A technique presented in Nature Communications this week may help predict the dispersal and drift patterns of large pumice rafts. The ability to pre-empt where these rafts will end up could give enough advance warning for protective measures to be put in place on shipping routes or in harbours where the presence of pumice is hazardous.
Pumice rafts are large mobile floating accumulations of pumice fragments generated by oceanic volcanic eruptions; these rafts can disrupt shipping routes and damage vessels. An eruption at certain underwater seamounts or volcanic island can generate a thick raft that may spread to affect a considerable area of the ocean, disrupting maritime industries for months or even years. Martin Jutzeler and colleagues simulated the drift of a massive 400km2 raft of pumice from Havre, a deep submarine volcano in the southwest Pacific, using a high-resolution model of global ocean circulation. They then tested the results against satellite imagery plus direct observations from sailing crews. The team show that they can accurately reproduce surface drift using this method and note that this large-scale natural experiment validates the physics of the model.
For future eruptions that produce potentially hazardous pumice rafts their technique will allow forecasts of dispersal routes, mitigating potential risks to ships and allowing authorities to protect harbours. The same high-fidelity particle tracking can also be used to predict the spread of other floating objects in surface ocean waters, such as anthropogenic waste or passively drifting organisms.