NSW Sea Level Trends – The Ups & Downs

Ed Couriel, Ben Modra, Rob Jacobs - NSW Public Works MHL , 30 October, 2014

Following the removal of the NSW Sea Level Rise Policy Statement in September 2012, there has been great interest in NSW sea level records to provide often misguided “evidence based” estimates of local/regional sea level trends. One of the great difficulties in climate change and sea level rise planning is that the level of common knowledge on the subject is highly diverse, often biased by urban myths and interspersed by detailed knowledge in particular aspects with poor overall congruence of fact and meaning to a particular issue at hand. This paper will help develop a good understanding of undisputed baseline ocean water level drivers and responses across different timescales to avoid misinterpretation of sea level data. It also will demonstrate how despite over 25 years of highly valuable continuous quality controlled sea level data available for NSW, sea level rise trends based on these and other historical data are not necessarily representative of expected future long-term sea level change.

The paper will describe where sea level data is collected in NSW and how it is measured both today and in the past, including NSW’s longest records from Fort Denison which commenced in 1886 and provide quality controlled sea level data since 1914. The importance of maintaining recording station metadata will be demonstrated, including instrumentation details, datum changes and monitoring intention(s), as the future value of data will be highly dependent on traceability of these metadata. Through the NSW State Government’s recognition of the value of sustaining continuous quality controlled coastal data, the importance of NSW sea level records continues to increase, both in day to day activities and far longer-term. The paper will discuss key factors necessary to ensure that continuous data collection activities can be sustained. This includes understanding both the physical process development and effective communication of the value of these data.