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The glacier sedimentary system
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
It is helpful to recognize three main types of glacier on the basis of the relative importance of ice supply and the nature of the topography (Figure 17.1). Ice sheets or icecaps form broad domes which submerge the underlying topography. Ice radiates out from the centre as a sheet, although near the periphery it may be confined and flow through uplands in outlet glaciers. The difference between an ice sheet and an icecap is conventionally accepted to be one of scale, with icecaps generally less than around 50,000 km2 in area. The Antarctic provides a fine example of a large ice sheet, with two components, one in west Antarctica over 2000 m high and one in east Antarctica nearly 4000 m high (Figure 17.2). The latter is some 5000 km across. Smaller icecaps occur in Arctic Canada, Iceland and Norway and may measure only a few tens of kilometres across. An alpine or valley glacier is one which is severely controlled by topography in that it flows in a mountain valley and is overlooked by rock valley walls. Unlike an ice sheet or icecap, glacier flow is strongly influenced by topography. Such glaciers are characteristic of steep mountains, both in the polar regions and in mountain ranges worldwide. An ice shelf is in essence a floating ice sheet or icecap. It is loosely controlled by topography in that one side is bounded by a coastal embayment. The main feature is that, unlike other glaciers, there is no friction with the bed and the ice can spread freely. The largest examples occur in Antarctica, namely the Ross and Ronne-Filchner ice shelves (Figure 17.2). The former is larger than France and yet moves up and down with each tide.
High-resolution spatio-temporal analysis of snowmelt over Antarctic Peninsula ice shelves from 2015 to 2021 using SAR images
Published in International Journal of Digital Earth, 2023
Qi Zhu, Huadong Guo, Lu Zhang, Dong Liang, Xuting Liu, Heng Zhou, Yiting Gou
Unusually intense and long-term surface melting is the common precursor to sudden ice shelf collapse (McGrath et al. 2012). In July 2017, the A-68, a 1-trillion-ton iceberg, with an area of 5,800 km, broke off from the LCIS. Figure 6 shows the 2016/2017 snowmelt information of the LCIS before the A68 iceberg broke off. During the austral summer, surface snowmelt of the LCIS was significantly intense, which was likely affected by the El Nino phenomenon. And the duration of melt days near the A68 iceberg was significantly higher, as shown in Figure 6(a). Surface meltwater was found on the LCIS when large-scale surface melting has not yet occurred on the LCIS. The melt then gradually spread into the interior of the ice shelf (Figure 6(c–f)), during which the surface of A68 iceberg filled with snowmelt. In February 2017, meltwater was still found on the surface of A68 (Figure 6( h,i)). The high-resolution snowmelt information can show melting patterns of the ice shelf at a finer scale, which allows for qualitative analysis of the correlation between surface snowmelt and ice shelf collapse and disintegration, but an exhaustive explanation for these events still require further research.
Correlation and interaction between temperature and freeze-thaw in representative regions of Antarctica
Published in International Journal of Digital Earth, 2022
Dong Liang, Huadong Guo, Qing Cheng, Lu Zhang, Lingyi Kong
The freeze–thaw cycle has an important impact on the mass balance of the Antarctic ice sheet (Shepherd et al. 2018). The meltwater generated by ice sheet melting has three main effects. (1) The meltwater forms runoff and causes ice sheet thinning. (2) The melt water is transmitted vertically and moves deeper into the ice, changing the thermal and hydrological state of the bottom of the ice sheet. (3) The melt water accumulates in ice cracks resulting in further fracturing when the water refreezes. The ice lakes formed by meltwater create pressure on the ice shelf, causing the ice shelf to bend and crack and eventually disintegrate (Hanna et al. 2013). Additionally, the surface albedo of the wet snow is much lower than that of dry snow, facilitating absorption of solar radiation and consequently leading to further melting.