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Type of Document	Dissertation
Author	Eltgroth, Selene Farrell
Author's Email Address	selene AT gps.caltech.edu
URN	etd-05262006-110220
Persistent URL	http://resolver.caltech.edu/CaltechETD:etd-05262006-110220
Title	Unraveling deep-ocean connections to climate with deep-sea coral records of radiocarbon and Cd/Ca
Degree	PhD
Option	Geological and Planetary Sciences
Advisory Committee	Advisor Name Title John Eiler Committee Chair Alex Sessions Committee Member Andrew P. Ingersoll Committee Member Claudia Pasquero Committee Member Jess F. Adkins Committee Member
Keywords	paleoceanography deep-sea coral cadmium radiocarbon Younger Dryas
Date of Defense	2005-12-16
Availability	unrestricted
Abstract We generated records of radiocarbon and trace metals in deep-sea corals to investigate the role of the deep ocean during episodes of rapid environmental change. Our record of radiocarbon ages measured in a modern deep-sea coral from the northeastern Atlantic shows the transfer of bomb radiocarbon from the atmosphere to the deep ocean. We detect bomb radiocarbon at the coral growth site starting in 1975–1979. Our record documents a Delta14C increase from –80 ± 1‰ (average 1930–1979) to a plateau at –39 ± 2‰ (average 1994–2001). From a suite of fossil deep-sea corals, variability in North Atlantic intermediate water Delta14C during the Younger Dryas (13.0–11.5 ka) supports a link between abrupt climate change and intermediate ocean circulation. We observe rapid shifts in deep-sea Delta14C that require the repositioning of large Delta14C gradients within the North Atlantic. The shifts are consistent with changes in the rate of North Atlantic Deep Water formation. We also observe a decadal scale event at 12.0 ka that is marked by the transient return of radiocarbon to the eastern and western basins of the North Atlantic. To develop a nutrient proxy for use in deep-sea corals, we measured Cd/Ca in 14 modern corals. Several of these corals had anomalously high Cd/Ca that we explain with a systematic bias in Cd/Ca obscuring the signal of seawater Cd/Ca. When these high Cd/Ca corals are removed from the calibration, the best-fit coral-water partition coefficient is 1.3 ± 0.1. Examining Cd/Ca in fossil deep-sea corals, we find that our coral from the Younger Dryas (12.0 ka) resembles the high Cd/Ca corals of the modern calibration and probably does not reflect seawater Cd/Ca. The Cd/Ca record from a 15.4 ka coral resembles our low Cd/Ca calibration samples and probably reflects average seawater Cd/Ca.
Files	Filename       Size       Approximate Download Time (Hours:Minutes:Seconds)     28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access    00FrontMatter.pdf 59.56 Kb 00:00:16 00:00:08 00:00:07 00:00:03 < 00:00:01   01Chapter1.pdf 46.07 Kb 00:00:12 00:00:06 00:00:05 00:00:02 < 00:00:01   02Chapter2.pdf 12.40 Mb 00:57:24 00:29:31 00:25:50 00:12:55 00:01:06   03Chapter3.pdf 9.23 Mb 00:42:44 00:21:58 00:19:14 00:09:37 00:00:49   04Chapter4.pdf 20.14 Mb 01:33:15 00:47:57 00:41:58 00:20:59 00:01:47   05Appendix.pdf 67.96 Kb 00:00:18 00:00:09 00:00:08 00:00:04 < 00:00:01   SeleneThesisFinal.pdf 120.38 Mb 09:17:18 04:46:37 04:10:47 02:05:23 00:10:42