Details of Award
NERC Reference : NE/G01602X/1
Testing the Panama Closure Hypothesis
Grant Award
- Principal Investigator:
- Dr S Jung, University of Edinburgh, Sch of Geosciences
- Co-Investigator:
- Professor D Kroon, University of Edinburgh, Sch of Geosciences
- Grant held at:
- University of Edinburgh, Sch of Geosciences
- Science Area:
- Marine
- Earth
- Overall Classification:
- Marine
- ENRIs:
- Global Change
- Science Topics:
- Ocean Circulation
- Ocean - Atmosphere Interact.
- Quaternary Science
- Palaeoenvironments
- Abstract:
- Long-term climate change has been controlled by a number of factors amongst which closure of the Panama Isthmus gateway (PIG) may have been instrumental in enforcing lasting shifts in Earth's climate. The central goal of this project is to ground-truth the importance of the closure of the PIG for the long-term evolution of North Atlantic Deepwater (NADW). The final phase of the PIG closure around ~4.6 and ~3.6 MYR would have led to enhanced formation of better oxygenated NADW to ventilate the deep Atlantic and is thought to have been pivotal in paving the way toward late Pleistocene icehouse conditions. This scenario initially was based on a comparison of ventilation records from the deep Caribbean Sea and from the N-Atlantic (using d13C in benthic foraminifera as a proxy for deepwater ventilation). The overall d13C-increase in these records appears to suggest enhanced advection of increasingly ventilated NADW filling the Caribbean basin. Complementary evidence from the Southern Ocean (Atlantic sector) also shows a d13C-increase during the closure of the PIG. Deepwater in this region, however, consists of a blend of water masses of northern and southern origin. Hence, a d13C-increase in deepwater from this region cannot be unequivocally assigned to a particular water mass such as NADW. Consequently, we currently lack South Atlantic evidence that reflects largely undiluted change in NADW ventilation close to the exit of the Atlantic sector of the global thermohaline circulation. Here we propose to close this gap by completing the preliminary stable isotope profile from South Atlantic Site 1264, drilled on the crest of Walvis ridge. This site is currently bathed in upper NADW. The preliminary isotope profile shows no marked increased ventilation during the closure of the PIG. The stable isotope record of Site 1264 is, however, incomplete preventing an in-depth assessment of the broader importance of these preliminary findings. Within this project we aim to complete this isotope record to obtain a full picture of upper NADW ventilation variability through the entire Pliocene-Pleistocene period. Also, and possibly more important, we propose to establish a stable isotope record for deep water equivalent Site 1267 at the bottom of Walvis Ridge that is currently bathed in lower NADW. Using these new results as a nucleus, a synoptic appraisal of deep ocean records from other parts of the Atlantic, Southern Ocean and Pacific will allow testing two crucial predictions of the PIG closure hypothesis that reflect on the advocated overall increase in NADW ventilation: (1) The closure would have resulted in increased ventilation of NADW and thus all records, reflecting downstream change in NADW properties, should display increase in ventilation; (2) The closure would have caused reduced exchange of deep waters between the Atlantic and the Pacific. This should have resulted in a larger d13C-difference of deep waters between the two oceans. A tentative comparison of deep ocean d13C-records indeed seems to suggest that the overall N- S-Atlantic and N-Atlantic-Pacific ventilation gradients, respectively, did not change significantly during the PIG closure. The strongest and lasting shift in ventilation gradients occurred between the Caribbean Sea and the N-Atlantic, but would largely reflect local changes in deepwater chemistry, rather than a globally important change in NADW ventilation. New records (Sites 1264 and 1267) of largely undiluted changes in NADW documenting the final stages of deep ocean change across one of the major climate transitions in Earth's history are required to address consequences of the closure of the PIG for deep ocean circulation. South Atlantic data are crucial. These new data would not only address local changes in deepwater prevalence at the Walvis Ridge, but more importantly, they are likely to prove instrumental in determining the role of the PIG closure for Atlantic wide deep ocean circulation and beyond.
- NERC Reference:
- NE/G01602X/1
- Grant Stage:
- Completed
- Scheme:
- Directed (Research Programmes)
- Grant Status:
- Closed
- Programme:
- UK IODP Phase2
This grant award has a total value of £43,815
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DA - Estate Costs | DI - Staff | DA - Other Directly Allocated | DI - T&S |
|---|---|---|---|---|---|---|
| £1,632 | £8,799 | £6,993 | £2,757 | £4,291 | £16,470 | £2,874 |
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