Please reply to the Potomac Geophysical Society <email@example.com> by November 14 by noon if you plan to attend the dinner and/or the meeting at Crowne Plaza Tysons Corner. Please find the flyer for this talk attached this email, feel free to post and spread the word.
Please join us for the November 17, 2016, meeting of the Potomac Geophysical Society (PGS) at 7:00 p.m. at Crowne Plaza – Tysons Corner hotel, 1960 Chain Bridge Road, 22102. This location is within one-half mile of the Tysons Corner Metro station, near I-495, and has free parking available. Our private meeting room is located in the back of the Tuscan Grille restaurant on the second floor of the hotel. The optional dinner cost will be discounted to $30 for members in good standing (have paid dues) and students, and $40 for non-members, and is inclusive of iced tea, coffee, tax and gratuity. Members and guests may attend the presentation after dinner for no charge; we estimate that the presentation will begin at 8:15 p.m. For attendees who arrive early, the social will be held in O’Malley’s Pub on the first floor of the Crowne Plaza hotel. Drinks may also be purchased in the private meeting room on a cash basis.
Social: 6:00-7:00 p.m. O’Malley’s Pub, first floor Crowne Plaza
Dinner: 7:00-8:15 p.m. Tuscan Grille, second floor Crowne Plaza
Meeting & Presentation: 8:15-9:30 p.m. Tuscan Grille, second floor Crowne Plaza.
This Month’s Talk: Active Source Seismic Investigation of Firn Aquifer Structure in Southeastern Greenland by Nick Schmerr, University of Maryland
In 2011, it was discovered that there is perennial storage of water in the firn of the southeastern Greenland ice sheet, a region of both high snow accumulation and high melt. This aquifer is created through percolation of surface meltwater downward through the firn, saturating the pore space above the ice-firn transition. The aquifer may play a significant role in sea level rise though storage or draining freshwater into the ocean. Our team carried out a series active source seismic experiments that used refracted P-wave arrivals, inverted with a transdimensional Bayesian approach, to identify the seismic velocities associated with the base of the aquifer. When our seismic approach is combined with a radar sounding of the water table situated at the top of the firn aquifer, we are able to quantify the volume of water present. In our study region, the base of the aquifer lies on average 27.7±2.9 meters beneath the surface, with an average thickness of 11.5±5.5 meters. We found the aquifer had an average water content of 26.7±6.3%, with considerable variation in volume fraction of water along the studied regional flow line. Between 2015 and 2016, we observed a 1-2 km uphill expansion of the aquifer system, with a site dry in 2015 with over 4000 kg m-2 water in 2016. We estimate the volume of water stored in the aquifer across the entire region upstream of Helheim glacier to be 7.9±3.3 gigatons. Elucidating the volume of water stored within these recently discovered aquifers is vital for determining the hydrological structure and stability of the southeastern Greenland ice sheet.
Dr. Schmerr has over a decade and a half of experience in seismology and geophysical research on planetary objects. He received his PhD in geophysics from Arizona State University in 2008 where he worked with Dr. Ed Garnero on deep Earth research topics. He was a postdoc at the Department of Terrestrial Magnetism at the Carnegie Institution of Washington from 2008-2010 where he worked on terrestrial mantle seismology with Drs. Paul Silver and David James. He went on from DTM to another postdoctoral position at NASA Goddard from 2010-2013, where he became involved in a number of planetary research problems, including studying the interiors of the Moon, Mars, and the icy worlds of the outer Solar System. He has since become an assistant professor at the University of Maryland in the Department of Geology where he leads a group of 3 PhD students and multiple undergraduates in Earth and planetary research. He has conducted seismic experiments in the United States, Greenland, and Canada, has grown his interests in terrestrial and cryosphere seismic science. Dr. Schmerr is a science collaborator on the upcoming InSight mission to place a seismometer on Mars. He resides in Seabrook, MD with his wife, Dr. Amy McAdam.