When More Means Less

Recent news that Arctic winter sea ice bounced back to previous levels after an unprecedented summer melt prompted speculation that the global warming scenario had been exaggerated. Indeed, it’s been a surprisingly cold winter across much of the northern hemisphere — so is there really anything to worry about? Yes, says a new report backed by NASA.

Animation of Arctic Ice Shrinkage, compiled from Earth Observatory composite images - the first image shows the minimum sea ice concentration in 1979, the second shows the minimum sea ice concentration in 2003Since the end of December 2007, I’ve written several items concerning the rapidly changing scenario in the Arctic. In particular, on 28th December 2007, scientists reported that the 2007 summer melt of Arctic sea ice had beaten all previous recorded measurements, whereas on 21st February 2008 came news that the apparent expansion of Arctic sea ice during the winter months had been so extensive that the summer’s loss was completely recovered — even surpassed. Some took this to mean that the global warming of recent years could well be nothing more than a blip, a brief anomaly in a greater cycle of natural climate variation.

Now, data released by NASA show that the oldest, thickest Arctic sea ice is under considerable stress. That’s bad news, according to Walt Meier of the National Snow and Ice Data Center (an organisation partly funded by NASA). “Thickness is an indicator of long-term health of sea ice, and that’s not looking good at the moment,” he told reporters on Tuesday 18th March 2008.

Wolves on Perennial Arctic Sea Ice - from AOSB ProgramsThere is a layer of long-lived ice known as perennial sea ice — year-round ice cover that remains even when the surrounding short-lived seasonal sea ice melts in summer. According to NASA-processed microwave data, the perennial sea ice has been rapidly declining from year to year: whereas perennial ice used to cover 50 to 60 percent of the Arctic, this year it covers less than 30 percent. Very old ice that remains in the Arctic for at least six years comprised over 20 percent of the Arctic area in the mid to late 1980s, but this winter it decreased to just six percent.

Because Arctic sea ice is already floating in water, it doesn’t raise sea levels as it melts — unlike the effect glaciers melting on Greenland or Antarctica have, because they’re on land — but its loss does contribute to global warming when the white ice that reflects heat from the sun is replaced by dark water that absorbs the sun’s heat energy.

Meier said that some 965,300 square miles (2.5 million sq kms) of perennial ice have been lost — about one and a half times the area of Alaska — a 50 percent decrease between February 2007 and February 2008. He added that the oldest “tough as nails” perennial ice has decreased by about 75 percent this year, losing 579,200 square miles (1.5 million sq kms), or about twice the area of Texas.

This means that in many areas, the stronger perennial ice is being replaced by younger, thinner new ice — ice that’s much more readily disturbed by wind and warm sea temperatures.

Movie Set (Deadwood) - from Patty Whisenhunt DecorThe BBC reported Meier saying of an Arctic largely covered with younger ice: “It may look OK on the surface, but it’s like looking at a Hollywood movie set — you see the facade of a building and it looks OK, but if you look behind it, there’s no building there.”

Turning their attention to Antarctica, the scientists found less dramatic change, attributed to the difference in the two polar regions: the Arctic is an ocean surrounded by land, while the Antarctic is a continent surrounded by ocean.

But the scientists did notice dramatic warming on the Western Antarctic Peninsula — warming recently documented in the field by British scientists and on which I reported in a write-up dated 25th February 2008.

Clearly, there’s still much to keep an eye on, both north and south.

Read my Climate Change posts in chronological order by using the Climate Change Log.

Antarctic’s PIG Threatening Sea Levels

It was recently suggested that the amount of Antarctic ice has been growing in volume. Now comes news of glacial shrinkage that has the British Antarctic Survey worried: they say it could lead to a significant rise in global sea levels.

Pine Island Glacier (PIG), West Antarctica, in 1985 - from Scott Polar Research InstituteIt was only a few days ago that I posted Being Economical With The Truth, in which I discussed how Christopher Booker, writing in Telegraph Online, pooh-poohed the recent findings about 2007′s Arctic sea ice summer shrinkage because, in the ensuing winter months, it’s expanded again to previous winter coverage. What I didn’t include in my post was his further assertion that, according to a graph recently published by the US National Oceanic and Atmospheric Administration (NOAA) titled “Southern Hemisphere Ice”, Antarctic ice has expanded in recent years, well above its 30-year mean — further proof, he thinks, that all the guff about global warming is nonsense.

However, research conducted in part by the University of Bristol and recently published in Nature Geoscience (to which I referred in my January 14th post Antarctic Ice Loss Confirmed) refuted this — it said increasing amounts of ice mass have been lost from West Antarctica and the Antarctic peninsula over the past ten years. I guess that leaves Mr. Booker out in the cold, so to speak.

And now further research from another authoritative source shows that a number of huge Antarctic glaciers are giving cause for concern because of the speed with which they’re rushing headlong into the ocean.

Map of West Antarctica - from BBC NewsThe British Antarctic Survey has recently had a group of scientists camped out on a collection of West Antarctica glaciers — what BAS scientist David Vaughan described as the weak underbelly of the West Antarctic ice sheet — in a remote part of the continent. The glaciers cover an area the size of Texas, and their findings show that they’re slipping more swiftly towards the ocean than ever previously recorded.

According to satellite measurements, three of the huge glaciers in this area have been speeding up for more than a decade. The biggest of them, the Pine Island Glacier, or the PIG, is causing the most concern. Julian Scott, who’s just returned from the region, told the BBC: “This is a very important glacier; it’s putting more ice into the sea than any other glacier in Antarctica. It’s a couple of kilometres (1.2 miles) thick, it’s 30km (18.6 miles) wide and it’s moving at 3.5km (2.2 miles) per year, so it’s putting a lot of ice into the ocean.”

BAS Skidoos In West Antarctica - from BBC NewsThe team drove skidoos over the ice for thousands of kilometres taking measurements as they went, using radar and boreholes. The last time this area was visited by scientists was in 1961. More recently, satellites have been used to track changes. According to those measurements, the glacier was accelerating by around 1% a year throughout the 1990s. Julian Scott’s sensational finding this season is that “The measurements from last season seem to show an incredible acceleration, a rate of up to 7%. That is far greater than the accelerations they were getting excited about in the 1990s.”

The reason for this sudden acceleration does not seem to be warming in the surrounding air. It could be something to do with a deep ocean current that’s channelled onto the continental shelf, close by the glacier’s mouth. As there’s not much sea ice to protect it from the warm water, it could be undercutting the ice and lubricating its flow. But there’s also evidence of a 2,000-year-old volcano that erupted through the ice. It’s possible that the whole region could be volcanically active, releasing geothermal heat which is melting the base of the ice and helping its slide towards the sea. David Vaughan believes the risk of a major collapse of this section of the West Antarctic ice sheet should be taken seriously.

Julian Scott In West Antarctica - from BBC NewsJulian Scott hopes to figure out whether what’s been recorded is an exceptional surge or whether it heralds a major collapse of the ice, and he’s left some GPS measuring instruments behind on the glacier. The BAS researchers say that if the glacier continues to race along, discharging most of its ice into the sea, the PIG alone could raise global sea levels by 25cm (9.8 inches). That might take quite a while — perhaps decades, or even a century, they suggest — but neighbouring glaciers are accelerating too. If the entire region lost its ice, global sea levels would rise by 1.5 metres (59 inches).

This is definitely one PIG that needs to be kept under close surveillance.

Read my Climate Change posts in chronological order by using the Climate Change Log.

Polar Meltdowns: More Evidence Emerges

When the Antarctic’s Larsen B ice shelf broke apart in 2002, human-induced climate change was blamed. Now two scientists claim there was rather more to it. Meanwhile, up north, a huge fracture in the Beaufort Sea ice pack has researchers worried about its implications for the future.

Iceberg debris after collapse of Larsen B - image from the BBCIt was 656 feet (200 metres) thick, had an area of 1,255 square miles (3,250 sq. km) and weighed around 500 billion tonnes. In March 2002, the Larsen B ice shelf broke apart. This was not an entirely unexpected event — in 1998, researchers from the British Antarctic Survey had predicted that several ice shelves around the western peninsula were doomed because of rising temperatures in the region, but they were shocked at the speed with which Larsen B collapsed. At the time the reason seemed to be Antarctic summer heatwaves linked to global warming, pure and simple. But now Neil Glasser of Aberystwyth University in Wales and Ted Scambos of the USA’s Colorado University have claimed, in a new study, that it had been teetering on the brink of collapse for decades, and that glaciological and atmospheric factors were also invoved.

Speaking to the BBC, Professor Glasser acknowledged that while global warming had a major part to play, he emphasised that it was only one of a number of factors that contributed to the collapse. Because meltwater in large amounts appeared on the ice shelf just before it broke up, it was assumed that air temperature increases were responsible. But their new study explains that ice-shelf break up is more complex and not simply controlled by climate. “A number of other atmospheric, oceanic and glaciological factors are involved,” he said. “For example, the location and spacing of fractures on the ice shelf such as crevasses and rifts are very important too because they determine how strong or weak the ice shelf is.”

Dr Scambos, of the University of Colorado’s national snow and ice data centre, added that Larsen B had probably been in distress for decades before its ultimate collapse. “It’s likely that melting from higher ocean temperatures, or even a gradual decline in the ice mass of the peninsula over the centuries, was pushing Larsen to the brink.”

Beaufort Sea Ice Pack Fracture - image from Environment Canada/NOAAMeanwhile, at the other end of the world, a huge fracture in the Beaufort sea ice pack is causing concern amongst scientists. Discovered this winter, the fracture could be a sign of things to come as climate change continues to warm the Arctic, says David Barber, a climate scientist with the University of Manitoba. First discovered in December, the fracture occurred in the Beaufort ice pack off the west coast of Banks Island in Canada’s Northwest Territories.

Normally, the central ice pack is pushed away from the coast during the winter as coastal ice expands and forces it into the sea. Usually when this occurs, there’s enough old ice in the central ice pack to resist the coastal ice, but that’s not the case this year, said Barber. Coastal ice, pushed by high pressure systems, has sent the central ice pack deep into the Beaufort Sea and towards Siberia, creating the vast fissure.

Banks Island location - image from Wikipedia“It’s the first time we’ve seen it happening so dramatically like this because we lost so much ice last summer,” Barber told CBC News. “We’re starting to think this is what the future’s going to look like.” Barber’s been leading a team of researchers who’ve been aboard the ice-breaker Amundsen, currently over-wintering in the ice of the Beaufort Sea so they can study the changes close-up. The expedition, said Barber, has proved invaluable, if not particularly encouraging. “It’s been an extremely interesting year but kind of depressing,” he said. “It’s interesting in a bad way.”

The polar regions are a concern to climate specialists studying global warming because those regions are expected to feel the impact of climate change sooner and to a greater extent than other areas.

Read my Climate Change posts in chronological order by using the Climate Change Log.