If you are worried about big changes in Arctic sea ice, you are not alone - but it is hard to know how much is worth worrying about.  If you are worried, there is some slightly good news - even if we lose half, it will not be a 'point of no return' according to a new study.

Sea ice comes and goes without leaving a record so our knowledge about variations and extent was limited before we had satellite surveillance and observations from airplanes and ships.  Not any more.  Researchers at The Centre for Geogenetics at the Natural History Museum of Denmark, University of Copenhagen say have developed a method by which it is possible to measure the variations in the ice several millennia back in time.

Arctic Ice August 2011

In the days of sailing ships and the early days of steam, even into the early years of the 20th century, much of the Arctic remained inaccessible due to the extensive pack ice.

When explorers attempted to penetrate the ice, it is often found from their journals that they did so in late August.  There are many references to be found of an 'open season' during which it was possible to maneuver a ship through an open lead during a period which was often only of two weeks duration, or less.  In some years, the ice simply did not open as expected, and the explorers would either go home or overwinter nearby, to try again the next year.

Arctic Ice July 2011 - Update

Are we headed for another 2007 style crash ?

In my Arctic Ice March 2011 - Update #1,  I gave these figures for September minimum -

an extent below 4 million km² is highly probable.
an extent below 3 million km² is entirely possible if Arctic weather continues to follow the overall trends of the last decade.

In April I revised that, based on some projections from IARC - IJIS figures to -

I project an end of season extent range between 3.9 million km² and 4.5 million km².

An unusual number of destructive storm surges along the East Coast during the 2009-2010 El Niño winter could be a taste of things to come - with more destructive storm surges in future El Niño years, according to a new study by NOAA.

El Niño conditions are characterized by unusually warm ocean temperatures in the Equatorial Pacific that normally peak during the Northern Hemisphere 'cool season.' They occur every three to five years with stronger events generally occurring every 10-15 years. El Niño conditions have important consequences for global weather patterns, and within the U.S., often cause wetter-than-average conditions and cooler-than-normal temperatures across much of the South.

New research on Jakobshavn Isbrae, a tongue of ice extending out to sea from Greenland's west coast, shows that large, marine-calving glaciers don't just shrink rapidly in response to global warming, they also grow at a remarkable pace during periods of global cooling.  Glaciers change.

Through an analysis of adjacent lake sediments and plant fossils, the researchers determined that the glacier, which retreated about 40 kilometers inland between 1850 and 2010, expanded outward at a similar pace about 200 years ago, during a time of cooler temperatures known as the Little Ice Age.

Arctic Ice July 2011

For much of the written history of the Arctic, exceptional extents of open water were reported in terms of what the explorer, fisherman, whaler or sealer had previously experienced.  That would make such events likely every 20 to 30 years.  However, for each report of open ice in a specific area there is likely to be found in the archives a report from 180 degrees opposite across the pole of a greater than usual ice extent.

A new study shows that the rate of sea-level rise along the U.S. Atlantic coast is greater now than at any time in the past 2,000 years - and a consistent link between changes in global mean surface temperature and sea level.

Nares Ice Bridge Breakup

The ice bridge in Nares Strait at the Kane Basin outlet to Baffin Bay has begun to break up.

There was a plug of consolidated ice solidly wedged across the channel.  Consolidated ice is very strong in compression, but weak in tension, as I have noted in other articles, such as Bridges That Build Themselves.  From that article:

An Arctic Decade 2001 - 2011


For thousands of years the Arctic has been covered in perennial ice with seasonal changes at the margins and some natural variation, seen as losses and recoveries of extent.

For hundreds of years observers have noted that seasonal and local variations at the margins can leave some relatively small regions ice free one year, and solidly iced up in other years.