Snowball Earth May Have Featured Dynamic Climate and Open Seas, New Rock Evidence Suggests

United States - Ekhbary News Agency

Snowball Earth May Have Featured Dynamic Climate and Open Seas, New Rock Evidence Suggests

New findings based on ancient rock formations suggest that Earth, even during its most extreme global freezing events known as 'Snowball Earth' over 600 million years ago, experienced a dynamic climate with unexpected cycles and potentially partially open oceans. These discoveries, published in the journal Earth and Planetary Science Letters, challenge the conventional understanding that such glacial periods were characterized by a highly stable and quiescent climate system.

During the Cryogenian period, roughly between 720 and 635 million years ago, Earth endured two severe global ice ages. The first, termed the Sturtian glaciation, is believed to have covered most of the planet in ice from approximately 717 to 658 million years ago. This era was often conceptualized as a period of relative climate stability, with a thick ice sheet potentially insulating the planet's surface from complex atmospheric and oceanic interactions.

However, a team of earth scientists led by Dr. Chloe Griffin of the University of Southampton in England has examined rocks from the Garvellach Islands, off the west coast of Scotland. These rocks, dating back to the Sturtian glaciation, exhibit exceptionally well-preserved layered structures. The layers alternate between coarse and fine sediments, a pattern rarely found in rocks from this epoch, as most Cryogenian rocks are heavily eroded and jumbled by glacial activity.

Dr. Griffin and her colleagues interpret these layers as annual records. In modern glacial lakes, coarse sediments are deposited by glacial meltwater during the summer, while finer clays settle during the winter when meltwater ceases. This process creates two distinct layers each year. The studied rocks contain approximately 2,600 pairs of these layers, suggesting they recorded about 2,600 years of climatic history.

"It’s unprecedented to find annual records this far back in time," stated study co-author Thomas Gernon, an earth scientist also at the University of Southampton. He explained that the thickness of each layer offers clues about seasonal weather conditions. For instance, a warmer summer might lead to increased glacial movement and erosion, resulting in a thicker sediment layer.

Through mathematical analysis of the layer thickness patterns, the researchers identified four distinct climatic cycles. These cycles repeat with intervals corresponding to approximately 4-4.5 layers, 9 layers, 13.7-16.9 layers, and 130-150 layers. These patterns remarkably align with well-known modern climate cycles. The 4-to-4.5-year cycle, in particular, strongly resembles the El Niño-Southern Oscillation (ENSO), a phenomenon that influences global weather patterns through heat exchange between the tropical Pacific Ocean and the atmosphere.

Dr. Griffin noted that this observation supports the existence of "some form of heat transport between an ocean and atmosphere occurring in the tropics." This, in turn, implies that there must have been a partially open ocean, likely near the equator, during the Snowball Earth period. The other three identified cycles are hypothesized by the researchers to represent fluctuations in solar intensity.

Other experts highlight the significance of these findings. Geologist Tony Prave of the University of St. Andrews in Scotland, who was not involved in the study, commented, "It's a reasonable interpretation to consider these layers as annual. You could go to a glacial lake in Switzerland and find similar deposits."

These discoveries contribute to the ongoing debate about the extent and severity of the Snowball Earth events and the presence of open water areas. While global data often supports the notion of a complete glaciation that shut down biogeochemical cycles and minimized ocean-atmosphere interaction, sites like the Garvellach Islands suggest a more dynamic climate regime. Gernon suggests these rocks might reflect short-term warming events, possibly triggered by volcanic activity or asteroid impacts. Although the studied layers span about 2,600 years, the Sturtian glaciation itself lasted for 59 million years. It's also possible, as Prave suggests, that these rock formations date from the transitional periods at the beginning or end of the Sturtian glaciation, when the Earth was partially thawing.

Ekhbary News Agency