By Matt Owens January 20, 2014
Arctic sea ice has been declining steeply in recent years - with many serious implications for the planet's weather - and climate change itself.
In fact, the decline has been so rapid, exceeding most global climate model projections,¹ that many observers have become quite concerned that we may not have enough time to stop using fossil fuel energy sources before suffering widespread damage from global warming.
Or to put it another way, we may have already used up our emissions budget.
The logic behind the worry is this: without the reflective sea ice covering the Arctic Ocean in summer and fall seasons, the global energy imbalance increases substantially² beyond the current imbalance we already have from cumulative greenhouse gas emissions. Specifically, where the sea ice is missing, the dark exposed ocean absorbs the summer and fall sunlight and warms up, thereby also melting more of the sea ice.
There are numerous other feedbacks involved too, however, the bottom line is that if summer and fall Arctic sea ice continues to decline faster than projected, we will be in for a faster progression of global warming.³
I received a more nuanced perspective on the situation in a recent interview with Jennifer Francis. We were discussing the extremely cold Arctic air excursions that have been freezing the US Midwest and East, and the role that global warming and melting Arctic sea ice is playing in the weather.
She said that we're already experiencing early impacts of the sea ice decline, in her opinion. And that she sees the consequences from the loss of sea ice as a continuum where (1) progressively thinner ice transmits more heat through the ice, (2) progressively less coverage of the Arctic Ocean by sea ice allows more sunlight into the water and heat back out, (3) progressively longer durations of open water in summer and fall do the same, and (4) a number of other progressively changing factors like encroachment of darker and thicker vegetation northwards and less snow cover in the sunny months in the same areas, all tend to amplify greenhouse gas warming in the Arctic.
All these progressive changes have been underway for many years now. According to Francis, they are contributing to substantially more heat and moisture in the arctic and subarctic air, especially in the winter months when absorbed heat from the summer is released back from the ground and ocean, into the air.
Francis says the net effect so far has been increasingly extreme weather in the Northern Hemisphere, and that unusual weather events, like Hurricane Sandy,⁴ are happening more frequently.⁵
Interestingly, research by Jacob Sewall one decade ago showed that a large decline in Arctic sea ice would result in up to 50% reductions in winter precipitation (December through February) over California and nearby states. In terms of the annual average change in precipitation, he wrote "a reduction in Arctic sea ice cover is clearly linked to shifts in the precipitation regime over western North America with northern regions [parts of Canada and Alaska] getting wetter by up to 44% and southern regions [parts of Washington, Oregon, Idaho, California, Nevada, Utah, Arizona, Colorado, and New Mexico] drying by up to 20%."⁶
Below is a comparison of the same day from this year, 2013, and 2012, showing Arctic sea ice thickness as estimated by the updated US Navy sea ice model. The color scale has been modified to make comparison easier. The scale is in meters of thickness of sea ice. Notice the trend in ice thicker than three meters, and the trend north of the 80-North line of latitude.
A good source of ongoing coverage and engaging discussion about the Arctic sea ice can often be found at the Arctic Sea Ice Blog.
¹ Overland et al., 2013 - "When will the summer Arctic be nearly sea ice free?" doi: 10.1002/grl.50316.
² Matsoukas et al., 2010 - 'The effect of Arctic sea-ice extent on the absorbed (net) solar flux at the surface, based on ISCCP-D2 cloud data for 1983–2007;" doi: 10.5194/acp-10-777-2010.
³ Deser et al., 2010 - "The Seasonal Atmospheric Response to Projected Arctic Sea Ice Loss in the Late Twenty-First Century;" doi: 10.1175/2009JCLI3053.1.
⁴ Greene et al., 2013 - "Superstorm Sandy: A series of unfortunate events?" doi: 0.5670/oceanog.2013.11.
⁵ Francis et al., 2012 - "Evidence linking Arctic amplification to extreme weather in mid-latitudes;" doi:10.1029/2012GL051000.
⁶ Sewall 2005 - "Precipitation Shifts over Western North America as a Result of Declining Arctic Sea Ice Cover: The Coupled System Response;" doi: 10.1175/EI171.1.