A 20th century acceleration of sea-level rise in New Zealand

Sea levels in New Zealand have remained relatively stable throughout the past 7000 years, but salt- marsh cores from southern New Zealand show evidence of a recent rapid rise. To date and quantify this rise we present a proxy sea- level record spanning the past 500 years for Pounawea, southeastern New Zealand, based on foraminiferal analyses. Ages for ten sea- level index points are established from AMS C-14, Pb concentrations, stable Pb isotopes, pollen markers, charcoal concentrations and Cs-137. Sea level was rising slowly ( 0.3 +/- 0.3mm yr(-1)) from AD 1500 to AD1900, but during the 20th century the rate increased to 2.8 +/- 0.5 mm yr(-1), in agreement with instrumental measurements commencing in 1924. This is the first sea- level record from the southern hemisphere showing a significantly higher rate of sea- level rise during the 20th century as compared with preceding centuries.