Is there an ice-free belt of open water around the equator where sponges and other forms of life could live? The survival of life during the Cryogenian can't be explained by a climate that allows a waterbelt, according to a team of researchers from theKIT and the University of Vienna. Clouds have an uncertain impact on the climate. The results of the study have been presented.
Earth may have been a giant snowball during the global ice ages. The Snowball Earth theory is based on the idea that the oceans were frozen over. It is not known how sponges were able to survive in the very cold Snowball Earth climate. The alternative theory of an ice-free waterbelt has been proposed.
Life was still going on despite the oceans being icebound.
Global climate models and an idealized energy balance model were used by researchers at KIT. They wanted to investigate the conditions under which the waterbelt would remain stable. "We were surprised to see that the state wasn't stable in the models," says Braun. Life may have been subject to the harsh evolutionary conditions of the global icebound oceans.
New insights into the role played by clouds were found in the study. The stability of a waterbelt depends on the amount of radiation reflected by the clouds. Braun is the lead author of the study. The paper suggests that the results of previous studies could be combined to produce a more coherent picture.
Clouds make it hard to see past climate.
Braun says that with the global climate models and an idealized climate budget model, we can explain the underlying processes. There is a lot of uncertainty about the simulation of clouds in global climate models.
The amount of aerosols that can act as ice nuclei is a factor that affects the efficiency with which water droplets are converted into ice. Computational grids used in the models have scales on the order of more than 100 kilometers. Clouds are important to the prediction of climate changes and to our understanding of geological time, according to the results. Braun says that clouds don't just make it harder to see into the future, but also to look back.
Habitability of planets outside the solar system is assessed.
In the future, the findings of the researchers could be used to determine if planets outside our solar system are suitable for human habitation. Braun says that it could be of interest when the James Webb Space Telescope makes it possible to see clouds in the atmosphere of extrasolar planets. The researchers used the Mistral supercomputer to perform their simulations. "In our next step, we have begun to mimic clouds under Cryogenian climatic conditions using fine computational grids so that we can investigate whether and how the uncertainties involving the clouds can be reduced."
More information: Christoph Braun et al, Ice-free tropical waterbelt for Snowball Earth events questioned by uncertain clouds, Nature Geoscience (2022). DOI: 10.1038/s41561-022-00950-1 Journal information: Nature Geoscience
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