Computational analysis of the biophysical controls on Southern Ocean phytoplankton ecosystem dynamics

• Main Author: Rohr, Tyler W.
• Other Authors: Scott Doney and David Nicholson., Joint Program in Oceanography/Applied Ocean Science and Engineering., Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences., Woods Hole Oceanographic Institution., Joint Program in Oceanography/Applied Ocean Science and Engineering, Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences, Woods Hole Oceanographic Institution
• Format: Thesis
• Language: English
• Published: Massachusetts Institute of Technology 2019
• Subjects: Joint Program in Oceanography/Applied Ocean Science and Engineering; Earth; Atmospheric; and Planetary Sciences; Woods Hole Oceanographic Institution; Plankton; PlanktonGrowth; Phytoplankton; Chemical oceanography; Southern Ocean
• Online Access: https://hdl.handle.net/1721.1/122325

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2019 Cataloged from PDF version of thesis. Includes bibliographical references (pages 193-220). 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 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 ...