FIG Peer Review Journal


The Problems and Challenges in Using Tide Gauges to Monitor Long-term sea Level Change (3786)

John Hannah (New Zealand)
Professor John Hannah
School of Surveying
University of Otago
PO Box 56
New Zealand
Corresponding author Professor John Hannah (email: john.hannah[at], tel.: + 64 3 479 9010)

[ abstract ] [ paper ] [ handouts ]

Published on the web 2010-01-14
Received 2009-11-19 / Accepted 2010-01-14
This paper is one of selection of papers published for the FIG Congress 2010 in Sydney, Australia and has undergone the FIG Peer Review Process.

FIG Congress 2010
ISBN 978-87-90907-87-7 ISSN 2308-3441


Climate change has a variety of important impacts, one of which is reflected in sea levels. Indeed, long term rising trends in global sea levels are often used to corroborate the assertion of long term climate change. When tide gauge records are examined in order to determine the long-term trends in sea level, it is typical for a single number, representing the derived trend, to be quoted. However, the problems in deriving such numbers are rarely, if ever, discussed. Indeed, there appears to be a widespread ignorance as to the fragility of tide gauge records and hence the accuracy of derived long-term sea level trends. This paper uses specific examples from New Zealand to illustrate and explain the problems that exist in deriving an accurate figure for the eustatic changes in sea-level at a tide gauge site. It highlights the importance of assessing accurately the influence of anthropological factors, changes in tide gauge datums, and geophysical effects. These factors, which can compromise or even completely invalidate a record, must be able to be assessed over the entire history of the tide gauge record (often 100+ years). This paper, after exploring these factors and their potential influence, concludes by making recommendations on procedures to be followed if we are to leave future generations better quality sea level data than is often available at present.
Keywords: Hydrography; Coastal Zone Management; Deformation measurement