Sea Ice Ends Year at Same Level as 1979
Rapid growth spurt leaves amount of ice at levels seen 29 years
Thanks to a rapid rebound in recent months, global sea ice levels
now equal those seen 29 years ago, when the year 1979 also drew
to a close.
Ice levels had been tracking lower throughout much of 2008, but
rapidly recovered in the last quarter. In fact, the rate of increase
from September onward is the fastest rate of change on record,
either upwards or downwards.
The data is being reported by the University of Illinois's Arctic
Climate Research Center, and is derived from satellite observations
of the Northern and Southern hemisphere polar regions.
Each year, millions of square kilometers of sea ice melt and
refreeze. However, the mean ice anomaly -- defined as the seasonally-adjusted
difference between the current value and the average from 1979-2000,
varies much more slowly. That anomaly now stands at just under
zero, a value identical to one recorded at the end of 1979, the
year satellite record-keeping began.
Sea ice is floating and, unlike the massive ice sheets anchored
to bedrock in Greenland and Antarctica, doesn't affect ocean levels.
However, due to its transient nature, sea ice responds much faster
to changes in temperature or precipitation and is therefore a
useful barometer of changing conditions.
Earlier this year, predictions were rife that the North Pole
could melt entirely in 2008. Instead, the Arctic ice saw a substantial
recovery. Bill Chapman, a researcher with the UIUC's Arctic Center,
tells DailyTech this was due in part to colder temperatures in
the region. Chapman says wind patterns have also been weaker this
year. Strong winds can slow ice formation as well as forcing ice
into warmer waters where it will melt.
Why were predictions so wrong? Researchers had expected the newer
sea ice, which is thinner, to be less resilient and melt easier.
Instead, the thinner ice had less snow cover to insulate it from
the bitterly cold air, and therefore grew much faster than expected,
according to the National Snow and Ice Data Center.
In May, concerns over disappearing sea ice led the U.S. to officially
list the polar bear a threatened species, over objections from
experts who claimed the animal's numbers were increasing.