Ice Age occurs more often than previously thought

(ORDO NEWS) — An accidental discovery of an unexplored core of Antarctic deposits allowed researchers at the University of Otago to turn our understanding of how often ice ages occurred in Antarctica.

Lead author of the study, Dr. Christian Ochnaiser, of the Department of Geology, says they appear to have occurred much more frequently than previously thought.

“Before this study, it was common knowledge that over the past million years, the global volume of ice, including the ice sheets of Antarctica, has expanded and retreated every 100,000 years.

“However, this study shows that they actually expanded and receded much more frequently – every 41,000 years – until at least 400,000 years ago,” he says.

The study, published in the journal Nature Geosciences, comes after Dr. Ochnaiser sampled sediment cores from the Ross Sea for another project that aimed to reconstruct the retreat of the Ross Ice Shelf after the last ice age.

“The 6.2-meter core was extracted in 2003 and archived in the US, but has not been further studied. I selected it because I expected the core to contain a record spanning the last 10,000 or so years.

“I did a paleomagnetic analysis of the core, which reconstructs changes in the Earth‘s magnetic field, and found a magnetic reversal showing that the core was much older and had a record spanning over 1 million years.”

Sedimentary and magnetic mineral data allowed Dr. Ochnaiser to reconstruct the size of the Ross Ice Shelf and the West Antarctic Ice Sheet that feeds it.

“Icebergs that form on an ice shelf have sediment and rocks attached to their underside. When the icebergs break off, they float into the sea and shed rocks and sediment when they melt. These rocks and sediment can also come directly from the ice shelf. if the ice was above the core sampling point.

“By finding out how much of this debris is in the core over time, we can build a picture of the change in the size of the ice sheet,” he says.

Previous understanding of the frequency of ice ages was based on assumptions and incomplete datasets, but knowing them is important as the world faces climate change.

“Antarctica’s ice sheets have the potential to significantly raise sea levels in the coming centuries. Paleoclimatic reconstructions can give us clues about how ice sheets might behave as atmospheric CO2 rises.

“Because the response of ice sheets to any climate change is very slow, reconstructions of how ice sheets have behaved in the past can determine how big or small ice sheets were and how quickly they retreated and re-gained under different climatic conditions.

These reconstructions provide basic information about natural behavior ice sheets in the past before man began to interfere with the atmosphere.”

Dr. Ochnaiser believes this study highlights that New Zealand is making great strides in Antarctic exploration.

“New Zealand is a world leader in this area – the Antarctic Science Platform project team will soon drill to study sediment near the West Antarctic Ice Sheet line. This New Zealand-led expedition will be the southernmost sediment drilling expedition in the world.”


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