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New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning

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. Click to enlarge.

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 new results, based on data from a NASA Earth-orbiting spacecraft, provide further evidence for the rapid, ongoing transformation of the Arctic’s ice cover.

Scientists from NASA and the University of Washington in Seattle conducted the most comprehensive survey to date using observations from NASA’s Ice, Cloud and land Elevation Satellite (ICESat) to make the first basin-wide estimate of the thickness and volume of the Arctic Ocean’s ice cover. Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., led the research team, which published its findings July 7 in the Journal of Geophysical Research-Oceans.

The Arctic ice cap grows each winter as the sun sets for several months and intense cold ensues. In the summer, wind and ocean currents cause some of the ice naturally to flow out of the Arctic, while much of it melts in place. But not all of the Arctic ice melts each summer; the thicker, older ice is more likely to survive. Seasonal sea ice usually reaches about 6 feet in thickness, while multi-year ice averages 9 feet.

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—i.e., the amount of ice above the water line relative to the local sea level.

Buoyancy causes a fraction (about 10%) 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.

Kwok2   Kwok3
ICESat measures the distances to the top of the snow cover and to the sea surface to determine the freeboard measurement. Courtesy of Norbert Untersteiner, University of Washington. Click to enlarge.   This schematic shows the geometric relationship between freeboard (the amount of ice above the water line), snow depth, and ice thickness. Credit: Ron Kwok, NASA/JPL. Click to enlarge.

Using ICESat measurements, scientists found that overall Arctic sea ice thinned about 7 inches a year, for a total of 2.2 feet over four winters. The total area covered by the thicker, older multi-yea" ice that has survived one or more summers shrank by 42%.

Previously, scientists relied only on measurements of area to determine how much of the Arctic Ocean is covered in ice, but ICESat makes it possible to monitor ice thickness and volume changes over the entire Arctic Ocean for the first time. The results give scientists a better understanding of the regional distribution of ice and provide better insight into what is happening in the Arctic.

Ice volume allows us to calculate annual ice production and gives us an inventory of the freshwater and total ice mass stored in Arctic sea ice. Even in years when the overall extent of sea ice remains stable or grows slightly, the thickness and volume of the ice cover is continuing to decline, making the ice more vulnerable to continued shrinkage. Our data will help scientists better understand how fast the volume of Arctic ice is decreasing and how soon we might see a nearly ice-free Arctic in the summer.

—Ron Kwok

In recent years, the amount of ice replaced in the winter has not been sufficient to offset summer ice losses. The result is more open water in summer, which then absorbs more heat, warming the ocean and further melting the ice. Between 2004 and 2008, multi-year ice cover shrank 595,000 square miles—nearly the size of Alaska’s land area.

During the study period, the relative contributions of the two ice types to the total volume of the Arctic’s ice cover were reversed. In 2003, 62% of the Arctic’s total ice volume was stored in multi-year ice, with 38% stored in first-year seasonal ice. By 2008, 68% of the total ice volume was first-year ice, with 32% multi-year.

One of the main things that has been missing from information about what is happening with sea ice is comprehensive data about ice thickness. US Navy submarines provide a long-term, high-resolution record of ice thickness over only parts of the Arctic. The submarine data agree with the ICESat measurements, giving us great confidence in satellites as a way of monitoring thickness across the whole Arctic Basin.

—Jay Zwally, study co-author and ICESat project scientist at NASA’s Goddard Space Flight Center

The research team attributes the changes in the overall thickness and volume of Arctic Ocean sea ice to the recent warming and anomalies in patterns of sea ice circulation.

To sum up, the primary changes in the overall thickness and volume of the Arctic Ocean sea ice are attributable to the thinning of the MY [multiyear] ice cover and the decline in MY ice coverage. Over the winter record, there is a net loss of 57% of MY sea volume (6300 km3) and a 33% reduction in MY coverage of the Arctic Ocean relative to their values in winter of 2004. These are dramatic changes. At the same time, the thickness of the FY [first-year] ice cover has not changed significantly. Over this short record, there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the Arctic Ocean ice cover. Examining the ice export together with the decline in MY ice coverage suggest that the near-zero replenishment of the MY ice cover, an imbalance in the cycle of replenishment and ice export after the summers of 2005 and 2007, has played a significant role in the loss of Arctic sea ice volume over the ICESat record. Changes in MY ice export, by itself, do not explain the record minimums in recent years.

—Kwok et al. (2009)


  • Kwok, R., G. F. Cunningham, M. Wensnahan, I. Rigor, H. J. Zwally, and D. Yi (2009) Thinning and volume loss of the Arctic Ocean sea ice cover: 2003–2008. J. Geophys. Res., 114, C07005, doi: 10.1029/2009JC005312

  • 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

  • Data 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



Many nay-sayers will maintain that NASA is all wrong and that sea ice melting has nothing to do with man-made pollution.

With crude price down to almost $60/barrel, it may be the proper time to impose a small but progressive fuel tax partly based on reversed average crude price.

This tax could stablize fuel price at the pump, promote the purchase of more efficient vehicles, reduce man-made pollution, reduce oil import, supply much needed extra revenues to upgrade the national road network and create needed jobs.

Of course, some of the extra revenues will not materialize due to fuel consumption reduction but this could be addressed on a monthly basis as the tax rate progres.


Harvey - this certainly would be more doable than the ridiculous cap n trade tax. But with the recession, unemployment, and financial "crisis" in place - it won't fly.

"Climate has always been driven by the Sun, the Earth’s orbit and plate tectonics and the oceans, atmosphere and life respond. Humans have made their mark on the planet, thrived in warm times and struggled in cool times. The hypothesis that humans can actually change climate is unsupported by evidence from geology, archaeology, history and astronomy. The hypothesis is rejected. A new ignorance fills the yawning spiritual gap in Western society. Climate change politics is religious fundamentalism masquerading as science. Its triumph is computer models unrelated to observations in nature. There has been no critical due diligence of the science of climate change, dogma dominates, skeptics are pilloried and 17th Century thinking promotes prophets of doom, guilt and penance."
Ian Plimer, "Heaven and Earth"


"...first time on record" - okay, what is the duration of the record? If the record is 4.5 billion years, the appx age of Earth, then we should all be worried. But the record is probably more like 50,000-100,000 years, a tiny snapshot of the record, which is unknown (has no ice data). It's like freaking out about 1 hour of performance of the stock market, for which you have no data going back to beginning but you know something was going on. This is one of the biggest problems with global warming.

And another thing - why does it always have to be a tax INCREASE HarveyD? Why can't it be a tax DECREASE, a CUT.

Willy Bio

No, this is lies! Global Cabal of Knights Templar and IPCC intent that "All your climate monies are belong to us".

All truth loving people know that global ice pack is at largest ever! Drudge tells us so, there is no question.

I am a proud, Drudge-reading skeptard. All others are lackeys of pancreas stealing Cabal!

Stan Peterson

Lots of sound and fury signifying ... not much at all. All this is true, except they don't report what happened after 2007.

The Arctic Ice volume came back with a fury. By this year a mere 2.5 years later, it EXCEEDS the mean Arctic Ice volume ever since the modern satellite records started in 1979. Before 1979, the ice volume measurements were sporadic, not very accurate, or widespread.

As for the Antarctic, the sea ice volume exceeds all the satellite measurements since 1979, except for last year. Source:

Willy Bio

Stan is fellow defender of pancreases! He knows, you do well to listen to him. International Pancreas Co-optors and Controllers will NOT prevail! Their evil plot to steal all climate monies to fund final solution of mass pancreas theft will NOT succeed!


"except they don't report what happened after 2007"

They report the ice thinned in 2008, as for 2009 - it's not over yet.


The tax increase is just for GAS - to reduce consumption and oil importation, which is urgently required, regardless of opinions on pollution, CO2, sea ice or warming.

The public acceptance of the bailouts, bankruptcies, bonuses, “stimulus” billions and pork earmarks brings an eerie feeling of dread when combined with the public’s unwillingness to increase gas taxes.


The US national debt is now more than $11.5 trillion.


Like we believe ANYTHING claimed by the alarmists. Now that the G8 Summit has confirmed the failure of developed and undeveloped nations to agree on CO2 reductions - they have in their infinite wisdom decided to lower Earth's temperature.

It is a raging climate crisis! Not for skeptics. For Alarmists. NOW the alarmist goal is to keep the Earth's temperature from rising 2.0 degrees C from pre-industrial times (Medieval Warm period probably.) Whew! Now that they don't have to sweat dastardly carbon reductions - maybe they can focus on Energy Independence like they should've been doing from the start.

Ah well. Another fabrication unearthed. Rock on.

Willy Bio

Reel$$, you too are fellow skeptard! I welcome you brother, we shall defeat these alarmist pancreas thieves! Our climate monies will not be used for final solution! CO2 is life, warm time means lives saved of all those poor souls who freeze to death in winter! We are the savers of civilization and debunkers of abominable science!


Hey Willy Bio-
Take a break!

Willy Bio

And let you steal my climate monies and pancreas? I think NOT!


I think we all need to be understanding and tolerant of poor 'Willy Bio'. He's fully invested, emotionally at least, in the whole global warming thing, and it's not surprising that he's going a little unstable now that the wheels are flying off that particular bus. Much like James Hansen, he'd be better off in a padded cell.

Will S

For the denialists here, a simple recap of the article will help to put your comments in perspective;

To sum up, the primary changes in the overall thickness and volume of the Arctic Ocean sea ice are attributable to the thinning of the MY [multiyear] ice cover and the decline in MY ice coverage. Over the winter record, there is a net loss of 57% of MY sea volume (6300 km3) and a 33% reduction in MY coverage of the Arctic Ocean relative to their values in winter of 2004. These are dramatic changes.

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