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Posts tagged "ice age"


Woolly Mammoth Fossils Raise Red Flags on the Road to Extinction

A surprising discovery in woolly mammoth fossils recovered from the North Sea off the coast of the Netherlands suggests that inbreeding and harsh conditions plagued the ice age giants near the end of their reign on Earth.

Learn more from Liza Gross at KQED Science. 


New and exciting discoveries in the earth’s past ice age

DURING the summer of 2008, workers excavating Ground Zero in Lower Manhattan dug right down to the bedrock. There, they found something unexpected: a huge pothole more than 10 metres deep, the crevices around it crammed with stones of several different kinds of rock. The consulting geologist immediately recognised these features. The stones had been carried there from many miles away by a glacier that had ground across the bedrock. At some point, a swirling torrent of glacial meltwater had carved out the pothole.

From potholes in New York City to forests beneath the sea, evidence of the time ice dominated the world is all around us. The last great ice age began around 120,000 years ago. One massive ice sheet, more than 3 kilometres thick in places, grew in fits and starts until it covered almost all of Canada and stretched down as far as Manhattan. Another spread across most of Siberia, northern Europe and Britain, stopping just short of what is now London. Elsewhere many smaller ice sheets and glaciers grew, vast areas turned into tundra and deserts expanded as the planet became drier.

With so much ice on land, sea level was 120 metres lower than it is today. Britain and Ireland were part of mainland Europe. Florida was twice the size it is now, with Tampa stranded far from the coast. Australia, Tasmania and New Guinea were all part of a single land mass called Sahul. The planet was barely recognisable.

Then, 20,000 years ago, a great thaw began. Over the following 10,000 years, the average global temperature rose by 3.5 °C and most of the ice melted. Rising seas swallowed up low-lying areas such as the English Channel and North Sea, forcing our ancestors to abandon many settlements. So what drove this dramatic transformation of the planet? Continue reading 

(via kenobi-wan-obi)


Scandinavian trees ‘survived last Ice Age’

Some Scandinavian trees survived the last Ice Age, challenging a widely held notion that they were killed off by the huge ice sheet that covered the region.

Modern trees in Scandinavia were thought to descend from species that migrated north when the ice melted 9,000 years ago.

But research suggests some conifers survived on mountain peaks that protruded from the enormous ice sheet, on islands and in coastal areas.

The work appears in Science journal.

“Our results demonstrate that not all the Scandinavian conifer trees have the same recent ancestors, as we once believed,” said Prof Eske Willerslev from the Centre for GeoGenetics, University of Copenhagen.

“There were groups of spruce and pine that survived the harsh climate in small ice-free pockets, or in refuges, as we call them, for tens of thousands of years, and then were able to spread once the ice retreated.

» Read more.

(via geologise)


Gifford Miller collects vegetation samples on Baffin Island. (Credit: Photo courtesy of Gifford Miller, University of Colorado)

A new international study may answer contentious questions about the onset and persistence of Earth’s Little Ice Age, a period of widespread cooling that lasted for hundreds of years until the late 19th century.


The study, led by the University of Colorado Boulder with co-authors at the National Center for Atmospheric Research (NCAR) and other organizations, suggests that an unusual, 50-year-long episode of four massive tropical volcanic eruptions triggered the Little Ice Age between 1275 and 1300 A.D. The persistence of cold summers following the eruptions is best explained by a subsequent expansion of sea ice and a related weakening of Atlantic currents, according to computer simulations conducted for the study.

The study, which used analyses of patterns of dead vegetation, ice and sediment core data, and powerful computer climate models, provides new evidence in a longstanding scientific debate over the onset of the Little Ice Age. Scientists have theorized that the Little Ice Age was caused by decreased summer solar radiation, erupting volcanoes that cooled the planet by ejecting sulfates and other aerosol particles that reflected sunlight back into space, or a combination of the two.

“This is the first time anyone has clearly identified the specific onset of the cold times marking the start of the Little Ice Age,” says lead author Gifford Miller of the University of Colorado Boulder. “We also have provided an understandable climate feedback system that explains how this cold period could be sustained for a long period of time. If the climate system is hit again and again by cold conditions over a relatively short period — in this case, from volcanic eruptions — there appears to be a cumulative cooling effect.”

“Our simulations showed that the volcanic eruptions may have had a profound cooling effect,” says NCAR scientist Bette Otto-Bliesner, a co-author of the study. “The eruptions could have triggered a chain reaction, affecting sea ice and ocean currents in a way that lowered temperatures for centuries.”

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Volcanoes and the Little Ice Age: Not the Smoking Gun?

There is the tendency in our fast-paced world for lots and lots of articles to get written about science before anyone beyond the researchers and the reviewers actually sees the science. This is mostly thanks to the fact that press releases come out before the actual study – and who has time to read a study when there is a handy press release with all the bits? Yesterday saw an example of just this – a whole lot of “news” without a lot of assessment of the study itself.

The paper itself is called “Abrupt Onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks” by Gifford Miller and a host of coauthors (mostly climatologists) in the Geophysical Research Letters. After seeing a post about it on Dot Earth, I knew that the media would eat this up and wouldn’t you know it, within hours there were dozens of articles mostly telling us what the initial press release already said … and not much else. It took a while for the PDF of the article to appear on the GRL website, but after it did, I sat down with it to see what the “smoking guns” were that they identified.

I’m not going to discuss the climate models or interpretation – more or less, they sampled moss and lake sediment in Canada and Iceland to constrain the dates of the onset of the Little Ice Age. Then, they used climate models and data about volcanic atmospheric sulfur (from Gao et al., 2008, more on this paper in a bit) to model how the atmosphere and oceans would respond and if it correlated with their ages. The long and short is they found that a large sulfur loading in the atmosphere could trigger increased sea ice that would prompt cooler global climate, thus the Little Ice Age.

Continue reading over at Wired.