Tag Archives: Ice Age

Colossal Antarctic Ice Shelf Collapsed At End Of Last Ice Age

At the end of the last ice age, an armada of icebergs, each twice the height of the Empire State Building, broke off from the shoreline of Antarctica. According to a new study in the Proceedings of the National Academy of Sciences, they were created when a 280,000-square-kilometer (108,000-square-mile)section of the colossal Ross Ice Shelf collapsed in just 1,500 years.

The current stability of Antarctic ice shelves, the floating seaward extensions of ice sheets, is incredibly low. Man-made climate change is leading to unprecedented degrees of warming, causing the undersides of huge ice masses to melt and weaken. As a result, Larsen-A in the Antarctic Peninsula collapsed in 1995, followed by Larsen-B in 2002. Larsen-C, which is roughly 2.5 times the size of Wales, is due to follow suit.

Although these land-anchored ice shelves do not significantly contribute to sea level rise as they tumble into the ocean, they are acting as barricades for the landlocked ice sheets behind them. When removed, these enormous sheets may begin to join their watery grave, dramatically raising sea levels. For these reasons, researchers are keen to try and predict the future of gigantic ice shelves, and the Ross Ice Shelf, which is currently the size of France, is no exception to this.

The research vessel peeking at the ancient striations within the basin. L. Simkins/Rice University

At the height of the last ice age, we know that the sheet of ice covering the Antarctic continent was larger and thicker than it is today, said John Anderson, a professor of oceanography at Rice University and co-author of the paper, in a statement. This continent-enveloping ice sheet extended all the way to the continental shelf, and in western Antarctica it filled the entire Ross Sea basin.

Up to 18,000 years ago, this basin was packed with thick, heavy ice all the way down to the seafloor. The team decided to look for the telltale signatures of the movement of ice, large grooves in the seafloor known as striations, within this basin. To accomplish this, they used cutting-edge seafloor mapping systems aboard a U.S. research vessel the most sensitive ever employed in the Antarctic.

By tracing the paths of these massive striations, they found that around 10,000 years ago, as the ice age ended, a huge number of icebergs broke off from the shelf and pushed themselves out to sea. As this happened, the remaining part of the shelf retreated back onto the land as the warmer and more acidic sea eroded its exposed front.

Within 1,500 years, an area the size of Colorado had fallen into the sea. Theres a chance that in our rapidly warming world, such collapses could become more commonplace, unleashing massive volumes of ice on the continent into the oceans.

When Larsen-B broke apart, the glaciers behind it began to move forwards toward the sea 10 times faster than they used to. If the Ross Ice Shelf follows the same path, a fleet of glaciers could plunge into the sea soon afterwards. Worryingly, the modern day Ross Ice Shelf is considered by glaciologists to be unstable, behaving in a similar way to its ancient predecessor prior to its dramatic, rapid collapse.

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Read more: http://www.iflscience.com/environment/colossal-antarctic-ice-shelf-collapsed-end-last-ice-age

Humans, Not Climate Change, To Blame For Ice Age Animal Extinction

Our last glacial period lasted from about 115,000-12,500 years ago. By the end, 177 large mammal species had gone extinct. There has been considerable debate over the last half century regarding what caused the loss of these animals, including saber-tooth cats, mastadons, and giant sloths. While many have argued that these animals simply weren’t able to adapt to the warmer climate, others blame human activity. A new study led by Jens-Christian Svenning of Aarhus University has strongly suggested that humans are squarely responsible for the disappearance of megafauna during the last 100,000 years. The results have been published in the Proceedings of the Royal Society B.

For this study, the researchers focused on megafauna, which is categorized as animals weighing at least 10 kg (22 lbs) that lived in the last 132,000 years. They also identified the regions where these animals lived, comparing the data with climate and human activity. While there are invariably going to be animals lost after a great climate change such as the ending of an ice age, the loss of megafauna that followed the most recent glacial event is an anomaly when compared to the ending of other ice ages.

“Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals,” co-author Søren Faurby said in a press release.

The team had identified that out of the 177 large mammals that went extinct, 62 species were native to South America, 43 from North America, 38 from Asia, 26 from Australia and the surrounding region, 19 from Europe, and 18 of the extinct species were from Africa. Surprisingly,  the areas where the animals went extinct spanned all climate regions, even the warmer regions that hadn’t been particularly affected by the ice age. While there is a slight correlation between the changing climate and the animals dying out, the researchers feel it isn’t nearly strong enough to explain such a drastic series of events across the globe. If anything, it would only explain the extinctions in Eurasia.

“The significant loss of megafauna all over the world can therefore not be explained by climate change, even though it has definitely played a role as a driving force in changing the distribution of some species of animals,” lead author Christopher Sandom explained. “Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer.”

Unfortunately, the correlation between extinctions and human activity was quite strong. Hunting activity is believed to be the root cause of the animals’ extinction, through both direct and indirect methods. Humans either hunted the animals themselves, or competed with them for smaller prey. With the animals’ food source gone, they wouldn’t be able to sustain their populations.

“We consistently find very large rates of extinction in areas where there had been no contact between wildlife and primitive human races, and which were suddenly confronted by fully developed modern humans (Homo sapiens). In general, at least 30% of the large species of animals disappeared from all such areas,” stated Svenning.

The extinction of these ice age animals is not completely unlike the overhunting that has threatened the lives of modern megafauna, including sharks, rhinoceroses, elephants, and big cats, such as the tiger. These results also support a paper published in March in which genetic analyses revealed that humans drove Moas to extinction so quickly, it didn’t even have time to affect the birds’ biodiversity. An unrelated study a week later suggested that woolly mammoths suffered inbreeding depression, likely due to a declining population from human hunting, making severe birth defects common before the species went extinct.

[Header image “Spring Break 2013: Day 4” by Jennifer Carole via flickr, used in accordance with CC BY-ND 2.0 and has been cropped to fit]

Read more: http://www.iflscience.com/plants-and-animals/humans-not-climate-change-blame-ice-age-animal-extinction