Author:John Hannah, Rob Bell, Ryan Paulik
Source:Auckland Regional Council | NIWA
The Auckland Regional Council has sought an assessment of past, present and future sea level change in the Auckland Region.
The assessment of past changes in sea level has an important role in informing likely future change. Geological evidence suggests that at specific periods in the past, New Zealand sea levels have risen by rates well in excess of 15 mm/yr. Current evidence suggests that during the mid-Holocene climatic optimum (5,500 to 3,000 years before present), when global temperatures are thought to have been 2:C or more higher than at present, New Zealand sea levels stood 0.5 m – 1.0 m above present day levels. The range of different climate change scenarios produced by the Intergovernmental Panel on Climate Change (IPCC) in 2007, predict a possible rapid return to these temperatures and sea levels by 2100 AD. Sea levels during the mid-Holocene climatic optimum can thus be expected to provide a likely upper bound for sea level rise over this century, provided the ice sheet response doesn’t reach a tipping point due to the rapidity of the future change in global temperatures. Temperature rise during the mid-Holocene is thought to have been at a slower rate than is anticipated over the next century.
It is now well established that after a considerable period of stability, global sea levels began to rise towards the end of the 19th Century.
Auckland Regional Council technical report TR2010/065
University of Otago
National Institute for Water and Atmospheric Research, NIWA