Eddie Gonzales Jr.-AncientPages.com- By reconstructing the sea level history of the Bering Strait, scientists found that the strait remained inundated until about 35,700 years ago, shortly before humans began migrating to the Americas.
During the Beringia-Bering land bridge deglaciation period. Image Credits: giftagger – public domain
A new study reconstructing the history of sea level in the Bering Strait suggests that the Bering land bridge connecting Asia to North America did not emerge until about 35,700 years ago, 10,000 years before the height of the last Ice Age (known as known as the Last Glacial Maximum).
New findings published the week of December 26 in the Proceedings of the National Academy of Sciences indicate that ice sheet growth – and sea level decline – occurred surprisingly early and much later in the glacial cycle than previous studies suggested. Hui. suggested.
“This means that more than 50 percent of the global ice volume at the Last Glacial Maximum increased 46,000 years ago,” said Tamara Pico, assistant professor of Earth and planetary sciences at UC Santa Cruz and a corresponding author of the paper.
“This is important for understanding the feedback between climate and ice sheets, as it implies that ice sheet growth was significantly delayed after the decline in global temperatures.”
Global sea levels fall during ice ages as more and more of Earth’s water is locked in massive ice sheets, but the timing of these processes has been difficult to determine. During the Last Glacial Maximum, which lasted from about 26,500 to 19,000 years ago, the ice sheet covered large areas of North America. The dramatically lower sea levels exposed a vast land area known as Beringia, which stretched from Siberia to Alaska and supported herds of horses, mammoths, and other Pleistocene fauna. As the ice sheets melted, the Bering Strait was again flooded about 13,000 to 11,000 years ago.
The new findings are interesting in relation to human migration because they narrow down the time between the opening of the land bridge and the arrival of humans in the Americas. The timing of human migration to North America remains unresolved, but some studies suggest that people may have lived in Beringia during the height of the Ice Age.
“People must have started crossing as soon as the land bridge was built,” Pico said.
The new study used analysis of nitrogen isotopes in sea floor sediments to determine when the Bering Strait flooded during the past 46,000 years, allowing water from the Pacific Ocean to flow into the Arctic Ocean. First author Jesse Farmer of Princeton University led the isotope analysis, measuring nitrogen isotope ratios in the remains of marine plankton preserved in sediment cores collected from the ocean floor at three locations in the western Arctic Ocean. Because of differences in the nitrogen composition of Pacific and Arctic waters, Farmer was able to identify a nitrogen isotopic signature that indicates when Pacific waters flowed into the Arctic.
Pico, whose expertise is in sea level modelling, compared Farmer’s results with sea level models based on different scenarios for ice sheet growth.
“The exciting thing to me is that it provides a completely independent constraint on global sea level during this time period,” Pico said. “Some of the ice sheet histories that have been proposed vary greatly, and we were able to look at what the predicted sea level would be in the Bering Strait and see which ones are consistent with the nitrogen data.”
The results support recent studies showing that global sea level was much higher before the Last Glacial Maximum than previous estimates, she said. During the Last Glacial Maximum the mean global sea level was approximately 130 m (425 ft) lower than today. The actual sea level at a particular site, such as the Bering Strait, however, depends on factors such as deformation of the Earth’s crust from the weight of ice sheets.
“It’s like punching down bread dough—the crust sinks under the snow and rises up around the edges,” Pico said. “Also, the ice sheets are so massive that they have a gravitational effect on the water. I model those processes to see how sea level will vary around the world and in this case look at the Bering Strait.” For.
The findings indicate a complex relationship between climate and global ice extent and suggest new avenues for investigating the underlying mechanisms of glacial cycles.
Via press release EurekAlert
written by Eddie Gonzales Jr. -AncientPages.com – MessageToEagle.com Staff