Acoustic Waveform Inversion for Ocean Turbulence

Abstract

The seismic oceanography method is based on extracting and stacking the low-frequency acoustic energy scattered by the ocean heterogeneity. However, a good understanding on how this acoustic wavefield is affected by physical processes in the ocean is still lacking. In this work an acoustic waveform modeling and inversion method is developed and applied to both synthetic and real data. In the synthetic example, the temperature field is simulated as a homogeneous Gaussian isotropic random field with the Kolmogorov–Obukhov spectrum superimposed on a background stratified ocean structure. The presented full waveform inversion method is based on the ray-Born approximation. The synthetic seismograms computed using the ray-Born scattering method closely match the seismograms produced with a more computationally expensive finite-difference method. The efficient solution to the inverse problem is provided by the multiscale nonlinear inversion approach that is specifically stable with respect to noise. Full waveform inversion tests are performed using both the stationary and time-dependent sound speed models. These tests show that the method provides a reliable reconstruction of both the spatial sound speed variation and the theoretical spectrum due to fully developed turbulence. Finally, the inversion approach is applied to real seismic reflection data to determine the heterogeneous sound speed structure at the west Barents Sea continental margin in the northeast Atlantic. The obtained model illustrates in more detail the processes of diapycnal mixing near the continental slope.

Efficient parallel random field generator for large 3-D geophysical problems

“…The results of this approach can also be used, for example, for sensitivity analysis or uncertainty quantification. Stochastic simulations of random fields with multi-scale resolution have found application in studies of turbulent flows [1,2,3], flow in porous media [4], seismic volcanology [5,6], large-scale density structure of the universe [7] and other geophysical and astrophysical problems. Some other geoscience applications and simulation techniques are described in the monograph by Christakos [8].…”

The Next Decade of Seismic Oceanography: Possibilities, Challenges and Solutions

“…Sound speed can thus be directly estimated from seismic data and mapped into values of temperature and salinity using an assumed temperature-salinity relationship and the hydrographic equation of state (see Appendix D.1 and Table D.1 for a summary of proposed methods). Hydrographic inversion has been used, for example, to investigate stirring at baroclinic fronts, to describe temperature variance in turbulent waters above a continental slope, and to reassess heat transport onto the Antarctic shelf (Biescas et al, 2014;Minakov et al, 2017;Gunn et al, 2018). Inversion results can also act as constraints for other calculations that are made using seismic records (e.g., estimation of diapycnal heat flux, Gunn et al, 2021; see Sections 3.1 and 3.2).…”

Pencitraan Thermohaline Fine Structure Menggunakan Seismik Refleksi Multikanal Di Laut Maluku

“…Perekaman dilakukan dengan menggunakan perekam digital Sercel 408XL dengan frekuensi sampling 2 ms. Ilustrasi akuisisi data dilakukan sepanjang lintas seismik dengan kecepatan kapal 5 knot. Ilustrasi akuisisi data seismik disajikan oleh Gambar 2 (Minakov et al, 2017).…”

“…Figure 2. Marine seismic acquisition scheme (Minakov et al, 2017). derau sehingga penampang seismik bisa diinterpretasikan dan siap untuk diinversikan.…”