Somali Piracy and the Monsoon

Authors: Duncan Cook and Sally Garrett

Discipline: Geography, Environmental Science

Hazard of Interest: Pirates

Methods: Remote sensing, mapping

Key Research Issues: Somali-based pirates operate across a vast ocean area that includes some of the busiest shipping lanes on the planet. This research set out to characterize the wind and wave conditions that existed during pirate attacks in recent years.

Key Findings: In 2011-2012, pirate attacks in the Indian Ocean region mainly occurred in the early and later half of the year, with very few attacks launched during the summer monsoon period. We propose that the rough seas and strong surface winds of the summer monsoon (JJA) have prevented piracy for periods of up to three months during 2011-2012. Remote sensed and surface weather data suggest clear environmental thresholds exist that have prevented pirates launching successful attacks. Once wind speeds exceeded 9 m/s and waves of sea state 4 (wave heights above 2.5 m) were recorded, open-water maritime piracy was halted. In contrast, the lower wind speeds and wave heights during the winter monsoon, premonsoon [March–May (MAM)], and postmonsoon [September–November (SON)] seasons were not a deterrent for pirates operating in the Indian Ocean region.