Monitoring polynyas with Ocean Acoustic Tomography: afeasibility study in Terra Nova Bay

[摘要] This study looks at the feasibility of using Ocean Acoustic Tomography for long-term monitoringof polynyas using both observations in Terra Nova Bay polynya (Ross Sea) and simulations with a rangedependent, multi-layered adiabatic normal mode acoustic propagation model. The summer sound speedprofile is characterized by surface values of around 1450 m s−1, a minimum of 1441 m s−1 around 50 m depthand a linear increase with a 0.016 s−1 slope. Thus, the sound propagation is apparently ducted in the nearsurface layer and is refracted upward below it. During winter, due to water cooling and mixing processes, thesubsurface minimum disappears, the surface sound speed is about 1440 m s−1 and no near surface layerducted propagation occurs. Because of the specificity of the Terra Nova Bay seasonal sound speed profileand to cope with both deep and shelf water applicability, the feasibility study of acoustic inversion wasundertaken using normal mode Match Field Tomography instead of the more classical travel-time inversion.The results from simulations demonstrate that ocean acoustic tomography is able to reproduce quite well thevertical sound speed profile, in particular the temporal evolution of summer stratification and winter mixingprocesses, thus providing information on the upper layer, where direct measurements are not possible.

[学科分类] 自然科学（综合）