10 



longer term data set of 12 stations, the eustatic values on the West and 

 East coasts were found to be rising by averages of 1.4 mm/year and 

 1.3 nun/year, respectively. For the shorter term (40 years) of 41 stations, 

 the rates of change for West and East coasts were -0.3 mm/yr and +2.5 

 mm/yr, respectively. It was found that the long-term rates of sea level 

 rise are increasing from Cedar Key on the Florida west coast to Cape 

 Hatteras, decreasing from Cape Hatteras to Cape Cod and increasing from 

 Cape Cod to Eastport, Maine. These results are presented in Fig. 2.2. 

 Finally, it was concluded that there is no evidence from this analysis that 

 rates of SLR are increasing over the past 10 years. 



Pirazzoli (1986) has analyzed the results from 1,178 tide gage 

 stations provided primarily by the Permanent Service for Mean Sea Level. 

 This appears to be the largest data set considered in an individual 

 analysis. The analysis method was straightforward, first taking averages 

 for each station over five year periods, then averaging over the two ends 

 of the resulting data to obtain a change in sea level from which the rate 

 is determined. The results are presented regionally and on a global basis. 

 The effects of glacio-eustatic adjustment to the last ice age are very 

 apparent in the data with relative sea level (RSL) rising and lowering in 

 most low and high latitudes, respectively. The possible effects of 

 earthquakes in causing sudden displacements and altering the trend after 

 the earthquake are illustrated. As an example, the tide gage at Messina, 

 Italy recorded an abrupt increase in RSL of 57 cm during the earthquake of 

 1908. Anthropogenic effects, primarily the extraction of water and 

 hydrocarbons, causing compaction are noted with Venice, Italy particularly 

 evident as a consequence of ground water pumping. In attempting to infer 

 global rates from the available data, it is noted that if the earth is 

 divided into 30° latitude and longitude sectors, a total of 72 compartments 

 result of which 71 have marine coasts. The data distribution in these 

 compartments is very non-uniform. Most of the tide gages (70%) are 

 situated in only 4 compartments whereas there are no data in 70% of the 

 compartments. Long-term tide gage data in the southern hemisphere are 

 particularly sparse with over 97% of the stations examined by Pirazzoli in 

 the northern hemisphere. Without the assumption that the results from the 

 northern hemisphere are globally representative , the available data are 



