11:00 AM - 11:15 AM
[SSS04-08] Linking Ocean Storms and Earth's Hum Excitation: Seasonal Infragravity Wave Observations in the Pacific Ocean
Keywords:Pacific Ocean, infragravity waves, ocean storms, Earth's Hum, ocean-bottom-seismometer
Infragravity waves are long-period ocean waves that bridge the atmosphere, ocean, solid Earth and polar ice, influencing sea level measurements, coastal sediment transport, the breakup of Antarctic ice shelves and the excitation of Earth's seismic hum. We collected ocean-bottom pressure data recorded by up to 700 pressure gauges from 15 ocean-bottom seismometer arrays deployed on the Pacific seafloor and computed cross-correlation functions between each station pair to extract coherent energy of infragravity waves. Beamforming analysis was conducted to determine the incoming direction of infragravity waves and ray-tracing calculations were applied to locate their sources. Our results reveal pronounced seasonal variations in the spatial extent of infragravity wave sources. During boreal winter, coastlines of the northern and eastern Pacific Ocean are distinct sources, particularly in the northeastern segment, strongly correlating with significant wave height triggered by eastward-moving storms and with infragravity wave height predictions. By contrast, during boreal summer (i.e., austral winter), waves predominantly originate from the western coast of South America and New Zealand coasts. A secondary hotspot is illuminated along the Antarctic coast, which we hypothesize originates from distant primary sources in the Southern Hemisphere, reflecting off the Antarctic coast. The reflected waves then propagate northward several hundred to thousands of kilometers seaward toward the Northern Hemisphere, where they are recorded by stations in the Northern Pacific Ocean. The detected infragravity wave source locations in this study support that Earth's seismic hum is triggered unevenly, with distinct seasonal patterns.