R. Steven Nerem
Ph.D. Aerospace Engineering, 1989
University of Texas at Austin
Professor
Aerospace Engineering Sciences
Associate Director, CCAR
E-mail: nerem@colorado.edu
Office: ECNT 319
Phone: 303-492-6721
Web: http://ccar.colorado.edu/nerem/
CV: PDF
Research Interests
Satellite altimetry, sea level change, Earth gravity field determination, time variations of the Earth's gravity field, planetary geodesy, precision orbit determination, astrodynamics.
Current Research: The impact of changes in terrestrial water storage on global mean sea level variations
During the satellite radar altimeter era (1993 to present), global mean sea level has been increasing at a rate of 3.2 millimeters per year. However, there is considerable year-to-year variation (Figure 1). Much of this variability is understood to be due to changes in land/ ocean precipitation patterns in response to climate variability (El Niño Southern Oscillation, ENSO, Pacific Decadal Oscillation, PDO, etc.). The launch of the Gravity Recovery and Climate Experiment (GRACE) satellite gravity mission in 2002 gave us an additional tool with which to study these variations. GRACE allows us to track changes in land/ ocean water storage, and determine where on the land the water is being stored or lost. In addition, GRACE can tell us how the mass of the water in the oceans is changing due to changes in land water storage (Figure 1).
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Global mean sea level variations from satellite altimetry (TOPEX/Poseidon, Jason-1, and Jason-2) and global ocean mass variations from GRACE. Note the decrease in both during the 2011 La Niņa event. http://sealevel.colorado.edu.
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Change in water mass from beginning of 2010 (JFM average) to mid 2011 (MAM average). Blue colors indicate an increase in water mass over the continents.
It is important to understand the causes of changes in global mean sea level so we can better isolate the anthropogenic and non-anthropogenic climate signals. The former is likely accelerating, but detecting this acceleration is difficult with the short 21-year satellite record. ENSO and PDO also have significant impacts on regional sea level, which is an important consideration when studying the regional impacts of sea level change.
Boening, C, JK Willis, FW Landerer, RS Nerem, and J Fasullo. 2012. The 2011 La Niña: So strong, the oceans fell. Geophys. Res. Lett. 39:L18607.
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The evolution of detrended GRACE land mass anomalies is shown for the globe and for continents with substantial contribution to the 2011 global mass increase including Australia (AUS), South America (SA), and North America (NA). The multi-estimate range is shaded. The 2010 minimum and 2011 maximum are highlighted, as are related deficits (red) and excesses (blue). Also shown are the runoff ratio (RR) and contribution to the global change from the 2010 minimum to the 2011 peak. [Fasullo et al., 2013]
Click here for a complete list of published works »
Professor Nerem is a CIRES Professor.