The North Pacific Subtropical Gyre (NPSG) is one of largest ecosystems on Earth and plays a critical role in global ocean productivity and carbon cycling. The NPSG is also one of world’ largest oceanic desert during the summer months as a result of the ocean current circulation and enhanced stratification. The NPSG is also the home to Kīlauea volcano, one of the most active volcanoes in the world with nearly continuous seismic activity from 1983 to 2018. 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, there has yet to be a report linking volcanic ash released from Kīlauea eruptions to phytoplankton bloom in the Pacific Ocean to date especially in the nutrient-poor NPSG, despite multiple eruptions releasing large amount of volcanic ashes occurring in the past 40 years. Utilising a combination of in situ observations such as ship-based, Argo floats, satellite remote sensing and data from reanalysis products, we showcase how a volcanic ash released from Kīlauea volcano eruption in 2018 and combination of favourable atmospheric and oceanic conditions fuelled one of the largest phytoplankton blooms (> 1.5 million km²) ever detected by satellite ocean colour in the NPSG in summer. Export production esti mated from satellite data show that the 2018 bloom could remove about half of CO₂ released by the Kīlauea volcano eruption back into the ocean.

oligotrophic ocean,kilauea,summer