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Special Session 4: Biogeochemical cycling of trace elements in the ocean: GEOTRACES and beyond |
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Deep ocean ventilation constrained by absolutely dated radiocarbon variability of deep-sea corals during the last deglaciation
Monday 9th @ 1605-1625
Room 4
Tianyu Chen* , University of Bristol
Laura F. Robinson, University of Bristol
Presenter Email: tc14502@bristol.ac.uk
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| Deep ocean overturning circulation plays a central role in driving the abrupt climate events during the last glacial period and deglaciation. An accurate understanding of the deep oceanic processes in these climate events relies on high-quality, high temporal-resolution and absolutely dated marine records. Traditional geochemical reconstructions based on marine sediments suffer from the lack of absolute ages as well as other complicating factors such as bioturbation. Deep-sea corals thrive in the intermediate depth ocean and can be absolutely dated by U-series disequilibrium method. Here we are going to show how deep-sea scleractinian fossil corals can be an exciting new archive that would provide critical information on seawater chemistry changes from centennial to millennial time scales since the last glacial period. Among various geochemical proxies, radiocarbon of intermediate waters (500-2000 m) holds clue to the timing and roles of high-latitude surface oceans in contributing past deep ocean ventilation, a key process driving atmospheric CO2 concentration increase during the last deglaciation (18-10.5 ka, thousand years ago). However, available intermediate water 14C studies are not consistent with each other, leading to diverse paleoceanographic understandings. We have reconstructed U-series dated deep-sea coral 14C records from intermediate waters of the Eastern Equatorial Pacific (EEP), Equatorial Atlantic as well as the Drake Passage in the Southern Ocean. The records from Equatorial Atlantic and Southern Ocean provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation [1]. A coherent deglacial intermediate water 14C variability was found in the low latitude regions (EEP and Equatorial Atlantic), pointing to the dominant role of Southern Ocean and North Atlantic in controlling deglacial deep ocean ventilation. In addition, the seawater 234U/238U evolution inferred from U-series dating can also provide valuable information on the past continental weathering changes [2]. [1] Chen, T. et al., 2015. Science, 349, 1537-1541. [2] Chen, T. et al., 2016. Science, in press, doi: 10.1126/science.aag1015. |
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