Significant discharge of CO2 from hydrothermalism associated with the submarine volcano of El Hierro Island

摘要

The residual hydrothermalism associated with submarine volcanoes, following an eruption event, playsan important role in the supply of CO2 to the ocean. The emitted CO2 increases the acidity of seawater.The submarine volcano of El Hierro, in its degasification stage, provided an excellent opportunity tostudy the effect of volcanic CO2 on the seawater carbonate system, the global carbon flux, and localocean acidification. A detailed survey of the volcanic edifice was carried out using seven CTD-pH-ORPtow-yo studies, localizing the redox and acidic changes, which were used to obtain surface maps ofanomalies. In order to investigate the temporal variability of the system, two CTD-pH-ORP yo-yostudies were conducted that included discrete sampling for carbonate system parameters. Meridionaltow-yos were used to calculate the amount of volcanic CO2 added to the water column for eachsurveyed section. The inputs of CO2 along multiple sections combined with measurements of oceaniccurrents produced an estimated volcanic CO2 flux = 6.0 105 ± 1.1 105 kg d−1 which is ~0.1% of globalvolcanic CO2 flux. Finally, the CO2 emitted by El Hierro increases the acidity above the volcano by ~20%.