Seismic ocean thermometry uses sound waves generated by repeating
earthquakes to measure temperature change in the deep ocean. In this
study, waves generated by earthquakes along the Japan Trench and
received at Wake Island are used to constrain temperature variations in
the Kuroshio Extension region. This region is characterized by energetic
mesoscale eddies and large decadal variability, posing a challenging
sampling problem for conventional ocean observations. The seismic
measurements are obtained from a hydrophone station off and a seismic
station on Wake Island, with the seismic station's digital record
reaching back to 1997. These measurements are combined in an inversion
for the time and azimuth dependence of the range-averaged deep
temperatures, revealing lateral and temporal variations due to Kuroshio
Extension meanders, mesoscale eddies, and decadal water mass
rearrangements. These results highlight the potential of seismic ocean
thermometry for better constraining the variability and trends in
deep-ocean temperatures. By overcoming the aliasing problem of point
measurements, these measurements complement existing ship- and
float-based hydrographic measurements.