April 20th US Global Change Seminar - "Arctic Sea-Ice: Changes,Causes, and Implications"
tsocci at usgcrp.gov
Wed Apr 14 14:56:09 EDT 1999
U.S. Global Change Research Program Seminar Series
Arctic Sea-Ice: Changes, Causes, and Implications
What is the evidence for Arctic sea-ice thinning? Is Arctic sea-ice
thinning everywhere or in specific regions or areas? How substantial is
the sea-ice thinning? Is there evidence of changes in the aerial
distribution of Arctic sea-ice? Is Arctic sea-ice now forming later in the
season and melting earlier? What are the likely causes of the observed
changes in Arctic sea-ice? What are the long and the short-term
implications of Arctic sea-ice thinning in terms of climate change and in
terms of possible impacts on humans and ecosystems? Have Alaskan Native
Peoples, in particular, observed similar changes, and if so, what has been
the impact of these and other changes?
Tuesday, April 20, 1999, 12:00-1:45 PM
Russell Senate Office Bldg., Room 385
Buffet Lunch Reception
Charles (Chip) Groat, Director, US Geological Survey, Department of the
Interior, Reston, VA
Douglas G. Martinson, Lamont-Doherty Earth Observatory, Columbia
University, Palisades, NY
Caleb Pungowiyi, Director, Natural Resources Program, Eskimo Walrus
Commission, Nome, AK
Sea ice has covered the majority of the Arctic Ocean, year-round, with a
9-foot thick blanket of ice as expansive as the United States, for as long
as civilization can recall. In sunlight, this vast area is blindingly
radiant; a reflective surface remarkably efficient in reflecting sunlight
back into space, before the sun's rays can heat the region. Likewise, the
presence of sea-ice serves to insulate the frigid atmosphere from the
relatively warm ocean water (which cannot be colder than the freezing
point) thus preventing the ocean from significantly warming the atmosphere.
Sea ice is such an efficient insulator that in its absence, the exposed
ocean water would warm the overlying air, in winter, by some 20 to 40 C.
Moreover, the exposed ocean is nearly as impressive in its ability to
absorb the warming sunlight as the ice is in reflecting it back into space.
Consequently, the presence or absence of ice leads to considerable
differences in the temperature (and with that, circulation) of the
overlying atmosphere. This dramatic contrast makes polar climate highly
sensitive to changes in sea ice - even small changes in the sea ice can
result in large changes in the polar climate. On a grander scale, these
same characteristics that constrain the polar temperatures help define the
temperature contrast between the tropics and the poles. Climate can be
thought of as the Earth's attempt to eliminate this contrast, that is, to
redistribute excess heat received in the tropics to the heat-starved polar
regions. In the simplest sense, the vigor, and many other characteristics
of climate, are controlled by the magnitude of this temperature contrast.
Thus, anything that influences polar temperatures can influence global
climate as well.
Observations are beginning to document and reveal just how changes in the
Arctic climate influence the climate outside of the Polar Regions. Global
climate model simulations, on the other hand, provide additional insights
into how the Earth's climate might change as a result of specific changes
in extent, thickness, and duration of sea ice. These models also provide
insights as to how the sea ice may change as global climate changes, thus
presenting clues as to how to interpret observed changes in sea ice.
Instrumental and Observational Records of Changes in Arctic Sea-Ice
Though scientists have been aware of the potential sensitivity of the
climate system to changes in sea ice cover for many years, it has only been
since the early 1970s that scientists have finally been able to regularly
observe sea ice through constant monitoring via satellites. During this
interval of time, scientists have observed a clear and steady decline in
the extent of the Arctic sea-ice cover, showing it to be disappearing at a
rate of approximately 3% each decade. There have also been a number of
exceptionally abnormal years recently, even in light of this steady
decline. For example, this decade has witnessed four summers in which the
aerial extent of Arctic sea-ice was the smallest ever observed.
Furthermore, other, less complete records of Arctic sea-ice suggest that
the decline in extent has been continuous since mid-century. While the
reduction in ice extent is unequivocal, changes in thickness are also
apparent, but more ambiguous. Last year, during a year-long experiment in
the Arctic, the thickest ice floe found for the purposes of setting up an
ice station, was only 60% of the average (not even maximum) sea-ice
Measurements in the upper Arctic Ocean also indicated an excess of freshwater
(largely confined to regions of thin ice), which was consistent with the
notion of excess melting during the previous year. Likewise, recently
documented changes in other parts of the Arctic Ocean are strongly suggestive
(indirectly) of a more pervasive thinning of Arctic sea-ice. The changes
to introduce considerable heat from the ocean to the ice. Such changes imply
that winter sea-ice growth will be reduced by 70-80% in those regions in
which these and other changes have occurred. On the other hand, recent
results from submarine surveys under the ice do not reveal any clear
indication of a general basin-wide thinning. While differences in these
observations are yet to be reconciled, the steady decline in the aerial extent
of sea-ice cover, predominantly in summer, suggests a steady decline in the
volume of sea-ice and a decline in the amount of freshwater locked up in
The causes for the observed sea ice changes are still uncertain, though
there are some likely candidates, such as the global warming that has been
documented over the majority of this century. Relative to mean global
temperatures, temperatures in the Polar Regions show the same general
trends, but are amplified relative to the changes observed in the tropics.
Therefore, a general climate warming of a degree or two at lower Latitudes,
is equivalent to a warming of several degrees at the poles. The changes in
Arctic sea ice do indeed track changes in polar temperature, but whether
increased temperature is a cause or an effect of the sea ice change is
unclear. The sea ice changes are also remarkably consistent with model
predictions given increases in atmospheric carbon dioxide. On the other
hand, changes in sea-ice also accompany changes in the regional atmosphere
and as such, may or may not be related to a global warming. In fact, some
of the above changes have been attributed to El Nino/La Nina cycles. These
atmospheric changes can modify the sea ice by altering the upper ocean
structure and the winds, both of which influence ice growth, melt and
drift. Whether the changes in the atmosphere are responding to the change
in sea ice or vice versa is not currently known. Confounding the
interpretations further is the fact that all of the various changes are
generally consistent with the global warming trends. At present, despite
considerable uncertainties, global warming seems to be the most likely
candidate driving the changes (and the one most consistent with the
disparate observational evidence and modeling studies).
While there is some indication of what might be driving the observed
changes, the most compelling unanswered question at this time is whether
these changes are part of a long-term climate trend, or part of a climate
cycle. In the latter instance, one would expect to see a future reversal
in the observed changes. However, at present there is evidence that may
support both possibilities, in which case the most likely future projection
would involve a long term decline in the Arctic sea ice cover, tempered in
some years by a cooling (ice build-up) phase of the cycle, and enhanced in
other years by coinciding with the warming (melting) phase of the cycle.
If the decline in Arctic sea-ice cover does continue at the present rate,
the year-round (perennial) ice will eventually disappear and ice will only
appear in winter.
Impacts of Changes in Arctic Sea-Ice: A Native Alaskan Perspective
The Bering Sea and the Arctic Ocean sea-ice are important supporters and
providers of life to the indigenous people whose lives depend on the
resources from these very productive seas. For those who live in the
Arctic regions, climate change has had, and will have, serious
consequences. While the scientific community studies climate change and
tries to determine whether the observed changes are part of a long-term
global climate warming trend, many of the indigenous peoples of the Arctic
are already feeling some of the impacts of a changing, warming climate. It
is important to understand that from the perspective of many indigenous
peoples who live in the Arctic region, even small changes in the climate or
environment can have dramatic impacts on the lives of those whose
livelihood is often directly dependent upon, and tied to natural resources
and the functioning of ecosystems.
The Yupik and other indigenous peoples of the Arctic have observed and
experienced the following changes which have had the following impacts:
A reduction in sea-ice and changes in the timing of ice formation and
thaw in the Bering and Chukchi Seas.
Impact - When sea-ice is late in forming certain forms of hunting are
delayed or may not take place at all. When sea-ice in the spring melts or
deteriorates too rapidly, it greatly decreases the length of the hunting
season for all communities. In both, the spring and the fall hunting
season, the window of opportunity is very limited and is also affected by
others environmental conditions such as changes in wind, precipitation, and
surf. The fall of 1997 and 1998 were two of the warmest in recent years,
especially 1998. In both years hunters reported poor seal hunting.
Impact - Different species of fish have historically followed or
accompanied the freeze-up of sea-ice. In the fall of 1998, freeze-up did
not occur until late November. Up until that time, no fish or seals were
caught in any abundance.
Changes in precipitation in the summer, fall, and winter.
Impact - Many traditional foods are dried (e.g., seal, walrus, whale, fish,
and birds) in the spring and summer in order to preserve them for
consumption over the long winter months. When the air is too damp and wet
during the "drying" seasons, food that is set out for drying gets moldy and
sour. The Yupik and other indigenous communities have observed the
prevalence of more rain, fog, and cloudy skies during the "drying seasons.
Impact - The length of the wet season also affects the ability to gather
greens such as willow leaves, beach greens, sour dock, wild celery, stink
weeds, Labrador tea, etc., The Yupik and other indigenous peoples have been
experiencing wetter, earlier springs, and wetter, earlier falls which
affect the drying and gathering of traditional plants.
Changes in storm surges, shore erosion, and wind.
Changes in migration patterns and habitat of terrestrial and marine mammals.
Changes in the availability of food resources for sea birds and marine life.
Impact - Each species of marine mammals requires a certain type of sea-ice
for resting, molting, socializing, breeding, rearing, and migration. As
marine mammal hunters, the Yupik and other indigenous peoples of the Arctic
closely observe the quality of ice for spring hunting. If it has been a
mild fall and winter, ice quality is poor. In this case the ice is soft,
thin, and disintegrates easily from wind, waves, and warm temperatures. As
a result, some of the newborn seal and walrus pups do not have sufficient
time to wean properly and typically, will not survive. In June of 1996
many seal pups washed up dead on the shores of St. Lawrence island. Few
walrus calves were reported in 1997 and 1998 as well. In addition, the
lack of ice or poor ice conditions will result in stress on marine mammals
and affect productivity.
Caleb Pungowiyi is the current Director of the Natural Resources Program of
the Subsistence and Eskimo Walrus Commission. He also serves as
Commissioner on the Bering Straits Regional Commission and as an active
Member on the following Boards and Commissions: Marine Mammal Commission;
Advisory Committee of the Office of Polar Programs of the National Science
Foundation; Alaska Scientific Review Group; Rural Alaska Resources
Association; Bering Sea Impact Study; and the Indigenous Peoples Council
for Marine Mammals.
Mr. Pungowiyi is the former President and CEO of the Inuit Circumpolar
Conference, representing 120,000 Inuit of Alaska, Canada, Greenland and
Chukotka, Russia. In addition, he has served as a Member of the following
Boards and Commissions: Alaska Native Science Commission; the National
Academy of Sciences Polar Research Board's Committee on Bering Sea
Ecosystems; Advisory Panel on Arctic Impacts from Soviet Nuclear
Contamination, with the former Congressional Office of Science and
Technology; Native American Rights Fund; Alaska Coastal Policy Council; and
the Alaska Conservation Foundation.
Douglas Martinson is a senior research scientist at the Lamont-Doherty
Earth Observatory, and an Adjunct Professor in the Department of Earth and
Environmental Sciences at Columbia University. His primary research
interest is directed at understanding how changes in Polar Regions affect
the global climate. His research also involves both modeling and field
work. In this capacity Dr. Martinson has been to the Arctic and Antarctic
polar oceans many times, and was awarded the United States Antarctic
Service Medal in 1987. He was Chief Scientist for the first sea ice camp
in the Antarctic region (Ice Station Weddell, 1992), Chief Scientist on the
inaugural science cruise of the first U.S. Ice-Breaking Research Vessel
(the Nathaniel B. Palmer), and a member of the Science Steering Committee
and a Principal Investigator for the recently concluded NSF (National
Science Foundation/Office of Naval Research SHEBA (Surface Heat Budget of
the Arctic) project, which operated from a field camp situated in the
Arctic for an entire year. Dr. Martinson is presently preparing for his
next field trip to study the Antarctic winter, which will be underway in a
couple of months. He is author of dozens of articles in the peer-reviewed
literature, the latest one dealing with the future of the Arctic Sea-Ice
Cover. Dr. Martinson also teaches a graduate course on "quantitative
methods of data analysis".
Dr. Martinson is a member of a number of national and international
committees dealing with global climate change, and the role of Polar
Regions in climate. He was Chairman of the National Research Council's
(NRC's) Panel on Climate Variability over Decade to Century Time Scales
which recently produced the U.S. Science Strategy for Studying Climate
Variability over Decade-to-Century Time Scales. He is a member of the NRC
Global Change Research Committee, and NRC Climate Research Committee. He
is a member of the Science Steering Group for the World Climate Research
Programme's (WCRP's) Climate Variability and Prediction (CLIVAR) project,
the Science Steering Group for the WCRP Arctic Climate System (ACSYS)
project, and a member of the WCRP Task Force defining the new Climate and
Cryosphere project, among others. He has also served on a number of
advisory committees (as Chair or as a member) at the following institutions
and agencies: the National Science Foundation, the National Aeronautics and
Space Administration, and the American Meteorological Society.
Dr. Martinson received his Ph.D. at Columbia University, NY, in 1982 in
paleoclimatology and polar oceanography. He was later awarded a
Post-Doctoral Fellowship in the Department of Physical Oceanography at the
Woods Hole Oceanographic Institution, where he stayed until returning to
Lamont-Doherty and Columbia University in 1985.
The Next Seminar is scheduled for Monday, May 17, 1999
Tentative Topic: Surface Temperature Changes in the Northern Hemisphere
during the Last 1,000 Years
For more information please contact:
Anthony D. Socci, Ph.D., U.S. Global Change Research Program Office, 400
Virginia Ave. SW, Suite 750, Washington, DC 20024; Telephone: (202)
314-2235; Fax: (202) 488-8681 E-Mail: TSOCCI at USGCRP.GOV.
Additional information on the U.S. Global Change Research Program (USGCRP)
and this Seminar Series is available on the USGCRP Home Page at:
http://www.usgcrp.gov. A complete archive of seminar summaries can also be
found at this site. Normally these seminars are held on the second Monday
of each month.
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