Variable winter moisture in the southwestern United States linked to rapid glacial climate shifts
Variable winter moisture in the southwestern United States linked to rapid glacial climate shifts
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DOI：
10.1038/ngeo754
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发表时间：
2010-02-01
影响因子：
18.3
通讯作者：
Burns, Stephen J.
中科院分区：
文献类型：
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作者：
Asmerom, Yemane;Polyak, Victor J.;Burns, Stephen J.
在最后一次冰川时期，北半球的气候以几千年(1-3)周期的快速、大幅度的温度波动为特征。这些波动在格陵兰温度重建中很明显(2，3)，整个北半球记录了相应的温度和水文变化(4，5)。在这里，我们展示了56,000到11,000年前美国西南部的降水记录，这是根据新墨西哥州洞穴方解石的O-18增量测量得出的。我们的记录显示，美国西南部冬季降水的增加与北半球的降温有关，我们将其归因于极地急流的南移，这调制了北美上空冬季风暴路径的位置。在太平洋盆地的西侧，由于热带辐合带的南移，夏季风降水的减少与北半球的冷却有关(4)。我们的结论是，北半球的冷却和变暖漂移导致热带辐合带和太平洋上的极地急流同时发生纬向位移。我们的数据与现代证据一致，即极地急流因全球变暖而北移(6-8)，这可能导致未来北美西南部日益干旱的条件。
During the last glacial period, the climate of the Northern Hemisphere was characterized by rapid, large-amplitude temperature fluctuations through cycles lasting a few thousand years(1-3). These fluctuations are apparent in Greenland temperature reconstructions(2,3), and corresponding temperature and hydrological variations have been documented throughout the Northern Hemisphere(4,5). Here we present a record of precipitation in the southwestern United States from 56,000 to 11,000 yr ago, on the basis of delta O-18 measurements of speleothem calcite from New Mexico. Our record shows that increased winter precipitation in the southwestern United States is associated with Northern Hemisphere cooling, which we attribute to a southward shift in the polar jet stream, which modulated the position of the winter storm track over North America. On the western side of the Pacific Ocean basin, decreases in summer monsoon precipitation are associated with Northern Hemisphere cooling, due to southward displacement of the intertropical convergence zone(4). We conclude that cooling and warming excursions in the Northern Hemisphere lead to concurrent latitudinal displacement of both the intertropical convergence zone and the polar jet stream over the Pacific Ocean. Our data are consistent with modern evidence for a northward shift of the polar jet stream in response to global warming(6-8), which could lead to increasingly arid conditions in southwestern North America in the future.