Oceanic sea-surface temperature

  • Image, Ocean sea-surface temperature.

    The oceans store most of the excess energy accumulated due to increased greenhouse gases in the atmosphere warming the surface layer. These long-term increases in temperature caused by climate change are in addition to natural variability where ocean temperatures change in response to climate oscillations like the El Niño Southern Oscillation.

    Changes in sea-surface temperatures can affect marine processes, environments, and species. Some species may shift range or find it hard to survive in changing environmental conditions. Warmer water also takes up more space, which contributes to sea-level rise.

    We classified Oceanic sea-surface temperature as a national indicator.

    Key findings

       Indeterminate trend

    No sea-surface temperature trend could be determined for New Zealand’s oceanic, subtropical, and subantarctic waters and the Tasman Sea for 1993 to 2016. Trends were assessed at the 95 percent confidence level.

    From 1993 to 2016, averaged over large areas:

    • annual sea-surface temperatures varied by 0.74–1.20 degrees Celsius.
    • our sea-surface temperatures can vary by up to 0.84 degrees Celsius from year to year. The large inter-annual variability in sea-surface temperatures, coupled with the relatively short duration of our data, make identifying a trend unlikely. We expect to find an increasing trend in New Zealand’s ocean temperatures over longer timeframes.

    Figure 1

     

    Figure 2

    Note: The normal temperature is calculated as the average temperature for 1993–2012.

    Figure 3

    Annual average sea-surface temperature 1993–2012 and anomaly 2014–2016 – interactive map

    Map, Average annual sea-surface temperature 1993–2012 and anomaly 2014–16.

    Note: The sea-surface temperature anomaly for each year from 2014 to 2016 is calculated as the difference between the annual average temperature for that year and the normal (1993–2012) 20-year average.

    Definition and methodology

    Energy has increased in the global climate system, due mainly to human-made emissions of carbon dioxide (CO2) and other greenhouse gases (IPCC, 2013). Globally, oceans absorbed more than 90 percent of the accumulated energy in the global climate system between 1971 and 2010, leading to higher ocean temperatures (IPCC, 2013). Oceans also absorbed 30 percent of human-induced emissions of CO2, leading to increased ocean acidification (IPCC, 2013). It takes a lot of energy to heat water and because the oceans are so large, small temperature variations still represent a significant variation in heat for the climate system (IPCC, 2013).

    Over the last century, we know that New Zealand’s sea-surface temperature has increased 0.71 degrees Celsius (Mullan et al, 2010), which is consistent with worldwide increases (Hartmann et al, 2013). We are virtually certain that climate change has caused higher sea-surface temperatures globally (IPCC, 2013). Given the increases in global sea-surface temperature (IPCC, 2014), we expect to find an increasing trend in New Zealand’s ocean temperatures over longer timeframes.

    The relatively short time series of our data and large inter-annual variability in sea-surface temperatures make determining a trend unlikely. Datasets with longer time series are available, but we used this dataset because it covers the New Zealand region and the spatial variability of temperatures in our waters.

    We used NIWA’s sea-surface temperature archive, which is derived from the Advanced Very High Resolution Radiometer (AVHRR) satellite data it receives from the US National Oceanic and Atmospheric Administration. The archive provides high spatial (approximately 1km) and high temporal (approximately six-hourly in cloud-free locations) resolution estimates of sea-surface temperatures over the New Zealand region, dating from January 1993. Uddstrom & Oien (1999) and Uddstrom (2003) describe the methods used to derive and validate the data.

    Our data extends from about 30°S to 55°S, and from 160°E to 170°W and is grouped into five areas: the exclusive economic zone (EEZ), the Chatham Rise, northern subtropical waters, subantarctic waters, and the Tasman Sea.

    See Ocean acidification for more information.

    Data quality

    We classified Oceanic sea-surface temperature as a national indicator.

    Relevance

       This national indicator is a direct measure of the ‘Natural pressures' topic.

    Accuracy

       The accuracy of the data source is of high quality.

    See Data quality information for more detail.

    References

    Hartmann, D, Klein Tank, A, Rusticucci, M, Alexander, L, Brönnimann, S, Charabi, Y, & Zhai, P (2013). Observations: Atmosphere and surface. In Stocker, TF, Qin, D, Plattner, GK, Tignor, M, Allen, SK, Boschung, J,… Midgley, PM (Eds), Climate change 2013: The physical science basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge and New York: Cambridge University Press.

    Intergovernmental Panel on Climate Change (IPCC) (2013). Climate change 2013: The physical science basis. Working Group I Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. [Stocker, TF, Qin, D, Plattner, GK, Tignor, M, Allen, SK, Boschung, J,… Midgley, PM (Eds)], Cambridge and New York: Cambridge University Press.

    Intergovernmental Panel on Climate Change (IPCC) (2014). Climate change 2014: Synthesis report (PDF, 11MB). Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Retrieved from www.ipcc.ch.

    Mullan, AB, Stuart, SJ, Hadfield, MG, & Smith, MJ (2010). Report on the review of NIWA’s ‘seven-station’ temperature series. NIWA Information Series No 78. Retrieved from www.niwa.co.nz.

    Uddstrom, M (2003). Lessons from high-resolution satellite SSTs. Bulletin of the American Meteorological Society, 84(7), 896–897.

    Uddstrom, MJ, & Oien, NA (1999). On the use of high-resolution satellite data to describe the spatial and temporal variability of sea surface temperatures in the New Zealand region. Journal of Geophysical Research: Oceans, 104(C9), 20729–20751. http://doi.org/10.1029/1999JC900167

    Archived pages

    See Oceanic sea-surface temperature (archived 19 October 2017).

     

     

    Updated 19 October 2017

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