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Multi-Decadal Analysis of the Global Microseism in Climate Context

Description: 

It has been recognized for over a century that the oceans produce a continuous microseism signal that is detectable everywhere on Earth. Standardized global digital seismographic networks such as the GSN and GEOSCOPE now facilitate the uniform analysis of microseism energy across more than three decades including recently accelerating anthropogenic climate change. The globally observable primary microseism signal at 14–20 s period is a particularly apt proxy for global near-coastal wave energy because it is produced by propagating ocean wave tractions on the seafloor at depths of less than a few hundred m and does not require the interfering wave conditions necessary for the secondary microseism source process. For continuous vertical component seismic records beginning in the late 1980s, robust trend estimation reveals increasing primary microseism amplitudes at significance at 41 of 52 long running GSN stations and decreasing trends at just eight sites confined to the North and West Pacific region and at two in the southern United States. Greatest absolute rates of increase are observed for PMSA on the Antarctic Peninsula with amplitude and energy trends through August 2022 () of 0.0370.008 nm/s²/y (0.360.08 %/y) and 4.161.07 (nm/s)²/y (0.580.15 %/y), respectively. Assuming linearity and consistent ocean-seismic coupling, the rate of global near-coastal ocean wave energy increase is 0.270.03 %/y for the full record and 0.350.04 %/y beginning 1 January 2000. 61-day-smoothed primary microseism signal station histories regionally cluster to beyond 50^o of separation, demonstrating large spatial integration kernels. Similar analysis of the 8–14 s secondary microseism signal shows smaller temporal trends attributed to the additional ocean conditions necessary for its excitation. Primary and secondary histories show consistent station-specific seasonal phase relationships. Primary intensities also correlate with El Nino and La Nina conditions, with increasing energy in the southwest Pacific under positive ENSO conditions and in the southeast Pacific for negative ENSO conditions.

Session: ESC-SSA Joint Session: Climate Change and Environmental Seismology - I

Type: Oral

Date: 5/3/2024

Presentation Time: 02:00 PM (local time)

Presenting Author: Richard

Student Presenter: No

Invited Presentation: 

Authors