Projects

Ocean Alkalinity Enhancement Field Observations

Ocean alkalinity enhancement (OAE) adds alkaline minerals to seawater so that the ocean takes up more carbon dioxide from the atmosphere. Efficient OAE requires that the particles dissolve in the mixed layer, so their size, settling velocity, and dissolution rate are essential quantities for verifying the intervention. In October 2025 we made the first field deployment of the RTSSV particle camera in Halifax Harbour, Nova Scotia, to observe Planetary Technologies’ magnesium oxide feedstock in situ. We sampled the effluent directly at the outfall with an ex-situ chamber, profiled it near the surface and on the bottom with a gimbaled shallow-water lander carrying an ADCP and a CTD with pH and turbidity sensors, and measured background conditions far downstream.

From the tracked particles we obtain the particle size distribution, shape characteristics, and settling velocity, which can be compared with the Stokes velocity for the observed sizes. Initial results from the field and from lab experiments with the same feedstock show a dominant particle size from 7 to 20 microns. More experiments are needed to determine the dissolution rate and how the settling velocity distribution changes with time.

The campaign was a collaboration with Dalhousie University and was supported by the MIT Energy Initiative.

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Presentations

Andriatis, A., T. Peacock, R. Musgrave, and J. Ostiguy: Applying a novel instrument to study particle dynamics for near-field MRV of ocean alkalinity enhancement. Ocean Sciences Meeting, February 2026.

Andriatis, A., et al.: Constraining the effects of mixing on mCDR efficiency through near-field observations. Gordon Research Conference on Ocean Mixing, June 2026 (poster); Carbon to Sea Convening, April 2026 (poster).