Geostationary satellite reveals increasing marine isoprene emissions in the center of the equatorial Pacific Ocean

Isoprene is the most abundant non-methane biogenic volatile organic compound in the Earth's atmosphere and has the potential to influence photochemistry in the remote ocean-atmosphere. Marine isoprene emission estimates vary over multiple orders of magnitude using different methods, and the paucity of continuous in-situ measurements makes it challenging to distinguish their spatiotemporal variations. Here we present marine isoprene emission estimates inferred from Himawari-8 observations and model simulation covering the western Pacific Ocean and the eastern Indian Ocean. Although most isoprene emission hotspots were near coasts, we found an unexpected emission pool in the center of the equatorial Pacific Ocean with 18% higher emissions than those in the North and South Pacific Oceans. Remarkably, the isoprene emissions increased by 5.5 ± 0.1% per year in the center of the equatorial Pacific Ocean between August 2015 and December 2020, while no significant trend for emissions in other ocean regions. We investigated marine isoprene oxidation impacts based on satellite observations, and the results suggest NO2 may play a critical role during aerosol formation from isoprene in the remote ocean air.

Wentai Zhang, Dasa Gu