[unav_all] IRIS WEBINAR 5/13 2 PM EST: Seismological constraints on solid earth-ice interactions in Antarctica

Danielle Sumy danielle.sumy at iris.edu
Thu May 7 10:07:40 MDT 2015

Please register for Seismological constraints on solid earth-ice sheet interactions in Antarctica on May 13, 2015 2:00 PM EDT at: 


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

After registering, you will receive a confirmation email containing information about joining the webinar. Please note that the webinar software limits attendance to 100 participants; join the webinar early in case it is oversubscribed. Recordings are typically posted shortly afterwards at: https://www.youtube.com/playlist?list=PLD4D607C2FA317E6D

Danielle Sumy, PhD
Project Associate
Instrumentation Services
Education and Public Outreach
Phone: 202-682-2220 x168
Email: danielle.sumy at iris.edu

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