Global Sea Level Measurement Program

The sea level along the east coast of the United States from Maine to Florida, as determined from long-term (50-100 years) measurements using conventional coastal tide gauges leveled to nearby geodetic bench marks, is apparently rising at a rate of between 1 mm/year to 4 mm/year. There are also some indications that the overall rate of rise may have increased in recent decades. Trends of this nature are also speculated to occur on a global basis. Given the persistence of the trend over decades, many coastal communities and shore installations are likely to be seriously threatened. Unfortunately, the nature and quality of existing sea level measurements make interpretations and predictions highly speculative and any overall response strategy is, therefore, difficult. The existing measurements only provide a rise of sea level relative to land. Considering geological phenomena (including positive and negative glacial rebound, land subsidence, and earthquake motions) along with nongeologic ones (rising atmospheric concentration of CO
2
and other trace gases), the analysis of sea level data becomes significantly complex and determining its temporal and spatial domains is a scientific and technological challenge. The major objective of a program effort described by National Oceanic and Atmospheric Administration (NOAA) will be to determine the individual contributions and nature of major large-scale land motions and oceanographic effects on the measured global sea level signature.