Expanding OCO‐2's Volcanic Observation Record to the Low‐Intensity 2021 Fagradalsfjall and the Ninth Sundhnúkur Crater Row Eruptions

Abstract Since 2021, Iceland experienced 12 volcanic eruptions, all located on the Reykjanes peninsula. From these events, the 2021 Fagradalsfjall and the ninth Sundhnúkur crater row (16 July–5 August 2025) eruptions were detected by the Orbiting Carbon Observatory‐2 (OCO‐2). This study uses the OCO‐2 column‐averaged dry‐air mole fractions of () to compare the plume characteristics of both events. The Fagradalsfjall eruption produced a remarkably small enhancement of ∼ 0.5 ppm, demonstrating that sub‐ppm volcanic signals can be observed with OCO‐2. Thereafter, the estimated flux from Fagradalsfjall was 53.4 which is larger than ground‐based estimates (5–20 ), due to parameter uncertainties, unaccounted additional sources, and observational constraints. In contrast, due to cloud cover, the flux from Sundhnúkur could not be reliably quantified. However, this second case is informative regarding the limits of OCO‐2 for localized point sources in the high north. These events represent the third and fourth analyses of volcanic emissions observed by OCO‐2 since its launch in 2014, and add important insights for quantification of such natural sources.