Date of Award
2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Oceanography
Department
Oceanography
First Advisor
Melissa Omand
Abstract
Satellites and airborne sensors reveal submesoscale (1 - 10 km) variability in ocean color in the form of filaments, eddies, and patches. The variability in ocean color is closely tied to the physical dynamics that restructure phytoplankton distributions and drive active biological responses like changes in primary productivity and community structure. As the base of the marine food web and a key component of the biological carbon pump, phytoplankton are crucial to the overall health of marine ecosystems and to the ocean's role in climate. This dissertation focuses on the use of airborne and satellite remote sensing to study the impact of submesoscale processes on phytoplankton and particulate organic carbon export.
Chapter 1 focuses on the Modular Aerial Sensing System (MASS), an airborne remote sensing platform measuring simultaneous ocean color, currents, temperature, and other variables without the spatiotemporal aliasing affecting in situ sensors. We paired concurrent snapshots of sub-kilometer kinematic properties (i.e., vorticity, divergence, and strain) with ocean color to characterize submesoscale processes influencing phytoplankton ecosystems. We developed airborne proxies of chlorophyll-a and particulate organic carbon, demonstrating that MASS is a suitable platform for capturing variability in biogeochemical parameters even without first correcting for atmospheric effects. We also explored examples of submesoscale features, with signatures in ocean color, temperature, and surface kinematics, to highlight potential impacts of submesoscale dynamics like frontogenesis and internal waves on phytoplankton distributions.
In Chapter 2, we provided novel estimates of physical particulate organic carbon (POC) flux by pairing airborne-derived vertical velocities (NASA DopplerScatt) with satellite ocean color in a seasonally re-occurring upwelling front in the central California Current System. Submesoscale vertical velocities made significant contributions to net downward POC flux (-44.1 ± 23.1 mg C m-2 day-1) and upward heat flux (186.2 ± 101.6 W m-2). Spatial distributions of instantaneous fluxes, surface kinematics, and ship-based high resolution profiles indicated that POC flux below the mixed layer was driven by frontal overturning and filament subduction. This study contributes to the understanding of how submesoscale processes modify carbon export in the highly productive California Current System. Methods can be expanded to other regions to further understand the influence of submesoscale-driven flux on the marine carbon cycle.
In Chapter 3, we shifted our focus to the satellite remote sensing of currents and ocean color in the Gulf Stream, where large energetic eddies peeling off the main current influence phytoplankton ecosystems in the Sargasso Sea. Following a cold-core Gulf Stream eddy, we diagnosed the impacts of horizontal mesoscale (10-100 km) eddy dynamics on phytoplankton patchiness and community structure by leveraging state-of-the-art satellite currents, hyperspectral data from the PACE satellite, and Lagrangian analysis. Homogenization of variance within the coherent eddy core occurred rapidly (O(days)) likely due to enhanced mixing, while in the periphery, stirring and exchange of waters with diverse geographical sources maintained high variance. Interestingly, chlorophyll-a homogenization was delayed in the core relative to a passive tracer and SST. Phytoplankton accessory pigments derived from PACE data pointed to the role of phytoplankton species succession in delaying chl-a variance homogenization, modulated by the interactions between eddy-driven and seasonal dynamics. Applying these methods to other eddies could help uncover the lateral processes responsible for the wide range of ecological outcomes often observed at eddies.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Lang, Sarah E., "SUBMESOSCALE DYNAMICS OF PHYTOPLANKTON AND CARBON EXPORT REVEALED BY HIGH-RESOLUTION AIRBORNE AND SATELLITE REMOTE SENSING OF CURRENTS AND OCEAN COLOR" (2026). Open Access Dissertations. Paper 4585.
https://digitalcommons.uri.edu/oa_diss/4585