New!
“Glacial Deep Pacific Carbon Storage and Effects on CaCO3 Preservation”
Map of ML1208 Line Islands Sediment Cores (Lynch-Stieglitz et al., 2015) with cores to be targeted by this work indicated by red ovals.
NSF P2C2 Project with Kassandra Costa (WHOI)
The oceans are threatened by climate change, and understanding how they will respond to higher CO2 levels has never been more important. Past changes in the ocean’s carbon cycle can provide data to check and improve models that help us predict future changes. These data can also help us ‘balance’ Earth’s carbon budget by showing where and how much carbon was stored in the ocean at times when the Earth has been much colder. Research will be carried out by two early career, female scientists and includes roles for college and graduate students. This work also increases access to information about climate change by creating activities for high school classrooms. This work advances discovery, integrates research and education, increases the participation of underrepresented groups in the geosciences, and fosters the inclusion of the public in fundamental science research. This project is jointly funded by OCE-Marine Geology and Geophysics (OCE-MGG) and the Established Program to Stimulate Competitive Research (EPSCoR).
Despite the importance of understanding whole-ocean carbon system changes in glacial periods, and the volumetric dominance of the Pacific Ocean, the Atlantic Ocean has been the primary locus of most quantitative carbon cycle reconstructions. This means that longstanding questions about Pacific carbon storage and dissolution feedbacks remain largely unanswered. The Pacific Ocean’s carbon budget in the past will be explored using several geochemical proxies. The B/Ca ratio of benthic foraminifera is a state-of-the-art proxy for examining these questions, as it records the difference between seawater’s carbonate ion concentration and its concentration at saturation Delta[CO32-]. The research plan pairs this new proxy with classical methods of reconstructing carbon cycle changes in the deep ocean including planktonic foraminifera species assemblages and individual weights, calcium carbonate fluxes, carbon isotope analysis of benthic foraminifera, and reconstructions of organic carbon fluxes (Baxs). The multiproxy approach is designed to constrain different carbon cycle feedbacks, and to calibrate less expensive microscope-based techniques in an effort to harness the wealth of existing paleoclimate datasets for quantitative reconstructions and model-data cross validation.
Biomarker Preservation and respired carbon storage
Transect of proposed study sites in the Line Islands region of the central equatorial Pacific Ocean. Colors show the surface productivity gradient in the modern ocean.
NSF MG&G Proposal to investigate the controls on the alkenone biomarker preservation proxy with Tim Herbert (Brown U).
As the global oceans experience increasing stress from anthropogenic climate forcing, improving models of ocean responses to carbon cycle perturbations is ever more crucial. In response to this challenge, increasingly sophisticated mechanisms of carbon exchange have been integrated into biogeochemical models. Critical for refining the accuracy and sensitivity of these models are quantitative, and spatially well-resolved reconstructions of past changes in ocean-atmosphere carbon partitioning. At present, paleoceanographic proxies for deep ocean respired carbon storage are limited, due to multiple proxy influences and uncertainties about post-depositional alteration. We are proposing research into a newly proposed proxy for ocean respired carbon storage. This work will advance our ability to quantitatively reconstruct past carbon cycle changes in a range of deep ocean settings, and provide quantitative constraints on deep ocean respired carbon storage at the last glacial maximum (~20 ka), and penultimate glacial maximum (~140 ka).
Nitrogen Fixation in the Southeast Pacific
Ocean Data View map of excess phosphate in the Southeast Pacific
This project springs from NSF-funded work initiated by Mark Altabet (SMAST) and Tim Herbert (Brown), and my participation stems from my longstanding interest in dust and iron fertilization and my role as a Voss Postdoctoral Fellow at Brown University.
Our work uses foraminifera-bound nitrogen isotopes in planktonic foraminifera to examine whether the downwelling region of the southeast Pacific gyre may have been a ‘hotspot’ for nitrogen fixation during the last glacial maximum. Nitrogen is not biologically available in the ocean without ‘fixation’ by microbes which convert nitrogen gas to ammonium, nitrite and nitrate. In turn, these microbes require either phosphorous, iron or both. Evidence from my past work, and that of other researchers, has shown that glacial dust levels in the central and equatorial Pacific were up to three times higher than at present, suggesting that glacial iron fertilization of the southeast Pacific gyre may have stimulated biological productivity and led to carbon drawdown.