Arctic sea ice: profound seasonal changes confirmed by new study
ClimateProgress.org reports, 26th March 2015: “The 2015 Arctic sea ice maximum is the lowest on record.
“Arctic sea ice has been in a virtual death spiral for over three decades now with serious implications for extreme weather, sea level rise, and permafrost melt. Not only has the surface area or extent of sea ice declined sharply, but so has the ice thickness during the summer minimum (when the melt season ends in September) — dropping a remarkable 85 percent from 1975 to 2012, according to a recent study.
“The extent of Arctic sea ice hits a winter maximum in early March. This year, the National Snow and Ice Data Centre (NSIDC) — along with NOAA and NASA — said the maximum extent was likely reached on February 25th. This was not only the second earliest maximum, “it is also the lowest in the satellite record.”
“As NASA points out, this record low winter maximum does not guarantee a record summertime minimum. Moreover the maximum is less significant than the minimum. “Scientifically, the yearly maximum extent is not as interesting as the minimum. It is highly influenced by weather and we’re looking at the loss of thin, seasonal ice that is going to melt anyway in the summer and won’t become part of the permanent ice cover,” explained NASA sea ice scientist Walt Meier. “With the summertime minimum, when the extent decreases it’s because we’re losing the thick ice component, and that is a better indicator of warming temperatures.”
The best indicator of the sustained impact of global warming on the Arctic is the stunning decline in the thickness of the sea ice that has accompanied the shrinking of its surface area. A February study published in The Cryosphere, “Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations,” offers the most comprehensive and up-to-date analysis of the Arctic death spiral, combining eight different data sets, including ones from submarines, aircraft, and satellites.
This study’s conclusion is alarming. Annual mean ice thickness has decreased from 3.59 meters [11.8 feet] in 1975 to 1.25 m [4.1 feet] in 2012, a 65% reduction. This is nearly double the 36% decline reported by an earlier study.
In September the mean ice thickness has declined from 3.01 to 0.44
m [from 9.9 to 1.4 feet!], an 85 % decline.
“The ice is thinning dramatically,” explained climatologist Ron Lindsay, the lead author — much faster than previously estimated. The study includes this chart of the average annual sea ice thickness, in meters, for the central Arctic Ocean, in recent decades:
Summertime Arctic sea ice is not long for this world. Because of Arctic amplification, the Arctic warms twice as fast (or more) than the Earth as a whole does. Earlier this month, a study projected the rate of warming for the Arctic will soon exceed 1.0°F (0.55°C) per decade — and could hit 2°F per decade post-2050 if we don’t reverse carbon pollution trends ASAP.
This is especially troublesome because a key accelerator of Arctic amplification is sea ice loss. Global warming melts highly reflective white ice and snow, exposing in its place the dark blue sea or dark land, both of which absorb much more solar energy.
A great deal of recent research suggests that Arctic amplification, including sea ice loss, is already worsening extreme weather. Similarly, such amplified warming means that the rapidly-melting Greenland ice sheet, which warming has already made unstable, is likely to start collapsing even faster, which would push sea level rise higher than previously estimated, upwards of six feet this century.
Source: ClimateProgress.org, 26th March 2015. For the full text, see http://thinkprogress.org/climate/2015/03/26/3633019/arctic-death-spiral-sea-ice
