Quantifying periglacial erosion: insights on a glacial sediment budget, Matanuska Glacier, Alaska

Abstract

Glacial erosion rates are estimated to be among the highest in the world. Few studies have attempted, however, to quantify the fl ux of sediment from the periglacial landscape to a glacier. Here, erosion rates from the nonglacial landscape above the Matanuska Glacier, Alaska are presented and compare with an 8-yr record of proglacial suspended sediment yield. Non-glacial lowering rates range from 1·8 ± 0·5 mm yr −1 to 8·5 ± 3·4 mm yr −1 from estimates of rock fall and debris-fl ow fan volumes. An average erosion rate of 0·08 ± 0·04 mm yr −1 from eight convex-up ridge crests was determined using in situ produced cosmogenic 10 Be. Extrapolating these rates, based on landscape morphometry, to the Matanuska basin (58% ice-cover), it was found that nonglacial processes account for an annual sediment fl ux of 2·3 ± 1·0 × 10 6 t. Suspended sediment data for 8 years and an assumed bedload to estimate the annual sediment yield at the Matanuska terminus to be 2·9 ± 1·0 × 10 6 t, corresponding to an erosion rate of 1·8 ± 0·6 mm yr −1 : nonglacial sources therefore account for 80 ± 45% of the proglacial yield. A similar set of analyses were used for a small tributary sub-basin (32% ice-cover) to determine an erosion rate of 12·1 ± 6·9 mm yr −1 , based on proglacial sediment yield, with the nonglacial sediment fl ux equal to 10 ± 7% of the proglacial yield. It is suggested that erosion rates by nonglacial processes are similar to inferred subglacial rates, such that the ice-free regions of a glaciated landscape contribute signifi cantly to the glacial sediment budget. The similar magnitude of nonglacial and glacial rates implies that partially glaciated landscapes will respond rapidly to changes in climate and base level through a rapid nonglacial response to glacially driven incision.

Recent High-Arctic glacial sediment redistribution: A process perspective using airborne lidar

“…Such events may provide some control of sediment mobilisation and yield from the fluvial-periglacial system of deglaciating basins and the significant moraine stores (Beylich and Gintz, 2004;Etienne et al, 2008), which can represent up to 60% of sediments stored within alpine-style, deglaciating catchments (e.g., Otto et al, 2009). Combined, the findings here emphasise the significance of the nonglacial area for control of a deglaciating catchment's sediment yield (e.g., O'Farrell et al, 2009) and infer caution for interpretations of moraines as analogues or indicators of palaeoenvironments, landforming processes, or climate. Notably, these arguments do invoke a degree of speculation, particularly given the brief 2-year time period between lidar surveys; however, Barrand et al (2010) report the mass balance of Midtre Lovénbreen during 2003-2005 to be −0.51 ± 0.02 m w.e.…”

MODIS observed increase in duration and spatial extent of sediment plumes in Greenland fjords

“…A complex and highly variable relationship exists between the glacier hydrologic network and the transport of sediment (Fenn et al, 1985;O'Farrell et al, 2009;Østrem, 1975). Spatio-temporal variability in sub-glacial hydrologic networks can drive variability of sediment emerging from glaciers (Collins, 1990) and transient flushes of sediment from glaciers in Greenland have been observed (Stott and Grove, 2001).…”

7.29 Changing Hillslopes: Evolution and Inheritance; Inheritance and Evolution of Slopes

“…A quantitative understanding of this process has led to the development of numerical models that predict the relative intensity of periglacial activity that promotes sediment transport (Hales and Roering, 2007). Sediment budgets created within periglacial landscapes highlight the high rates of periglacial erosion, which represent up to 80% of the glacial sediment budget (Harbor and Warburton, 1993;O'Farrell et al, 2009). Recent use of shallow subsurface geophysics has provided a more detailed picture of the volumes of sediment created within glacial valleys (Sass and Wollny, 2001), again highlighting the rapid response of glacial valleys to deglaciation.…”