Were Earth’s oceans completely covered by ice during the Cryogenian period, about 700 million years ago, or was there an ice-free belt of open water around the equator where sponges and other forms of life could survive?
Were Earth’s oceans completely covered by ice during the Cryogenian period, about 700 million years ago, or was there an ice-free belt of open water around the equator where sponges and other forms of life could survive? Using global climate models, a team of researchers from Karlsruhe Institute of Technology (KIT) and the University of Vienna has shown that a climate allowing a waterbelt is unlikely and thus cannot reliably explain the survival of life during the Cryogenian. The reason is the uncertain impact of clouds on the epoch’s climate. The team has presented the results of its study in the journal Nature Geoscience (DOI: 10.1038/s41561-022-00950-1).
Viewed from space, Earth may have looked like a giant snowball during the global ice ages of the Cryogenian period. In the geosciences, this hypothesis that the oceans were completely frozen over has become established as the Snowball Earth theory. But it’s still not clear how sponges, which are found in the fossil record, were able to survive in the very cold Snowball Earth climate. To explain that, some scientists have proposed the alternative theory of an ice-free equatorial waterbelt.
Life in spite of oceans that were probably icebound
Working with colleagues from the University of Vienna, researchers at KIT used global climate models and an idealized energy balance model to investigate Cryogenian climatic conditions. They expected to find a waterbelt in their simulation scenarios and wanted to investigate the conditions under which it would remain stable. “We were surprised to find that this state wasn’t stable in the models,” says Christoph Braun from KIT’s Institute of Meteorology and Climate Research – Department Troposphere Research (IMK-TRO). This means life during the Cryogenian was probably subject to the harsh evolutionary conditions of globally icebound oceans.
Read more at: Karlsruher Institut fur Technologie (KIT)
Clouds have had a strong influence on glaciation throughout Earth’s history. The simulation shows a snapshot of cloud cover in the lowest layer of the atmosphere (up to approx. three kilometers above the Earth’s surface) in an assumed waterbelt climate state. The color scale ranges from no cloud cover (dark blue) to completely overcast (white) (graphic: IMK-TRO). (Photo Credit: IMK-TRO)
