Kı̄lauea Volcanic Ash Induced a Massive Phytoplankton Bloom in the Nutrient-Poor North Pacific Subtropical Gyre

Abstract

Kı̄lauea volcano is one of the most active volcanoes in the world with nearly continuous seismic activity from 1983 to 2018. In May 2018, the Kı̄lauea volcano erupted and released volcanic ash into the atmosphere. Carried by easterly winds, the volcanic ash plume dispersed westward and by June 2018, the plume was observed over the central part (150$${}^{\circ}$$E to 160$${}^{\circ}$$W) of the nutrient-poor North Pacific Subtropical Gyre (NPSG). Coincident with precipitation during the same period, anomalously high dust deposition comprised mostly of wet dust was observed over the same region. Consequently, patches of high chlorophyll $$a$$ (chl $$a$$) waters were observed approximately 5$${}^{\circ}$$ north of the high dust deposition area from the middle of June to early August 2018 via satellite images. The phytoplankton bloom peaked in July encompassing $${ >} $$1.5 million $${\text{km}}^{2}$$, about 5 or 50 times the size of Malaysia or Taiwan, respectively. In addition to the large dust deposition, shoaling of the mixed layer in the range of 25–50 m is believed to have concentrated the bloom within the optical depth detected by satellite. Net primary production and export production estimated from satellite observations show that the July 2018 bloom generated an additional 1.91 Tg C of net carbon production, and 0.34 Tg C was exported from the euphotic zone.

Key Points

• A rare and massive (>1.5 million km²) summertime phytoplankton bloom was observed in the nutrient-poor North Pacific Subtropical Gyre in the summer of 2018

• The bloom was related to the ash deposition released from the Kı̄lauea volcano located approximately 2,000 km east of the bloom

• Easterly winds, coincident precipitation, and wind induced Ekman transport were the potential mechanisms driving and sustaining the bloom

Plain Language Summary

Deposition of ash released from volcano eruptions have been showed to be capable of enriching surface ocean waters with nutrients such as iron and phosphorus. However, to date there has yet to be a report linking volcanic ash released from Kı̄lauea eruptions to phytoplankton blooms in the Pacific Ocean, despite being one of the most active volcanoes in the world with multiple eruptions in the past 40 years. In this study, we show how volcanic ash released from Kı̄lauea eruption in 2018 and favorable atmospheric and oceanic conditions fueled a massive phytoplankton bloom in the nutrient-poor North Pacific Subtropical Gyre, one of Earth's largest oceanic deserts. Export production estimated from satellite data show that the 2018 bloom could remove about half of $${\text{CO}}_{2}$$ released by the Kı̄lauea volcano eruption back into the ocean.