Douglas Carlson Louisiana Geological Survey, Louisiana State University, Baton Rouge, Louisiana, 70803-001
The rate of relative sea-level-rise (RSLR) rise has been measured for approximately 200 years for ports mainly in the north Atlantic and for nearly 100 years for ports in Gulf of Mexico coast. The acceleration of RSLR has been correlated to global warming measured over the past 130 years. However, in the past 18 to 20 years there has been observed a pause of global warming when the temperature has remained approximately constant. Has the temperature pause impacted RSLR for Louisiana? For the Louisiana coast line RSLR was impacted more by local subsidence than global sea level rise. A number of studies have determined Louisiana RSLR is to up to ten times greater than that due to only global RSLR. For the Louisiana coast line has a reduction in oil production during the past twenty years impacted RSLR significantly?
Values of RSLR in Louisiana and Florida were determined using United States Geological Survey (USGS) and National Oceanic and Atmospheric Administration (NOAA) tidal gaging stations located in estuaries, rivers, and streams where records clearly show the daily influence of tides. These two sources of data include over 40 stations in both Louisiana and Florida. The RSLR value at each station was determined by taking a linear regression of daily mean gage values for USGS data and monthly mean gage values for NOAA data. Stations records are typically 10 to 15 years in length. Florida is considered a stable area where RSLR lacks any significant impact from local subsidence. By contrast Louisiana is an area where RSLR is dominated by local subsidence due to isostatic flexure caused by a thick pile of sediment, over 40,000 feet thick that has been dumped into this region by the Mississippi River and ancestral versions since the Jurassic. This explains the difference of average RSLR between Louisiana and Florida.