Tinna Jokulsdottir
Graduate Student
Office: HGS 429
Phone: (773) 795-6696
E-mail: tinna at uchicago.edu
My research interests are focused on furthering our understanding of the ocean carbon cycle and how it will respond to global warming. Feedbacks and interaction between different processes in the ocean are complex. How they work together is fascinating to me. Using the particle model I developed during my graduate studies, I am studying the biological pump, looking at how changes in environmental parameters such as SST, pH, ecological structure and productivity affect how much organic carbon reaches the seafloor.
My model is a stochastic, particle-resolved model that includes the main processes affecting transport of material down the watercolumn. Briefly, coagulation and disaggregation occur stochastically according to probabilities calculated theoretically. Organic carbon is both respired by bacteria and zooplankton. An ecological model predicts zooplankton biomass but zooplankton encounter with particles is determined stochastically. Dissolution of calcium carbonate and opal is due to thermodynamics and some calcium carbonate also dissolves in the guts of zooplankton. Particle properties such as their fractal dimension, porosity and sinking velocity are calculated for each modeled particle. By including as many processes as possible that affect the sinking particles, we hope to learn more about the importance of individual processes and the effect on the whole system when one process is altered due to changes at the surface.
I am interested in coupling my model to other models and to think about the possibility of imbedding this model into a GCM and then what kind of simplifications would be necessary. In my graduate program I coupled the particle model to Archer’s sediment calcite dissolution model to look at how the lysocline is affected by different surface conditions. Below are some of my ideas for future research. Although they focus on using this model I am open to and interested in working with other models.
Thorium-234 is a short lived, particle-reactive isotope that has been used to study aggregation and fragmentation of particles (Cochran et al., 1993). Th-230 is also particle reactive but its half-life is on the order of glacial cycles. I would like to add these two isotopes to the model and compare concentrations on different sizes of particles to measurements to learn more about particle cycling in the ocean. A conundrum in glacial sediment layers is a focusing of Th-230 that occurs at the equator (Kienast et al., 2007). Th-230 could be used to investigate how particle cycling and upwelling circulation at the equator play a role in this focusing.
Blooms appear to be responsible for a large fraction of the sedimentation of material over a year, especially in high latitudes. At the end of a bloom when nutrients are low phytoplankton produce TEP which aids aggregation and promotes sedimentation (Engel, 2004). It has been suggested that spring blooms occur in cold waters where metabolic rates in microzooplankton are low enough so they can not keep up with phytoplankton growth (Rose and Caron, 2007). This is an area of study that requires further analysis to which my model is well suited.
One big advantage of particle-resolved models is that variability in chemical composition of the particular matter is more easily resolved. These types of models are used in different fields like astrophysics, atmospheric chemistry and now oceanography. I am looking to collaborate with scientists in other fields to fine-tune the method so that it is more efficient and easily accessible to others.
I am currently looking for a post-doctoral research position to continue working on biogeochemical cycling in the ocean.
