Storm-driven ocean swells travel across the Pacific Ocean and break along the coastlines of North and South America, where they are transformed into very long-period ocean waves called "infragravity waves." The transformed waves then travel vast distances to Antarctica.
The Authors of the study propose that the southbound travelling infragravity waves "may be a key mechanical agent that contributes to the production and/or expansion of the pre-existing crevasse fields on ice shelves," and that the infragravity waves also may provide the trigger necessary to initiate the collapse process.
Using seismic data collected on the Ross Ice Shelf, researchers identified signals generated by infragravity waves that originated along the Northern California and British Columbia coasts, and modeled how much stress an ice shelf suffers in response to infragravity wave impacts. Only recently has technology advanced to allow scientists to deploy seismometers for the extended periods on the ice shelf needed to capture such signals.
The study found that each of the Wilkins Ice Shelf breakup events in 2008 coincided with the estimated arrival of infragravity waves. The authors note that such waves could affect ice shelf stability by opening crevasses, reducing ice integrity through fracturing, and initiating a collapse. "(Infragravity waves) may produce ice-shelf fractures that enable abrupt disintegration of ice shelves that are also affected by strong surface melting," the authors note in the paper.
Whether increased infragravity wave frequency and energy induced by heightened storm intensity associated with climate change ultimately contribute to or trigger ice shelf collapse is an open question at this point, said Bromirski. More data from Antarctica are needed to make such a connection, he said.
Citation: Bromirski, P. D., O. V. Sergienko, and D. R. MacAyeal, 'Transoceanic infragravity waves impacting Antarctic ice shelves', February 2010, Geophys. Res. Lett., 37, L02502, doi:10.1029/2009GL041488