new study published online by the journalNature this week
has found that the decline in Arctic sea ice over the last few
decades is "unprecedented" over the last 1450 years.
Since the advent of satellite monitoring at the end of the 1970s
it has been clear that Arctic sea ice is declining, losing around
3% of its area per decade over the last thirty years. This
loss has been particularly extreme in the summer months - the
September minimum in sea ice extent is decreasing at around 12% per
decade. This has been accompanied by the sea ice
becoming thinner, along
with a decrease
in older ice reserves.
These sorts of changes have concerned scientists, and provide
evidence for the so-called 'Arctic
amplification' effect projected by climate models
simulations where temperatures are expected to rise at about double
the global average in the Arctic.
But the small number of long-term records of changes to Arctic
sea ice have meant that up until now it has been difficult to
determine whether the sea ice is fluctuating naturally, or if, as
scientists suspect, the current ice loss is unusual.
Now an international team of scientists have produced a record
of Arctic sea ice change which spans the last 1450 years, using
data from ice cores, tree ring records, lake sediments and
The researchers have found that there have been some occasions
over the last 1450 years when Arctic sea ice has retreated at a
similar pace to the current ice loss, but the decline in ice on
these occasions has never reached the volume of ice lost over the
last few decades. As the researchers put it:
"...Both the duration and magnitude of
the current decline in sea ice seem to be unprecedented for the
past 1,450 years."