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IRIS WEBINAR 5/13 2 PM EST: Seismological constraints on solid earth-ice interactions in Antarctica
From: Danielle Sumy <danielle.sumy@xxxxxxxx>IRIS WEBINAR 5/13 2 PM EST: Seismological constraints on solid earth-ice interactions in Antarctica
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Please register for Seismological constraints on solid earth-ice sheet interactions in Antarctica on May 13, 2015 2:00 PM EDT at:
https://attendee.gotowebinar.com/register/2255390085489526017
Presenter: Doug Wiens, Washington University of St. Louis
The dynamics of ice sheets and their interaction with the solid earth is an important topic, with crucial implications for climate change and sea-level rise. Projections of ice sheet retreat and sea level rise are heavily influenced by solid earth properties such as basal heat flow, bed properties, lithospheric thickness and mantle viscosity. Recently installed seismic networks in Antarctica and developments in technology allowing year-round unattended seismograph operation even in the coldest regions now allow us to use seismology to investigate these interactions. We use seismic velocity maps to constrain parameters important for ice sheet models such as heat flow and mantle viscosity. Inferred mantle viscosity is lowest beneath Marie Byrd Land and highest beneath East Antarctica, and the variation is large enough to have a first order effect on glacial isostatic adjustment (GIA). Inferred mantle viscosity in West Antarctica is much lower than used in recent GIA models, and limits the GIA response to ice sheet mass changes to the last several hundred years. The Transantarctic Mountains lie along a first order boundary in mantle viscosity, probably leading to a complicated GIA response poorly modeled by 1-D viscosity models. West Antarctica shows low mantle seismic velocities associated with late Cenozoic rift systems and with a large mantle thermal anomaly supporting the Marie Byrd Land dome. These structures suggest high geothermal heat flow may have a first order effect on glacial dynamics in West Antarctica, as indicated by recent high heat flow measurements from the WAIS ice core. In addition, the recent discovery of deep-long period volcanic earthquakes beneath the ice sheet in Marie Byrd Land demonstrates the existence of active subglacial magmatic systems and suggests volcanic eruptions may have an important effect on the ice sheet.
Seismic
data also provides important constraints on the movement and dynamics
of ice sheets. For example, co-located seismographs and GPS receivers
deployed on the Whillans Ice Stream allow us to obtain very broadband
records of ice velocity during the twice-daily stick-slip events. These
records, combined with observations of far-field Rayleigh waves, reveal
that the stick-slip motion is controlled by high friction regions
located along the grounding line.
View system requirements at: http://support.citrixonline.com/webinar/all_files/G2W010003
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