Arctic fire hints at warming cue

28 July 2011 Last updated at 16:33 GMT By Richard Black Environment correspondent, BBC News In the summer of 2007, more than 1,000 sq km of Alaskan tundra burned near Anaktuvuk River An exceptional wildfire in northern Alaska in 2007 put as much carbon into the air as the entire Arctic tundra absorbs in a year, scientists say.

The Anaktuvuk River fire burned across more than 1,000 sq km (400 sq miles), doubling the extent of Alaskan tundra visited by fire since 1950.

With the Arctic warming fast, the team suggests in the journal Nature that fires could become more common.

If that happens, it could create a new climate feedback, they say.

Fires in the tundra are uncommon because the ground is covered in snow and ice for large periods of the year.

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Melting can lead to other huge changes... releasing carbon that's been frozen since the Pleistocene”

End Quote Michelle Mack University of Florida Temperatures are low even in summer, and the ground can also remain wet after the ice has melted.

But 2007 saw unusually warm and dry conditions across much of the Arctic - resulting, among other things, in spectacularly fast melting of Arctic sea ice.

This created conditions more conducive to fire, and when lightning struck the tundra in July, the Anaktuvuk River fire ignited.

"Most tundra fires have been very small - this was an order of magnitude larger than the historical size," said Michelle Mack from the University of Florida in Gainesville, who led the research team on the Nature paper and is currently conducting further field studies in Alaska.

"In 2007, we had a hot, dry summer, there was no rain for a long period of time.

"So the tundra must have been highly flammable, with just the right conditions for fire to spread until the snow in October finally stopped it."

Nasa satellites image Arctic ice, water, land - and the Anaktuvuk fire, the black portion at bottom-right

According to the team's calculations, the statistics of the fire are remarkable.

It is the largest on record, doubling the cumulative area burned since 1950.

It put carbon into the atmosphere about 100 times faster than it usually escapes from the ground in the Arctic summer, and released more than 2 million tonnes.

Although a small contribution to global emissions, this is about the same amount as the entire swathe of tundra around the Arctic absorbs in a single year.

The melting of Arctic sea ice suggests 2007's record may be broken this year

There is some vegetation on the summer lands, which did burn; but the main fuel is carbon in the ground itself.

The Anaktuvuk fire burned down to a maximum depth of 15cm (6in), and was burning carbon sequestered away over the last 50 years.

What this implies for the future is uncertain.

Climate models generally predict warmer temperatures across the Arctic, which could increase the frequency of fires and so a net loss of carbon into the atmosphere - reinforcing global warming.

On the other hand, plant life could flourish under these conditions, potentially increasing absorption and sequestering of carbon from the atmosphere.

In a news story published well before the Nature paper came out, another of the US research team, Gaius Shaver from the Marine Biological Laboratory in Woods Hole, said the northern region of Alaska could become "vastly different from the frozen, treeless tundra of today.

"And it's one that may feed back positively to global climate change."

On reflection

Another impact of the fire that has yet to be fully assessed is that the blackened soil absorbs more solar energy than normally vegetated tundra.

This abets melting of the permafrost layer below.

"Once permafrost melts beyond a certain depth on a slope, then all of the organic layer slides down the slope like a landslide," Dr Mack told BBC News.

"This whole issue of melting can lead to other huge changes in drainage, in areas of wetlands - releasing carbon that's been frozen since the Pleistocene [Epoch, which ended more than 10,000 years ago]."

The latest data on Arctic sea ice, meanwhile, reveals that 2011 could well see a melting season that will beat the 2007 record.

Currently, about the same area of sea is covered in ice as at the same point in 2007, which the US National Snow and Ice Data Center (NSIDC) ascribes to "persistent above-average temperatures and an early start to [the] melt".

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Moon soil hints at water bonanza

26 May 2011 Last updated at 18:01 GMT By Jason Palmer Science and technology reporter, BBC News The study looked at pockets of volcanic material locked in glass An analysis of sediments brought back by the Apollo 17 mission has shown that the Moon's interior holds far more water than previously thought.

The analysis, reported in Science, has looked at pockets of volcanic material locked within tiny glass beads.

It found 100 times more water in the beads than has been measured before, and suggests that the Moon once held a Caribbean Sea-sized volume of water.

The find also casts doubt on aspects of theories of how the Moon first formed.

A series of studies in recent years has only served to increase the amount of water thought to be on the Moon.

The predominant theory holds that much of the water seen on the lunar surface arrived via impacts by icy comets or watery meteorites.

But this recent find is shedding light on how much water is contained in the Moon's interior, which in turn gives hints as to how - and from what - it formed.

In 2008, a team of researchers from the Carnegie Institution and Brown and Case Western Reserve universities analysed the water content found in samples of lunar magma returned by Apollo missions.

They wrote in a Nature paper that the samples contained about 10 times more water than they expected.

The orange soil was discovered during the Apollo 17 mission

However, the magma they studied had formed in "fire fountain" volcanic events, much like those seen in locations on Earth such as Hawaii, which would have boiled off much of the water that they contained.

Now the same team has found a number of geological "time capsules" among the beads.

"What we've done now is find samples of magma that are present as 'inclusions' that are trapped inside solid crystals called olivine," explained Erik Hauri, a geochemist from the Carnegie Institution and lead author of the new research.

"Because this magma is trapped inside a crystal, during an eruption it can't lose its water, so these melt inclusions preserve the original water content of the magma," he told BBC News.

The team found that those lockets of lunar magma contained some 100 times as much water as the previous samples - meaning that the lunar interior once held as much water as the layer of the Earth lying just below the crust.

'Not consistent'

As with the 2008 study, the find adds even more confusion to theories of how the Moon formed.

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I think in its very basic form, the impact theory idea is probably still correct, but there's something fundamental... that we don't understand”

End Quote Erik Hauri Carnegie Institution It is widely thought that a Mars-sized object slammed into the Earth just as it was forming, throwing out a disc of fragmented, molten material that eventually coalesced into the Moon.

But in that scenario, the extreme temperatures generated by the impact would have simply boiled off the water, and the moon should have started out relatively dry.

While there is a great deal of evidence to support the theory, both in terms of computer models of planetary formation and of the comparable amounts of various elements found both here and on the Moon, Dr Hauri said something just doesn't add up.

"These things are not consistent with the amount of water that we find," he said.

"I think in its very basic form, the [impact theory] idea is probably still correct, but there's something fundamental about the physics of the process that we don't understand."

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