UTIG Seminar Series: Ben Keisling, UMass - Amherst

Speaker: Benjamin Keisling, University of Massachusetts - Amherst

Host: Sean Gulick

Title: Using geochemical data to constrain the Pleistocene dynamics of the Greenland Ice Sheet

Abstract: Understanding the behavior of ice sheets during past warm interglacial periods is critical for predictions of sea-level rise in a warming world. Recent measurements of cosmogenic isotopes from beneath the Greenland ice sheet, along its margin, and in marine cores offshore reveal a dynamic history that implies Greenland may be far less stable than has long been assumed. We present ice-sheet modelling simulations motivated by these new observations, and show how numerical models can be used to scale spatially disparate observations and provide physically consistent estimates of Greenland’s contributions to past warm periods. We show results of data-model integration from the Pliocene, the late Pleistocene, and the last deglaciation. These examples illustrate the utility of data-validated ice-sheet models for studying the processes and mechanisms governing collapse of the Greenland ice sheet during warm climates.

DeFord Lecture: Elvira Mulyukova

UTIG Seminar Series: Tom Ballinger, Texas State University

Speaker: Tom Ballinger, Assistant Professor of Geography, Texas State University - San Marcos

Host: Duncan Young

Title: Local cryosphere consequences and large-scale climate implications of the recent shift in North Atlantic atmospheric circulation

Abstract: Arctic sea ice has become younger, thinner, and less extensive over the last four decades. Warm-season open water expansion has especially been pronounced in the North Atlantic Arctic, concomitant with longer melt season duration. However, attributing preconditioning and feedback processes to sea ice melt season changes in this region remains challenging amidst increasing frequency and extremes in high-pressure blocking patterns and regional ocean surface and lower tropospheric air temperature warming since the early 1990s.
This seminar focuses primarily on Baffin Bay ice-atmosphere interactions and related, physical linkages with the Greenland Ice Sheet and boreal mid-latitude weather and climate. Feedback mechanisms involving open water/sea-ice anomalies, persistent blocking patterns, and observed and statistically-downscaled reanalysis surface air temperatures are explored over Greenland coastal and tundra areas. A hypothesis is also tested that longer periods of open water on Baffin Bay coupled with local meteorological conditions influence late-season melt events observed on the western Greenland Ice Sheet. Lastly, sea ice anomalies are linked to overlying polar jet stream patterns and south and downstream weather conditions over North America and Europe, providing further evidence that the changing Arctic, especially within the North Atlantic sector, has an impact on human and natural systems at great distances.

DeFord Lecture: Noel Bartlow

DeFord Lecture: Daniel Trugman

UTIG Seminar Series: Jeff Freymueller, Michigan State University

Speaker: Jeff Freymueller, Endowed Chair for Geology of the Solid Earth, Dept. of Earth & Environmental Sciences, Michigan State University

Host: Gail Christensen

Title: Separating Long-term Tectonic Motions, Surface Loading and Other Sources of Earth Deformation

Abstract: Plate tectonics is driven by forces internal to the solid Earth, and measuring tectonic motions has been a fruitful focus for geodesy for the last few decades. However, geodetic observations depend not only on long-term tectonic motions, but also on elastic and viscoelastic effects of locked faults and the earthquake cycle. In addition, motions that ultimately result from surface loading (including glacial isostatic adjustment, GIA) also contribute to the measurements, both directly and in subtle indirect ways. As our field moves increasingly to the study of smaller amplitude steady motions and transient, time-dependent fault deformation, identifying these non-tectonic contributions becomes increasingly important. In this talk, I will take a tour around the North American continent to illustrate how these sources of Earth deformation can be separated, and how the continental-scale impact of GIA impacts estimates our estimates of tectonics.

DeFord Lecture: Brandon Schmandt

DeFord Lecture: Sunyoung Park