Collaborative Research: Measuring abyssal warming with seismic Scholte waves

Due to its large heat capacity, the ocean absorbs most of the excess energy trapped by anthropogenic greenhouse gases and thus regulates the rate of global warming. Accurate measurements of the ocean's warming are critical for understanding Earth's energy imbalance and climate anomalies. This project will employ a novel method of using seismic Scholte waves excited by repeating natural submarine earthquakes to monitor the global large-scale abyssal ocean warming. Preliminary results demonstrate the feasibility of the method, which will be expanded to the global ocean. Existing seismic data can be used to track abyssal oceawn warming back to the 1990s. The results will complement hydrographic measurements and improve understanding of the dynamics of the response of the abyssal ocean to surface forcing. This work will provide new observational constraints on abyssal ocean warming over the past few decades. The investigators will systematically search for shallow submarine repeating earthquakes since the 1980s. Scholte waves excited by these repeating events travel along the seafloor, and their propagation speed is sensitive to abyssal temperatures. Scholte wave travel time changes between repeating events thus constrain abyssal temperature change. The sensitivity of Scholte wave travel times to abyssal temperatures will be calculated using numerical simulations of wave propagation. Sensitivity kernels will be used to interpret the measured travel time changes, to infer average abyssal ocean warming along the waves' path, and to quantify uncertainties. The inferred warming will be compared against hydrographic and Argo data where available. Providing direct estimates of basin-scale abyssal ocean warming. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.