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| Collaborative Research: Tracking the Subtropical Front across the Mid Pleistocene Transition Using Sea Surface Temperature and Nutrients | |
| 项目编号 | 1736938 |
| Rebecca Robinson | |
| 项目主持机构 | University of Rhode Island |
| 开始日期 | 2017-09-01 |
| 结束日期 | 08/31/2022 |
| 英文摘要 | This project seeks to reconstruct changes in the position of the Subtropical Front (STF) in the Agulhas region of the Southern Ocean south of Africa over the last 1.5 million years. Ocean currents play a significant role in the distribution of heat and salt in the global ocean. Ultimately, changes in these currents influence marine nutrient distribution, ocean uptake of atmospheric CO2, and global climate. South of Africa, the Agulhas Current moves warm, salty water from the southern Indian Ocean into the South Atlantic Ocean. However, during intervals of near-global cooling, it is thought that the amount of this warm water escaping around Africa decreases or is even stopped, cutoff by a northward migration of the STF. Because a northward shift of the STF has the potential to both expand the surface area of the Southern Ocean and limit water exchange between the Indian and Atlantic Oceans, the region south of Africa is an important climate target to advance our understanding of how the physical movements of the STF may impact regional and global climate. Migrations of the STF are relatively poorly resolved for the past 1.5 million years, in part due to a prior lack of sediment cores in the critical region of front migration. This research combines multiple proxy records of ocean changes at a location sensitive to STF position to study how STF movement may have influenced ocean circulation and CO2 uptake. The project will support two female PIs (one early career) as well as two graduate students and several undergraduates. Broader public outreach is planned in the context of K-12 classroom and web-based materials. The investigators will generate an integrated reconstruction of upper ocean dynamics along the Subtropical Front over the last 1.5 million years from sediments in a new International Ocean Discovery Program core (Site U1475) recovered from the southern Indian Ocean at a location well suited to monitor STF position. They will use multiple sediment proxies to generate an integrated reconstruction of upper ocean dynamics along the STF using reconstructions of water temperature, export production, and nutrient utilization. North-south migrations of the STF have been hypothesized to control movement of water through the Indo-Atlantic Gateway, an exchange that has important implications for the air-sea balance of CO2 and the strength of the meridional overturning circulation of the Atlantic. The resulting data will be used to document the location of the STF with respect to the core site and the nutrient status of the subantarctic region of the Southern Ocean during episodes of expansion. Specifically, the investigators will produce new high-resolution records of water temperature (using Uk37, TEX86, and foraminiferal census counts using a Modern Analog Technique), export production (using total organic carbon, biogenic silica, and total alkenone (C37tot) content), and nutrient dynamics (using foraminiferal-bound organic matter d15N) for the last 1.5 million years to constrain the history of the STF and its response to climate change. Emphasis will be placed on the Mid Pleistocene Transition (MPT), the time interval between 1.25 and 0.7 million years ago when the dominant periodicity of climate cycles changed from 41 kiloyears to 100 kiloyears in the absence of substantial change in orbital forcing. Reconstructing the location of the STF across the MPT is key to understanding the role that STF migration may have played in altering the Southern Ocean biological pump (with consequent changes in atmospheric CO2). |
| 资助机构 | US-NSF |
| 项目经费 | $390,647.00 |
| 项目类型 | Standard Grant |
| 国家 | US |
| 语种 | 英语 |
| 文献类型 | 项目 |
| 条目标识符 | http://gcip.llas.ac.cn/handle/2XKMVOVA/210820 |
| 推荐引用方式 GB/T 7714 | Rebecca Robinson.Collaborative Research: Tracking the Subtropical Front across the Mid Pleistocene Transition Using Sea Surface Temperature and Nutrients.2017. |
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