Calving speed and climatic sensitivity of New Zealand lake-calving glaciers.

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    Abstract

    Calving speeds and calving mechanisms in fresh water contrast with those in tidewater. We obtained calving speeds for six lake-calving glaciers in New Zealand's Southern Alps, and surveyed the depths and temperatures of their ice-contact lakes. The glaciers are temperate, grounded in shallow (less than or equal to20 in) water, and exhibit compressive flow at their termini. These data increase the global dataset of fresh-water calving statistics by 40%, bringing the total to 21 glaciers. For this dataset, calving rates (u(c)) correlate positively with water depths (h(w)) (r(2) = 0.83), the relationship being expressed by: u(c)= 17.4 + 2.3h(w). This is an order of magnitude lower than values of u(c) at temperate tide-water glaciers. For a subset of 10 glaciers for which ice-proximal water temperature (t(w)) data are available, u(c) also correlates positively with t(w), supporting a physical relation between calving and melting at and below the water-line. Fluctuations of New Zealand lake-calving glaciers in the period 1958-97 show that although the transition from non-calving to calving dramatically increases frontal retreat rates, the onset of calving does not isolate terminus change from climatic forcing. In terms of climatic sensitivity, lake-calving glaciers occupy an intermediate position between tidewater glaciers (least sensitive) and non-calving glaciers (most sensitive).

    Original languageEnglish
    Pages (from-to)173-178
    Number of pages6
    JournalAnnals of Glaciology
    Volume36
    Publication statusPublished - 2003

    Keywords

    • COOK NATIONAL-PARK
    • TASMAN GLACIER
    • SOUTHERN PATAGONIA
    • RATES
    • FLUCTUATIONS
    • TEMPERATURE
    • DYNAMICS
    • TERMINUS
    • WATER

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