The sharp drop in Arctic sea ice area has been matched by a harder-to-see — but equally sharp — drop in sea ice thickness. The combined result has been a collapse in total sea ice volume.
Many experts now say that if recent volume trends continue we will see virtually ice-free conditions sometime in the next ten years. And that may well usher in a permanent change toward extreme, prolonged weather events “Such As Drought, Flooding, Cold Spells And Heat Waves.”
It will also accelerate global warming in the region, which in turn will likely accelerate both the disintegration of the Greenland ice sheet and the release of the vast amounts of carbon currently locked in the permafrost.
The European Space Agency’s CryoSat-2 probe confirms what the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) at the Polar Science Center has been saying for years: Arctic sea ice volume has been collapsing faster than sea ice area (or extent) because the ice has been getting thinner and thinner.
In fact, the latest satellite CryoSat-2 data shows the rate of loss of Arctic sea ice is “50% higher than most scenarios outlined by polar scientists and suggests that global warming, triggered by rising greenhouse gas emissions, is beginning to have a major impact on the region,” as the UK Guardian reported last month:
If the current annual loss of around 900 cubic kilometres continues, summer ice coverage could disappear in about a decade in the Arctic.
I have focused on sea ice volume for the past 6 years, since I was fortunate enough to hear Dr. Wieslaw Maslowski of the Oceanography Department at the Naval Postgraduate School in a 2006 American Meteorological Society seminar. He reported that models suggested Arctic ice volume had dropped sharply since the mid 1990s. He then made an alarming forecast:
That was in 2006, so he was talking about the possibility of being ice free in 2016.
Looking at volume and thickness helped me avoid the mistake that so many others made in thinking that the sea ice “recovered” after the 2007 minimum in sea ice extent. The scientific literature and actual observations continued to vindicate Maslowski’s projection.
Since Maslowski’s warning appears to now have been vindicated by the CryoSat-2 data, I asked him for a comment. He said he didn’t want to comment on that data specifically until he’s seen the published results — since there are many inherent uncertainties involved. But he then added:
Regardless of all these uncertainties and for the record, if any of these estimates of arctic sea ice volume decline is close to reality, a near ice-free Arctic in summer can happen not in 2100, 2050 or 2037 but much sooner. One of the main reasons I believe it will happen sooner (i.e. the trend of sea ice volume decline will continue) is that with the shrinking sea ice cover in summer the Arctic Ocean increases its net annual heat content through absorption and redistribution, especially in the upper water column, below the surface mixed layer.
This constitutes a positive feedback to sea ice melt in addition to ice-albedo and other feedbacks, mainly because it can affect the sea ice cover year around, including in winter through upward heat entrainment and reduction of ice growth. The warmer Arctic Ocean can also affect air temperatures and circulation, not only during freeze-up but also in winter and spring. Observational evidence (Jackson et al., 2010 and 2011) suggests increasing sub-surface temperatures and over increasing area in the Canada Basin through 2009, which independently of models supports the argument about the increasing upper ocean heat content.
I do realize that the above sounds ‘alarmist’ and I’ve heard such criticism more than once before but I believe it’s my obligation to make sure that this message is heard by the policymakers and general public.
Maslowski did not make a new timing prediction, but instead directed me to a recent article he was lead author on, “The Future of Arctic Sea Ice,” in Annual Review of Earth and Planetary Sciences.
That article estimated a loss of 1,120 cubic kilometres per year from 1996 to 2007, quite close to the recently reported CryoSat-2 measurements. It continued:
Given the estimated trend and the volume estimate for October–November of 2007 at less than 9,000 km3 (Kwok et al. 2009), one can project that at this rate it would take only 9 more years or until 2016 ± 3 years to reach a nearly ice-free Arctic Ocean in summer. Regardless of high uncertainty associated with such an estimate, it does provide a lower bound of the time range for projections of seasonal sea ice cover.
This is the same estimate Maslowski made in 2006, although he has couched it more conservatively here and has explained that he wouldn’t be surprised if some summer ice lingers above Greenland and Eastern Canada into the 2020s. That’s why he uses the term “nearly ice-free.”
What’s interesting is that the volume trend has in fact continued according to PIOMAS and CryoSat-2. Many other experts are warning that we have effectively passed the point of no return and nearly ice-free are imminent. Fen Montaigne, senior editor of Yale e360, reports:
Peter Wadhams, who heads the Polar Ocean Physics Group at the University of Cambridge and who has been measuring Arctic Ocean ice thickness from British Navy submarines, says that earlier calculations about Arctic sea ice loss have grossly underestimated how rapidly the ice is disappearing. He believes that the Arctic is likely to become ice-free before 2020 and possibly as early as 2015 or 2016 — decades ahead of projections made just a few years ago.
Mark Drinkwater, mission scientist for the European Space Agency’s CryoSat satellite and the agency’s senior advisor on polar regions, said he and his colleagues have been taken aback by the swiftness of Arctic sea ice retreat in the last 5 years. “If this rate of melting [in 2012] is sustained in 2013, we are staring down the barrel and looking at a summer Arctic which is potentially free of sea ice within this decade,” Drinkwater said in an e-mail interview.
Wadhams told the BBC how much warming is accelerated by just replacing the reflective white ice with the more absorptive open ocean:
Prof Wadhams calculates that this increased absorption of the sun’s rays is “the equivalent of about 20 years of additional CO2 being added by man”.
The Cambridge University expert says that the Arctic ice cap is “heading for oblivion.”
Not every expert thinks the Arctic will be necessarily be nearly ice free by 2020. And Dr Seymour Laxon who has been working on the CryoSat-2 data said this of the 2020 projection:
Laxon urged caution, saying: “First, this is based on preliminary studies of CryoSat figures, so we should take care before rushing to conclusions. In addition, the current rate of ice volume decline could change.” Nevertheless, experts say computer models indicate rates of ice volume decline are only likely to increase over the next decade.
But whenever the nearly ice free conditions occur (and I’ve long been in the camp that says it’ll be by 2020), those who think we have not effectively crossed a point of no return — those who think we are not in a death spiral — are not paying attention to the thickness and volume analysis. As Yale e360 reported:
Jay Zwally, chief cryospheric scientist at NASA’s Goddard Space Flight Center and an observer of Arctic ice for 40 years, places little stock in the likelihood of a reversal of disappearing Arctic ice. New satellite technology has given scientists the ability to measure the height of sea ice above the water, and hence ice volume. Those measurements, he said, have vividly underscored that Arctic sea ice is in a swoon.
For example, a recent analysis of data from CryoSat and NASA’s ICESat satellite estimates that the volume of sea ice in a large area of the central Arctic Ocean has plummeted in late winter — February and March — by nearly half in just eight years, from an estimated 13,000 cubic kilometers in 2004 to 7,000 cubic kilometers in 2012.
“We’ve gone through a tipping point, and of all the things a tipping point applies to, sea ice is the most appropriate, because the idea is when it goes below a certain thickness it doesn’t go back under present conditions,” said Zwally. “People can get hung up on the specifics and lose track of the big picture, which is that it’s getting worse and it’s going to get [even] worse.”
And that has serious consequences for every person on this planet and countless future generations.
- Why The Arctic Sea Ice Death Spiral Matters
- Polar bear, Arctic sea ice all-but doomed: Misleading Naturecover story misleads the media, public