Climate change refers to long-term shifts in temperatures and weather patterns driven by increasing greenhouse gases. Tsunamis are a series of ocean waves caused by sudden, large-scale disturbances of the seafloor. While global warming does not directly create the tectonic forces responsible for the most powerful tsunamis, it significantly alters the environment in which these waves propagate. The changing climate modifies the secondary sources of tsunamis and substantially increases the destructive potential of all resulting wave events. Understanding this relationship is important for coastal preparedness and long-term risk assessment.
Understanding Tsunami Generation
Tsunamis are generated by any event that rapidly displaces a massive volume of water, creating an expansive series of waves that travel across an ocean basin. The most frequent and powerful source is a megathrust earthquake beneath the ocean floor, causing a sudden vertical shift of the seabed. This movement instantaneously pushes the overlying water column upward, forming the initial wave disturbance. Non-seismic events also trigger tsunamis, including major volcanic eruptions, large-scale submarine landslides, or rockfalls plunging into the water. These seismic sea waves are distinct from normal wind-driven waves due to their immense speed and wavelength in the deep ocean.
Amplification through Sea Level Rise
The most direct and quantifiable way climate change modifies tsunami impact is through global sea level rise. This rise is primarily the result of thermal expansion, as ocean water warms, and the addition of meltwater from glaciers and ice sheets. This effectively raises the baseline elevation from which a tsunami wave begins its journey toward the shore.
A higher baseline allows the wave to travel much farther inland, increasing the inundation distance. Research modeling has shown that a modest sea level increase of approximately 1.5 feet can dramatically increase the frequency of tsunami-induced flooding by a factor of 1.2 to 2.4 in some regions.
This means that smaller tsunamis, which previously might have caused minimal damage, can now have the same devastating impact as much larger historical events. The total water volume impacting the shore and the distance it travels inland are amplified by the elevated sea surface, increasing the potential for property damage and loss of life.
Destabilized Landscapes and Non-Seismic Triggers
Climate change increases the risk of tsunamis generated by non-seismic mechanisms through the destabilization of land and submarine features. As global temperatures rise, melting ice sheets and glaciers remove immense weight from the Earth’s crust, a process known as isostatic rebound. This removal of pressure can lead to increased stress and movement along underlying faults, potentially triggering earthquakes and subsequent landslides.
In high-latitude regions, retreating glaciers leave coastal slopes unsupported, making them vulnerable to massive rockfalls and landslides that crash into fjords and bays. Such events have generated localized mega-tsunamis, like the rock avalanche in Dickson Fjord, Greenland, which produced a wave over 200 meters high. The increasing frequency of these climate-driven rock avalanches poses a significant new threat for communities in places like Alaska, Norway, and Chile.
Warming ocean temperatures and the melting of permafrost also destabilize the marine environment. Permafrost thaw decreases the stability of coastal and submarine slopes, making them more susceptible to failure. When these unstable underwater slopes collapse, they trigger massive submarine landslides, which are a potent source of tsunamis that can travel vast distances.
Increased Coastal Vulnerability
Climate change diminishes the natural resilience of coastlines, making the receiving environment more susceptible to damage. Coastal erosion, exacerbated by rising sea levels and more intense storm surges, removes sand and sediment that naturally dissipates wave energy. This leaves communities and infrastructure more exposed to the destructive force of an incoming tsunami.
Natural defense systems, such as mangrove forests, coral reefs, and coastal wetlands, are also being degraded by climate change factors like ocean warming and acidification. These ecosystems traditionally act as natural buffers, absorbing much of a tsunami’s energy before it reaches populated areas.
Their loss means that any tsunami will encounter less friction and resistance, allowing more destructive power to reach further inland. Coastal communities face a dual risk: waves are gaining reach, and the coastal landscape is losing its ability to protect against them. This reduced resilience translates directly into greater economic damage and higher risks to human life when a tsunami strikes.