As oceans waves rise and fall, they apply forces to the sea floor below and generate seismic waves.
These seismic waves are so powerful and widespread that they show up as a steady thrum on seismographs, the same instruments used to monitor and study earthquakes.
That wave signal has been getting more intense in recent decades, reflecting increasingly stormy seas and higher ocean swell.
Global seismographic networks are best known for monitoring and studying earthquakes and for allowing scientists to create images of the planet’s deep interior.
These highly sensitive instruments continuously record an enormous variety of natural and human-caused seismic phenomena, including volcanic eruptions, nuclear and other explosions, meteor strikes, landslides and glacier-quakes.
They also capture persistent seismic signals from wind, water and human activity.
For example, seismographic networks observed the global quieting in human-caused seismic noise as lockdown measures were instituted around the world during the coronavirus pandemic.
However, the most globally pervasive of seismic background signals is the incessant thrum created by storm-driven ocean waves referred to as the global microseism.
The oceans have absorbed about 90% of the excess heat connected to rising greenhouse gas emissions from human activities in recent decades.
That excess energy can translate into more damaging waves and more powerful storms.
Our results offer another warning for coastal communities, where increasing ocean wave heights can pound coastlines, damaging infrastructure and eroding the land.
The impacts of increasing wave energy are further compounded by ongoing sea level rise fueled by climate change and by subsidence.
And they emphasize the importance of mitigating climate change and building resilience into coastal infrastructure and environmental protection strategies.