Bering Land Bridge formed surprisingly late during last ice age

The Last Glacial Maximum occurred less than 10,000 years before the emergence of the land bridge connecting Asia to North America, according to a new study.

The growth of the ice sheets and the resulting drop in sea level was found to be much later in the cycle than previously thought.

More than 50% of the global ice volume at the Last Glacial Maximum grew after 46,000 years ago, according to the paper. It means that there was a delay in the development of ice sheets after global temperatures fell.

The timing of global sea levels dropping during ice ages has been difficult to pin down. Ice sheets covered large areas of North America during the last Glacial Maximum. There were herds of horses, mammoths, and other prehistoric animals in the land area that was uncovered by lower sea levels. The ice sheets melted around 11,000 years ago, flooding the Strait again.

The time between the opening of the land bridge and the arrival of humans in the Americas is shortening. Some studies suggest that people may have lived in Beringia during the height of the ice age.

Pico said that people may have crossed the bridge as soon as it was built.

The study used an analysis of nitrogen isotopes in the seafloor to determine when the Bering Strait was flooded. Jesse Farmer was the first author to lead the analysis of the nitrogen isotope ratios in the remains of marine plankton. Farmer was able to identify a nitrogen isotope signature because of the differences in the nitrogen composition of the waters.

Pico compared Farmer's results with sea level models based on different scenarios for ice sheet growth.

Pico said that the exciting thing to him was that this provided a completely independent constraint on global sea level. Some of the ice sheet histories that have been proposed differ by a lot, and we were able to look at what the predicted sea level would be at the Bering Strait and see which ones are consistent with the nitrogen data

Recent studies show that global sea levels were higher before the Last Glacial Maximum than had been thought. The Last Maximum Glacial sea level was lower than it is today. Factors such as the weight of the ice sheets and the Earth's crust can affect the sea level at a specific site.

Pico said it's like punching down on bread dough and it rises up around the edges. The ice sheets affect the water in many ways. To see how sea level would vary around the world, I modeled those processes to see how they would change.

There is a complicated relationship between climate and global ice volume.

In addition to Pico and Farmer, the other co-authors are Ona Underwood and Daniel Sigman at Princeton University, Rebecca Cleveland-Stout at the University of Washington, and Franois Fripiat at the U.S. Geological Survey. The work was supported by a foundation.

There is a story

The materials were provided by the University of California. Tim wrote the original. The content can be edited for style and length.