Biogeochemical In Situ Observations – Motivation, Status, and New Frontiers

We begin this chapter on in situ biogeochemical observations by presenting the three major areas of societal benefit related to ocean observations: climate, operational ocean services, and ocean health. Biogeochemistry constitutes a varying proportion of each of these areas, while climate and ocean health benefit more from sustained flow of accurate information than operational ocean services. Once the societal drivers are presented, we focus on identifying the relevant phenomena that need quantifying. These phenomena are closely related to the scientific dimension, which helps to establish specific observing targets and observing system design. Scales, seasonality, and geographic limitations are briefly discussed. Consideration is also given to the fact that often a given biogeochemical phenomenon is primarily driven by physical processes (e.g., ventilation, air-sea fluxes) or biological and ecosystem mechanisms (e.g., organic matter cycling, eutrophication) and, therefore, parameters across all three disciplines ought to be measured. Next, we provide an overview of the current capabilities of the global ocean observing system (GOOS) for biogeochemistry. The capacity is considered as an ability (or lack thereof – a gap in capacity) to address the requirements stated in the earlier part of the chapter. A holistic approach to thinking about platforms and sensors is presented. In the following section, the data quality requirements and efforts, as well as data management practices are briefly explained. There has been a strong, long-standing effort among the carbon and biogeochemical observationalists to make biogeochemistry data not only freely available, but also quality-controlled and inter-comparable. These grassroots efforts eventually led to the successful creation of two information products: SOCAT and GLODAP, which are predominantly carbon-focused and represent almost exclusively ship-based, benchtop instrument-based observations. We also discuss an urgent need to expand biogeochemical data availability, quality control, and inter-comparability beyond carbon parameters and onto a wider suite of available platforms and observing techniques (sensors). Finally, to the extent possible, a perspective on existing and planned prototype technology is provided.