New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning
08 July 2009
| 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.
| 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)
Resources
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.
Posted by: HarveyD | 08 July 2009 at 07:00 AM
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"
Posted by: sulleny | 08 July 2009 at 09:29 AM
"...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.
Posted by: ejj | 08 July 2009 at 10:47 AM
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!
Posted by: Willy Bio | 08 July 2009 at 10:59 AM
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: http://icecap.us/index.php
Posted by: Stan Peterson | 08 July 2009 at 11:48 AM
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!
Posted by: Willy Bio | 08 July 2009 at 12:45 PM
"except they don't report what happened after 2007"
They report the ice thinned in 2008, as for 2009 - it's not over yet.
Posted by: ai_vin | 08 July 2009 at 03:53 PM
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.
Posted by: ToppaTom | 08 July 2009 at 04:48 PM
@ejj
The US national debt is now more than $11.5 trillion.
Posted by: ai_vin | 08 July 2009 at 09:32 PM
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.
http://tinyurl.com/lo4rmv
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.
Posted by: Reel$$ | 08 July 2009 at 09:43 PM
Reel$$, 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!
Posted by: Willy Bio | 09 July 2009 at 05:13 AM
Hey Willy Bio-
Take a break!
Posted by: RD | 09 July 2009 at 05:34 AM
And let you steal my climate monies and pancreas? I think NOT!
Posted by: Willy Bio | 09 July 2009 at 05:41 AM
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.
Posted by: Matthew | 09 July 2009 at 06:46 AM
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.
Posted by: Will S | 09 July 2009 at 08:23 AM
Hmm, yes, VERY DRAMATIC. We'd best give them more research grant money before the drama overwhelms us all.
Posted by: Matthew | 09 July 2009 at 08:41 AM
Matthew,
Your facade of being skeptard is failed. You are disinformation agent of International Pancreas Co-optors and Controllers. True Drudge reading truthers like me and Reel$$ will expose you and smite you.
Posted by: Willy Bio | 09 July 2009 at 09:26 AM
Matthew, et. al,
Look at the graph. Top line.
Its DATA.
In the last 4 years, total artic sea ice volume has decreased a total of about 5% per year as detected by satellite measurements, and confirmed in part by submarine measurements.
Posted by: matt | 09 July 2009 at 02:29 PM
"Everyone said I was daft to build a castle on a swamp, but I built in all the same, just to show them. It sank into the swamp. So I built a second one. That sank into the swamp. So I built a third. That burned down, fell over, then sank into the swamp" from Monty Python & HG.
Ignorance is bad. Willfull ignorance is worse. Trying to keep ignorance alive is the underside of the barrel, not just the bottom.
There is the presence of trillions of dollars of oil & gas underneath all that ice and you may think that in defending ignorance keeps you from acknowledging AGW but it also means that you give up on those resources, something Russia, Canada, Denmark and every other country that can have a stake in is not giving up on.
The 5 P rule, without the profanity requires proper planning. You cannot properly plan without information and knowledge. Willfull ignorance is a recipe for the other 5 p rule : poor planning produces poor performance.
Posted by: aym | 09 July 2009 at 03:51 PM
Indeed, it is data.
It shows the cyclical nature of the Earth's climate. Why everyone is so excited about it is beyond me.
Posted by: Matthew | 09 July 2009 at 05:28 PM
Let's put all this into the calm light of enlightened observation:
"Burning just the oil and gas sitting in known fields will drive atmospheric CO2 well over 400 ppm and ignite a devil’s cauldron of melted icecaps, bubbling permafrost, and combustible forests from which there will be no turning back.”
Now this gives one pause. Maybe the Reel Climate people are on to something.
Posted by: sulleny | 09 July 2009 at 06:27 PM
Previous quote from Doc Hansen.
Posted by: sulleny | 09 July 2009 at 06:28 PM
ejj:
If the word fuel tax is to hard to accept, it could be turned into an 'equivalent revenue' progressive road usage fee. Something like $0.02 to $0.05 per mile per vehicle ton could be a good starting point.
A small one ton vehicle driving 12000 miles/year would pay $240 to $600 a year road fees.
Of a two ton vehicle would pay twice as much etc.
Collecting all those road usage fees would cost much more than equivalent fuel tax.
However, yearly revenues of $108 B to $270+ B could be enough to improve road quality within 5 to 10 years. If not, users fees could be raised.
For those who do not like fuel taxes, the current Federal fuel tax could also be replaced with road usage fees.
Basically it does not make a difference but in the longer term it would be a way to levy fees from e-vehicles of the future.
Posted by: HarveyD | 09 July 2009 at 06:41 PM
The arctic icecap is melting as in this article about peer study.
The permafrost is bubbling out enough methane that is visible and ignitable.
Forest fires have gotten larger in recent years. Enough that, Tom Boatner, the chief of fire operations for the federal government said that 7 out of 10 of the busiest fire seasons have occured since 1999 and that fires of 200000 hectares are now common when they weren't 10 years ago.
Given the human need for resources highly dependent on stable climate, like himilayan glacier water, is it any surprise that a bunch of ex generals and admirals stated that global warming posed a threat to national security. Given the Stern Report, which outlines the huge costs of GW, a devil's cauldron is an apt adjective of the possible social coming from not planning.
Posted by: aym | 10 July 2009 at 08:18 AM
It is interesting that after satellite photos disproved the claim that the area covered by sea ice is shrinking the global warming (or is it climate change) crowd now shifts to the much harder to disprove claim that while the ice area may not be shrinking, it is now much thinner and the poor polar bears are going to fall right through.
However, I see a couple of problems. 1. NASA has confirmed that global temperatures, inclusing ocean temperatures have been decreasing for a decade, so if something is happening to the sea ice, Al Gore's massive carbon footprint is not to blame. http://science.nasa.gov/newhome/headlines/essd06oct97_1.htm
2. For those who point to thin ice at the north pole, or worse yet, "Open Water" as a sign that the Dennis Quaid was right, U.S. Submarines have been surfacing through thin ice, or no ice at all at the north pole since the 1950's.http://wattsupwiththat.com/2009/04/26/ice-at-the-north-pole-in-1958-not-so-thick/
Posted by: ESabre | 12 July 2009 at 03:34 AM