Do Tropical Glaciations Record Heinrich Events?

9422220 DORN近年来，关于气候变化的动态发生了相当大的争论。流行的模式认为，气候在几个世纪的时间里逐渐变化。哈特穆特·海因里希（Hartmut Heinrich）等人积累的越来越多的证据表明，在过去7万年的不同时期，变化可能要突然得多。四次所谓的“海因里希事件”的特点是，覆盖北美东北部的劳伦泰德冰盖向北大西洋释放了大量冰山。在海底沉积物的岩心中发现了这些冰山携带的细小碎片。在陆地花粉堆积、冰川沉积物、湖泊波动以及海洋珊瑚和沉积物中发现了世界其他地区气候突然变化的相关证据。这个研究项目将包括美国和墨西哥的科学家对夏威夷莫纳克亚山山坡上的冰川沉积物和墨西哥中部的火山进行检查。在海因里希事件发生的时期，北回归线附近的这两个高地都已被冰川覆盖。冰川沉积物将使用各种高精度测年技术进行测年，包括14-碳、36-氯、3-氦和21-氖的同位素分析。该项目将为这些热带高地提供详细的冰川年代学，并将有助于重建附近低地地区的土壤、地貌系统和生物地理系统的变化。这些数据将通过评估这些快速变化是否影响到热带高地，促进对海因里希事件具有全球性特征的假设的考虑。通过这样的研究收集到的证据的积累将大大有助于理解全球变化的动力、时间和速度。

9422220 DORN Considerable debate has occurred in recent years regarding the dynamics of climatic change. Prevailing models have held that climates change gradually over periods of centuries. A growing body of evidence accumulated by Hartmut Heinrich and others indicates that changes may have been much more abrupt at various times during the last 70,000 years. Four so-called "Heinrich events" were characterized by the release of large numbers of icebergs into the North Atlantic from the Laurentide Ice Sheet covering northeastern North America. Fine debris carried by these icebergs have been found in cores of sediments from the bottom of the ocean. Correlative evidence of sudden climatic changes in other parts of the world has been found in terrestrial pollen accumulations, in glacial deposits, in lake fluctuations, and in marine corals and sediments. This research project will involve U.S. and Mexican scientists in an examination of glacial deposits on the slopes of Mauna Kea in Hawaii and the volcanoes of central Mexico. Both of these highlands near the Tropic of Cancer are known to have been glaciated during the period when Heinrich events occurred. Glacial deposits will be dated using a variety of high-precision dating techniques, including isotope analyses of 14-Carbon, 36- Chlorine, 3-Helium, and 21-Neon. This project will provide a detailed glacial chronology for these tropical highlands, and it will assist in reconstruction of transformations of soils, geomorphic systems, and biogeographic systems in nearby lowland areas. These data will advance consideration of the hypothesis that Heinrich events were global in character by assessing whether these rapid changes affected tropical highlands. The accumulation of evidence gathered through studies like this will contribute considerably to understandings of the dynamics, timing, and speed of global change.