Detection of the 2012 Havre submarine eruption plume using Argo floats and implications for vertical ocean mixing by submarine eruptions

Tushar Mittal, Penn State, Earth and Planetary Science, University Park, United States and Brent G Delbridge, Harvard University, Earth and Planetary Sciences, Cambridge, MA, United States
More than 85% of the Earth’s volcanism and geothermal heat release occurs underwater at mid-ocean ridges, intra-plate hotspots, and oceanic island arcs. However, we lack a clear understanding of how a submarine eruption interacts with the overlying water column, the structure of the submarine eruptive plume, and the transport of volcanic products in the ocean by these plumes. A useful test example to study some of these processes is the Havre Submarine Caldera eruption in 2012 from ~900 m water depth which produced a > 1 km3 pumice raft at the surface as well as a weak subaerial plume. We describe here the detection of eruption-derived temperature increase and salinity decrease from the 2012 Havre submarine caldera eruption (eruption at ~900 m water depth) by an existing array of temperature/salinity profiling floats, known as Argo. The Argo floats observed the signal, significant at >3 sigma level with respect to the background ocean variability (noise), at ocean depths of ∼1750–2000 m deeper than the eruptive vent itself. In order to understand this signal, we develop a new conceptual and numerical submarine plume model which suggests that the sub-vent level temperature and salinity anomalies are caused by large-scale ocean mixing induced by the eruptive plume, rather than heating directly from the eruption. Our results show that submarine eruptions can efficiently advect water masses from the deep ocean closer to the surface and form multiple subsurface intrusions during the process with observable anomalies on 100's of km scale. Finally, we use a model parameter space exploration to quantify the efficiency of submarine eruptive as well as hydrothermal plumes for vertical transport in the ocean for a variety of buoyancy fluxes and provide a global budget of the importance of subaqueous volcanism on ocean mixing and nutrient supply in the modern time-period as well as time-periods in Earth history with significant underwater eruptions e.g. submarine Large Igneous Provinces such as the Ontong Java plateau. Our results and observations suggest that submarine volcanism associated plumes can initiate significant vertical ocean mixing, a process with significant implications for both long- and short-term influence of submarine volcanism on ocean chemistry, dynamics, and ecology.