Isotopes in the teeth of an ancient shark show how the climate changed during the Eocene

Sharks have inhabited Earth's oceans for more than 400 million years, recording the history of the planet. New study of isotopes in

the teeth of one of them will help resolve a long-standing dispute aboutdepth and timing of the opening of the Drake Passage. This is an intercontinental strait connecting the southern parts of the Atlantic and Pacific oceans. To the north of the strait is the southernmost point of the South American continent and the entire American continent - the islands of Diego Ramirez and Cape Horn, and on the opposite side are the South Shetland Islands. By the way, it is the Drake Passage that is one of the stormiest places on the planet.

Many explanations for climate change in the Eoceneare concentrated in the Southern Ocean, where tectonics and water circulation have reduced heat transfer and reduced greenhouse gas emissions have led to glaciation. To date, few studies have focused on marine vertebrates at high latitudes to reveal the paleoecological and paleoecological implications of this climate transition.

Sharks' body temperature is regulated by their environment.water, so the cold polar regions support limited species. There have been periods of time in the past (such as the Eocene geological period, 56–33.9 million years ago) when the Earth was much warmer and sharks were abundant in ocean waters around the world. For example, fossilized shark teeth have been found in Eocene sediments in Antarctica. Scientists analyzed their chemical composition. This gave them clues about how the climate changed during the Eocene. The study found that sand tiger sharks of all ages lived in the Drake Passage area, and the water temperatures recorded by their teeth remained constant over time, despite apparent continental movement and changes in ocean circulation.

It is believed that it was the discovery of thisThe strait, 1000 km wide and 3 km deep, led to the fact that the climate on Earth changed from greenhouse to glacial. However, data analyzed by paleoecologist Sora Kim of the University of California and her colleagues shows otherwise.

“By analyzing isotopes in shark teeth,we can track the transfer of water masses between ocean basins and see when the passage opened. However, we do not see evidence of climate change at the time. This will force people to reconsider their hypotheses,” Kim explains.

Scientists used to carry out isotopicanalysis of shark teeth collected around Seymour Island near Antarctica. Isotopes are found in the environment and, along with food, enter various organisms, accumulate in their bones and teeth (while they are being formed). The amount of these isotopes (and their percentage) depends primarily on the geological features of the area.

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