Gakkel ridge is the slowest spreading mid-ocean ridge with full rates <10 mm/y. In 1999, a teleseismic earthquake swarm signalled the onset of an eruptive episode at the 85°E volcanic complex. The Arctic Mid-Ocean Ridge expedition in 2001 detected a hydrothermal event plume and explosive seismoacoustic signals and, in 2007, the Arctic Gakkel Vents Expedition found evidence for recent deep submarine explosive activity at this site. The new data allowed a reassessment of the seismoacoustic events recorded in 2001. We undertake 2D finite difference wavefield modelling to locate the source of the signals and investigate the source mechanism: The explosion sounds result from mild submarine Strombolian eruptions at the southern rift valley wall at about 4000 m water depth. We believe that the explosion sounds are produced by bursting gas bubbles rising from a deep magmatic reservoir along a major fault which was activated during the large seismic and volcanic event in 1999. While ash particles in sediment samples of mid-ocean ridges yield increasing evidence for a widespread explosive component to the predominantly effusive mid-ocean ridge volcanism, we present here the first in-situ observation of deep submarine Strombolian explosions.