Cyclones and tsunamis

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Cyclones and tsunamis in the Pacific

There are several regions of high cyclonic activity in the Pacific, including one in the Central Pacific (cyclones, southern hemisphere, directed to Polynesia and northern Australia) and one in the Western Pacific (typhoons, northern hemisphere, directed to south-east Asia). Climatologists observed a recent increase in typhoon activity in the Pacific Ocean. Changes to the uppermost layer of Earth’s oceans due to rising temperatures are also likely causing an increase in intense Pacific Ocean typhoons, suggesting strong typhoons may occur more frequently in the coming decades. The most intense Pacific cyclonic events also shifted to the poles at a rate of 50km per decade, while their intensity increased simultaneously to climate change. This implies that typhoon trajectories and intensity are more difficult to anticipate in a context of climate change.

In the Pacific, trajectories of cyclones do spatially and temporally overlap with trajectories of migratory shorebirds, including godwits, curlews, plovers and tattlers. These birds are therefore good models to study how they anticipate cyclonic conditions during migration or on wintering grounds.

Cross-map of migration corridors of two migratory birds (godwit and curlew) and tropical storm tracks recorded between 1994 and 2014.

As the Pacific is a region of intense sismic activity, this ocean and adjacent marginal seas are the largest most tsunami-prone ocean on the earth. Pacific Ocean nations face and must be prepared for distant and local tsunami threats. Although the direct impact of tsunamis is limited to coastal areas, their destructive power can be enormous, and they can affect entire ocean basins.

The 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history, with at least 230,000 people killed or missing in 14 countries. The principal generation mechanism of a tsunami is the displacement of a substantial volume of sea water, usually attributed to earthquakes. Climate change should not impact the frequency of tsunami occurrence in the tropics, but rising sea levels following climate change could increase the destruction risk faced by coastal areas, putting some previously safe areas at risk, especially on oceanic islands. In the Pacific Ocean, many islands and archipelagos hardly culminate high above sea level, and many islands and atolls should become uninhabitable because of sea-level rise and associated wave-driven overwash and its impact on freshwater availability.

In the Pacific, the sismic activity in particularly intense in the Hawaï and New Caledonian region.