Estimating Southern Ocean Storm Positions With Seismic Observations

• Main Authors: Hell, Momme C, Gille, Sarah T, Cornuelle, Bruce D, Miller, Arthur J, Bromirski, Peter D, Crawford, Alex D
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2020
• Subjects: Earth Sciences; Oceanography; Physical Geography and Environmental Geoscience; Climate Action; Life Below Water; storms; wave propagation; sea ice; optimization; Ross Ice Shelf; surface winds; Geophysics; Southern Ocean; Pacific; Ice Shelf; Sea ice
• Online Access: https://escholarship.org/uc/item/68x5f09k

Abstract: Surface winds from Southern Ocean cyclones generate large waves that travel over long distances (>1,000km). Wave generation regions are often colocated with enhanced air‐sea fluxes and upper ocean mixing. Ocean wave spectra contain information about storm wind speed, fetch size, and intensity at their generation site. Two years of seismic observations on the Ross Ice shelf, combined with modern optimization (machine learning) techniques, are used to trace the origins of wave events in the Southern Ocean with an accuracy of ±110km and ±2hr from a hypothetical point source. The observed spectral energy attenuated within sea ice and in the ice shelf but retains characteristics that can be compared to parametric wave models. Comparison with the Modern‐Era Retrospective Analysis for Research and Applications, Version 2, and ERA5 reanalyses suggests that less than 45% of ocean swell events can be associated with individual Southern Ocean storms, while the majority of the observed wave events cannot be matched with Southern Ocean high wind events.Reanalysis cyclones and winds are often displaced by about 350 km or 10 hr in Modern‐Era Retrospective Analysis for Research and Applications, Version 2, and ERA5 compared to the most likely positions inferred from the seismic spectra. This high fraction of displaced storms in reanalysis products over the South Pacific can be explained by the limited availability of remote sensing observations, primarily caused by the presence of sea ice. Deviation of wave rays from their great circle path by wave‐current interaction plays a minor role.