A talk by UoB Benjamin Meaker Visiting Professor Robert Steven Nerem, University of Colorado, USA.

Biography

Dr. Nerem is a professor in Aerospace Engineering Sciences at the University of Colorado. He is currently Associate Director of CU’s Colorado Center for Astrodynamics Research, and a Fellow of CU’s Cooperative Institute for Research in Environmental Sciences. He joined the faculty in 2000 after spending over 6 years at NASA/Goddard Space Flight Center as a geophysicist, and over 4 years at the University of Texas at Austin as an assistant and associate professor. He received his B.S. degree in Geology from Colorado State University in 1982, and his M.S. and Ph.D. degrees in Aerospace Engineering from The University in 1985 and 1989 respectively. Dr. Nerem also worked for NOAA and the Jet Propulsion Laboratory during his graduate training. Dr. Nerem is a specialist in satellite remote sensing and geodesy, with a main research focus on measuring sea level change using satellite altimetry and satellite gravity data. He pioneered the use of satellite altimetry for measuring long-term sea level change related to climate variations and determining the causes of the observed changes. He was a Lead Author for the IPCC 5th Asessment Report. Dr. Nerem has participated in several NASA satellite flight projects including TOPEX/Poseidon, Jason-1, GRACE, and Jason-2. He is currently a member of the Science Definition Team for the Surface Water Ocean Topography (SWOT) Mission and the Project Science Advisory Team for the GRACE Follow-On Mission. In 1995, Dr. Nerem was awarded NASA's Exceptional Scientific Achievement Medal for his research in the area of gravity field determination for satellite altimeter applications, in addition to a dozen NASA achievement and performance awards he received while at NASA. NASA recently named Dr. Nerem the Team Leader of the NASA Sea Level Change Team (N-SLCT), a three year effort to better understand future sea level change. He also received the American Geophysical Union’s Geodesy Section Award in 2006 and was elected a Fellow of the AGU in 2008.

Summary

The 25-year record of global sea level change from satellite altimetry is one of our most valuable climate data records of how the Earth is responding to anthropogenic warming. But what have we learned from this record? This presentation will summarize our current understanding of sea level change based on the satellite altimeter record. One important fact we have learned from these observations is that the 25-year altimeter record occurs during a remarkably unusual time in the 100+ year sea level record. As a result, we must ask ourselves how this affects our interpretation of the altimeter record – are the changes we are observing short term or long term? Sorting out the natural and anthropogenic climate signals is a continuing challenge as we move into the future and look for answers to the many questions that remain. We know now that this record was impacted by the eruption of Mount Pinatubo about a year prior to the launch of TOPEX/Poseidon. Most of the interannual variations in the record are related to ENSO, but no two events look the same. The rate of sea level rise, ~3 mm/year over 25 years, represents an acceleration relative to the tide gauge record of sea level change. Now, it appears that an acceleration can be detected in the altimeter record itself, and this acceleration appears to be driven by ice melting in Greenland and Antarctica. This is also an appropriate time to pause and ask if we have the measurements we need to answer these questions, or if new measurements are needed? Several new satellite measurement systems are planned – how will they enhance our understanding of sea level change? This presentation will look back at the 25-year satellite altimeter record – but also look forward to measurements and discoveries yet to be made.

During his stay in Bristol Dr Nerem will be hosted by Professor Jonathan Bamber (Geographical Sciences) and will give a departmental seminar on sea level research (open to all) and a graduate student seminar on satellite geodesy related to sea level and ocean processes (dates and times TBC).