Climate change and tsunamis operate on vastly different timescales and through distinct mechanisms. Climate change, defined as long-term shifts in temperatures and weather patterns, does not directly trigger the vast majority of tsunamis, which are most often caused by sudden geological events. Nevertheless, a warming planet significantly increases the risk of certain non-seismic tsunami types and greatly amplifies the destructive potential of all tsunamis that occur. The influence is indirect, yet substantial, connecting the slow, cumulative effects of global warming to the rapid, devastating force of a harbor wave.
The Primary Geological Causes of Tsunamis
The vast majority of tsunamis are fundamentally geological in origin, beginning with a massive, rapid displacement of the water column. The most common cause, accounting for approximately 72% of all events, is a large submarine earthquake in a subduction zone. These zones occur where one tectonic plate is forced beneath another, and when the locked plates suddenly slip, the seafloor snaps upward, pushing the entire overlying body of water toward the surface. This enormous bulge of water then flattens out, generating a series of waves that can travel across entire ocean basins at speeds of up to 600 miles per hour in deep water.
Submarine landslides are the next most frequent cause, often occurring in conjunction with a large earthquake. During these events, sediment on the ocean floor gives way, and the resulting movement of this mass displaces a large volume of water. Large volcanic eruptions or caldera collapses, though less common, can also generate a tsunami by rapidly pushing water aside or through massive underwater explosions. These non-seismic mechanisms are typically responsible for localized tsunamis that dissipate quickly, rarely affecting coastlines far from the source area.
Climate Change Influence on Non-Seismic Tsunami Triggers
Climate change increases the frequency of tsunami-generating events that are not seismic in nature. A warming climate can destabilize coastal and underwater landscapes, creating new pathways for water displacement. Intense rainfall events, a consequence of a warmer atmosphere holding more moisture, can saturate rock and soil on steep coastal slopes. This saturation reduces land stability, leading to more frequent terrestrial landslides that plunge into the ocean and generate localized tsunamis.
The massive retreat of glaciers and ice sheets is also creating conditions ripe for large-scale landslides and tsunamis in polar regions. As glaciers melt, they no longer buttress the rock walls of fjords and valleys, leaving formerly supported slopes fractured and unstable. The melting of permafrost further decreases soil stability in high-latitude areas, making them susceptible to gravitational movement. When a large mass of rock and ice collapses into the water, as seen in a recent Greenland event that triggered a tsunami over 200 meters high, the resulting displacement wave can be catastrophic in the immediate area.
Warming ocean temperatures may also affect the stability of the deep-sea floor by destabilizing methane hydrates. Methane hydrates are ice-like structures trapping methane gas within ocean sediments. If deep ocean temperatures rise significantly, the hydrates can melt, causing the sediments to become unstable and prone to massive submarine landslides. The resulting catastrophic sediment collapse could then displace enough water to trigger a tsunami, though the full extent of this risk is still being investigated.
How Rising Sea Levels Intensify Tsunami Damage
The most direct link between climate change and tsunami events is global mean sea level rise intensifying their destructive power. A higher baseline sea level means that when a tsunami wave is generated, it is starting from an elevated position. This effectively increases the wave’s height relative to the land, allowing it to penetrate much farther inland than it would have historically.
Even modest increases in sea level, such as the projected 50-centimeter rise in some regions, can dramatically increase the frequency of tsunami-induced flooding. Studies have shown that a smaller tsunami in the future could have the same devastating impact as a much larger one today simply because of the increased water level. For coastal communities, this means that even tsunamis generated by smaller magnitude earthquakes, which currently pose little threat, could cause significant inundation.
Climate change indirectly removes natural protective barriers that absorb the wave’s energy. Rising sea levels and more intense storm surges contribute to the erosion and loss of coastal features like mangroves, coral reefs, and sand dunes. The loss of these natural defenses leaves coastal infrastructure and populations exposed to the tsunami’s full force. A higher starting point for the water, combined with degraded natural defenses, creates a compounding effect that significantly elevates the hazard worldwide.