Tuesday, September 25, 2012

Arctic Sea Ice Matters

A record low in the Arctic sea ice extent occurred on September 16, 2012 and it was the lowest in the satellite record which started in 1979. Even more troubling was that this year also saw a record low in sea ice volume.

Click on the image for a high-resolution version. Image Credit: NSIDC.

The previous record minimum extent occurred in 2007.  What was extraordinary about this year was that weather conditions were not as favorable for melting as in 2007.  That year was noted for long periods of sunshine which allowed the ice to melt over much of the Arctic.  This year came on the heels of a cold winter in which the ice extent came close to normal.  There were more clouds and a powerful storm which hit the Arctic in early August which helped to break up more of the thin ice.

Click on the image for a high-resolution version. Image Credit: Climate Central.

Arctic sea ice has been on the decline since the introduction of satellite monitoring in 1979.  This is illustrated by the graphic above.  In addition, the rate of decline has been accelerating.  In fact, this year’s minima was half what it was at the start of the record.  Notice that the ice minima for Antarctica have increased only slightly during the same time.  Far more ice is being lost in the Arctic than in the Antarctic.  This is not surprising at this time because the Antarctic is a much colder environment.  Ice mass is being lost in the Antarctic even though the extent has increased slightly.

Annual sea ice minimum.  Image Credit: Open Mind.

Temperatures in the Arctic have been warming at least twice as fast as global temperatures.  It is warmer now than at any time is the last 2,000 years.  What is more disturbing is that the rate of warming has been faster in the last 30 years.

Image Credit: Skeptical Science.

Clearly the trends show that the Arctic sea ice is in a death spiral.  At some point there will be a sea ice-free summer.  Could is all be from global warming?  The answer is that it is related to the warming of the planet, but the evidence indicates that it is also from the ice-albedo effect.  Ice and snow are highly reflective and can reflect up to 90% of the solar insolation (incoming solar radiation).  As the ice melts the albedo (the radiation that is reflected) changes to about 10-25% from the darker ocean.  Thus the ocean absorbs far more energy than the ice.  The NASA video below illustrates the effect:

Why does the loss of sea ice matter?

The loss of sea ice changes both the ecology and meteorology as well as the climate.  Just in the past year there have been two powerful storms to hit the region; the one in November, 2011, was described as epic, while the one in August was a very powerful storm.  The loss of the ice and warming of the ocean is already impacting larger mammals like polar bears and some species of seals.  Scientists are now discovering numerous examples.

Peter Sinclair has put together a great video of the Arctic sea ice and how it is changing.  Much of the change has occurred in the past 30 years.  This has prompted some scientists to speculate that a sea ice-free summer could occur in the next 15 years.

I like to think that the Arctic is like the “canary in the coal mine.”  Nature is telling us that the changes are occurring now and at an unprecedented pace.  The science is clear and we ignore it at our peril.

Other articles on the Arctic situation can be found here: