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Posts Tagged ‘Geophysical Research’

Lakes Worldwide Rapidly Warming

Posted by feww on December 20, 2015

Climate change rapidly heating up lakes globally

Climate change is rapidly heating up the lakes, threatening freshwater supplies and ecosystems globally, according to a comprehensive study spanning six continents, said a report.

The research, published in the journal Geophysical Research Letters, was carried out by  more than 60 scientists and was announced at the fall meeting of the American Geophysical Union.


Ice on Lake Vortsjarv in Estonia. Ice-covered lakes warm faster than those with open water. Credit: T. Noges

“Our knowledge of how lakes are responding to global change has been lacking,” said the program director in the Division of Environmental Biology at the National Science Foundation, which funded the research. “That has made forecasting the future of lakes—and the life and livelihoods they support—very challenging. These newly reported trends are a wake-up call to scientists and citizens, including water resource managers and those who depend on freshwater fisheries.”

Lakes warming faster than oceans or atmosphere

Lakes are warming an average of 0.61 degrees Fahrenheit each decade, which greater than the both the warming rate of oceans and atmosphere.

“Lakes are important because society depends on surface water for the vast majority of human uses—not just for drinking water, but manufacturing, energy production, irrigation and crops,” said paper co-author Stephanie Hampton of Washington State University. “Protein from freshwater fish is especially important in the developing world.”

The team monitored more than 235 lakes for at least 25 years. That’s a fraction of the world’s lakes, but those contain more than half the world’s freshwater supply.

Various climate factors are linked with the warming trend, which is melting the ice in the lakes earlier. Additionally, many areas, receiving less cloud cover, are exposed to more sunlight.

Temperatures in both northern climates and tropical regions are rising faster than the average, researchers said. Northern lakes are warming 1.3ºF, per decade. Tropical lakes are warming 0.95ºF, per decade.

Warm- and cold-water lakes equally important

Warm-water lakes such as the African Great Lakes, home to one quarter of the planet’s freshwater supply and a major source of fish for food, are undergoing  less dramatic temperature increases, “but their waters may have already nearly reached the highest temperatures fish can tolerate,” Hampton said.

Report is posted HERE.

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Antarctic Flood Forms ‘Ice Crater’

Posted by feww on July 2, 2013

Enormous flood under Antarctica drained six billion tons of water: Report

The ice surface collapsed as the water in Cook Sub-Glacial Lake drained away, probably into the ocean, according to a new report.

Antarctic Ice Crater - esa3D view of the crater created using CryoSat data. The ice surface collapsed as six cubic km of water drained away from Cook SGL. The crater is located in Victoria Land, East Antarctica at about 73ºS and 156ºE. Copyright: ESA/McMillan

ESA’s CryoSat satellite has discovered a massive ‘ice crater’ in Victoria Land, East Antarctica, which researchers believe was left behind when a lake lying under about 3 km of ice suddenly drained.

“It covers an area of about 260 sq km, which is about the size of Edinburgh, and was as much as 70m deep,” said Dr Malcolm McMillan from the UK’s University of Leeds and lead author of a report in the journal Geophysical Research Letters.

“We knew from the Icesat data there had been a big elevation change, but it’s only now with Cryosat that we’ve been able to appreciate the true scale of what happened.” He told reporters.

The event occurred during an 18-month period in 2007-2008 at the Cook Sub-Glacial Lake (SGL) in the east of the continent, says the report.

The water would have been flowing away from the SGL at a rate of 160 cubic meters per second during peak discharge, the report says.

Cook is one of about 400 SGLs believed to exist on the White Continent, which is losing mass at a rate of between 50-100 billion tons a year.

ESA PAGE

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Arctic sea ice has thinned dramatically

Posted by feww on July 8, 2009

Arctic sea ice thinned dramatically between the winters of 2004 and 2008—NASA

Analysis of data from a NASA Earth-orbiting spacecraft shows that “Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thin seasonal ice replacing thick older ice as the dominant type for the first time on record.”  The latest discovery “provide further evidence for the rapid, ongoing transformation of the Arctic’s ice cover.”

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ICESat measures the distances to the top of the snow cover and to the sea surface. The difference between the two quantities gives the total “freeboard” measurement; that is, the amount of ice above the water line relative to the local sea level. Credit: Courtesy of Norbert Untersteiner, University of Washington

NASA says their and the University of Washington in Seattle researchers carried out “the most comprehensive survey to date using observations from NASA’s Ice, Cloud and land Elevation Satellite, known as ICESat,” to determine “the first basin-wide estimate of the thickness and volume of the Arctic Ocean’s ice cover.”  Their research team, led by Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., published its findings on July 7 in the Journal of Geophysical Research-Oceans.

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This schematic shows the geometric relationship between freeboard (the amount of ice above the water line), snow depth, and ice thickness. Buoyancy causes a fraction (about 10 percent) of sea ice to stick out above the sea surface. By knowing the density of the ice and applying “Archimedes’ Principle” — an object immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object — the total thickness of the ice can be calculated. Credit: Ron Kwok, NASA/JPL

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ICESat measurements of winter multi-year ice cover in the Arctic Ocean between 2004 and 2008, along with the corresponding downward trend in overall winter sea ice volume, and switch in dominant ice type from multi-year ice to first-year ice. Credit: Ron Kwok, NASA/JPL

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ICESat measurements of winter multi-year ice cover in the Arctic Ocean between 2004 and 2008, along with the corresponding downward trend in overall winter sea ice volume, and switch in dominant ice type from multi-year ice to first-year ice. Credit: Ron Kwok, NASA/JPL


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Data visualization of Arctic sea ice thickness, as measured by ICESat, shows the decline of the thickest ice (white, 4 to 5 meters thick) and increase in thinner ice (deep blue, 0 to 1 meter) from 2003 to 2008. Credit: NASA Goddard’s Scientific Visualization Studio.

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326208main_seaicediscretecolorbarData visualization of ice thickness, as measured by ICESat, shows the yearly growth (winter) and retreat (fall) of ice in the Arctic Ocean. Credit: NASA Goddard’s Scientific Visualization Studio


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Posted in Archimedes’ Principle, arctic ocean, freeboard ice, winter sea ice | Tagged: , , , , | 2 Comments »