(1) The Role of the Biological Pump in Deglacial CO2 Rise:
The initial trigger of atmospheric CO2 rise during Heinrich Stadial 1 remains elusive. Explanations often invoke the Southern Ocean release of carbon stored in the abyssal ocean. Proxy records of abyssal circulation, however, lack evidence for variability coincident with the initial CO2 rise, inconsistent with a Southern Ocean driver. An alternate explanation for CO2 rise during Heinrich Stadial 1 involves the effect of a weakened Atlantic Meridional Overturning Circulation on the ocean's biological pump. My main postdoctoral research involves creating and compiling records of planktonic and benthic δ13C from intermediate depth sites to assess if they are consistent with either a Southern Ocean or biological pump driver. Study locations include the Brazil Margin, Chatham Rise, Australia Margin, Eastern Equatorial Pacific, and the Southeast Atlantic. Mg/Ca and Cd/Ca measurements will be used to assess the influence of air-sea gas exchange on δ13C.
(2) Reconstructing the Tropical Pacific Mean State and ENSO Variability across Marine Isotope Stage 3:
Prior attempts to characterize the mean state of the Tropical Pacific across MIS 3 have been unsuccessful, as hydrologic records predominantly reflect shifts in the ITCZ. We are attempting to circumvent this issue by reconstructing thermocline temperatures using Mg/Ca paleothermometry on the thermocline-dwelling foraminifera Neogloboquadrina dutertrei from a sediment core recovered from the Carnegie Ridge in the Eastern Equatorial Pacific. Thermocline temperatures in this region are strongly correlated to ENSO variability. Once the mean state variability is established, we plan to perform individual shell Mg/Ca analyses on the same thermocline-dwelling species in an effort to relate ENSO variability to changes in the mean state. This project is part of an ongoing collaboration with my PhD advisor, Matthew Schmidt, and Tom Bianchi of the University of Florida. The Bianchi lab is utilizing biomarkers to reconstruct upwelling variability across MIS3 utilizing the same sediment core.
(3) Understanding Paleo Proxies: The interface between modern oceanographic observations and paleoceanographic proxies:
I am interested in how oceanographic parameters, such as temperature and salinity, are recorded in marine sediments. To this end, I go out to sea to collect seawater samples and newly deposited sediments from the ocean floor to examine the relationship between the chemical composition of the seawater and the sediments. I am also interested in how marine sediments are altered once they are deposited on the sea floor by processes such as dissolution, and how these processes affect paleoceanographic proxies. Ongoing research projects in this area include:
· Understanding the Barium/Calcium – seawater salinity relationship of the Eastern Equatorial Pacific. The goal of this project is to establish the relationship between these two seawater parameters in combination with seawater δ18O measurements to disentangle freshwater sources to the EEP. Ultimately, foraminiferal Ba/Ca ratios could be used to reconstruct seawater salinity.
· Refining the seawater δ18O – salinity relationship of the North Atlantic Ocean. Seawater samples were collected in a latitudinal transect from the North Atlantic down to the Equator in an effort to establish regional relationships in the δ18OSW – salinity to better reconstruct δ18OSW in the past through combinations of formainiferal calcite δ18O and Mg/Ca temperature measurements.
(1) Refining Globigerinoides ruber Mg/Ca Paleothermometry in the Atlantic Ocean
(2) Utilizing Multi-Species Foraminiferal Mg/Ca Paleothermometry to Understand TEX86 Temperatures in the Eastern Equatorial Pacific across the Holocene and Last Glacial Maximum