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Expanding marine biogeochemical observations utilizing ISFET pH sensing technology and autonomous platforms


The ocean plays an integral role in the global carbon cycle and serves as the largest planetary reservoir for carbon. As more anthropogenic CO2 is released to the atmosphere it is essential to understand and quantify the impact of elevated pCO2 on the ocean’s role in the uptake, transfer, and transformation of carbon as well as cascading effects on biogeochemical processes. Direct observations are limited in space and time due to shortage of autonomous technology available to effectively monitor the aqueous carbon dioxide system at seasonal, interannual, and longer timescales. This dissertation describes novel sensors that are being developed and implemented to expand available marine biogeochemical observations.

The first two chapters describe the development of a solid state sensor capable of rapid and simultaneous measurement of pH and Total Alkalinity of seawater for monitoring the aqueous carbon dioxide system. This novel sensor requires no external reagents, has low power consumption, and meets the rugged demands required for integration with autonomous platforms. Chapter 1 focuses on the development and analytical assessment of the working sensor. Chapter 2 provides a more detailed description of all the processes and methods that were explored in reaching the working sensor described in Chapter 1.

Chapters 3 and 4 both use profiling floats equipped with existing biogeochemical sensing technology deployed through the Southern Ocean Carbon and Climate Observations and Modeling project to look at biogeochemical processes in the Southern Ocean. SOCCOM is a pilot program that will hopefully lead to global scale array of biogeochemical sensors on profiling floats. In Chapter 3, the influence of sea ice on the relative role of physical versus biological components of the pH and O2 signal is explored. While Chapter 3 primarily focuses on organic biogeochemical processes, Chapter 4 focuses on the role of CaCO3 reactions in the Southern Ocean carbon budget.

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