Tracer release experiments in Halifax Harbour and implications for coastal ocean alkalinity enhancement

[Geoengineering News]

https://essopenarchive.org/doi/full/10.22541/essoar.15001904/v1

Authors: Ms. Ruby M Yee, Dr. Ruth Musgrave, Dr. Dariia Atamanchuk,, Mr. Mathieu Dever et al.

https://doi.org/10.22541/essoar.15001904/v1

13 April 2026

Abstract

Seven hours-long dye tracer experiments were performed during different months and tidal phases to study the dispersion of a tracer released from a coastal outfall in the Halifax Harbour estuary, a location where alkalinity is also being added for the purpose of the carbon dioxide removal method known as ocean alkalinity enhancement (OAE). Strong stratification was found to inhibit vertical mixing, and in some instances caused tracer subduction along downsloping isopycnals. Lateral transport of the tracer was observed over O(1000 m) without appreciable dilution during one spring tide experiment when advection dominated over diffusion, although typically dilution increased with distance from the outfall. Significant spatiotemporal variability was observed during all release experiments, including filament formation in the nearfield (defined as having O(10)-fold dilution), and effects from wind- and tidally-driven sheared flows in the nearfield and midfield (defined as having O(100)-fold dilution). The dilution of the tracer plume was consistent across different days only in the ultra near- and nearfields (~20 m distance from the outfall; O(10)-fold dilution and less). Using the dilution measurements from the dye experiments, some hypothetical alkalinity releases are performed for idealized plume geometries, demonstrating that the carbon flux induced by OAE will proceed most rapidly at sites with strong lateral and minimal vertical dilution.

Source: ESS Open Archive