科研之友
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摘要
Depending on thickness, debris-cover can enhance or reduce ablation, compared to bare-ice conditions. In the geological record, hummocky moraines often represent the final product of the melt-out of ice-cored moraines, and the presence or absence of such moraine deposits can have paleoclimatic implications. To evaluate the effects of varying debris-cover and climate on ice-melt in a maritime mid-latitude setting, an 11-day ablation stake study was undertaken on ice-cored moraine at Fox Glacier, on the western flank of the New Zealand Southern Alps. Ablation rates varied from 1.3 to 6.7 cm d-1, with enhancement of melt-rate under thin debris-covers. Highest melt-rates (effective thickness) occurred under debris-cover of c. 2 cm, with similar to 3 cm being the debris thickness at which melt-rates are equal to adjacent bare-ice (critical thickness). Air temperature from nearby Franz Josef Glacier allowed for a simple degree-day approach to ablation calculations, with regression relationships indicating air temperature is the key climatic control on melt. Digital elevation models produced from topographic surveys of the ice-cored moraine over the following 19 months indicated that ablation rates progressively decreased over time, probably due to melt-out of englacial debris increasing debris-cover thickness. The morphology of the sandur appears to be strongly determined by episodic high-magnitude fluvial flows (jokulhlaups), in conjunction with surface melt. Thus, hummocky moraine appears to be a transient landform in this climatic setting.
- 出版日期2012
