The 1789 Christmas Eve collision of the HMS Guardian with an iceberg in the southwest Indian Ocean

Abstract In the evening of 24 December 1789, 2100 km southeast of Cape Town and after encountering three icebergs, the HMS Guardian under Captain Edward Riou collided with the submerged foot of a large iceberg. Despite severe damage to the ship and its abandonment by many of its crew and passengers, Riou sailed the hulk back to Cape Town, arriving on 22 February 1790. From present-day research and field studies, the formation of the foot in the collision is consistent with the above-freezing seawater temperatures inferred from Riou's commentary. Further, the observed 60 m iceberg height suggests that it calved from the Filchner Ice Shelf in the Weddell Sea. Comparison of the positions of Riou's icebergs with historic sightings, satellite observations and iceberg drift and fracture models also shows that they originated in the Weddell Sea and that their likelihood of occurrence in the collision region is small.