Showing posts with label thin ice. Show all posts
Showing posts with label thin ice. Show all posts

Monday, September 22, 2014

2014 Arctic Sea Ice Minimum Sixth Lowest on Record

Arctic sea ice hit its annual minimum on Sept. 17, 2014. 

The red line in this image shows the 1981-2010 average minimum extent. 

Data provided by the Japan Aerospace Exploration Agency (JAXA) GCOM-W1 satellite.

Image Credit: NASA/Goddard Scientific Visualization Studio

Arctic sea ice coverage continued its below-average trend this year as the ice declined to its annual minimum on Sept. 17, according to the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder.

Over the 2014 summer, Arctic sea ice melted back from its maximum extent reached in March to a coverage area of 1.94 million square miles (5.02 million square kilometers), according to analysis from NASA and NSIDC scientists.

This year’s minimum extent is similar to last year’s and below the 1981-2010 average of 2.40 million square miles (6.22 million square km).

"Arctic sea ice coverage in 2014 is the sixth lowest recorded since 1978. The summer started off relatively cool, and lacked the big storms or persistent winds that can break up ice and increase melting," said Walter Meier, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“Even with a relatively cool year, the ice is so much thinner than it used to be,” Meier said. “It’s more susceptible to melting.”

This summer, the Northwest Passage above Canada and Alaska remained ice-bound.

A finger of open water stretched north of Siberia in the Laptev Sea, reaching beyond 85 degrees north, which is the farthest north open ocean has reached since the late 1970s, according to Meier.


An animation of daily Arctic sea ice extent from March 21 to Sept. 17, when the ice appeared to reach it’s minimum extent for the year. 

It’s the sixth lowest minimum sea ice extent in the satellite era. The data was provided by the Japan Aerospace Exploration Agency (JAXA) GCOM-W1 satellite.

Image Credit: NASA/GSFC Scientific Visualization Studio/T. Schindler

While summer sea ice has covered more of the Arctic in the last two years than in 2012’s record low summer, this is not an indication that the Arctic is returning to average conditions, Meier said.

This year’s minimum extent remains in line with a downward trend; the Arctic Ocean is losing about 13 percent of its sea ice per decade.

To measure sea ice extent, scientists include areas that are at least 15 percent ice-covered. The NASA-developed computer analysis, which is one of several methods scientists use to calculate extent, is based on data from NASA’s Nimbus 7 satellite, which operated from 1978 to 1987, and the U.S. Department of Defense’s Defense Meteorological Satellite Program, which has provided information since 1987.

Due to global warming, larger and larger areas of sea ice melt in the summer and when sea ice freezes over in the winter it is thinner and more reduced. 

As the Arctic summers are getting warmer we may see an acceleration of global warming, because reduced sea ice in the Arctic will remove less CO2 from the atmosphere, according to Danish scientist Dorte Haubjerg Søgaard, PhD Fellow, Nordic Center for Earth Evolution, University of Southern Denmark and the Greenland Institute of Natural Resources, Nuuk..

In addition to monitoring sea ice from space, NASA is conducting airborne field campaigns to track changes in Arctic sea ice and its impact on climate.

Operation IceBridge flights have been measuring Arctic sea ice and ice sheets for the past several years during the spring.

A new field experiment, the Arctic Radiation – IceBridge Sea and Ice Experiment (ARISE) started this month to explore the relationship between retreating sea ice and the Arctic climate.

Monday, February 3, 2014

ESA ERS-2 satellite: Arctic lakes show climate on thin ice

Floating ice (light blue) and grounded ice (dark blue) in lakes of Alaska’s North Slope near Barrow, as seen by ESA’s ERS-2 satellite in 2011. 

Credit: Planetary Visions / University of Waterloo, Canada / ESA

Ice in northern Alaska's lakes during winter months is on the decline.

Twenty years of satellite radar imagery show how changes in our climate are affecting high-latitude environments.

Changes in air temperature and winter precipitation over the last five decades have affected the timing, duration and thickness of the ice cover on lakes in the Arctic.

In this region, warmer climate conditions result in thinner ice cover on shallow lakes and, consequently, a smaller fraction of lakes freezing all the way through during winter months.

The Alaskan Arctic coastal plain is covered in a great swathe of shallow lakes 

Credit: NASA USGS

These changes in ice cover affect the local and regional climate, the dynamics of the underlying permafrost and the availability of water for residential and industrial use throughout the winter.

They also alter the physical, thermal and chemical properties of the water, affecting the ecology dependent on them.

But the magnitude of these changes had not yet been comprehensively documented until now.

In a recent study of Alaska's North Slope, published in The Cryosphere, the ice regimes of shallow lakes were documented using radar images from ESA's ERS-1 and -2 satellites.

The study reveals a 22% decrease of 'grounded ice' – or ice frozen through to the lakebed – from 1991 to 2011. This is equivalent to an overall thinning of ice by 21–38 cm.

Cristina Surdu
"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 Cristina Surdu, lead author of the study.

"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 greatest change was observed during late winter (April–May) over the 20-year period, which gradually decreased from 1991 to 2005.

The ice experienced a more abrupt decline during the final six years of the analysis, reaching its lowest in 2011.

ERS-2 was launched in 1995, four years after ERS-1, the first European Remote Sensing satellite. 

At the time, these two satellites were the most sophisticated European Earth observation spacecraft ever developed, delivering new information to study Earth's land, oceans, atmosphere and polar ice, as well as being called upon to monitor natural disasters such as earthquakes and floods. 

Credit: EADS Astrium