Coastal sea-level rise

  • Image, Coastal sea-level rise.

    Archived 27 October 2016

    Sea-level rise is a consequence of climate change. Increases in global temperature cause ocean waters to expand, and glaciers and ice sheets to melt into oceans. Sea-level rise affects estuaries, coastal wetlands, and intertidal and sub-tidal habitats and species. The increased likelihood of coastal erosion from sea-level rise presents a risk for seaside communities and their infrastructure, and for the marine environment itself, from increased suspended sediments.

    We classified Coastal sea-level rise as a national indicator.

    Key findings

     Increasing trend (declining state)

    Our coastal sea level (relative to land) is rising.

    • Available tide gauge data showed rising trends in all long-term monitored sites over approximately 100 years, between 1900 and 2013.
    • The Wellington tide gauge showed the most marked trend: + 2.14 ± 0.16 mm/year. Other sites with less marked changes were:
      • Auckland + 1.55 ± 0.08 mm/year
      • Dunedin + 1.36 ± 0.08 mm/year
      • Lyttelton + 1.98 ± 0.09 mm/year
      • New Plymouth + 1.31 ± 0.28 mm/year.

     

    Note: Sea levels are relative to data for a particular port. No information is available for New Plymouth before 1955, apart from some data for 1918–21. The relative sea-level trend for New Plymouth is strongly influenced by the mean value for relative sea level for this period. This single value, found in old correspondence files, is derived from the original tide charts. Data are not available for all years.

    Definition and methodology

    This indicator presents data on the rise in annual mean coastal sea levels relative to land for five locations across New Zealand (Auckland, New Plymouth, Wellington, Lyttelton, and Dunedin) and the trends over time.

    These results are consistent with previously published information using the same tide gauges (Hannah, 1990; 2004).

    Melting sea ice has little direct effect on sea-level rise, compared with the main factors of ocean expansion, and glacial and ice-cap melt.

    The 2014 Intergovernmental Panel on Climate Change (IPCC) report had a high confidence that coastal squeeze (when natural habitats are eroded by the sea and cannot retreat due to arable, built, or unsuitable land on their landward edge) will accelerate with rising sea levels (Wong et al, 2014). This can lead to habitat loss for resident or migrant species.

    Data quality

    We classified Coastal sea-level rise as a national indicator.

    Relevance

    relevance-direct This national indicator is a direct measure of the ‘Sea level, temperature, and circulation’ topic.

    Accuracy

    accuracy-high The accuracy of the data source is of high quality.

    See Data quality information for more detail.

    References

    Hannah, J (1990). Analysis of mean sea level data from New Zealand for the period 1899–1988, Journal of Geophysical Research, 95(B8): 12399–12405.

    Hannah, J (2004). An updated analysis of long-term sea level change in New Zealand. Geophysical Research Letters, 31(3): L03307, doi:10.1029/2003GL019166.

    Wong, PP, Losada, IJ, Gattuso, JP, Hinkel, J, Khattabi, A, McInnes, KL, Saito, Y, & Sallenger, A (2014). Coastal systems and low-lying areas. In Field et al (Eds.). Climate change 2014: Impacts, adaptation, and vulnerability. Part A: Global and sectoral aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Available from http://ipcc-wg2.gov.

     

    Published 21 October 2015

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