Esa's Cryosat sees Arctic sea-ice volume bounce back

Arctic sea ice thickness - late Oct 2013

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The bounce back in the extent of sea ice in the Arctic this summer was reflected also in the volume of ice.

Data from Europe's Cryosat spacecraft suggests there were almost 9,000 cu km of ice at the end of this year's melt season.

This is close to 50% more than in the corresponding period in 2012.

It is a rare piece of good news for a region that has witnessed a rapid decline in both area cover and thickness in recent years.

But scientists caution against reading too much into one year's "recovery".

"Although the recovery of Arctic sea ice is certainly welcome news, it has to be considered against the backdrop of changes that have occurred over the last few decades," said Prof Andy Shepherd of University College London, UK.

"It's estimated that there were around 20,000 cu km of Arctic sea ice each October in the early 1980s, and so today's minimum still ranks among the lowest of the past 30 years," he told BBC News.

Cryosat is the European Space Agency's (Esa) dedicated polar monitoring platform.

It has a sophisticated radar system that allows scientists to work out the thickness of the ice floes covering the Arctic Ocean.

In the three years following its launch, the spacecraft saw a steady decline in autumn ice volume, with a record low of 6,000 cubic km being recorded in late October 2012.

But after a sharply colder summer this year, the autumn volume number has gone up.

Measurements taken in the same three weeks in October found the floes to contain just shy of 9,000 cu km.

Ice breaker Thicker ice has been retained in the Arctic

Part of this stronger performance can be put down to the greater retention of older ice.

This is evident particularly around the Canadian archipelago and North Greenland, where there is much more two-year-old and three-year-old ice than in previous years.

"One of the things we'd noticed in our data was that the volume of ice year-to-year was not varying anything like as much as the ice extent - at least for the years 2010, 2011 and 2012," explained Rachel Tilling from the UK's Nerc Centre for Polar Observation and Modelling (CPOM).

"This is why we're really quite surprised by what we've seen in 2013.

"We didn't expect the greater ice extent left at the end of the summer melt to be reflected in the volume.

"But it has been. And the reason is related to the amount of multi-year ice in the Arctic."

Dr Don Perovich is a sea-ice expert at Dartmouth College, US.

He said Cryosat's data tallied with observations made by other spacecraft.

"In previous summers, some of the [multi-year ice] migrated over to the Alaska and Siberia areas where it melted. But this past summer, it stayed in place because of a change in wind patterns. And so there'll likely be more multi-year ice next year than there was this year," he told BBC News.

Satellite altimetry: How to measure sea-ice volume

Infographic (BBC)
  • Cryosat's radar has the resolution to see the Arctic's floes and leads
  • Some 7/8 of the ice tends to sit below the waterline - the draft
  • The aim is to measure the freeboard - the ice part above the waterline
  • Knowing this 1/8th figure allows Cryosat to work out sea-ice thickness
  • The thickness multiplied by the area of ice cover produces a volume

The minimum ice extent in the Arctic this summer was recorded as 5.10 million sq km. Again, this was a figure almost 50% larger than the all-time satellite-low mark achieved 12 months previously - when floes were reduced to just 3.41 million sq km by mid-September.

Area/extent is easier to measure, but scientists regard thickness/volume to be the best metric with which to judge the health of the ice pack, which is why Cryosat's unique data-set is so important.

For a while, it was uncertain whether the European satellite would get any autumn measurements this year.

The spacecraft suffered a major fault in its onboard power system at the beginning of October, and all science activity was halted.

But engineers managed to switch the satellite over to a back-up system and normal operations were resumed on 11 October.

"We lost the side 'A' of the power subsystem we believe for good, although we still have hope to be able to use part of it in the future in case we experience another issue," said Esa Cryosat mission manager Dr Tommaso Parrinello.

"Since 2 October, we have been operating on the redundant chain, but all other subsystems are still being operated on their prime chain 'A'. Therefore, the science instruments and the quality of data have not been affected."

The new Cryosat study was presented here in San Francisco to the American Geophysical Union (AGU) Fall Meeting, where the annual Arctic Report Card was also released.

Thickness comparison The observations show clearly that more thick ice (red/yellow) has been retained this year and follow me on Twitter: @BBCAmos


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  • rate this

    Comment number 919.

    one thing people need to learn is that if a reporter asks a scientist a question for an article the answer is an opinion & often an off the cuff one, not a definitive statement on behalf of the whole of science. A peer reviewed paper has strict rules about evidence & claims but even that's not a definitive statement on behalf of the whole of science.

  • rate this

    Comment number 918.

    I notice that a number of commenters are under the mistaken impression that increasing Antarctic sea ice extent is due to cooling temperatures.

    Beware of simplistic explainations. The Antarctic is warming. The result is stronger currents and stronger winds breaking up the ice and spreading it further from the coast.

    Hence the greater extent.

  • rate this

    Comment number 917.

    The first thing that strikes me in that BBC article is the word "could" that immediately tells me we're looking at an estimate, then in a quote from the lead scientist "My claim is that the global climate models underestimate the amount of heat delivered to the sea ice" it then claims all other models are wrong, so this was a "one off" result not a consensus agreed result

  • rate this

    Comment number 916.

    @912.Peter N
    So why are the climate models still so terribly wrong?

    they're not they're very good, there are different types of model though, some do an overall picture some look at specifics & those ones aren't supposed to be good at everything, they were able to claculate global warming due to Co2 very accurately in the 70's, regional warming due to everything is much much tougher

  • rate this

    Comment number 915.

    I think this will benefit species like Polar bears for a little while, but the long term trend is still bleak. Like any tiny bit of good news, however, some humans will to use it as an excuse to become even more complacent.
    I seem to remember this very same "borrow now, pay later" attitude before the credit crunch. Well, here we're all the evil bankers.

  • rate this

    Comment number 914.

    Ignore the headline, read the article. It says "It might not be as early as 2013 but it will be soon, much earlier than 2040."
    This is what we find. Deniers quote very selectively. It's like reading the Daily Mail!

  • rate this

    Comment number 913.

    910 anotherfakename
    not that many. Eugenics, for instance, was pushed a lot by social scientists and race supremacists, rather than scientists per se. You could find some scientists who would agree with eugenics, but only a small percentage, just like a small percentage say climate change is a myth.

  • rate this

    Comment number 912.

    911. fuzzy - "[science]...making models from observations & using them to predict future behaviour. The model is pushed to its limits, so we can know where it breaks down...We then do more observations to fix the breakdown & form a new, more complex..."

    So why are the climate models still so terribly wrong? They obviously need far greater 'fixes' than they dare admit.

  • rate this

    Comment number 911.

    909.Alan Kenny

    Science is about deducing the truth from observations.
    I see it as making models from observations and using them to predict future behaviour. The model is pushed to its limits, so we can know where it breaks down and where it's safe to use. We then do more observations to fix the breakdown and form a new, more complex, model to use in those cases. And so on and so on.

  • rate this

    Comment number 910.

    @868.David Wallis
    You seem to suggest scientists are infallible, for all the things you list there are others where scientists got it spectacularly wrong. Eugenics was one of them

  • rate this

    Comment number 909.

    Science is about deducing the truth from observations. The climate debate is full of spite, from both sides, because it is charged with politics and money. Lets get back to the science.

  • rate this

    Comment number 908.

    Nice balanced editors picks on this one. Sheesh!

  • rate this

    Comment number 907.

    903.Sally the Rothbardian

    Please understand that we don't have Capitalism.
    It did not say we did, I said "Due to capitalism's market forces". Besides, you make it sound as if there's only one Capitalism, when there are all sorts (including social), so it could be disputed that we don't have it.

  • rate this

    Comment number 906.

    TuRbO-DD: all your comments are about tax.

    Are you a tax-advisor?

    While you may be the person I would consult on tax matters, I think I would prefer to ask a geophysicist on questions of geophysics and the terrestrial climate system.

    Each to his own.

  • rate this

    Comment number 905.

    A new Ice Age is upon us! Save the planet - burn coal, oil, wood, anything to bolster the greenhouse effect! Such may be the headlines in a few years' time. But just as now, the science will be dubious and the actions just as futile. And just as now, someone will make lots of money out of it.

  • rate this

    Comment number 904.

    BBC year 2007: "Arctic summers ice-free 'by 2013'" -

    Obviously the science's models are not as good as some non scientists think.

  • Comment number 903.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • rate this

    Comment number 902.

    This whole discussion is like trying to explain statistical analysis to a toddler, and one who keeps pointing out that the cat's being naughty.

    It's hopeless. Luckily at least some of the grown-ups seem to know what's going on.

    So toddle on, and enjoy yourselves until you have to grow up too.

  • rate this

    Comment number 901.

    NEWSFLASH: We are not all the same and do not all believe in the same values or concepts despite what we are 'advised' to adhere to or tolerate.

    I don't think you can box it up into melting/or not, male/female gay/straight .... life is what it is and will do what it will do. The Muppet masters are just playing with concepts, they have no definitive idea either, apart from taxing everything!

  • rate this

    Comment number 900.

    Due to capitalism's market forces we continue to be more and more productive, that's good. As time goes by each generation can produce more than the prior (even if the population's static) OR it can produce the same and WORK FEWER HOURS. But we're told work is good and not working is bad. Gap between top and bottom is widening. Is greater productivity the reason - profits always up not so wages?


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