Yet another Feedback. Why Arctic Ice is melting so fast.

July 1, 2011


The Winnepeg Free Press:

A 500-kilometre walk over treacherous Arctic terrain has resulted in a possible explanation for why sea ice in northern waters is melting so much more rapidly than anyone thought it would.

“We’re trying to understand why the ice is melting so fast,” said Simon Boxall of the Catlin Arctic Survey. “It’s not just down to simple warming. There are more complicated processes.”

For some time now, the story of climate change is of real world processes far exceeding model studies, particularly in the realm of arctic sea ice.

As the graph above shows, observed losses are far exceeding the expectation.

A 2007 paper from the National Snow and Ice Data Center in Boulder, Colo., found that the projections of the UN-sponsored Intergovernmental Panel on Climate Change were already obsolete three years after they were published.

When projections from the panel were compared with actual observations, the authors found that between 1953 and 2006 the sea ice was retreating three times faster than it should have. Between 1979 and 2006, when satellite data was available, the actual retreat was twice as fast as climate models predicted.

The report concluded that sea ice retreat is 30 years ahead of where scientists thought it would be.

Now an explanation has been proposed for yet another feedback in the complex loops of interacting processes that govern the arctic.

Data for studies like these is usually gathered from ships, but during the time scientists wanted to study, the springtime melt period, when changes are most rapid, there is still too much ice for ships to make the passage. So the scientists, lead by Simon Boxall of the Catlin Arctic Survey, walked, for 500 kilometers – taking measurements as they went.

What they found surprised them. Water at a depth of 200 meters was colder than previously measured. That is not generally what is expected from an ocean that is storing more heat.

But when they realized that the colder water was also saltier than they expected, an explanation began to suggest itself.

Boxall points out that the older sea ice is, the less salt it contains. Ice that’s two or three years old already contains very little salt.

Year-old ice, however, remains fairly salty. And when it melts, it produces meltwater that’s denser than the relatively fresh water from older ice.

As multi-year ice declines throughout the Arctic, more of the saltier meltwater from younger ice is mixing into the ocean. That colder, denser water sinks more quickly and forces less dense water from deeper in the ocean up to the surface.

Because fresh meltwater is colder than seawater, that means relatively warm water is being forced upwards. And that, said Boxall, may be part of the reason that sea ice is melting so much faster than anyone thought it would.

“What we’re seeing is that (fresh meltwater) being taken away from the surface and replaced by slightly warmer water,” said Boxall. “The evidence is that the surface waters are (now) slightly warmer.”

The results are preliminary, and obviously, there will be more observations, more expeditions. Nature continues to pull the rug out from under us in the arctic and elsewhere, and no doubt this will not be the last surprise or paradox.

We’re going to learn a lot about how the planet operates in the next 100 years – but we already know well enough that we are pushing a very complex and non-linear system in some ways harder than nature has in billions of years since life began.

Read More: Washington Post – Arctic Headed for another big melt

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One Response to “Yet another Feedback. Why Arctic Ice is melting so fast.”

  1. otter17 Says:

    Quote:
    “We’re going to learn a lot about how the planet operates in the next 100 years – but we already know well enough that we are pushing a very complex and non-linear system in some ways harder than nature has in billions of years since life began.”

    The current Great Warming is a crazy pace of change according to the Earth but “business as usual” according to humans.


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