期刊
SCIENCE
卷 364, 期 6438, 页码 386-+出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.aau5784
关键词
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资金
- U.S. NSF [OCE-1060947, 0960802, 1136345]
- Max Planck Society
- Tuttle Fund of the Department of Geosciences, Princeton University
- NOAA Climate and Global Change Postdoctoral Fellowship
- Directorate For Geosciences
- Division Of Ocean Sciences [1136345] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Ocean Sciences [0960802] Funding Source: National Science Foundation
The million-year variability of the marine nitrogen cycle is poorly understood. Before 57 million years (Ma) ago, the N-15/N-14 ratio (delta N-15) of foraminifera shell-bound organic matter from three sediment cores was high, indicating expanded water column suboxia and denitrification. Between 57 and 50 Ma ago, delta N-15 declined by 13 to 16 per mil in the North Pacific and by 3 to 8 per mil in the Atlantic. The decline preceded global cooling and appears to have coincided with the early stages of the Asia-India collision. Warm, salty intermediate-depthwater forming along the Tethys Seamargins may have caused the expanded suboxia, ending with the collision. From 50 to 35 Ma ago, delta N-15 was lower than modern values, suggesting widespread sedimentary denitrification on broad continental shelves. delta N-15 rose at 35 Ma ago, as ice sheets grew, sea level fell, and continental shelves narrowed.
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