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Near-surface environmentally forced changes in the Ross Ice Shelf observed with ambient seismic noise

TitleNear-surface environmentally forced changes in the Ross Ice Shelf observed with ambient seismic noise
Publication TypeJournal Article
Year of Publication2018
AuthorsChaput J., Aster R.C, McGrath D., Baker M., Anthony R.E, Gerstoft P, Bromirski P., Nyblade A., Stephen R.A, Wiens D.A, Das S.B, Stevens L.A
JournalGeophysical Research Letters
Date Published2018/10
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000451510500045
Keywordsaccumulation; antarctica; channel; firn; Geology; propagation; sensitivity; stability

Continuous seismic observations across the Ross Ice Shelf reveal ubiquitous ambient resonances at frequencies >5 Hz. These firn-trapped surface wave signals arise through wind and snow bedform interactions coupled with very low velocity structures. Progressive and long-term spectral changes are associated with surface snow redistribution by wind and with a January 2016 regional melt event. Modeling demonstrates high spectral sensitivity to near-surface (top several meters) elastic parameters. We propose that spectral peak changes arise from surface snow redistribution in wind events and to velocity drops reflecting snow lattice weakening near 0 degrees C for the melt event. Percolation-related refrozen layers and layer thinning may also contribute to long-term spectral changes after the melt event. Single-station observations are inverted for elastic structure for multiple stations across the ice shelf. High-frequency ambient noise seismology presents opportunities for continuous assessment of near-surface ice shelf or other firn environments. Plain Language Summary Ice shelves are the floating buttresses of large glaciers that extend over the oceans and play a key role in restraining inland glaciers as they flow to the sea. Deploying sensitive seismographs across Earth's largest ice shelf (the Ross Ice Shelf) for 2 years, we discovered that the shelf nearly continuously sings at frequencies of five or more cycles per second, excited by local and regional winds blowing across its snow dune-like topography. We find that the frequencies and other features of this singing change, both as storms alter the snow dunes and during a (January 2016) warming event that resulted in melting in the ice shelf's near surface. These observations demonstrate that seismological monitoring can be used to continually monitor the near-surface conditions of an ice shelf and other icy bodies to depths of several meters.

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