Volatile fluxes integrated over four decades at Grimsvotn volcano, Iceland

Samples of the subglacial lake in the crater of the tholeiitic basaltic caldera Grimsvotn in Iceland were obtained by using a hot-water drill to sink two boreholes through the 250-m- thick ice shelf covering the lake. The crater lake is assumed to be closed, with respect to volatile components released from subsurface magma, except for periodic draining by jokulhlaups. From the periodicity and water chemistry of the jokulhlaups, the volcano's average release rates of carbon, sulfur, chlorine and fluorine between 1954 and 1991 are estimated to be 5.3 × 10⁷ kg C yr^-1, 5.3 × 10 ⁶ kg S yr^-1, 6.6 × 10⁵ kg Cl yr^-1, and 1.5 × 10⁵ kg F yr^-1. The emission rate estimates for Grimsvotn, one of the most active volcanoes in Iceland, are the longest integrated estimates obtained for an active volcano and are equal to or lower than those of other major active volcanoes worldwide. This difference may imply that published release rates for other volcanoes are overestimated, because they are usually not integrated over time. -from Authors