The National Snow and Ice Data Center reported Monday:
[Arctic] ice older than two years accounted for less than 10% of the ice cover at the end of February.
So it is “thinner and more vulnerable than at anytime in the past three decades,” as the AP reports. “The amount of thick sea ice hit a record wintertime low of just 378,000 square miles this year, down 43 percent from last year.” Why is that a concern?
“That thick ice really traps ocean heat; it keeps the planet in its current state of balance,” said Waleed Abdalati, director of the Center for the Study of Earth from Space at the University of Colorado and NASA’s former chief ice scientist. “When we start to diminish that, the state of balance is likely to change, tip one way or another.”
Sounds like a tipping point to me — and to NSIDC and IPY (see NSIDC: Arctic melt passes the point of no return, “We hate to say we told you so, but we did.” and The International Polar Year: “Arctic sea ice will probably not recover.)
Why should we care about Arctic ice disappearing? Because, as a major 2008 study found, Permafrost loss linked to Arctic sea ice loss:
We find that simulated western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends. The accelerated warming signal penetrates up to 1500 km inland”¦.
In other words, the recent trend in sea ice loss is poised to triple Arctic warming, causing large emissions in carbon dioxide and methane from the tundra this century. What is especially worrisome is that 2007 provides strong evidence on behalf of this theory:
- NOAA reported that methane levels rose in 2007 for the first time since 1998 (see here).
- The tundra can emit vast amounts of methane when it defrosts (see Part 1).
- Scientific analysis suggests the rise in 2007 methane levels came from Arctic wetlands (see here).
- And 2007 saw record Arctic ice loss [see "Ice Ice Maybe (not)"] — as did 2008.
David Lawrence of the National Center for Atmospheric Research (NCAR) has analyzed permafrost loss this century under various warming scenarios:
[Lawrence told me that using the above figure is "still fine as long as one mentions the caveats that permafrost is probably degrading a bit too rapidly in the original" (see discussion, literature links here).]
Note that the B1 scenario is “stabilizing” at 550 ppm atmospheric concentrations of carbon dioxide, but in fact NCAR’s model doesn’t look at the feedback of the CO2 and methane emissions from the tundra loss, which would drive concentrations far higher! So we must avoid 550 at all cost, since the tundra feedback, coupled with the climate-carbon-cycle feedbacks that the IPCC models, could easily take us to the unmitigated catastrophe of 1000 ppm (see Tundra, Part 2: The point of no return).
We are, of course, on pace to exceed the A2 scenario — U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm “¦ the worst-case IPCC scenario trajectories (or even worse) are being realised” “” 1000 ppm.
So it will soon be time to retire the word “permafrost” from our vocabulary, along with “polar” bear and “glacial” change.
I’ll end with longer excerpts from yesterday’s NSIDC report on Arctic ice:
Arctic sea ice extent has begun its seasonal decline towards the September minimum. Ice extent through the winter was similar to that of recent years, but lower than the 1979 to 2000 average. More importantly, the melt season has begun with a substantial amount of thin first-year ice, which is vulnerable to summer melt….
How vulnerable is the ice cover as we go into the summer melt season? To answer this question, scientists also need information about ice thickness. Indications of winter ice thickness, commonly derived from ice age estimates, reveal that the ice is thinner than average, suggesting that it is more susceptible to melting away during the coming summer.
As the melt season begins, the Arctic Ocean is covered mostly by first-year ice, which formed this winter, and second-year ice, which formed during the winter of 2007 to 2008. First-year ice in particular is thinner and more prone to melting away than thicker, older, multi-year ice. This year, ice older than two years accounted for less than 10% of the ice cover at the end of February. From 1981 through 2000, such older ice made up an average of 30% of the total sea ice cover at this time of the year.
While ice older than two years reached record lows, the fraction of second-year sea ice increased compared to last winter. Some of this second-year ice will survive the summer melt season to replenish the Arctic’s store of older ice; however, in recent years less young ice has made it through the summer. To restore the amount of older ice to pre-2000 levels, large amounts of this young ice would need to endure through summer for several years in a row.
But conditions may not always favor the survival of second-year and older ice. Each winter, winds and ocean currents move some sea ice out of the Arctic ocean. This winter, some second-year ice survived the 2008 melt season only to be pushed out of the Arctic by strong winter winds. Based on sea ice age data from Jim Maslanik and Chuck Fowler at the University of Colorado, since the end of September 2008, 390,000 square kilometers (150,000 square miles) of second-year ice and 190,000 square kilometers (73,000 square miles) of older (more than two years old) ice moved out of the Arctic. View animation (1.1 MB).
The time to act is yesterday.