Tag Archives: Arctic

Arctic ‘warmest in 2,000 years’

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New research from the journal Science shows that arctic temperatures are higher now than they have been for the past 2000 years. Using ice cores, tree rings and lake sediments, Kaufmann et al were able to establish a comprehensive record of decadal change within the region, revealing that four of the five warmest decades occured between 1950 – 2000. One of the most striking factors is the rate of this change  – a gradual cooling is evident throughout the time series (0.2°C up untill 1900), yet the subsequent rate of warming in the last century is substantial (1.2°C – see the hockey-stick curve above). Click below to read more from the BBC News, or here for the article summary from Science.

“The most pervasive signal in the reconstruction, the most prominent trend, is the overall cooling that took place for the first 1,900 years [of the record],” said study leader Darrell Kaufman from Northern Arizona University in Flagstaff, US.

“The 20th Century stands out in strong contrast to the cooling that should have continued. The last half-century was the warmest of the 2,000-year temperature record, and the last 10 years have been especially dramatic,” he told BBC News. (Read More)

Revealed: the secret evidence of global warming Bush tried to hide

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Sensational headline by The Guardian newspaper? The Obama administration has unclassified over a thousand images of Arctic sea ice to aid scientists in the study of global warming and the impacts of climate change. The images are striking – see this comparison in Alaska between 2006 – 2007. The release of such images is great news – i’m not entirely sure whether these images were ‘kept secret’ by the Bush administration as claimed, but in the growing field of remote sensing, support from the US military satellite data is crucial to understanding local scale changes in the Arctic ice. Click here to see the images in full.

Graphic images that reveal the devastating impact of global warming in the Arctic have been released by the US military. The photographs, taken by spy satellites over the past decade, confirm that in recent years vast areas in high latitudes have lost their ice cover in summer months.

The pictures, kept secret by Washington during the presidency of George W Bush, were declassified by the White House last week. President Barack Obama is currently trying to galvanise Congress and the American public to take action to halt catastrophic climate change caused by rising levels of carbon dioxide in the atmosphere.

One particularly striking set of images – selected from the 1,000 photographs released – includes views of the Alaskan port of Barrow. One, taken in July 2006, shows sea ice still nestling close to the shore. A second image shows that by the following July the coastal waters were entirely ice-free.

The photographs demonstrate starkly how global warming is changing the Arctic. More than a million square kilometres of sea ice – a record loss – were missing in the summer of 2007 compared with the previous year.

Nor has this loss shown any sign of recovery. Ice cover for 2008 was almost as bad as for 2007, and this year levels look equally sparse. (Read More)

“Climate change hitting entire Arctic ecosystem, says report”

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arcticpic460The Guardian, 28th April 2008

Extensive climate change is now affecting every form of life in the Arctic, according to a major new assessment by international polar scientists. In the past four years, air temperatures have increased, sea ice has declined sharply, surface waters in the Arctic ocean have warmed and permafrost is in some areas rapidly thawing. In addition, says the report released today at a Norwegian government seminar, plants and trees are growing more vigorously, snow cover is decreasing 1-2% a year and glaciers are shrinking.

Scientists from Norway, Canada, Russia and the US contributed to the Arctic monitoring and assessment programme (Amap) study, which says new factors such as “black carbon” – soot – ozone and methane may now be contributing to global and arctic warming as much as carbon dioxide. “Black carbon and ozone in particular have a strong seasonal pattern that makes their impacts particularly important in the Arctic,” it says.

The report’s main findings are:

Land

Permafrost is warming fast and at its margins thawing. Plants are growing more vigorously and densely. In northern Alaska, temperatures have been rising since the 1970s. In Russia, the tree line has advanced up hills and mountains at 10 metres a year. Nearly all glaciers are decreasing in mass, resulting in rising sea levels as the water drains to the ocean.

Summer sea ice

The most striking change in the Arctic in recent years has been the reduction in summer sea ice in 2007. This was 23% less than the previous record low of 5.6m sq kilometres in 2005, and 39% below the 1979-2000 average. New satellite data suggests the ice is much thinner than it used to be. For the first time in existing records, both the north-west and north-east passages were ice-free in summer 2008. However, the 2008 winter ice extent was near the year long-term average.

Greenland

The Greenland ice sheet has continued to melt in the past four years with summer temperatures consistently above the long-term average since the mid 1990s. In 2007, the area experiencing melt was 60% greater than in 1998. Melting lasted 20 days longer than usual at sea level and 53 days longer at 2-3,000m heights.

Warmer waters

In 2007, some ice-free areas were as much as 5C warmer than the long-term average. Arctic waters appear to have warmed as a result of the influx of warmer waters from the Pacific and Atlantic. The loss of reflective, white sea ice also means that more solar radiation is absorbed by the dark water, heating surface layers further.

Black carbon

Black carbon, or soot, is emitted from inefficient burning such as in diesel engines or from the burning of crops. It is warming the Arctic by creating a haze which absorbs sunlight, and it is also deposited on snow, darkening the surface and causing more sunlight to be absorbed.

Melting Artic ice acts as a CO2 sink, whilst Antarctic wintertime ice is on the increase

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"Antarctic sea ice increases despite warming" (New Scientist, 12 September 2008)

The amount of sea ice around Antarctica has grown in recent Septembers in what could be an unusual side-effect of global warming, experts say.

In the southern hemisphere winter, when emperor penguins huddle together against the biting cold, ice on the sea around Antarctica has been increasing since the late 1970s, perhaps because climate change means shifts in winds, sea currents or snowfall.

At the other end of the planet, Arctic sea ice is now close to matching a September 2007 record low at the tail end of the northern summer, in a threat to the hunting lifestyles of indigenous peoples and creatures such as polar bears.

"The Antarctic wintertime ice extent increased…at a rate of 0.6% per decade" from 1979 to 2006, says Donald Cavalieri, a senior research scientist at the NASA Goddard Space Flight Center in Maryland.

At 19 million square kilometres, it is still slightly below records from the early 1970s of 20 million, he says. Since 1979 however, the average year-round ice extent has risen too.

(link to full article)

 

"Melting ice caps could suck carbon from atmosphere" (New Scientist, 10 September 2008)

It’s not often that disappearing Arctic ice is presented as good news for the planet. Yet new research suggests that as the northern polar cap melts, it could lift the lid off a new carbon sink capable of soaking up carbon dioxide.

The findings, from two separate research groups, raise the possibility – albeit a remote one – of weakening the greenhouse effect. The researchers say the process of carbon sequestration is already underway. Even so, the new carbon sink is unlikely to make a significant dent in the huge amounts of CO2 pumped into the atmosphere by industrial activities.

Kevin Arrigo and colleagues at Stanford University studied satellite data collected between 1998 and 2007 to see how sea surface temperatures and the quantities of sea ice and phytoplankton had changed during that time.

Phytoplankton produce chlorophyll to obtain energy from the sun and assimilate CO2, and so increased phytoplankton productivity would remove more carbon from the atmosphere.

"We found that as sea ice diminishes, annual productivity goes up," says Arrigo. Satellite remote sensing measures the amount of chlorophyll in surface waters, and so provides an estimate of ocean productivity.

(Link to full article)