Antarctica Records Hottest Day Ever, New Study Published in SCIENCE Finds Rapid Acceleration of Ice Melt

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The warmest temperature ever recorded on the continent of Antarctica may have occurred on Tuesday, March 24, 2015, when the mercury shot up to 63.5°F (17.5°C) at Argentina’s Esperanza Base on the northern tip of the Antarctic Peninsula. According to weather records researcher Maximiliano Herrera, the previous hottest temperature recorded in Antarctica was 63.3°F (17.4°C) set just one day previously at Argentina’s Marambio Base, on a small islet just off the coast of the Antarctic Peninsula. Prior to this week’s remarkable heat wave, the hottest known temperature in Antarctica was the 62.8°F (17.1°C) recorded at Esperanza Base on April 24, 1961. (The World Meteorological Organization—WMO—has not yet certified that this week’s temperatures are all-time weather records for Antarctica, though the Argentinian weather service has verified that the temperatures measured at Esperanza Base and Marambio Base were the highest ever measured at each site.) A new all-time temperature record for an entire continent is a rare event, and Weather Underground’s weather historian, Christopher C. Burt, has full details in his latest post.

The record heat coincides with the release of a new study from Science that finds “ice shelves in West Antarctica have lost as much as 18 percent of their volume over the last two decades, with rapid acceleration occurring over the last decade. The study found that from 1994 to 2003, the overall loss of ice shelf volume across the continent was negligible, but over the last decade West Antarctic losses increased by 70 percent,” says Think Progress.

The heat wave also coincides with Robert Swan and his 2041 team’s Antarctic Expedition, which wrapped up last week. The point of the trip was to document the firsthand effects of climate change, which was obviously very apparent.

The Antarctic Peninsula is one of the fastest warming spots on Earth. A 2012 Climate Central post by Michael Lemonick documented how while the Earth as a whole warmed up by 1.3°F between 1900 and 2011, the Antarctic Peninsula warmed by 5°, forcing massive ice shelves to disintegrate and penguin colonies to collapse. A 2012 paper in Nature found that the recent warming is faster than 99.7% of any other given 100-year period in the last 2000 years.

In May 2014, a study by researchers at NASA and the University of California, Irvine, found a rapidly melting section of the West Antarctic Ice Sheet to be in an irreversible state of decline, with nothing to stop the glaciers in this area from melting into the sea.

The study presents multiple lines of evidence, incorporating 40 years of observations that indicate the glaciers in the Amundsen Sea sector of West Antarctica “have passed the point of no return,” according to glaciologist and lead author Eric Rignot, of UC Irvine and NASA’s Jet Propulsion Laboratory in Pasadena, California. The new study has been accepted for publication in the journal Geophysical Research Letters.

These glaciers already contribute significantly to sea level rise, releasing almost as much ice into the ocean annually as the entire Greenland Ice Sheet. They contain enough ice to raise global sea level by 4 feet (1.2 meters) and are melting faster than most scientists had expected. Rignot said these findings will require an upward revision to current predictions of sea level rise.

“This sector will be a major contributor to sea level rise in the decades and centuries to come,” Rignot said.

Three major lines of evidence point to the glaciers’ eventual demise: the changes in their flow speeds, how much of each glacier floats on seawater, and the slope of the terrain they are flowing over and its depth below sea level. In a paper in April, Rignot’s research group discussed the steadily increasing flow speeds of these glaciers over the past 40 years. This new study examines the other two lines of evidence.

The glaciers flow out from land to the ocean, with their leading edges afloat on the seawater. The point on a glacier where it first loses contact with land is called the grounding line. Nearly all glacier melt occurs on the underside of the glacier beyond the grounding line, on the section floating on seawater.

Just as a grounded boat can float again on shallow water if it is made lighter, a glacier can float over an area where it used to be grounded if it becomes lighter, which it does by melting or by the thinning effects of the glacier stretching out. The Antarctic glaciers studied by Rignot’s group have thinned so much they are now floating above places where they used to sit solidly on land, which means their grounding lines are retreating inland.

“The grounding line is buried under a thousand or more meters of ice, so it is incredibly challenging for a human observer on the ice sheet surface to figure out exactly where the transition is,” Rignot said. “This analysis is best done using satellite techniques.”

The team used radar observations captured between 1992 and 2011 by the European Earth Remote Sensing (ERS-1 and -2) satellites to map the grounding lines’ retreat inland. The satellites use a technique called radar interferometry, which enables scientists to measure very precisely — within less than a quarter of an inch — how much Earth’s surface is moving. Glaciers move horizontally as they flow downstream, but their floating portions also rise and fall vertically with changes in the tides. Rignot and his team mapped how far inland these vertical motions extend to locate the grounding lines.

The accelerating flow speeds and retreating grounding lines reinforce each other. As glaciers flow faster, they stretch out and thin, which reduces their weight and lifts them farther off the bedrock. As the grounding line retreats and more of the glacier becomes waterborne, there’s less resistance underneath, so the flow accelerates.

Slowing or stopping these changes requires pinning points — bumps or hills rising from the glacier bed that snag the ice from underneath. To locate these points, researchers produced a more accurate map of bed elevation that combines ice velocity data from ERS-1 and -2 and ice thickness data from NASA’s Operation IceBridge mission and other airborne campaigns. The results confirm no pinning points are present upstream of the present grounding lines in five of the six glaciers. Only Haynes Glacier has major bedrock obstructions upstream, but it drains a small sector and is retreating as rapidly as the other glaciers.

The bedrock topography is another key to the fate of the ice in this basin. All the glacier beds slope deeper below sea level as they extend farther inland. As the glaciers retreat, they cannot escape the reach of the ocean, and the warm water will keep melting them even more rapidly.

The accelerating flow rates, lack of pinning points and sloping bedrock all point to one conclusion, Rignot said.

“The collapse of this sector of West Antarctica appears to be unstoppable,” he said. “The fact that the retreat is happening simultaneously over a large sector suggests it was triggered by a common cause, such as an increase in the amount of ocean heat beneath the floating sections of the glaciers. At this point, the end of this sector appears to be inevitable.”

Because of the importance of this part of West Antarctica, NASA’s Operation IceBridge will continue to monitor its evolution closely during this year’s Antarctica deployment, which begins in October. IceBridge uses a specialized fleet of research aircraft carrying the most sophisticated suite of science instruments ever assembled to characterize changes in thickness of glaciers, ice sheets and sea ice.

For additional images and video related to this new finding, visit:

http://go.nasa.gov/1m6YZSf

For additional information on the West Antarctic Ice Sheet and its potential contribution to sea level rise, visit:

http://go.nasa.gov/1oIfSlO

For more information on Operation IceBridge, visit:

http://www.nasa.gov/icebridge

About Mike Neuman

Identical twin; Long-time advocate of protection of our environment; Married; Father to three sons; Grandfather to one granddaughter; Born and raised in Wisconsin; Graduate of University of Wisconsin; post graduate degrees in agricultural economics and Water Resources Management fro UWMadison; Former School Crossing Guard for City of Madison; Bike to Work for 31 years with Wisconsin Department of Natural Resources; Retired from DNR in 2007; Biked to school crossing guard site 2 X daily for 7 years retiring in 2019; in addition to being an advocate of safeguarding our environment, I am also an advocate for humane treatment of animal, children, and people in need of financial resource for humane living. I am presently a Volunteer for Habitat for Humanity, Madison, Wisconsin. I oppose all long (>500 miles) distance travel (via fossil fuel burning) for nonessential purposes and all ownership of more than one home. I am opposed to militarism in any form particularly for the purpose of monetary gain. I am a Strong believer in people everywhere having the right to speak their minds openly, without any fear of reprisal, regarding any concerns; especially against those in authority who are not acting for the public good?in a timely fashion and in all countries of the world not just the U S.. My identical twin, Pat, died in June 2009. He was fired from his job with the National Weather Service despite having a long and successful career as a flood forecaster with the Kansas City National Weather Service. He took a new position in the Midwest Regional Office in Minneapolis. Unfortunately, Pat’s work for the NWS went sour after he began to see the evidence for concern about rising global temperatures shortly after relocating to Minneapolis, and how they appeared to effect of flooding on the Red River that flows out of Canada before entering the U.S. in North Dakota. . Pat and I conversed on a regular basis with other scientists on the Yahoo Group named “Climate Concern “ and by personal email. The NWS denied his recommendation to give his public presentation o n his research at the “Minneapolis Mall of America” in February 2000, which deeply affected h,im. I will h He strongly believed the information ought be shared with the public to which I concurred. That was the beginning of the vendetta against my brother, Patrick J. Neuman, for speaking strongly of the obligations the federal government was responsible for accurately informing the citizenry. A way great similar response to my raising the issue of too many greenhouse gases being emitted by drivers of vehicles on Wisconsin highway system, my immediate supervisors directed: “that neither global warming, climate change nor the long term impacts upon the natural resources of Wisconsin from expansion of the state highway system were to be any part of my job requirements, and that I must not communicate, nor in a memorandum to all the bureau, shall any person who works in the same bureau I do communicate with me, neither verbally on the phone, by email.

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