The subglacial thermal organisation (STO) of ice sheets |
| |
| Institution: | 1. Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada;2. Department of Earth Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada;1. Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa K1S 5B6, Ontario, Canada;2. Department of Earth Sciences, Carleton University, 2115 Herzberg Laboratories, 1125 Colonel By Drive, Ottawa K1S 5B6, Ontario, Canada;3. Natural Resources Canada, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada |
| |
| Abstract: | This paper examines ice-sheet wide variations in subglacial thermal regime and ice dynamics using the landform record exposed on the beds of former mid-latitude ice sheets (the Laurentide, Cordilleran, Fennoscandian and British-Irish Ice Sheets). We compare the landform patterns beneath these former ice sheets to the flow organisation beneath parts of the contemporary Antarctic Ice Sheet inferred from RADARSAT-1 Antarctic Mapping Project (RAMP) data. The evidence preserved in the landform record and observed on contemporary ice masses can be grouped into four major ice-dynamical components that collectively define the subglacial thermal organisation (STO) of ice sheets. These ice-dynamical components are frozen-bed patches, ice streams, ice-stream tributaries and lateral shear zones. Frozen-bed patches appear at a wide range of spatial scales, spanning four orders of magnitude. In some areas, frozen-bed zones comprise large proportions of the bed (e.g. near the ice divide in continental areas), whilst in other areas they constitute isolated “islands” in areas dominated by thawed-bed conditions. Ice streams, narrow zones of fast flow in ice sheets that are otherwise dominated by slow sheet flow, are also common features of Quaternary ice sheets. Tributaries to ice streams flow at velocities intermediate between full ice-stream and sheet flow, and may divert ice drainage from one primary ice-stream corridor to an adjacent one. Sharp lateral boundaries between landforms indicate sliding and non-sliding conditions, respectively. These lateral boundaries represent important discontinuities in the glacial landscape and mark the location of shear zones between thawed-bed ice streams and intervening frozen-bed areas. We use the landform evidence in the area around Great Bear Lake, Canada to trace the evolution of an ice-stream web through time, demonstrating that frozen-bed patches are integral components of this complex system. We conclude that frozen-bed patches are important for the stability of ice sheets because they laterally constrain and isolate peripheral drainage basins and their ice streams. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
