AUTONOMOUS MEASUREMENT OF PHYSICALLY AND BIOLOGICALLY DRIVEN CHANGES IN DISSOLVED OXYGEN IN THE NORTHERN GULF OF MEXICO

Abstract

Oceanic primary production is an important quantity that has both oceanographic and societal impacts. It forms the basis of the marine food web, and provides a pathway for carbon to be sequestered in the ocean’s interior. Despite its importance, the spatial and temporal variation of primary production in the ocean is poorly observed. This is in part because techniques for measuring production are often difficult and laborious. However, the emergence of miniaturized biogeochemical sensors and their integration into piloted and autonomous platforms such as gliders and profiling floats has opened new avenues for measuring primary production. In this thesis, I attempt to estimate primary production from measured diurnal changes in dissolved oxygen concentration in the upper ocean that were obtained by autonomous floats deployed in the northern Gulf of Mexico. I first examine whether profiling floats are a capable platform to measure diurnal changes in oxygen, and develop a novel method for correcting oxygen sensor response time in-situ. Then I characterize the various drivers, both physical and biological, that influence oxygen in this region, and evaluate if the diurnal biological signal can be observed. Analysis of the measurements is combined with a simple, one-dimensional numerical model to examine the relationship between sampling rate, sensor accuracy, and resulting estimates of primary production.