New Mexico Institute of Mining and Technology
Taking Earth’s Pulse and Temperature Using Seismology:
Roaring Oceans and Singing Icebergs
The worldwide network of seismographs designed to detect earthquakes is also recording aspects of Earth’s climate. Buried in the background of these continuous seismic recordings, even in the deep interiors of continents, are “microseisms” -- seismic waves created by ocean waves pounding the coast and interacting with the sea floor. From over 35 years of high-quality continuous global seismic recordings, my colleagues and I have been able to reconstruct a unique record reflecting past patterns of ocean-storm intensity. This work includes evidence suggesting that violent ocean storms across planet, and associated ocean waves, have been increasing in their frequency of occurrence during the past three decades.
Seismometers sited on the great ice sheets and icebergs of Antarctica are also revealing signals due to waves from extreme ocean storms and from regional iceberg calving. Hours-long collisions between Earth’s largest icebergs as they gyrate under the influence of coastal currents also cause the icebergs to “sing” with a newly discovered type of seismic and ocean acoustic tremor. Extreme storms occurring during the Arctic winter produce waves that propagate to Antarctica. One resulting hypothesis arising from seismic studies conducted atop giant icebergs is anecdotally supported by the breakup of Earth’s largest iceberg in late 2005. It seems that these waves can influence iceberg behavior in the Antarctic because they arrive during what is summer in the southern hemisphere, when large tabular icebergs and ice shelves are largely unprotected by sea ice and are thus susceptible to calving and breakup. Seismic investigations in polar regions will doubtless continue to reveal still more about these and other novel dynamic processes affecting Earth’s largest glacier systems and to illuminate previously unsuspected linkages between climate, oceanography, seismology, and glaciology.
Watch video of Dr. Aster's Lecture at the New Mexico Museum of Natural History
http://www.ees.nmt.edu/eesFlix/view.php?view=2BvPNS
About Dr. Richard C. Aster
Education
Ph.D., Earth Sciences, Scripps Institution of Oceanography, University of California,
San Diego (1991).
M.S., Geophysics, University of Wisconsin-Madison (1986).
B.S., Electrical and Computer Engineering with additional major completed
in Physics, University of Wisconsin-Madison (1983).
Positions Held
Chair, New Mexico Tech Department of Earth and Environmental Science (2008-2011)
Professor of Geophysics, New Mexico Tech (2000 – present)
Associate Professor of Geophysics, New Mexico Tech (1996-2000)
Assistant Professor of Geophysics, New Mexico Tech (1991-1996)
Postgraduate Research Geophysicist, Scripps Institution of Oceanography (1991)
Dr. Rick Aster joined the faculty at New Mexico Tech in 1991 and is currently a professor of geophysics and chair of the Department of Earth and Environmental Science. Much of his research uses seismology to learn about earthquakes, volcanoes, and unusual seismic sources, like icequakes and explosions, and to image the structure of the deep Earth. He is currently studying the upper mantle beneath the Rocky Mountains, the activity of Mount Ebrebus Volcano in Antarctica and seismic activity in New Mexico. He is also the principal investigator of the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) Instrument Center, a National Science Foundation facility of the IRIS Consortium, which supports seismological research for seismologists from research institutions throughout the world.
Dr. Aster has strong enthusiasm for and commitment to education and outreach on behalf of seismology and science, and he gives regular public lectures at primary and secondary schools, universities, museums and community groups. He also chaired the IRIS Education and Outreach Committee for four years.
Selected Recent Publications
Wilson, D., Aster, R., West, M., Ni, J., Grand, S., Gao, W., Baldridge, W.S., Semken, S., Lithospheric Structure of the Rio Grande Rift, Nature, 433, doi:10.1038/nature03297, 2005.
MacAyeal, D., Okal, E., Aster, R., Basis, J., Brunt, K., Cathles, L. Mac. Drucker, R., Kim, Y-J., Martin, S., Okal, M., Sergienko, O., Sponsler, M., Thom, J., Transoceanic wave propagation links iceberg calving margins of Antarctica with storms in tropics and northern hemisphere, Geop. Res. Lett., 33, L17502, doi:10.1029/2006GL027235, 2006.
Aster, R., McNamara, D., Bromirski, P., Multi-decadal climate-induced variability in microseisms, Seismological Research Letters 79, doi: 10.1785/gssrl.79.2.194, 2008.
MacAyeal, D. R., Okal, E., Aster, R., Bassis, J., Seismic and hydroacoustic tremor generated by colliding icebergs, J. Geophys. Res., 113, F03011, doi:10.1029/2008JF001005, 2008.
Sine, C., Wilson, D., Gao, W., Grand, S., Aster, R., Ni, J., Baldridge, W.S., Mantle structure beneath the western edge of the Colorado Plateau, Geop. Res. Lett., 35, L10303, doi:10.1029/2008GL033391, 2008.
Aster, R., Zandomeneghi, D., Mah, S., McNamara, Henderson, D.B., Yarbrough, H., Jones, K., Shallow Variability and Deep Stability in the Conduit System of Mount Erebus Indicated by Characteristics of Very Long Period Seismic Signals from Strombolian Eruptions, J. Volcanol. Geotherm. Res., in press, 2009.
