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

Abstract

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 14C, Pb concentrations, stable Pb isotopes, pollen markers, charcoal concentrations and 137CS. Sea level was rising slowly (0.3 ± 0.3 mm yr-1) from AD 1500 to AD 1900, 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. Copyright 2008 by the American Geophysical Union.