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Computational Analysis of the Biophysical Controls on Southern Ocean Phytoplankton Ecosystem Dynamics

Tyler Rohr, Ph.D., 2019
Scott Doney, Advisor
David Nicholson, Advisor

Southern 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, 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. Chapter 4 goes on to describe how anomalous division rates combine with anomalous loss rates and physical transport (i.e. dilution, stirring, advection) to drive anomalous biomass. 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.