Submarine Volcanism

More than 2/3 of volcanic eruptions on Earth are thought to occur underwater. Case studies show that these submarine eruptions significantly affect ocean ecosystems while posing an acute hazard to hundreds of millions of people living in volcanic tsunami zones. However, over the past 100 years, less than 10% of known eruptions were submarine, primarily due to limited detection capability. Consequently, submarine eruptions are poorly understood, especially their influence on global ocean bio-geochemistry, deep ocean circulation, and long term climate. My research addresses two questions: How do we detect submarine eruptions, and test theoretical models of eruption dynamics? How do their heat and nutrient emissions affect the ocean-atmosphere system and the biosphere?

My group and I use various remote sensing analyses and Earth system models to understand how submarine eruptions affect ocean productivity, ecosystems, and the global climate8,9. We have developed two techniques to detect previously unknown submarine eruptions as they occur: identifying deep ocean eruptive plumes using Argo floats (global autonomous temperature/salinity measurements) and finding eruption products (pumice rafts, hydrothermal fluids, aerial plumes) in satellite imagery via machine learning (ML) algorithms. Using the Argo technique, I made the first in-situ measurements of how the plume from a known submarine eruption affected water properties and dynamics [Mittal & Delbridge 2019]. With my ML algorithm, I detected multiple new pumice rafts. My analysis of these results has significantly advanced our understanding of raft behavior and longevity [Zheng, Mittal, et al., 2020] and has the potential to provide near real-time tracking of rafts from satellite imagery. This has important utility both from a biogeochemical perspective (understanding nutrient and marine species transport by rafts) and for human hazards associated with large rafts.

Me and my group am also currently developing novel ML/AI computational methods to detect and characterize products of submarine eruptions (pumice, hydrothermal fluids) using the analysis of satellite image data (ultra high-resolution satellites to geostationary), seismic/hydroacoustic data, and oceanographic datasets (temperature, salinity depth profiles) jointly. 

In work led by my postdoc, we used a range of satellite datasets to develop a multi-week eruption timeline (plume heights and volume fluxes) for the Hunga Tonga 2022 eruption [Gupta .. Mittal et al. 2022; Fauria .. Mittal et al. 2023 - similar analysis for another eruption] as well as quantify the eruption’s radiative response over the last two years (due to stratospheric water, aerosol, and ozone) [Gupta, Mittal, et al. 2024, in review] Our results help provide an excellent observational constraint on how a large submarine eruption can affect the climate and provide a basis for calibrating climate models.  

In parallel, my group and I are working on developing eruption plume models – both in the water column (1D to 3D rotational fluid dynamics) and in the atmosphere – to understand how submarine eruption dynamics vary for a range of volcanic heat and fluid fluxes, including the role of water in controlling aerial plume height of underwater eruptions. Combining models and data analysis would provide ground truth testing to calibrate models and understand how submarine eruptions affect the ocean environment. Overall, this work has exciting implications for the effects of large submarine eruptions on the ocean and climate, especially in deep time and in other planetary settings, e.g., icy ocean worlds (Europa, Enceladus).

Selected References : 

(I) Eruption chronology of the December 2021 to January 2022 Hunga Tonga-Hunga Haapai eruption sequence., Ashok Gupta, Ralf Bennartz, Kristen Fauria, Tushar Mittal, Communications Earth & Environment, 3(1), 314. 2022

(ii) Detection of submarine eruptions using Argo floats and its implications for ocean dynamics, Tushar Mittal, and Delbridge, Brent, EPSL 511, 105-116 2019

(iii) Pumice Raft Detection Using Machine-Learning on Multispectral Satellite Im-

agery, Maggie Zheng, Tushar Mittal, Kristen Fauria, Ajit Subramaniam, Martin

Jutzeler Front. Earth Sci., Sec. Volcanology 2022

(iv) Simultaneous creation of a large vapor plume and pumice raft by the 2021 Fukutoku-Oka-no-Ba shallow submarine eruption, Kristen Fauria, Martin Jutzeler, Tushar Mittal, Ashok Gupta, Liam Kelly, John Rausch, Ralf Bennartz, Brent Delbridge, Lise Retailleau, Earth and Planetary Science Letters, 609, 118076. 2023

(v) Ash deposition triggers phytoplankton blooms at Nishinoshima Volcano, Japan, Liam James Kelly, Kristen E Fauria, Tushar Mittal, Jan Riad El Kassar; Ralf Bennartz; David Nicholson; Ajit Subramanian; Ashok Kumar Gupta, Geochemistry, Geophysics, Geosystems 24, no. 11 (2023): e2023GC010914. 2023

(vi) The January 2022 Hunga eruption cooled the southern hemisphere in 2022, Ashok Gupta, Tushar Mittal, Kristen E. Fauria, Ralf Bennartz, and Jasper F. Kok, Communications Earth & Environment (in revision) 2024

Key research questions: What are the dynamics of submarine volcanism & their environmental effects?​​