Regional sea level trends in New Zealand Journal Paper
- Author
- Hannah, J. and Bell, R.G.
- Year
- 2012
- Journal / Source
- Journal of Geophysical Research
- Publisher / Organisation
- American Geophysical Union
- Volume
- 117
- Number
- C01004
- Pages
- 7
- Summary
- In terms of sea level data sets able to be used for long-term sea level trend analysis,the Southern Hemisphere is a data sparse region of the world. New Zealand lies in thisregion, presently having four (major port) data sets used for such trend analysis. This paperdescribes the process followed to compute new sea level trends at another six ports,each with very discontinuous tide gauge records. In each case the tide gauge has previouslyonly been used for precisely defining an historical local Mean Sea Level (MSL) datum.The process used involved a comparison of the old MSL datum with a newly defineddatum obtained from sea level data covering the last decade. A simple linear trend wasfitted between the two data points. Efforts were then made to assess possible bias in theresults due to oceanographic factors such as the El Niño–Southern Oscillation (ENSO)cycle, and the Interdecadal Pacific Oscillation (IPO). This was done by taking the longertime series from the four major ports and assessing the spatially coherent variability inannual sea level using the dominant principal component from an empirical orthogonalfunction (EOF) analysis. The average relative sea level rise calculated from these six newlyderived trends was 1.70.1 mm yr1, a result that is completely consistent with theanalysis of the long-term gauge records. Most importantly, it offers a relatively simplemethod of improving our knowledge of relative sea level trends in data sparse regionsof the world.