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Arctic sitting on thin ice… literally

Usually stories about arctic sea ice don’t pop up until the end of the summer melt season, but thanks to a relatively warm winter (at least in the arctic) this year we are already inundated with stories about the sorry state of the arctic sea ice.

Arctic sea ice younger, thinner as melt season begins

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.

This means that the sea ice is in for more rough summers as more and more of it melts away. There is however one possible glimmer of hope, that can be seen in the figure above.

This past year saw a continuing decline in multi-year ice, but a rebound in ice that’s survived two seasons. The reasons for this can be seen when the geographic distribution of the ice is examined [see the figure at the top of this post]. The older ice has largely been pushed against Greenland and the Canadian Arctic where, each year, a fraction is pushed out past the northern tip of Greenland, where it flows into the North Atlantic and melts. The better freezing conditions of the past year have meant that two-year-old ice has largely extended out towards the pole from Canada. These dynamics mean that it will take several years of similar conditions before multi-year ice can start recovering what’s lost to the Atlantic.

But as usual things aren’t nearly as simply as they first appear.  As Nature News point out, much of the new ice forming in the arctic is pancake ice.

Climate change is not only making Arctic sea ice disappear — it’s also changing the type of ice that forms. Researchers are now trying to determine how an increase in ‘pancake ice’ is affecting the far north, including whether it’s accelerating local warming…

New ice can form in several different ways. When water is surrounded by ice packs, as has been common in the Arctic, areas of open water are small and there is little chance for wind to work up vigorous waves. In such calm conditions, ice forms in unbroken sheets called ‘nilas’.

But now the Arctic has larger areas of open water, and more waves. “As soon as you introduce swell, you get an entirely different form of ice,” says Jeremy Wilkinson of the Scottish Association for Marine Science in Oban, UK. Under these conditions, globs of ice crystals tossed about in the water combine to form first a soupy mixture called ‘grease ice’, and then ‘pancakes’ of thin ice a metre or two in diameter.

This can have all sorts of knock-on effects. Because the pancakes are round, for example, they have areas of open water between them when joined up, making the surface darker overall. This could have a warming effect as a result of less of the Sun’s radiation being reflected. Water also slops up from these holes over the ice so that falling snow melts rather than settling, keeping the surface darker. “This whole cycle is not in models of the Arctic or the Antarctic. It’s one of these conundrums that people haven’t looked into,” says Wilkinson…

There are effects other than a change in albedo. Ice accumulates on the bottom of a single sheet more slowly than it does around crystals bobbing up and down in the water, so pancake ice 0-15 cm thick can form in the same time as 1 cm thickness of nilas ice. As ice formation extracts fresh water from the ocean, faster ice formation should mean saltier seas, which could in turn have an impact on ocean circulation, ice growth and air temperature.

Certainly  large uncertainties remain as to exactly what the effects of all this pancake ice will ultimately be. Young ice simply isn’t that well studied because there didn’t used to be that much of it. How things have changed.

But what does all of this mean? Why do we care about the arctic sea ice?

Well for one, sea ice reflects much of the incoming solar radiation, while open ocean (which is far darker) absorbs much more. This means that the more ice melts the more the arctic ocean will absorb heat. It is a classic example of a positive feedback mechanism.

Sea ice is important because it reflects sunlight away from Earth. The more it melts, the more heat is absorbed by the ocean, heating up the planet even more, said NASA polar regions program manager Tom Wagner. That warming also can change weather patterns worldwide and it alters the ecosystems for animals such as polar bears.

But there is more to it than that, a study published in Geophysical Research Letters by leading tundra experts has found Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss. The study concludes that:

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

Given what we already know, this probably isn’t that surprising, but it is very worrying given that vast amounts of methane and CO2 are locked away in the northern permafrost.

In other words, if it continues, the recent trend in sea ice loss may 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 here).
  • Scientific analysis suggests the rise in 2007 methane levels came from Arctic wetlands (see here).

This is exactly the kind of tipping points we should all be very worried about. If we hit them, it may be too late to do anything, short of a massive geo-engineering effort, to stave off catastrophic climate change.

What is the point of no return for the climate — the level of CO2 concentrations beyond which catastrophic outcomes are virtually unstoppable?

No one knows for sure, but my vote goes for the point at which we start to lose a substantial fraction of the tundra’s carbon to the atmosphere — substantial being 0.1% per year! As we saw in Part 1, frozen away in the permafrost is more carbon than the atmosphere currently contains (and much of that is in the form of methane, a far more potent greenhouse gas than carbon dioxide).

What is the point of no return for the tundra? A major 2005 study (subs. req’d) led by NCAR climate researcher David Lawrence, found that virtually the entire top 11 feet of permafrost around the globe could disappear by the end of this century.

Feedbacks like this are why Hansen of NASA’s GISS amongst others are saying that in order to avoid dangerous feedbacks we must ultimately stabilize atmospheric concentrations of GHG at 350ppm or less.

The time to act is yesterday.

Sadly this urgency seems to be lost on policymakers.

While the deadline [for the the U.N. summit in Copenhagen in December] may be getting nearer every day, the world seems to be largely running in place. The Bonn talks were the first international meeting to be attended by President Barack Obama’s climate negotiators — to the palpable relief of the rest of the world that former President George W. Bush’s much maligned team was gone — but on the big questions, including how to address carbon reduction in rich and poor countries, tangible progress remained elusive… on the whole, delegates left Bonn stuck in the same standoff that has all but paralyzed global climate talks over the past several years.

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