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.

Don Perovich: On this year's report card, Arctic sea ice "gets a D"

"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 139.

    Now, will the quick profit merchants on Wall Street go long Gas and Coal, or cut their losses and go short ?
    I'm just trying to understand their Mentality and the weird markets they operate.
    When Gas goes up Bankers get Bonuses !
    When it goes down they still make money from someone.
    Go figure.

  • rate this

    Comment number 138.

    Global warming my Piers Morgan!

  • rate this

    Comment number 137.

    A small piece of good news, funny how years of research into ice losses produce so many sceptics yet a one off good year and they are crowing from the roof tops.
    Still think we're pretty much doomed if we sit on our backsides and hope for the best.

  • rate this

    Comment number 136.

    can we remove the green subsidy on everything we buy now ?

  • rate this

    Comment number 135.

    Dear Man Made Climate Change Advocates,

    Why are these Harvard, MIT, Cambridge, University College London, NASA, and IPCC scientists who reject the man made climate change mania, and say CO2 is 1 of the smallest components of the atmosphere - also humans account for only a fraction of that negligible component; wrong?

  • rate this

    Comment number 134.

    @123. Will

    I take your point, but would argue that people really should start to understand the issues. I would have thought that it's obvious that you can't extract all that coal & oil for well over 100 years, burn it, and not expect there to be consequences. We're talking about millions of years worth of forest growth, with all that locked-in carbon, suddenly released into the atmosphere.

  • rate this

    Comment number 133.

    Humans (and other animals) breathe in air (20% O2), extract O2 and breathe out a higher concentration of CO2 (16% O2). Plants take in Air, convert CO2 to O2. There are billions of humans and breeding at an alarming rate! The vegetation is disappearing an alarming rate (rain forest, and my neighbours even rave about their plastic grass!!).

  • rate this

    Comment number 132.

    It means that the climate change issue is not settled.

    and that the BBC and other liberal outlets should not express it as settled science

  • rate this

    Comment number 131.

    Claiming this as evidence against global warming is akin to innoculating an entire population against a disease and then claiming the disease didn't exist when noone got ill.

  • rate this

    Comment number 130.

    Yes much safer for HYS to debate arctic ice than BBC cronyism over massive payouts to executives.

  • rate this

    Comment number 129.

    I hope people claiming that scientists are 'in it for the money' realise that the ENTIRE govt budget for scientific research in the UK is significantly less than the profits of a single oil company such as Shell.

    Who do you think has the better reason to cloud the facts here? Introducing the idea of 'controversy' around climate change science was the best PR move ever stop falling for it.

  • rate this

    Comment number 128.

    @113 Terrax
    So we are the sceptics are we.

    Please explain where the forests they have discovered under the ice came from.
    I assume it was a whole group of us who dug a big hole and buried them.
    The earth has to change. If the earth didn't warm up then the ice ages which occur every 30000 years or so would accumulate in effect and man would not be alive on this planet!!!!!

  • rate this

    Comment number 127.

    @58.New chav on the block
    I don't get scientists. If the ice melts it's an indication of an impending Armageddon but if the ice level increases it doesn't mean anything

    have to distinquish between sensationalist press like the BBC & scientists, not always easy because they hound scientists into giving quotes for their sensationalist stories. we're all doomed came from the press not the science

  • rate this

    Comment number 126.

    @Sally the Rothbardian

    "humans account for only a fraction of that negligible component."

    There are gaps in your understanding - look up The Carbon Cycle. All the increase in CO2 levels since the industrial times are down to humans. Around 50% of our emissions have been absorbed by natural carbon sinks (mainly oceans - contributing to ocean 'acidification').

  • rate this

    Comment number 125.

    Why do those who think it's a myth made up never produce anyone who was in on the plot? Documents of the meetings and agreed policies? It's like this is the perfect conspiracy, with no leaks. Our climate is affected by natural cycles, and mans interventions. The earth warms, and produces climate change.

  • rate this

    Comment number 124.

    102. Billy - Jeremy Clarkson WAS right then - I'd wait and see on that...

  • rate this

    Comment number 123.

    Good scientists welcome critical analysis and questioning. That is how theories develop.
    It is best not to demonise the public by calling them 'deniers' and 'ignorant' because it is the mums and dads with the genuine questions (many of which remian unanswered) that fund the climate change movement through taxes and carbon pricing.

  • rate this

    Comment number 122.

    Can we now please dig out all the hideous wind farms and throw them away?

  • rate this

    Comment number 121.

    Every argument for drastic man made global warming has been scientifically refuted. Does it make any difference? No. They still squawk and call us deniers. Any extreme weather is blamed on global warming but those events are actually very low at present. It has all happened before, and much worse. We're more likely heading (slowly) into another mini ice age!!
    Quick, buy loads of 4 x 4's !

  • rate this

    Comment number 120.

    Considering last year was the record low, I'd sure hope that this year showed some sort of rebound! Unlikely that you get two record breakers in a row.

    Strange that people who ignore 160+ years of temperature data, 1000s of years of long-term data & 35 years of satellite data suddenly pay attention to this single data point. Cherry picking on a rather extreme level there.


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