Video: Monitoring lake ice. In northern Alaska, within the Arctic circle, the ice regimes of shallow lakes were documented using 79 radar images from European Space Agency satellites. University of Waterloo ...
WATERLOO, ON, Feb. 3, 2014 /CNW/ - Arctic lakes have been freezing up
later in the year and thawing earlier, creating a winter ice season
about 24 days shorter than it was in 1950, a University of Waterloo
study has found.
The research, sponsored by the European Space Agency ESA and published in The Cryosphere, also reveals that climate change has dramatically affected the
thickness of lake ice at the coldest point in the season: In 2011,
Arctic lake ice was up to 38 centimetres thinner than it was in 1950.
"We've found that the thickness of the ice has decreased tremendously in
response to climate warming in the region," said lead author Cristina
Surdu, a PhD student of Professor Claude Duguay in Waterloo's Department of Geography and Environmental Management. "When we saw the actual numbers we were shocked at how dramatic the
change has been. It's basically more than a foot of ice by the end of
The study of more than 400 lakes of the North Slope of Alaska, is the first time
researchers have been able to document the magnitude of lake-ice
changes in the region over such a long period of time.
"Prior to starting our analysis, we were expecting to find a decline in
ice thickness and grounded ice based on our examination of temperature
and precipitation records of the past five decades from the Barrow
meteorological station," said Surdu. "At the end of the analysis, when
looking at trend analysis results, we were stunned to observe such a
dramatic ice decline during a period of only 20 years."
The research team used satellite radar imagery from ESA to determine
that 62 per cent of the lakes in the region froze to the bottom in
1992. By 2011, only 26 per cent of lakes froze down to the bed, or
bottom of the lake. Overall, there was a 22 per cent reduction in what
the researchers call "grounded ice" from 1992 to 2011.
Researchers were able to tell the difference between a fully frozen lake
and one that had not completely frozen to the bottom, because satellite
radar signals behave very differently, depending on presence or absence
of water underneath the ice.
Radar signals are absorbed into the sediment under the lake when it is
frozen to the bottom. However, when there is water under the ice with
bubbles, the beam bounces back strongly towards the radar system.
Therefore, lakes that are completely frozen show up on satellite images
as very dark while those that are not frozen to the lake bed are
Researchers used the Canadian Lake Ice Model (CLIMo) to determine ice cover and lake ice thickness for those years before
1991, when satellite images are not available.
The model simulations show that lakes in the region froze almost six
days later and broke up about 18 days earlier in the winter of 2011
compared to the winter of 1950. Shorter ice-cover seasons may lead to
shifts in lake algal productivity as well as thawing of permafrost
under lake beds.
"The changes in ice and the shortened winter affect Northern communities
that depend on ice roads to transport goods," said Surdu. "The dramatic
changes in lake ice may also contribute to further warming of the
entire region because open water on lakes contributes to warmer air
temperatures, albeit to a lesser extent than open sea water."
The ice regimes of shallow lakes were documented using radar images from
ESA's ERS-1 and -2 satellites. More information on the ESA is available online.
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Video with caption: "Video: Monitoring lake ice. In northern Alaska, within the Arctic circle, the ice regimes of shallow lakes were documented using 79 radar images from European Space Agency satellites. University of Waterloo researchers used the images to find that the Arctic winter ice season is about 24 days shorter than it was in 1950. ". Video available at: http://stream1.newswire.ca/cgi-bin/playback.cgi?file=20140203_C7023_VIDEO_EN_36174.mp4&posterurl=http://photos.newswire.ca/images/20140203_C7023_PHOTO_EN_36174.jpg&clientName=University%20of%20Waterloo&caption=Video%3A%20Monitoring%20lake%20ice%2E%20In%20northern%20Alaska%2C%20within%20the%20Arctic%20circle%2C%20the%20ice%20regimes%20of%20shallow%20lakes%20were%20documented%20using%2079%20radar%20images%20from%20European%20Space%20Agency%20satellites%2E%20University%20of%20Waterloo%20researchers%20used%20the%20images%20to%20find%20that%20the%20Arctic%20winter%20ice%20season%20is%20about%2024%20days%20shorter%20than%20it%20was%20in%201950%2E%20&title=Monitoring%20lake%20ice%2E%20In%20northern%20Alaska%2C%20within%20the%20Arctic%20circle&headline=Dramatic%20thinning%20of%20Arctic%20lake%20ice%20cuts%20winter%20ice%20season%20by%2024%20days
Image with caption: "Researcher Claude Duguay stands on the cracked ice of an Arctic lake. University of Waterloo researchers have found the Arctic winter ice season is about 24 days shorter than it was in 1950. (Credit: Claude Duguay/University of Waterloo) (CNW Group/University of Waterloo)". Image available at: http://photos.newswire.ca/images/download/20140203_C7023_PHOTO_EN_36152.jpg
Image with caption: "Graph showing the reduction in grounded ice between 1992 and 2011. The University of Waterloo team used satellite radar imagery to find that there was a 22 per cent reduction in lakes that freeze to their bed. (Credit: Planetary Visions / University of Waterloo / ESA) (CNW Group/University of Waterloo)". Image available at: http://photos.newswire.ca/images/download/20140203_C7023_PHOTO_EN_36153.jpg
SOURCE: University of Waterloo
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