Using ancient molecules to unravel the mystery of the ice ages

Using ancient molecules to unravel the mystery of the ice ages
Researchers from Cardiff University, Wales, have revealed how sea ice has been contributing to the waxing and waning of ice sheets over the last million years.

Researchers from Cardiff University, Wales, have revealed how sea ice has been contributing to the waxing and waning of ice sheets over the ice ages.

Published in the journal Nature Communications, the researchers have shown for the first time that the ice ages – which occur approximately every 100,000 years – are accompanied by a rapid build-up of sea ice in the Earth’s oceans.

Earth’s ice ages used to occur at intervals of every 40,000 years, which made sense to scientists as the seasons vary in a predictable way. However, there was a point known as the ‘Mid-Pleistocene transition’, where the ice age intervals changed from 40,000 to 100,000 years.

For a long time, the reason for this change remained unknown to scientists, but now the team have been tracking molecules produced by tiny marine algae preserved in ocean sediments, allowing them to reconstruct sea-ice conditions during the Mid-Pleistocene transition.

What have their results revealed?

The project led by Cardiff University in partnership with the University of Plymouth, the University of Exeter, UK, and the Norwegian Polar Institute, found that at the same time as the cycles changed there was a distinct increase in sea ice extent and a change in the rhythm of sea ice build up across climate cycles.

Henrieka Detlef, a postgraduate researcher at Cardiff University’s School of Earth and Ocean Sciences who led the study, said: “Prior to the Mid-Pleistocene transition, sea ice build-up and decay during ice ages was more gradual, whereas in the late Pleistocene, when the cyclicity of ice ages changed, we observed conditions characterised by a prominent short-lived peak in sea ice extent during late ice ages.”

With less water evaporating into the atmosphere, there would be less moisture being transported to continental glaciers which, in turn, would cause them to retreat and help in the transition from an ice age to a warm period.

Detlef concluded: “It’s clear that sea ice plays a fundamental role in the transition from an ice age into a warm stage every 100,000 years.”

Source: Cardiff University

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