Periodic Reporting for period 3 - CarbOcean (An integrative approach to unravel the ocean's biological carbon pump)
Reporting period: 2024-05-01 to 2025-10-31
The ocean’s biological carbon pump plays a crucial role in storing atmospheric carbon dioxide in the deep ocean, thereby isolating carbon from the atmosphere for decades to centuries. Yet, its capacity to do so is under-constrained and its mechanisms poorly understood. CarbOcean aims to develop a mechanistic and quantitative understanding of the biological carbon pump using a novel integrative approach that accounts for its two component pumps: (1) the organic carbon pump, which concerns the photosynthetic production of particulate organic carbon, POC, and (2) the carbonate pump, which concerns the production of particulate inorganic carbon, PIC. The differentiation between these components pumps is important as they have opposite effects on the ocean-atmosphere exchange of carbon dioxide.
Since the beginning of the project 30 months ago, the CarbOcean team has made signigicant strides forward in the development of an autonomous sensor for the measurement of PIC in seawater. We have proven the PIC sensor measurement concept based on depolarization of scattered light in the laboratory using suspensions of cultured calcifying phytoplankton that produce the PIC material that the sensor aims to detect in the real ocean. We have further developed novel optical models for light depolarization by randomly oriented PIC particles and found good agreement with our experimental results. We have also developed a way to calibrate the PIC sensor using tilted glass plates and experimentally validated the procedure, demonstrating agreement between optical theory and experimental results. Our results so far have been communicated in three peer-reviewed papers and the intellectual property generated has been protected by a patent.
CarbOcean is breaking grounds through the development of the PIC sensor, enabling autonomous observations of PIC (and POC) for the first time. Integration of this breakthrough technology onto robotic ocean profilers will provide the profilers with a unique capability to simultaneously observe the two components of the biological carbon pump over a continuum of spatiotemporal scales. We expect to deploy a pilot array of such robotic profilers allowing us to come up with an entirely new way of observing and quantifying the components of the biological carbon pump. New parameterizations of the carbon pump processes and their environmental drivers will be developed for implementation into biogeochemical models and links will be examined between deep carbon fluxes and remote sensing data potentially enabling to scale up observations.