Annual glacier ice volumes

  • Image, change in glacier volume.

    A glacier is a body of slow-moving ice, at least 1 hectare in area that has persisted for two decades or longer. New Zealand has 3,144 glaciers. Most are located along the Southern Alps on the South Island, although Mount Ruapehu on the North Island supports 18 glaciers. New Zealand’s large glaciers are noteworthy for their large debris cover. The exceptions, Franz Joseph and Fox glaciers, are rare examples of glaciers that terminate in a rainforest.

    Glacier volume is strongly influenced by climate factors, such as temperature and precipitation, which scientists expect to be affected by the warming climate. Glacial ice is an important water resource. Changes to ice storage and melting can affect ecological and hydropower resources downstream, as well as important cultural values and tourism.

    We classified Annual glacier ice volumes as a case study.

    Key findings

    There was a trend of decreasing glacier ice volume between 1977 and 2016 at the 95 percent confidence level. Glacier ice volume decreased 25 percent from 1977 to 2016.

    • An average of 0.33 km3 of glacier ice volume was lost each year from 1977 to 2016, enough to fill 133,000 Olympic swimming pools each year.
    • From the maximum volume in 1997 to 2016, 15.5 km3 of ice was lost, enough to fill Wellington Harbour 12 times.
    Note: Glacial ice year runs from 1 April to 31 March.

    Definition and methodology

    The annual total glacier ice volume is reported in water equivalents, using the units km3. A value of 0.9 was used to convert an ice volume to a water equivalent volume. Each glacial ice year runs from 1 April to 31 March, and is referred to by the year at the end of the period (eg the 2016 year runs from 1 April 2015 to 31 March 2016). This is the only time glaciers can be observed separately from temporary snow.

    Glacier ice volumes originate from the 1978 New Zealand Glacier Inventory and the annual New Zealand glacier snowline survey programme which commenced in 1977. These use the end of summer snowline of 50 index glaciers for determining the annual mass balance of glacier ice, and geodetic survey information for 12 large low-angle debris-covered glaciers.

    The two methods are applied separately due to the differing response of the 12 large glaciers which are losing ice steadily due to down-wasting of their trunks and the growth of proglacial lakes. An annual volume change for the 50 index glaciers is derived from an annual average net mass balance value based on a well-documented reference glacier that is applied to their respective surface areas.

    This report differs from earlier reports. We use a longer and more recent set of measured mass balance gradient data from the Brewster Glacier rather than data from 1965 to 1975 from the Ivory and Tasman glaciers. Because of this, ice volume estimates will differ between this and earlier reports.

    Most of New Zealand’s glaciers are in the South Island. Chinn (2001) completed a detailed inventory of 3,144 glaciers over 1 hectare in area across New Zealand, including 18 from Mount Ruapehu.

    Scientists expect temperature and precipitation to be affected by the warming climate (IPCC, 2014).

    Data quality

    We classified Annual glacier ice volumes as a case study.


      This case study is a partial measure of the ‘Sites of significance, including wāhi taonga and wāhi tapū' topic. 


      The accuracy of the data source is of high quality. 

    See Data quality information for more detail.


    Chin, TJ (2001). Distribution of the glacial water resources of New Zealand (PDF, 1.94MB). Journal of Hydrology (New Zealand), 139–187. Retrieved from

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

    Archived pages

    See Change in glacier ice volume (archived October 2017).


    Updated 30 January 2018

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