Supraglacial Re-Sedimentation from Melt-Water Streams on to Snow Overlying Glacier Ice, Sylgjujökull, West Vatnajökull, Iceland

• Published in: Journal of Glaciology
• Main Author: Dowdeswell, Julian A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1982
• Subjects: Earth-Surface Processes; Vatnajökull; glacier; Iceland; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000011709; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000011709

Abstract Sediment deposition on to snow overlying glacier ice occurs in a marginal zone extending 200–300 m up-glacier from the terminus of Sylgjujökull. Debris on ice above the marginal snow zone comes from debris-rich layers, and 85% of this debris falls between 1 and 4 ϕ , the characteristic grain-size of volcanic ash within Icelandic glaciers. The ash is transported down-glacier as suspended load in melt-water streams at concentrations between 61 and 430 mg l −1 , and loads from 0.2 to 32.7 g s −1 . A diurnal hysteretic loop is present in the relationship between suspended sediment and discharge for one stream. Supraglacial streams flow from relatively impermeable ice on to more permeable snow near the glacier terminus. As they move across the snow, stream discharge (up to 0.1 m 3 s −1 on ice) is reduced and debris is re-sedimented as linear debris trains 1–3 cm thick and orientated orthogonal to the glacier margin. Since sediment deposition reduces the permeability of the snow substrate, the debris trains are successively extended across the snow cover at rates of up to 36.5 m d −1 . If the debris is then let down on to glacier ice, linear dirt-cone assemblages may be produced. Re-sedimented debris trains are of little stratigraphic significance if deposited pro-glacially.