About the presentation: Changes in total water mass now can be measured by ground-based and space-based observations. As water moved around the planet, the entire Earth deforms as a result of the changing force exerted by the weight of the water, and we can measure these motions using precise GPS observations. The gravity changes due to the changing distribution of water can also be measured using data from the GRACE satellite mission. Because these observations provide estimates of the total water mass changes, we can combine them with measurements of surface water changes to infer changes in groundwater, which are otherwise hard to measure. Previous work showed that the 2012-2019 rise of Great Lakes water levels produced up to about 2 cm of ground subsidence, which we can observe in GPS data. To make accurate estimates of the water mass variations, we will need to fully understand noise and any biases, and carefully remove all signals that are not due to the water (for example, atmospheric pressure loading and glacial isostatic adjustment). We are about 1 year into a 5 year project to make these measurements and fuse them with groundwater modeling and other remote sensing data to develop a groundwater model for the Great Lakes Basin.

About the speaker: Freymueller is an internationally recognized leader in the field of geodesy, and utilizes satellites from the Global Positioning System (GPS) to make highly precise measurements of movement on Earth’s surface. In his far-reaching research activities, he has made discoveries in a wide range of topics including plate tectonics and plate boundary zones, faults dynamics, the continuing rebound of the Earth’s surface from the melting of ice-age glaciers, inflation and deflation of volcanoes, and interpreting how changing water and ice levels deform the Earth. He is particularly well-cited for his work on using GPS to understand the crustal deformation in China, related to the formation of the Himalayas and the Tibetan Plateau.

In addition to his research, Freymueller is the Director of the EarthScope National Office. EarthScope is a long-term, large-scale, NSF-funded program to study the structure and evolution of North America and associated hazards through the deployment of thousands of geophysical instruments throughout the country.

Freymueller also has served the scientific community as the US National Correspondent to the International Association of Geodesy and its representative to the International Union of Geodesy and Geophysics, has served terms as an Associate Editor for the Journal of Geophysical Research and Journal of Geodesy, and is currently Editor in Chief of the International Association of Geodesy Symposia Series.