Menu
Research
Nutrient Dynamics in the Western Pacific Warm Pool (WPWP) across the Mid-Pleistocene Transition (MPT)
Nutrient Dynamics in the Western Pacific Warm Pool (WPWP) across the Mid-Pleistocene Transition (MPT)
The overall objective of this project is to investigate changes in primary productivity and nutrient dynamics in the WPWP during the MPT (1.5 – 0.8 million years ago), a period of time in which the pacing of global ice ages shifted from every 40,000 years to every 100,000 years. The waxing and waning of global ice sheets are controlled in large part by changes in the geometry of the Earth’s orbit around the sun; however, changes on the 100,000-year period have comparatively little influence on the amount or spatial distribution of energy we receive from the sun relative to the other orbital changes. The dominance of this 100,000-year signal in recent (< 1 million years) climate records is known as the “100-kyr problem,” and indicates the importance of feedbacks (changes in ocean circulation, biological productivity, carbon transfer, greenhouse gases, etc.) to our climate system. Of particular interest is the idea that climate sensitivity, or the temperature increase in response to a doubling of CO2, may have varied in the past (and may vary in the future). The primary tools for investigating nutrient dynamics in the marine sediment record are proxies of productivity (%total organic carbon, %calcium carbonate, %opal), and nutrient cycling and source (stable isotopes of nitrogen and carbon).
|
Foraminiferal shell weight as a proxy for changing ocean chemistry
Utilizing microfossil shells collected in sediment traps and sediment cores from two regions that are a) highly productive, coastal upwelling zones and b) sensitive to changes in ocean chemistry, I am using a simple, non-destructive proxy (individual foraminiferal shell weight) to quantify changes in ocean carbon chemistry (i.e. CO2) in both the recent (decades) and geologic past. Foraminifera are heterotrophic protists that secrete a shell made of calcium carbonate (CaCO3). Their shell chemistry and formation are both highly sensitive to changes in ocean pH and the speciation of dissolved CO2 in seawater, with shell weight demonstrated to decrease as ocean pH decreases.
|
Benthic foraminifera as indicators of estuarine ecosystem health
In Summer 2019, I began a new collaboration with researchers at the Baruch Marine Field Laboratory (BMFL) that utilizes microfossils and sediment geochemistry to study climate and environmental changes in salt marsh ecosystems. Benthic foraminifera community composition and diversity are largely controlled by environmental parameters such as salinity, bottom water oxygenation, and nutrient concentration. These parameters, in turn, are influenced by anthropogenic activities. Thus, our faunal assemblages provide time-averaged estimates of estuarine health related to human activity. Benthic foraminifera are also sensitive to sea level (essentially, water depth), and can be used to reconstruct short-term (decades to centuries) sea level change rates that can be used to indicate rates of natural (pre-industrial) vs. anthropogenic (post-industrial) change. This project involves field (North Inlet, Murrell’s Inlet, ACE Basin) and lab with multiple field seasons and analyses of faunal composition, water and sediment geochemistry.
|