Research Title: Sea-Level Change
Funding Level (millions of dollars):
Committee on Environment and Natural Resources (CENR) Component:
(a) Subcommittee: Global Change Research Subcommittee (100%) NSTC Committee on Fundamental Science
(b) Environmental Issue: Natural variability (70%); Global change: exploratory research (30%)
(c) Research Activity System structure and function: Observations (60%); Understanding (40%)
National Science Foundation
4201 Wilson Blvd.
Arlington, VA 22230
Point of Contact:
Michael A. Mayhew
To monitor current changes in sea level using geophysical techniques and to characterize past sea level changes recorded in the geologic record.
Any substantial rise in sea level due to global warming will have a severe impact on low-lying coastal areas and oceanic islands. Mitigation of the effects of rising sea level on developed coastal regions (barrier islands, river estuaries, and deltas) over the short term would involve a large monetary investment in shoreline stabilization; over the long term, strategic retreat becomes necessary, with large economic costs and widespread social disruption. Prudent formulation of national and international public policy with respect to future sea level change requires a solid scientific understanding of the trend in absolute sea level in the decade time frame, and how local or regional tectonics may counter or amplify worldwide sea level change. In order to achieve this understanding, NSF plans to systematically expand its programs in space-based geodesy using the Global Positioning System (GPS) and in fundamental studies of active tectonic processes. This will result in strategically-placed geodetic networks at coastal locations and in places of tectonic activity. Through analysis of data from these networks, long-term trends in sea level due to glacial melting and ocean expansion can be distinguished from effects of post-glacial rebound and active tectonics. Analysis of data from coastal locations will be supported by analysis of data from tide gauges and absolute gravity instruments. Analysis of relative motions due to active tectonics in the vicinity of plate boundaries will be supported by investigations involving geologic field studies and the deployment of portable seismic arrays. Basic scientific investigations of internal processes within the solid Earth, coupled with well-distributed observations, careful data processing, and the development of long time series, are essential for an understanding of this important form of global change.
NSF's global geodetic program, which forms the basis for its support of studies of sea level change, is linked to NOAA's in situ global sea level network, NASA's satellite ocean topography experiment (TOPEX/Poseidon), and the space geodetic programs of the three agencies for high resolution measurement of both tectonic and climate-induced sea level change. NSF supports GPS investigations through the University NAVSTAR Consortium (UNAVCO), which has an international membership; a substantial fraction of the currently-supported projects are outside the U.S., and involve cooperation with the national geodetic agencies of other countries. NSF's program of studies of contemporary sea level.
Expansion of the space-based geodesy program based on GPS through updating and wider distribution of hardware and software associated with both permanent and portable GPS arrays. Continuation of GPS and seismic field programs focusing on relative plate motions in the Caribbean and the South Pacific from 1995 to 1998.
The long-term policy payoff of extracting the climate-induced sea level signal requires continuous, accurate time series from globally well-distributed geodetic marks. Thus, there is much short-term policy benefit in early establishing of such marks, in collaboration with international partners, along with support for research in data processing and analysis, which will provide a basis for policy judgments in the shortest possible time concerning how fast control measures must be implemented. In the short term, this activity is directly relevant to policy issues within the areas of Climate Change and Global Warming (in the contest of natural variability) and International Cooperation. Over the longer term, it is relevant to most of the "interactions" aspects of Human Dimensions and Economics as currently defined.