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dc.contributor.authorRohr, Tyler  Concept link
dc.date.accessioned2019-02-06T14:37:26Z
dc.date.available2019-02-06T14:37:26Z
dc.date.issued2019-02
dc.identifier.urihttps://hdl.handle.net/1912/23631
dc.descriptionSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Applied Ocean Science & Engineering at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2019.en_US
dc.description.abstractSouthern Ocean net community productivity plays an out sized role in regulating global biogeochemical cycling and climate dynamics. The structure of spatial-temporal variability in phytoplankton ecosystem dynamics is largely governed by physical processes but a variety of competing pathways complicate our understanding of how exactly they drive net population growth. Here, I leverage two coupled, 3-dimensional, global, numerical simulations in conjunction with remote sensing data and past observations, to improve our mechanistic understanding of how physical processes drive biology in the Southern Ocean. In Chapter 2, I show how different mechanistic pathways can control population dynamics from the bottom-up (via light, nutrients), as well as the top-down (via grazing pressure). In Chapters 3 and 4, I employ a higher resolution, eddy resolving, integration to explicitly track and examine closed eddy structures and address how they modify biomass at the mesoscale. Chapter 3 considers how simulated eddies drive bottom-up controls on phytoplankton growth and finds that division rates are, on average, amplified in anticyclones and suppressed in cyclones. Anomalous division rates are predominately fueled by an anomalous vertical iron flux driven by eddy-induced Ekman Pumping. Chapter 4 goes on to describe how anomalous division rates combine with anomalous loss rates to drive anomalous net population growth. Biological rate-based mechanisms are then compared to the potential for anomalies to evolve strictly via physical transport (i.e. dilution, stirring, advection). All together, I identify and describe dramatic regional and seasonal variability in when, where, and how different mechanisms drive phytoplankton growth throughout the Southern Ocean. Better understanding this variability has broad implications to our understanding of how oceanic biogeochemisty will respond to, and likely feedback into, a changing climate. Specifically, the uncertainty associated with this variability should temper recent proposals to artificially stimulate net primary production and the biological pump via iron fertilization. In Chapter 5 I argue that Southern Ocean Iron Fertilization fails to meet the basic tenets required for adoption into any regulatory market based framework.en_US
dc.description.sponsorshipThe CESM project is supported by the National Science Foundation and the Office of Science (BER) of the U.S. Department of Energy. Computing resources were provided by the Climate Simulation Laboratory at NCAR’s Computational and Information Systems Laboratory (CISL), sponsored by the National Science Foundation and other agencies. This research was enabled by CISL compute and storage resources. TR was supported by an NDSEG graduate fellowship. TR and SCD acknowledge support from the National Aeronautics and Space Administration Ocean Biology and Biogeochemistry Program (NNX14AL86G). TR, SCD and MTK acknowledge support from the National Science Foundation Polar Programs award 1440435 (Antarctic Integrated System Science) to the Palmer LTER program. Please contact trohr@mit.edu for further questions or to access to data.en_US
dc.language.isoen_USen_US
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen_US
dc.relation.ispartofseriesWHOI Thesesen_US
dc.titleComputational analysis of the biophysical controls on Southern Ocean phytoplankton ecosystem dynamicsen_US
dc.typeThesisen_US
dc.identifier.doi10.1575/1912/23631


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