文章来源:未知 文章作者:enread 发布时间:2016-10-07 08:19 字体: [ ]  进入论坛
The gusting1 westerly winds that dominate the climate in central Asia, setting the pattern of dryness and location of central Asian deserts, have blown mostly unchanged for 42 million years. A University of Washington geologist2 led a team that has discovered a surprising resilience to one of the world's dominant3 weather systems. The finding could help long-term climate forecasts, since it suggests these winds are likely to persist through radical4 climate shifts. "So far, the most common way we had to reconstruct past wind patterns was using climate simulations, which are less accurate when you go far back in Earth's history," said Alexis Licht, a UW assistant professor of Earth and space sciences who is lead author of the paper published in August in Nature Communications. "Our study is one of the first to provide geological constraints5 on the wind patterns in deep time."
Earlier studies of the Asian climate's history used rocks from the Loess Plateau in northwestern China to show dust accumulation began 25 million to 22 million years ago and increased over time, especially over the past 3 million years. It had been believed that these rocks reflected the full history of central Asian deserts, linking them with the rise of the Tibetan Plateau and a planetwide cooling.
But Licht led previous research at the University of Arizona using much older rocks, dating back more than 40 million years, from northeastern Tibet. Dust in those rocks confirmed the region already was already parched6 during the Eocene epoch7. This upended previous beliefs that the region's climate at that time was more subtropical, with regional wind patterns brought more moisture from the tropics.
The new paper traces the origin of this central Asian dust using samples from the area around Xining, the largest city at the northeastern corner of the Tibetan Plateau. Chemical analyses show that the dust came from areas in western China and along the northern edge of the Tibetan Plateau, like today, and was carried by the same westerly winds.
"The origin of the dust hasn't changed for the last 42 million years," Licht said.
During the Eocene, the Tibetan Plateau and Himalayan Mountains were much lower, temperatures were hot, new mammal species were rapidly emerging, and Earth's atmosphere contained three to four times more carbon dioxide than it does today.
"Neither Tibetan uplift nor the decrease in atmospheric8 carbon dioxide concentration since the Eocene seem to have changed the atmospheric pattern in central Asia," Licht said. "Wind patterns are influenced by changes in the Earth's orbit over tens or hundreds of thousands of years, but over millions of years these wind patterns are very resilient."
The study could help predict how climates and ecosystems9 might shift in the future.
"If we want to have an idea of the Earth's climate in 100 or 200 years, the Eocene is one of the best analogs, because it's the last period when we had very high atmospheric carbon dioxide," Licht said.
Results of the new study show that the wind's strength and direction are fairly constant over central Asia, so the amount of rain in these dry zones depends mostly on the amount of moisture in the air, which varies with carbon dioxide levels and air temperature. The authors conclude that winds will likely remain constant, but global warming could affect rainfall through changes in the air's moisture content.


1 gusting b935a53d4a54bfbe1ff80be0f64a4ae6     
  • Then the treacherous North Atlantic struck, with hail, rain, lightning and gusting wind. 这时,气候变幻莫测的北大西洋出现了冰雹、大雨、闪电和狂风。 来自英汉非文学 - 百科语料821
  • Jeff: Sometimes, the partiality and miscarriage of justice are dis-gusting too. 杰夫: 有时,裁判的不公平和误判也真是令人讨厌的一件事情。
2 geologist ygIx7     
  • The geologist found many uncovered fossils in the valley.在那山谷里,地质学家发现了许多裸露的化石。
  • He was a geologist,rated by his cronies as the best in the business.他是一位地质学家,被他的老朋友们看做是这门行当中最好的一位。
3 dominant usAxG     
  • The British were formerly dominant in India.英国人从前统治印度。
  • She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。
4 radical hA8zu     
  • The patient got a radical cure in the hospital.病人在医院得到了根治。
  • She is radical in her demands.她的要求十分偏激。
5 constraints d178923285d63e9968956a0a4758267e     
强制( constraint的名词复数 ); 限制; 约束
  • Data and constraints can easily be changed to test theories. 信息库中的数据和限制条件可以轻易地改变以检验假设。 来自英汉非文学 - 科学史
  • What are the constraints that each of these imply for any design? 这每种产品的要求和约束对于设计意味着什么? 来自About Face 3交互设计精髓
6 parched 2mbzMK     
  • Hot winds parched the crops.热风使庄稼干透了。
  • The land in this region is rather dry and parched.这片土地十分干燥。
7 epoch riTzw     
  • The epoch of revolution creates great figures.革命时代造就伟大的人物。
  • We're at the end of the historical epoch,and at the dawn of another.我们正处在一个历史时代的末期,另一个历史时代的开端。
8 atmospheric 6eayR     
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
9 ecosystems 94cb0e40a815bea1157ac8aab9a5380d     
n.生态系统( ecosystem的名词复数 )
  • There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
  • Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样,从雨林到半荒漠等不一而足。 来自辞典例句
TAG标签: Asian rocks winds