Project: Carbon Sedimentation In the Ocean Watercolumn (C-SNOW): Calibration

NSF Award Abstract:

Carbon sedimentation (10 Pg C/year) via the ocean biological carbon pump is important to the regulation of atmospheric CO2, yet is poorly observed in space and time due to limitations of current methodology (moorings/ships), and thus is poorly understood and consequently is poorly represented in carbon cycle simulations. Current estimates of the strength of the ocean biological carbon pump are highly uncertain. The one year project will deploy and calibrate low-cost robotic ocean-profiling current-following Carbon Flux Explorers (CFEs) which is a necessary step paving the way high frequency broad scale monitoring and prediction of carbon sedimentation in the ocean. Project scientists will work with the San Francisco Exploratorium to enhance public knowledge of the ocean carbon cycle, ocean robotics. UC Berkeley undergraduate students will be exposed to this research activity in the class-room, as laboratory assistants, and in hands-on experience at sea.

The CFEs represent the integration of an ocean profiling float-- similar to those widely deployed in the ocean as part of the ARGO program-- with the UC Berkeley / Lawrence Berkeley National Laboratory - developed Optical Sedimentation Recorder (OSR). The CFEs dive to depth and the OSR uses a camera and three modes of illumination to image particles over time as they accumulate in a sediment trap. Periodically the sample is removed and the imaging resumes. The use of transmitted, transmitted cross-polarized transmitted, and side illumination permits three modes of quantification sample loading as measured sample attenuance, sample cross-polarized photon yield, and sample reflectance. The project specifically aims to relate the three optical metrics of sample load to the amount of particulate organic carbon, particulate inorganic carbon (also known as calcium carbonate), and other biogenic particle phases. Thus, the development will demonstrate the ability of the Carbon Flux Explorer to measure the strength of carbon sedimentation in the ocean. In a one year project. Scientists at University of California, Berkeley and engineers at Lawrence Berkeley National Laboratory and Scripps Institution of Oceanography will build/modify 2 Carbon Flux Explorers to enable the collection of samples for their calibration. These and two other CFEs and a surface tethered OSR will be co-deployed during an oceanographic expedition in California coastal and offshore waters. Collected samples will be analyzed and compared with the optical metrics of sample load, collected at the same time. The project will thus meet its major goal of demonstrating that the CFEs can measure the strength of ocean carbon sedimentation as a function of depth, time, and ocean location, in a way here-to-fore impossible to achieve from ships.