

Ground-based surface temperature data shows that the rate of warming in
the Arctic from 1981 to 2001 is eight times larger than the rate of Arctic
warming over the last 100 years. There have also been some remarkable
seasonal changes. Arctic spring, summer, and autumn have each warmed,
lengthening the seasons when sea ice melts from 10 to 17 days per decade.

Recently, a research study led by atmospheric scientist Jiping Liu of
the Georgia Institute of Technology discovered that the total Arctic sea
ice extent and area decreased, respectively, by 30,848 km2/year (11,910
square miles per year) and 35,372 km2/yr (13,660 square miles per year)
using ice data between 1978 and 2002, derived from NASA's Nimbus 7
satellite and several defense meteorological satellites. And, "if the
current trends continue, Arctic sea ice will become much thinner in winter
and almost non-existent in the summer, in keeping with increased
greenhouse loading in the atmosphere," said Liu. The paper, "Recent Arctic
Sea Ice Variability: Connections to the Arctic Oscillation and the ENSO,"
was published in the May 2004 issue of Geophysical Research Letters.

The Arctic is so important to the world's climate because it acts as the
"collection bed" for the world's excess energy. In an attempt to balance
energy across the Earth's surface, heat is constantly being transported
through atmospheric circulations and ocean currents from the equator to
the poles, where it is ultimately released out to space.

But if the climate continues to warm faster in the Arctic than at lower
latitudes, this transfer of heat will slow down, weakening overall
atmospheric circulation. The weakening circulation would alter storm
tracks, and their intensity, but the most profound impact would be on
temperature. Oceans are capable of holding a tremendous amount of heat and
moisture, which, when transferred through its surface to the atmosphere,
can significantly alter temperature and pressure patterns.

Some scientists speculate that as low-latitude surface waters warm,
forces like the El Ni-Southern Oscillation (ENSO) will strengthen and
become even bigger players in the world's climate.

El Nino (EN) is signaled by a warming of the ocean surface off the
western coast of South America that occurs every 4 to 12 years when cold,
nutrient-rich water does not come up from the ocean bottom. It causes
die-offs of plankton and fish and affects Pacific jet stream winds,
altering storm tracks and creating unusual weather patterns in various
parts of the world. Southern Oscillation (SO) refers to a see-saw of high
and low pressure that varies between Tahiti and Darwin, Australia.

Other researchers believe another cyclical atmospheric pressure system,
called the Arctic Oscillation (AO) may also be responsible for declining
Arctic sea ice. This oscillation refers to a pattern of low- and
high-pressure systems between the Arctic and the mid-latitudes. When the
oscillation is in its positive phase, as it has generally been over the
last 20 years, air pressure tends to be low over the Arctic Ocean. Some
scientists theorize that a general warming of the Earth could be pushing
the oscillation toward a phase that warms the Arctic. The oscillation
helps explain why summer sea ice is thinner than in years past. Since the
1980s, wind changes associated with the oscillation have pushed ice apart
and shoved more ice from the Arctic into the Atlantic Ocean between
Greenland and Norway.

Although Liu's study showed that AO and ENSO trends cannot explain the
recent regional sea ice trends, his research found they do influence the
Arctic sea ice to some degree on time scales from year to year. "For
example, with a positive phase of the AO, we usually observe more ice in
the western Arctic and decreased ice coverage in the eastern Arctic," said
Liu. With strong El Nino events, however, there is more ice in both the
eastern and western Arctic.

Liu also says that more study is needed to better understand how
regional ice trends might respond to a warmer climate, including less
understood large-scale processes such as the Pacific Decadal Oscillation
(a long-lived, El Nino-like pattern of Pacific climate variability) and
other influences, like river discharge into the Arctic Basin from Russia
and Canada and glacier discharge from Greenland.

While melting Arctic sea ice will influence the atmospheric circulations
in the high- and mid-latitudes, therefore altering the world's weather
patterns and storm tracks, it could also threaten the biodiversity of the
Arctic Ocean.

A study led by Kevin Arrigo of Stanford University, "Annual Cycles of
Sea Ice and Phytoplankton in Cape Bathurst Polynya, Southeastern Beaufort
Sea, Canadian Arctic," published in the April 2004 issue of Geophysical
Research Letters, surveyed the impact of declining sea ice on marine
ecosystems in the Canadian Arctic. Specifically, the research examined the
association between annual sea ice cycles and biological productivity in
the Cape Bathurst polynya. Polynyas are areas of open water or reduced ice
cover, usually created by strong winds that blow ice away from the coast.

Although relatively small in area, coastal polynyas play a
disproportionate role in many physical and biological processes in polar
regions. In eastern Antarctica, for example, more than 90 percent of all
Adelie penguin colonies live next to coastal polynyas.

Arrigo found that the Cape Bathurst polynya contained considerable
variability, in terms of initial polynya formation and in the extent and
persistence of open water, over a five year period (1998-2002).
Phytoplankton blooms also varied considerably in intensity and timing.
Phytoplankton are plantlike organisms that contain green chlorophyll and
are a primary food source for many marine mammals and birds, are tiny
organisms that are responsible for most of the photosynthetic activity in
the oceans.

Polynyas, combined with shallow coastal waters, provide the top layers
of the ocean with added sunlight, creating ideal conditions for
phytoplankton to flourish. "The open waters retain more heat, further
thinning ice cover and leading to early, intense, and short-lived plankton
blooms," said Arrigo.

"Understanding the dynamics of polynya formation and phytoplankton bloom
development is important because of their ramifications for other
components of the marine ecosystem," added Arrigo. Several fish species
use polynyas as feeding and nursery grounds and since seasonal
temperatures influence polynya formation, it is clear that climate changes
can have a major impact on the marine food web, in both the short and long
term.

To determine the amount of phytoplankton produced in the Arctic, Arrigo
collected data from SeaWiFS -- NASA's Sea-viewing Wide Field-of-view
Sensor satellite. SeaWiFS measures the amount of light coming out of the
ocean at different wavelengths and can measure the intensity of the
greenness coming from the chlorophyll in the phytoplankton.

Global warming might reduce the amount of sea ice cover in the Arctic,
which could result in an increase in the amount of phytoplankton produced.
But, global climate change will do more than just melt ice; it will alter
precipitation and wind patterns. Increasing winds could reduce biological
productivity by mixing the surface waters where phytoplankton grows too
deeply, as happens now in much of the Antarctic. The effects of global
warming are complex, and scientists do not yet know how Arctic ecosystems
are likely to change in response.

"Many Arctic organisms have adapted to a life on, in, or near sea ice
and further reductions in ice cover will almost certainly have an impact
on these biological communities," said Arrigo. "Whether the Arctic will
become more or less biologically productive as a result in declining ice
cover is uncertain. What is virtually certain is that we will see shifts
in the types of species that we see today [because of changes in the food
chain]," Arrigo said.

Changes in the food chain will mean that some species will be able to
adapt to the sea ice changes, while others will won't and will die off.
Over time, the biology of the species may evolve to ensure survival in
their new environment and climate.

Scientists do know that adding greenhouse gases like carbon dioxide to
the atmosphere increases the greenhouse effect, warming the planet.
Because a warm atmosphere holds more water vapor, precipitation across the
Arctic has already increased more than at any other latitude on Earth, by
about 15 percent over the past 40 years. This water flows off the land and
into rivers. Records show that the fresh water in Siberia's three largest
rivers has swelled by roughly a quarter of the annual flow of the
Mississippi River, and that water is now being poured directly into the
Arctic Ocean.

The global ocean circulation is regulated by cold, dense water that
sinks in the Arctic. This water moves south toward the equator and well
below the surface in the Atlantic. Upon its circular return northward, it
pulls warm tropical water north along the surface, where, like a hot-water
heater, it releases heat back into the atmosphere. An influx of fresh
water to the Arctic Ocean could prevent the water there from sinking and
essentially halt this conveyor-belt-like flow. Changes in ocean currents
can greatly complicate overall climate change and, among other things,
leave some regions, like England and eastern Canada, much cooler than they
otherwise would be.

An important consequence of global warming is the possible reduction in
albedo, a measure of the reflection of the Sun's rays back into space.
Because of its white color, snow-covered sea ice reflects most of the
incoming solar radiation, which is in part why it is so cold throughout
the Arctic region. Melt the snow and ice, replace it with the darker
surface of water, and much of the energy will be absorbed leading to
warming. Heated oceans in turn will lead to further melting and removal of
snow and ice, increasing warming, a "positive feedback" to global warming.
It is especially this feedback process that leads to predictions that
warming in the Arctic will be more pronounced, fueling climate changes for
other areas of the world.

But, it's not quite that simple. Melting sea ice will also leave more of
the ocean exposed, increasing evaporation and cloud cover, which can block
sunlight and diminish warming -- a "negative feedback." Scientists are
still trying to understand the Arctic's feedbacks and how they might play
out in the future.

Perhaps the best tool scientists have today to answer these questions
are computer models, that simulate present oceanic-atmospheric behavior as
well as future and past climates. But, due to the limitations of today痴
computers, it is not possible to explicitly represent all the important
physical processes that govern the climate.

Most computer models predict continued precipitation increases in high
latitudes and some warming over the Arctic waters within the next 70
years, assuming a doubling of carbon dioxide. But, these models only offer
a "best guess" as to how scientists believe different climate processes
interact.

(end text)

(Distributed by the Bureau of International Information Programs, U.S.
Department of State. Web site: http://usinfo.state.gov)
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