In a new study, scientists reconstructed how sea levels have changed in the Bering Strait. They
The Bering Land Bridge is also known asThe Beringian Isthmus, or Beringia, has repeatedly connected Eurasia and North America. The scientists' findings prove that the growth of ice sheets and the fall of sea levels did not occur very quickly and much later than previously thought.
Global sea level is falling duringice ages, as more of the Earth's water becomes trapped in massive ice sheets. The problem is that these processes are difficult to date accurately.
During the Last Glacial Maximum,which lasted from 26,500 to 19,000 years ago, ice sheets covered large areas of North America. The dramatically lower sea levels exposed a vast area known as Beringia, which stretched from Siberia to Alaska. Horses, mammoths and other representatives of the Pleistocene fauna lived there. As the ice sheets melted, the Bering Strait flooded again around 13,000 to 11,000 years ago.
More than 50% of global ice volume duringof the last glacial maximum rose later than 46,000 years ago. Determining the timing of the changes is important for understanding the feedback between climate and ice sheets, the scientists explain, and provides evidence that ice sheet development was delayed after global temperatures fell.
The results confirm recent studies,showing that global sea level was much higher before the Last Glacial Maximum than previous estimates had suggested. Average global sea level during the Last Glacial Maximum was about 130 meters lower than it is today. However, the actual sea level at a particular location, such as the Bering Strait, depends on factors such as the deformation of the Earth's crust under the weight of ice sheets.
In the new study, scientists used analysisnitrogen isotopes in seafloor sediments to determine when the Bering Strait last flooded and Pacific waters poured into the Arctic. Scientists measured the ratio of nitrogen isotopes in marine plankton remains preserved in sediment cores collected from the seafloor at three sites in the western Arctic Ocean. Because of differences in the nitrogen composition of Pacific and Arctic waters, scientists have identified a nitrogen isotope signature that indicates when Pacific waters flowed into the Arctic.
The findings point to the complex relationship between climate and global ice volume and offer new ways to study the mechanisms that underlie glacial cycles.
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