Observing biogeochemical cycles at global scales with profiling floats and gliders

Abstract

This Ocean Carbon and Biogeochemistry (OCB) Scoping Workshop focused on the implementation of a long-term observing system for marine biogeochemistry using chemical and biological sensors deployed on autonomous platforms, such as profiling floats, gliders or other long-endurance autonomous vehicles. Several chemical and biological sensors can now be deployed for months to years in the ocean on floats and gliders. These systems are becoming sufficiently affordable that it is possible to envision biogeochemical sensor networks with hundreds of nodes or more, similar to the current Argo network of 3000 floats. This will allow the development of basin-scale and, ultimately, global-scale observing systems. These sensor networks will permit ocean scientists to quantitatively observe fundamental biogeochemical processes such as rates of nutrient supply, net community production, physical controls on bloom development (e.g. the Sverdrup Hypothesis), dynamics of oxygen minimum zones and their impacts on denitrification, and carbon export throughout the ocean with a level of detail hitherto impossible. The spatial and temporal responses of these processes to climate oscillations and greenhouse gas forcing will be observed with a resolution that is simply not possible when observations are limited to ships. An integrated observing system that combines in situ sensors deployed on long endurance platforms with satellite sensors and data-assimilating, biogeochemical-ecological models would provide previously unachievable constraints on the carbon cycle and its sensitivity to a changing climate. It would transform ocean biogeochemistry.

These capabilities are developing rapidly but they are not yet widely appreciated by the ocean science community. This Scoping Workshop had four specific goals: 1) to provide carbon cycle scientists with a critical review of currently existing technologies, their strengths, their weaknesses, and expected developments, 2) to identify problems that can only be solved with these types of observations over several years and to then discuss experiments that could be implemented in the near-term to address these topics, 3) to outline the requirements for a long-term observing system based on in situ sensors, satellites and data-assimilating models to monitor biogeochemical processes on a global scale, and 4) to identify factors limiting development of proven sensors and unmet technical developments required to expand our capability to an integrated observing system.