By reconstructing the sea level history of the Bering Strait, scientists found that the strait remained flooded until around 35,700 years ago, not long before humans began migrating into the Americas
藉由重建白令海的海平面史，科家，直到大35千7百年前。也就是，在人始徙到美洲之前不久，海仍然被水淹。
1. 此地明了白令，於上一次冰河作用期，在北美洲洲形成的地形。在此地描的冰河期中，人洲越白令到北美洲。
This map illustrates the geography of Beringia, the land bridge that formed between North America and Asia during the last glaciation. Humans crossed Beringia from Asia to North America during the glacial period depicted on this map.
A new study that reconstructs the history of sea level at the Bering Strait shows that the Bering Land Bridge connecting Asia to North America did not emerge until around 35,700 years ago, less than 10,000 years before the height of the last ice age (known as the Last Glacial Maximum).
一重建白令海海平面史的新研究示，接洲北美洲的白令，直到大35千7百年前，才出。在上一次冰河期(被通末次盛冰期)的峰前，不及1年。
The new findings, published the week of December 26 in Proceedings of the National Academy of Sciences, indicate that the growth of the ice sheets—and the resulting drop in sea level—occurred surprisingly quickly and much later in the glacial cycle than previous studies had suggested.
此些表於2022年12月26(及由此致海平面下降)，在冰河期中，出人意料地快速生，且比先前多研究已暗示的晚很多。
“It means that more than 50 percent of the global ice volume at the Last Glacial Maximum grew after 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.
篇文通撰文人，美加州大克分校，地球暨行星科助理教授，Tamara Pico宣：「意味著，全球超50%的冰量，是在46千年前之後的末次盛冰期增的。
“This is important for understanding the feedbacks between climate and ice sheets, because it implies that there was a substantial delay in the development of ice sheets after global temperatures dropped.”
就理解候冰原之的反而言，很重要。因意味著，全球下降後，在冰原的展上，有性的延。」
Global sea levels drop during ice ages as more and more of Earth’s water gets locked up in massive ice sheets, but the timing of these processes has been hard to pin down. During the Last Glacial Maximum, which lasted from about 26,500 to 19,000 years ago, ice sheets covered large areas of North America.
在冰河期，全球海平面下降。因，越越多的地球水被在巨大的冰原中。不，此些程的序一直很定。在大26千5百年持到19千年前的末次盛冰期期，冰原覆了北美洲的大片域。
Dramatically lower sea levels uncovered a vast land area known as Beringia that extended from Siberia to Alaska and supported herds of horses, mammoths, and other Pleistocene fauna. As the ice sheets melted, the Bering Strait became flooded again around 13,000 to 11,000 years ago.
急降低的海平面曝露了，西伯利延伸到阿拉斯加，且供了、猛象及其他更新世之物群，被通白令的大地域。著冰原融化，白令海在大13千到11千年前，再次遭海水淹。
The new findings are interesting in relation to human migration because they shorten the time between the opening of the land bridge and the arrival of humans in the Americas. The timing of human migration into North America remains unresolved, but some studies suggest people may have lived in Beringia throughout the height of the ice age.
在人徙相的此些新，是引人好奇的。因，它短了此路通人抵美洲之的。人徙到北美洲的序仍然未被解，不有些研究暗示，整此冰河期的鼎盛期，人可能曾生活於白令。
“People may have started going across as soon as the land bridge formed,” Pico said.
Pico宣：「此地一形成，人可能就已始穿越。」
The new study used an analysis of nitrogen isotopes in seafloor sediments to determine when the Bering Strait was flooded during the past 46,000 years, allowing Pacific Ocean water to flow into the Arctic Ocean.
新研究使用了，分析於海底沉物中的氮同位素定，在去46千年期，白令海何遭海水淹，而使太平洋海水得以流入北冰洋。
First author Jesse Farmer at Princeton University led the isotope analysis, measuring nitrogen isotope ratios in the remains of marine plankton preserved in sediment cores collected from the seafloor at three locations in the western Arctic Ocean.
定收集自位於北冰洋西部三地海底，被保存於沉物芯之海洋浮游生物骸中，氮同位素比率的同位素分析，是由首要撰文人，美普林斯大Jesse Farmer所。
Because of differences in the nitrogen composition of Pacific and Arctic waters, Farmer was able to identify a nitrogen isotope signature indicating when Pacific water flowed into the Arctic.
由於，在太平洋北海域之氮成分中的差，Farmer能分辨出，示太平洋海水何流入北地的氮同位素特徵。
Pico, whose expertise is in sea level modeling, then compared Farmer’s results with sea level models based on different scenarios for the growth of the ice sheets.
之後，是在海平面模型作的Pico，以有些冰原展之多不同本的海平面模型，比了Farmer的分析果。
“The exciting thing to me is that this 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 differ by quite 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.”
Pico宣：「我而言，令人振的事是，提供了，於在上述期之全球海平面，一完全立的制。」
The results support recent studies indicating that global sea levels were much higher prior to the Last Glacial Maximum than previous estimates had suggested, she said. Average global sea level during the Last Glacial Maximum was about 130 meters (425 feet) lower than today.
她表示，此些研究果支持了，最近多示全球海平面，在末次盛冰期之前，比先前多估高很多的研究。在末次盛冰期期，平均全球海平面比今低大130米(425英尺)。
The actual sea level at a particular site such as the Bering Strait, however, depends on factors such as the deformation of the Earth’s crust by the weight of the ice sheets.
然而，在如白令海等，特定地方的海平面，取於如，因冰原重量的地形等因素。
“It’s like punching down on bread dough—the crust sinks under the ice and rises up around the edges,” Pico said. “Also, the ice sheets are so massive they have gravitational effects on the water. I model those processes to see how sea level would vary around the world and, in this case, to look at the Bering Strait.”
Pico宣：「有如重。在冰下，地下沉，而在升起。同，冰原非常大，因此它海水具有重力作用。我作了那些程的模型，以解世界各地的海平面如何化，在此情下，白令海。」
The findings imply a complicated relationship between climate and global ice volume and suggest new avenues for investigating the mechanisms underlying glacial cycles.
此些研究暗示了，候全球冰量之的一，且查研究冰河循之在制，提出了新的途。
This work was supported by the National Science Foundation.
研究是由美家科基金所支持。
址：https://news.ucsc.edu/2022/12/bering-strait.html
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