Do we know when the Arctic will be sea ice-free?
- 03 Sep 2012, 12:40
- Verity Payne
Credit: NASA Earth Observatory
Over the past week,
news that sea ice extent has fallen to a new low according
to satellite measurements has prompted speculation about how long
it will be before the Arctic Ocean is completely free of ice in
The fate of Arctic sea ice has always captured attention. The
ice grows in winter and retreats in summer. Records since 1979 show
Arctic sea ice losing around
3% of its area per decade. The amount of ice at the summer
minimum is shrinking faster, at around 12% per
decade, and the sea
ice is also becoming thinner.
This long-term decline is clear. But it's not possible to
confidently predict how much ice there will be in a particular
year. In 2007 Arctic sea ice coverage fell to an unusual
low - unprecedented in the satellite record, and well below what was
This prompted widespread coverage, a suggestion from US National
Snow & Ice Data Center (NSIDC) director Mark Serreze that the
sea ice had entered a "
death spiral", and
speculation from others that the Arctic ocean might be clear of
sea ice in summer sooner than expected.
But 2008 through 2011 didn't see new records broken, although
sea ice levels remained consistent with the long-term downward
suggest that unusual weather conditions contributed to 2007's
record low, prompting
more conservative predictions for when we might sea ice-free
Natural variability or a 'fundamental change' in
But this year has seen another dramatic sea ice low, with Arctic
sea ice extent already below 2007 levels and a couple of weeks of
the melt season left:
Commentators are once again
questioning whether this year's fall in ice cover marks a
fundamental change in the pattern of Arctic sea ice melt, or
whether it's the result of natural variability.
Some scientists point out that the unusual weather conditions
that contributed to 2007's record low haven't happened this year.
"The previous record, set in 2007,
occurred because of near perfect summer weather for melting ice.
Apart from one big storm in early August, weather patterns this
year were unremarkable. The ice is so thin and weak now, it doesn't
matter how the winds blow."
Predictions are once again being made about when the Arctic
Ocean might be ice-free in summer. There's quite a range of
opinions. For example, Professor Peter Wadhams, ocean physicist at
the University of Cambridge,
tells the Scotsman:
"The entire ice cover is now on the
point of collapse [...] It is truly the case that it will be all
gone by 2015."
And Mark Drinkwater, mission scientist for the European Space
Agency's CryoSat satellite tells
Yale Environment 360:
"If this rate of melting [in 2012] is
sustained in 2013, we are staring down the barrel and looking at a
summer Arctic which is potentially free of sea ice within this
Other scientists offer estimates in terms of decades. Ted
Scambos, NSIDC senior research scientist,
suggests that Arctic sea ice-free summers aren't likely to be
reached until 2030, "plus or minus a decade."
And in 2011, NSIDC director Mark Serreze
"[W]e may [...] be looking at ice-free
summers only a few decades from now."
The scientific literature on the subject
Peer reviewed research in this area has developed over the last
few years. In 2007, before the dramatic melt that year, the
most considered scientific opinion came from the Intergovernmental
Panel on Climate Change (IPCC). The worst case scenario, it said,
was ice-free summer seas by the end of the century.
But a 2009 review of newer scientific literature by a
group of scientists concludes:
"The observed summer-time melting of
Arctic sea-ice has far exceeded the worst-case projections from
climate models of IPCC AR4 … The warming commitment associated with
existing atmospheric greenhouse gas levels means it is very likely
that in the coming decades the summer Arctic Ocean will become
ice-free, although the precise timing of this remains
research confirms the climate models used for IPCC's AR4
underestimate future Arctic sea ice loss.
Projections made since 2007 suggest the Arctic ocean could be
seasonally free of ice sooner. A
2007 paper concludes "decreasing ice coverage might lead to an
ice-free Arctic in summer sometime within the upcoming decades",
whilst a 2009
paper, which uses 2007/2008 September sea ice measurments as a
starting point for six IPCC climate models predicts "a nearly sea
ice free Arctic in September by the year 2037."
A more recent
assessment of sea ice projections using the latest generation
of IPCC climate models finds that the updated models more
realistically represent the present state of the sea ice cover, and
"[A] seasonally ice-free Arctic sooner
than [the older IPCC models], leading to the conclusion that a
seasonally ice-free Arctic Ocean within the next few decades is a
But the paper's authors point out that the updated models have
not reduced the range in model projections of when there might be a
seasonally ice-free Arctic Ocean.
So there are recent climate models that project seasonal
ice-free Arctic seas within the next few decades, but they cannot
yet pinpoint a precise year, or even decade. Lars-Otto Reiersen,
head of the Arctic Monitoring and Assessment Programme, tells
Reuters most models indicate ice-free conditions in 30 to 40
years, although "there are models that indicate 2015 as an
this Reuters headline probably offers the best summary of the
state of scientific opinion:
"Arctic summer sea ice might thaw by
2015 - or linger for decades"