In situ floe settling velocities and diameters of particles ranging in size from 0.63 to 5.05 mm equivalent circular diameter were measured under a buoyant discharge plume by deploying a bottom-tripod-mounted Floe Camera Assembly (FCA) in Tarr Inlet. Glacier Bay. Alaska. These observations were used to estimate floe effective densities. Three results emerge from this work. First, fits of settling velocity and effective density to diameter are consistent with expressions published for other environments, suggesting that common controls on floe size and settling velocity operate across diverse marine environments.
Second, the raw data show considerable scatter, with upper and lower 95% prediction intervals on settling velocity and excess density differing by about a factor of 7. Analysis of sources of error suggests that the variability is caused by differences in component-grain composition among floes and turbulent stirring within the stilling box. Third, bin-averaged effective densities and settling velocities are highly correlated with diameter. Thus, while it is not possible, based on diameter. to predict accurately the settling velocity of a single floe, it is possible to estimate the mean settling velocity of a population of like-sized floes.