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Oceans moved on ancient frozen Earth

by Margaret Mroziewicz Apr 1 / 13

The “Snowball Earth” theory, which was developed by CIFAR researchers Paul Hoffman (University of Victoria) and Daniel Schrag (Harvard), provides compelling evidence that our planet was covered in ice 600-700 million years ago.

Artistic concept of Snowball Earth.
Image credit: Shutterstock

Even though it has been widely accepted that the oceans of Snowball Earth were covered in ice, little has been understood about the nature of the oceans during this period. Scientists have suspected that, with a better understanding, they can more accurately predict the chemical signatures that are the hallmark of Snowball Earth and help to explain the movement of nutrients in the oceans during that time period.

In a recent paper published in Nature, Dr. Schrag and his team used 3D models to simulate oceans of Snowball Earth and found that they were not stagnant, but instead dynamic and well-mixed due to geothermal heating from the ocean floor. This contrasts with the earlier scientific view that the oceans were sluggish due to insulation from the sun by the thick ice-cover.

The team’s simulation accounted for geothermal heating under a global ice cover about a kilometre thick and showed that because of the oceans’ vigorous mixing, their temperature, salinity and density were more evenly mixed. This is different from what we see today in our oceans, which are much more stratified: warm buoyant water exists on top and cold dense water sinks to the bottom.

Ocean circulation and mixing processes would have had a major influence on the melting and freezing of ice on Snowball Earth, as well as nutrient circulation and the survival of photosynthetic life. For instance, vigorous mixing could have resulted in ice melting 10 times faster near continents than previously estimated. The team’s findings open the way to reinterpreting evidence of what happened during the history of our planet.

This work was supported by the National Science Foundation Climate Dynamics P2C2 program.