Breakup of the Arctic's Ward Hunt Ice Shelf
- January 20, 2004
In the summer of 2002, graduate student Derek Mueller made an
unwelcome discovery: the biggest ice shelf in the Arctic was breaking
apart. The bad news didn't stop there. Lying along the northern coast
of Ellesmere Island in northern Canada, the Ward Hunt Ice Shelf had
dammed an epishelf lake, a body of freshwater that floats on denser
ocean water. This epishelf lake, located in Disraeli Fiord, was host
to a rare ecosystem, and it was the largest and best-understood
epishelf lake in the Northern Hemisphere. When the Ward Hunt Ice
Shelf fractured, the epishelf lake suddenly drained out of Disraeli
Fiord, spilling more than 3 billion cubic meters of fresh water into
the Arctic Ocean.
Mueller and his graduate advisor Warwick Vincent, both of Laval
University in Quebec City, realized something unusual was happening
to the ice shelf when they found unexpected fractures while doing
fieldwork on the ice and during helicopter overflights. They
contacted geophysics professor Martin Jeffries at the University of
Alaska Fairbanks. Fortunately, Jeffries had planned ahead.
"Knowing that Derek and Warwick would be doing fieldwork, I'd already
placed data acquisition requests with the Canadian Space Agency
through the Alaska Satellite Facility DAAC," Jeffries said. Jeffries
requested data from the agency's RADARSAT-1 satellite. Equipped with
a Synthetic Aperture Radar (SAR) sensor, RADARSAT-1 can acquire
imagery in almost any kind of weather, with or without sunlight. "I
had almost real-time RADARSAT data on my computer in a very short
time, and I could confirm Derek's observation."
In their final flight over the Ward Hunt Ice Shelf on August 11,
2002, Mueller and his party learned something else: new icebergs had
just calved from the front of the ice shelf. Using the RADARSAT data
again, Jeffries confirmed that the icebergs had calved sometime
between August 6 and August 11, 2002. "We made an almost real-time
detection through a combination of field observations and RADARSAT
data," he explained.
January 20, 2004
Title graphic image credits: Warwick Vincent, Université Laval (left)
Vicki Sahanatien, Parks Canada (center) Mueller et al. 2003 (right)
By September 2002, the Ward Hunt Ice Shelf had split several times.
By looking at historical RADARSAT data, Mueller, Vincent, and
Jeffries determined that the ice shelf actually beganto crack as
early as April 2000, culminating a century-long decline in the
shelf's extent. Though the Ward Hunt is very small compared to
Antarctic ice shelves, its breakup and the resulting drainage from
Disraeli Fiord concerned the researchers for several reasons.
When the Ward Hunt Ice Shelf originally formed, it blocked the mouth
of Disraeli Fiord, cutting it off from the Arctic Ocean. In the
process, the ice shelf trapped driftwood inside the epishelf lake and
kept other pieces of driftwood from entering. Pieces of driftwood
found along the shores of Disraeli Fiord have been there since the
ice shelf formed, and by radiocarbon dating the wood, researchers
have been able to estimate the minimum age of the ice shelf. "There
simply are no radiocarbon dates more recent than 3,000 years before
present," said Jeffries. This ice shelf, in existence for at least
three millennia, has now encountered conditions it can no longer
In just the last century, scientists have discovered dramatic changes
in the Ward Hunt Ice Shelf. Changes became apparent in the 1950s when
ice-shelf investigators examined early 20th-century records of Arctic
explorer Robert Peary. "It was already clear there was a vast region
much greater than today of thick, ancient ice floating on the
ocean. We estimate that this ice has now retreated by about 90
percent relative to Peary's observations," said Vincent.
Drainage of the epishelf lake worries Jeffries and Vincent as much as
the loss of the ice shelf. Although the fresh water in Disraeli Fiord
floated on top of denser salt water, a small amount continually
flowed out of the fiord under the ice shelf. Because the Ward Hunt
Ice Shelf is not fed by glaciers, its existence depends on snow and
ice accumulation on top and freshwater freezing on the bottom. "Some
of our earlier studies indicated that the most likely source of
freshwater freezing was water flowing out of Disraeli Fiord,"
Jeffries explained. "The freshwater freezing was important because it
was happening at the same time that ice was melting off the top, but
now that source of fresh water is gone." Without the freshwater
freezing on the bottom of the ice shelf, Jeffries fears that the
shelf may start to thin, or thin at a faster rate.
The Ward Hunt Ice Shelf breakup comes at the same time as news of
unprecedented melting of sea ice in the Northern Hemisphere. "Sea ice
cover has been shrinking about 3 percent per decade over the past few
decades. We saw a record minimum in September 2002, and the summer of
2003 almost set a new record," said Mark Serreze, a research
scientist at the National Snow and Ice Data Center in Boulder,
Loss of sea ice can have major implications for global climate.
Because of its light appearance, sea ice reflects most of the Sun's
energy back into space, whereas darker seawater absorbs most of the
incoming radiation and could potentially warm Earth's climate. As sea
ice continues to melt, more radiation will be absorbed by the ocean.
This Canadian RADARSAT image, acquired in August 2002, shows the
central crack in the Ward Hunt Ice Shelf running down the center of
the image. (Image courtesy of the Alaska Satellite Facility,
Geophysical Institute, University of Alaska Fairbanks)
Additional images of the Ward Hunt Ice Shelf are available in News
and Natural Hazards.
Biodiversity loss concerns Vincent as much as potential climate
change. Both the ice shelf and the epishelf lake it dammed hosted
uncommon microenvironments. "As you fly over in a helicopter, you see
these beautiful Mediterranean-blue lakes on the ice. Within these
lakes are remarkable microbial communities. A lot of them are bright
orange because they're rich in carotenoids, the same pigments found
in carrots, which protect them from UV radiation. They look like
alien life forms, but they're actually micro-worlds of bacteria, and
microscopic plants and animals. As we're losing sections of the ice,
we're losing portions of these communities," he said.
Another type of community also disappeared with the epishelf lake.
Disraeli Fiord's combination of fresh, brackish, and salt water
created a rare ecosystem of cold-adapted, salt-tolerant organisms.
According to Vincent, further research on the epishelf lake's
microbial community might have discovered brand new
species. "Unfortunately, we didn't have enough time for the molecular
techniques needed to identify new species," he said.
Scientists study a luxuriant microbial mat on the Markham Ice
Shelf, one of the last remaining ice ecosystems on the northern coast
of Ellesmere Island. (Image courtesy of Warwick Vincent, Université
Beyond improving knowledge of modern biodiversity, polar
communities may help scientists understand Earth's past. A hypothesis
that has gradually developed since the 1960s postulates that between
800 and 600 million years ago, the Earth underwent a series of global
glaciations, a time nicknamed the Neoproterozoic "Snowball Earth." It
was after this period of worldwide freezing that multicellular life
forms began leaving a rich fossil record. "One of the arguments
against the Snowball Earth hypothesis is that life might not have
survived the massive freeze-ups," said Vincent. "But those of us
working in the polar regions see incredible opportunities for life in
Unfortunately, researchers may not get the chance to test their
hypotheses by examining modern life forms. "We're really running out
of time to understand these unique environments and their biota
before they disappear," Vincent said.
Understanding the impact of declining sea ice on marine wildlife may
be easier to assess, though the news is not encouraging. Microbial
ecosystems in sea ice comprise the base of much of the food chain in
the Arctic Ocean. Directly or indirectly, zooplankton, fish, whales,
seals, and polar bears depend on the energy provided by those
microbial ecosystems. "In western Hudson Bay, satellite data reveal a
significant change in sea ice cover, and we know from studies by the
Canadian Wildlife Service that polar bears have been adversely
affected by changes in their habitat that limit their access to
seals," said Jeffries.
Ice shelf decline may affect humans as well as wildlife. During its
breakup in 2002, the Ward Hunt Ice Shelf calved a number of ice
islands, and the heavily fractured ice shelf now has the potential to
release many more. Ranging in sizes up to tens of kilometers, these
ice islands could eventually drift into the Beaufort Sea and
jeopardize shipping and offshore development, such as oil rigs. "An
ice feature of this size could exert tremendous force on an offshore
structure, and there wouldn't be much we could do to divert it," said
Although researchers wouldn't be able to divert ice islands, they
could use satellite data to track ice island movement. RADARSAT data
was instrumental in tracking the movement of the giant B-15 iceberg
that calved from the Ross Ice Shelf in Antarctica in March 2000, and
the data may have similar applications in the Northern Hemisphere.
Big as the ice islands are, the Ward Hunt Ice Shelf breakup does not
approach the scale of ice shelf deterioration observed in
Antarctica. "The Ward Hunt Ice Shelf is a fairly small feature, and
in terms of global climate impact, the breakup of this ice shelf is
trivial. Yet it's another indication of what's happening in the
Arctic," said Serreze. Among the changes in the Northern Hemisphere
that Serreze has recently reported are earlier spring breakups of
river ice, increased freshwater runoff, shrinking glaciers, and trees
and shrubs invading Arctic tundra. "The Arctic is changing. This is
fact," he said.
One of the oldest fossils of multicelluar oganisms is Dickinsonia.
Estimated at 560 million years old, Dickinsonia may have evolved
after the end of the last Neoproterozoic global glaciation. (Image
Copyright © University of California Museum of Paleontology, 1994-
2004. All rights reserved.)
Some paleontologists suspect that the extreme conditions of the
Snowball Earth may have jump-started evolution, ultimately giving
rise to complex organs like this calcite-crystal eye of the trilobite
Phacops. (Image courtesy of An Enlightened View of Calcite in the
Ocean with MODIS from the GES Earth Sciences DAAC)
Changes observed in the Arctic confirm climate model predictions. "We
know from global circulation models the results of which are
broadly accepted among the polar climate and global climate
community that if global change is occurring, the effects will be
felt first and amplified in the polar regions, particularly the
Arctic," said Jeffries. "We've seen changes in the Arctic, and in
recent years, the changes seem to be occurring faster."
Vincent agrees. Prior to the Ward Hunt Ice Shelf breakup, his team
monitored Disraeli Fiord for five years. Though he had observed
gradual decreases in the lake's fresh water, its sudden disappearance
caught him off guard. "I think it underscores a fundamental problem
we have in climate change research," he said. "Climate change models
usually predict gradual, continuous change, but real-life impacts are
not continuous. Changes can be relatively small, and then suddenly
you can move to a new threshold. This ice shelf survived 3,000 years
of human civilization, but now it's gone."
An ice island about 1.5 kilometers long, 250 meters wide, and 30
meters thick moves into the Arctic ocean after the fracturing of the
Ward Hunt Ice Shelf in August 2002. (Image courtesy of Warwick
Vincent, Université Laval)
How much change can be attributed to human activity is difficult to
estimate. "We know the climate can vary on many different time scales
due to natural processes," said Serreze. "But when we look at the
longer-term record of paleoclimate information, the warming we're
seeing does appear to be very unusual. Carbon dioxide concentrations
in ice cores today are probably the highest they've been in 400,000
years. There's a growing consensus between the things we're observing
and climate model projections of change. I'm still a fence-sitter,
but I'm leaning more to the side of human causes for at least some of
what we're seeing."
Jeffries and Vincent plan to continue monitoring the Ward Hunt Ice
Shelf and Ellesmere Island. "It's at the northern limit of North
America, right in the bull's-eye of the region that climate models
predict will change most rapidly, most abruptly, and most severely,"
said Vincent. RADARSAT data will continue to play a role in that
monitoring. "We have been especially impressed with RADARSAT imagery
resolution. In combination with our field measurements, it's provided
an unprecedented time series showing the magnitude of change."
"I think this ice shelf breakup is another example of how valuable
remote sensing is, and how important it is that scientists have easy
access to these data on a frequent basis," said Jeffries. "Otherwise,
we miss things we really need to know."
Reductions in sea ice cover have put polar bear populations at risk.
Here, two orphaned cubs await transport to a zoo. (Image courtesy of
the NOAA Photo Library)
Mueller, Derek R., Warwick F. Vincent, and Martin O. Jeffries. 2003.
Break-up of the largest Arctic ice shelf and associated loss of an
epishelf lake. Geophysical Research Letters. 30(20):2031.
Sturm, Matthew, Donald K. Perovich, and Mark C. Serreze. 2003.
Meltdown in the north. Scientific American. 289(4):60-67.
Hoffman, Paul F. and Daniel P. Schrag. 2000. Snowball Earth.
Scientific American. 282(1):68-75.
RADARSAT-1 Antarctic Mapping Project. Accessed November 25, 2003.
RADARSAT-1. Accessed January 13, 2004.
For more information, visit the Alaska Satellite Facility DAAC.
This article contributed from Distributed Active Archive Center
(DAAC) Alliance: Supporting Earth Observing Science 2004 (to be
released in the fall of 2004)
The NASA Distributed Active Archive Center (DAAC) Alliance provides
data and user services in support of the Earth observing sciences.
For other articles about DAAC Alliance data, visit the DAAC Alliance
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