期刊
AMERICAN JOURNAL OF SCIENCE
卷 311, 期 1, 页码 63-75出版社
AMER JOURNAL SCIENCE
DOI: 10.2475/01.2011.03
关键词
Paleoclimate; carbon dioxide; stomata; Eocene; kimberlite; Metasequoia
资金
- Natural Sciences and Engineering Research Council of Canada
- Leverhulme Trust
- Royal Society
The transition from the extreme greenhouse of the early Paleogene (similar to 52 Ma) to the present-day icehouse is the most prominent change in Earth's Cenozoic climate history. During the late Middle Eocene climate transition (42-38 Ma), which preceded the onset of long-lived, continental-scale ice sheets, there is concordant evidence for brief pulses (<1 m.y. in length) of global warmth and ice sheet growth but few constraints on atmospheric CO2. Here we estimate the concentration of atmospheric CO2 during this critical interval using stomatal indices of fossil Metasequoia needles from ten levels in an exceptionally well-preserved core from the Giraffe kimberlite locality in northwestern Canada. Reconstructed CO2 concentrations are mainly between 700 to 1000 ppm, but include a secular decline to 450 ppm towards the top of the investigated section. Because the CO2 threshold for nucleating continental ice sheets at this time was similar to 500 to 750 ppm, the CO2 decline is compatible with a rapid (<10(4) yrs) transition from warm, largely ice-free conditions to cooler climates with ice sheets. These fossils provide direct evidence that high-latitude deciduous forests thrived in the geological past under CO2 concentrations that will likely be reached within the 21(st) century (500-1000 ppm).
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据