Publication Date:
2022-05-25
Description:
Submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy at the Massachusetts Institute of Technology
and the Woods Hole Oceanographic Institution September, 2005
Description:
Minor and trace element records from planktic and benthic foraminifera from
Atlantic sediment cores, as well as outputfrom a coupled OA·GCM, were used to investigate
the magnitude and distribution of the oceanic response to abrupt Climate events.of the past
20,000 years. The study addressed three major questions: 1) What is the magnitude of
high-latitude sea surface temperature and salinity variability during abrupt climate events?
2) Does intermediate depth ventilation change in conjunction with high-latitude climate
variability? 3) Are the paleoclimate data consistent with the response of a coupled OAGCM
to a freshwater perturbation? To address these questions, analytical methods were
implemented for the simultaneous measurement of Mg/Ca, Zn/Ca, Cd/Ca, Mn/Ca and All
Ca in foraminiferal samples using inductively-coupled plasma mass spectrometry.
Paired records of planktic foraminiferal ()IRO and Mg/Ca from the subpolar North
Atlantic reveal trends of increasing temperatures (-3°C) and salinities over the course of
the Holocene. The records provide the first evidence of open':'ocean cooling (nearly 2°C)
and freshening during the 8.2 kyr event, and suggest similar conditions at 9.3 ka.
Benthic foraminiferal Cd/Ca results from an intermediate depth, western South
Atlantic core (l,268 ni) are consistent with reduced export into the South Atlantic of North
Atlantic Intermediate Water during the Younger Dryas.
Paired records. of benthic foraminiferal Mg/Ca and bIRO from two intermediate
depth low latitude western Atlantic sites - one from the Florida Current (751 m) and one
from the Little Bahama Bank (l,057 m) - provicie insights into the spatial distribution of
intermediate depth temperature and sii!.inity variability during" the Younger Dryas. The
intermediate depth paleoceanographic temperature and salinity data are consistent with
the results of a GFDL R30 freshwater forced model simulation, suggesting that freshwater
forcing is a possible driver or amplifier for B011ing-Aller0d to Younger Dryas climate
variability.
Benthic foraminiferal Cd/Ca results from an intermediate depth Florida Current
core (751 m) are consistent with a decrease in the northward penetration of southern source
waters within the return flow of the Atlantic meridional overturning circulation (MOC)
and an increase in the influence of intermediate depth northern source waters during the
Younger Dryas.
Description:
This work was funded by a John Lyons Fellowship and a WHOI Ocean and Climate Change
Institute Fellowship. Analyses were funded by the Ocean and Climate Change Institute and the following grants from the National Science Foundation: OCE98-86748, OCE02-
20776, OCE96-33499,ATM05-01391, and OCE04-02565.
Keywords:
Ocean-atmosphere interaction
;
Climatic changes
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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