Integrating marine geochemistry, physical dynamics, and volcanology in the geological record: an Oceanic Anoxic Event 2 case study
PI: Isabel Fendley (Geosciences)
Plan for funding tuition for graduate students, or the remainder of the researcher’s salary for postdoc and research faculty: If graduate student: partial TA position and/or start up funds, or summer only. If postdoc: The postdoc would be expected to have additional funding sources already in place.
Past large climate perturbations are our best analog for modern climate change and aid in understanding how the Earth system responds to major carbon cycle changes. They are also our closest analogs to assess various strategies for large-scale carbon dioxide removal. The Cretaceous Period was punctuated by repeated, large-scale volcanic events that released massive amounts of carbon to the atmosphere. The geological record preserves both an imprint of these volcanic emissions and their associated global consequences as well as environmental recovery. One such event, the Cenomanian–Turonian Oceanic Anoxic Event (OAE2, ~94 Ma), is marked by a positive global carbon isotope excursion, the result of increased biological productivity, organic matter burial, and widespread oceanic anoxia. Like several other oceanic anoxic events, OAE2 is thought to have been driven by large igneous province (LIP) volcanism which released large volumes of CO2 and affected ocean dynamics..
Several LIPs around the world were active during this time interval, including the Kerguelen Plateau in the southern Indian Ocean, the High Arctic LIP, and the Caribbean LIP; however, the respective role of each LIP in driving OAE2 climatic change remains elusive. Recent work has used several geochemical proxies, including mercury (Hg), osmium (Os), strontium (Sr), and chromium (Cr) concentrations and their isotopic compositions, to constrain the timing, intensity, and location of LIP activity. However, these datasets have markedly different signals across OAE2: for example, Hg concentration datasets are extremely variable in both the presence and magnitude of anomalies and Os isotope records exhibit differing numbers of volcanic pulses. It is thus currently unclear whether these proxy records are consistent with the same underlying volcanic activity or are affected by local or regional oceanographic processes.
The proposed work would address two primary sources of uncertainty: 1) Each geochemical system reflects different aspects of LIP volcanic activity over time. Hg is dominantly released through volcanic degassing, whereas Os, Sr, and Cr are all released via hydrothermal fluids and/or by weathering of volcanic material, which is a slower and longer duration event. 2) Spatial variability in each of these signals is likely significant since the time resolution of the datasets is shorter than ocean mixing timescales. Thus, the volcanic proxy values are not globally homogenized for each record. The same LIP activity, therefore, would result in different signals preserved in different records spatially worldwide.
For this project, the junior researcher will develop a computational framework to integrate geochemical models for each of the key proxies (Hg, Os, and Sr). Global box models exist for each of these systems individually; however, they are currently at different time resolutions and set up in different computational languages and input formats (or exist only as equations). This combined framework is necessary to make sure that we can use consistent model inputs based on volcanological constraints, and then evaluate whether the outputs are consistent with observed proxy data.
Furthermore, a critical computational focus for the researcher would be incorporating first-order physical ocean dynamic models (both surface and deep ocean circulation), along with marine carbon cycle geochemistry (e.g., pH, temperature). The late Cretaceous world had a different continental configuration and ocean bathymetry than the modern Earth, so the ocean circulation is expected to be different, especially transport between different ocean basins. Furthermore, since OAE2 is potentially associated with multiple contemporaneous LIPs in different parts of the world, an accurate circulation model is needed to determine their varying levels of influence on the observed proxy data.
In parallel, the researcher will work with the PI to compile published volcanic proxy data (Hg, Os, Sr, Cr) from OAE2 sites around the world, as well as chronological constraints on emplacement for each of the relevant LIPs. The team will evaluate the OAE2 multiproxy compilation dataset in the context of varying sources of volcanic materials and sediment accumulation rates/lithological transitions.
The integrated model framework that this project aims to create will be a key tool for paleoclimate researchers as presently, there is no method to simultaneously evaluate these proxies for multiple volcanic processes (gas emissions, weathering). As LIP gas emissions are an analogue for anthropogenic carbon emissions, and LIP weathering is an analogue for carbon sequestration techniques, this combined framework will transform our understanding of major carbon cycle changes in the Earth system.
Level of effort: 1 year of graduate student funding @ 25% effort, or 2 summers or equivalent postdoc effort
Specific areas of computational and/or data science expertise or skills needed: Experience with Python required. Some experience with geochemical box models or circulation models, as well as geological background knowledge, is a plus.
Requirements or expectations of ICDS Junior Researcher: Experience working with geochemical datasets and the rock record. Availability to meet regularly with PI.
Specific objectives supported by this call: Integrate existing geochemical box models together to simultaneously evaluate multiple chemical systems, including first-order ocean circulation/spatial dynamics.
Medium to long term goal: Use results from this study to submit a collaborative proposal to NSF Marine Geology & Geophysics or NOAA Ocean Acidification Program
Statement explaining the connection of the project to ICDS’s mission: This project is led by a new (early career) Penn State faculty member. The proposed research is interdisciplinary and would lead to the development of advanced computational tools that can be used by geoscientists and volcanologists to understand the global effects of volcanic impacts in Earth history. The project also aligns with ICDS’s mission to combine topic expertise (in this case volcanology, geochemistry, and Earth history) with advanced computational and data science approaches. The tools developed in this project would be of broad use for the paleoclimate community.
Team member’s recent and/or planned engagement with ICDS: I (Fendley) am not currently associated with ICDS but I am a new faculty member at PSU. My research involves using computational techniques to understand geochemical changes in Earth history, and I look forward to collaborating with ICDS, especially using the various resources for research (both active projects and future proposals) as well as teaching activities.