Chinese-led study finds uneven melting of polar ice could lead to huge global disruption
The 28 researchers found that asynchronous expansion of the polar ice sheets – which saw growth in the Antarctic triggering rapid growth in the Arctic – was the likely cause of a transitional event that occurred between 700,000 and 1.2 million years ago.
This event, called the Mid-Pleistocene Transition, changed the length of the world’s glacial cycle – or periods between “ice ages” – from around 41,000 to 100,000 years.
By examining historical climate and ice sheet records, the researchers found that 1.25 to 2 million years ago, growth of the Antarctic ice sheet and southern sea ice triggered cooling in the northern high latitudes, and caused more moisture to be transported to the northern hemisphere.
This led to rapid growth of the northern ice sheet, which in turn could have caused the Mid-Pleistocene Transition, changing the length of time the Earth cycles between its warmer and colder eras.
The Earth entered an interglacial – or warmer – period around 11,700 years ago, marking the end of our last large glacial period.
The team said there were different hypotheses about why this transition occurred, such as a decline in atmospheric carbon dioxide or changes in ocean circulation, but the proposed mechanisms lacked compelling evidence.
Until now, the potential impact of the bipolar ice sheets developing at different times has not been explored as a driver.
Using model simulations of sea surface temperature, prevailing winds and other variables, the researchers could reconstruct changes in hemispheric ice volume and track their development.
Their reconstruction showed that increases in southern ice volume preceded those in the north, and that growth in Antarctic ice sheets were potentially an “important precursor to, or even a direct trigger of, [the Mid-Pleistocene transition].”
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“Our results highlight intricate dynamic linkages among Earth’s polar ice sheets with consequential global effects,” the team wrote.
“The proxy-model comparison suggests that asynchronous development of hemispheric ice sheets is indispensable for understanding global climate change.”
However, the disappearance of Arctic ice has sparked discussion about potential effects on shipping – including easier navigation, lower carbon emissions and decreasing reliance on Russia’s northern routes.