Tsunami weather

Monday marked the one-year anniversary of the great December 26, 2004 Indian Ocean tsunami, which killed over 283,000 people. The earthquake that generated the tsunami was the fourth strongest in the past century, and caused an oscillation of the Earth's surface of about 20-30 cm (8 to 12 in), equivalent to the effect of the tidal forces caused by the Sun and Moon. The shock waves of the earthquake were felt across the planet--even as far away as Oklahoma, where vertical movements of 3 mm (0.12 in) were recorded. The entire Earth's surface is estimated to have moved vertically by up to 1 cm.

What effect did this remarkable event have upon the Earth's weather? According to the Harris' Farmer's Almanac for 2006 (not to be confused with its competitor, the Old Farmer's Almanac), the unique weather of 2005 was largely attributable to the tsunami:

"The fact that the tsunami churned through the water, altering the sea surface temperatures, did have an influence. The unusual water temperatures changed the weather conditions above the water's surface and that, in turn, changed the weather locally, regionally, and even around the globe."

However, an examination of the sea surface temperature imagery from the days immediately following the earthquake shows that the tsunami had very little effect on the ocean temperature. While there was some minor cooling observed within 1 km of the shorelines closest to the earthquake's epicenter, by two days later (Figure 1), sea surface temperatures in the region showed no trace that anything unusual had happened. The impact of the tsunami on sea surface temperatures was less than that of a weak tropical storm! This is because while a tsunami can create tremendous waves and mixing of the water when it crashes ashore, this effect is limited to shallow waters 1 km or less from shore. The tsunami's impact in deep water is very limited. Satellite measurements of the tsunami's passage over the open ocean revealed a maximum wave height of only 50 cm (20 in), which caused very little stirring of the water over the open ocean. There is nothing at all to suggest that this tsunami, or any tsunami in recorded history, has had a significant impact on regional or global weather.


Figure 1.Sea Surface temperatures anomolies one day before and two days after the Dec. 26, 2004 tsunami. The anomalies (the difference between average sea surface temperature and observed temperature) show virtually no change due to the passage of the tsunami waves.

Jeff Masters