Influence of glacier hydrology on the dynamics of a large Quaternary ice sheet

Abstract

The influence of glacier hydrology on the time-dependent morphology and flow behaviour of the late Weichselian Scandinavian ice sheet is explored using a simple onedimensional ice sheet model. The model is driven by orbitally induced radiation variations, icealbedo feedback and eustatic sea-level change. The influence of hydrology is most marked during deglaciation and on the southern side of the ice sheet, where a marginal zone of rapid sliding, thin ice and low surface slopes develops. Such a zone is absent when hydrology is omitted from the model, and its formation results in earlier and more rapid deglaciation than occurs in the nohydrology model. The final advance to the glacial maximum position results from an increase in the rate of basal sliding as climate warms after 23000 yr BP. Channelised subglacial drainage develops only episodically, and is associated with relatively low meltwater discharges and high hydraulic gradients. The predominance of iceberg calving as an ablation mechanism on the northern side of the ice sheet restricts the occurrence of surface melting. Lack of meltwater penetration to the glacier bed in this area means that ice flow is predominantly by internal deformation and the ice sheet adopts a classical parabolic surface profile. J~~~~I of Quaternary Science

Theoretical equilibrium-line altitudes and glacier buildup sensitivity in southern Norway based on meteorological data in a geographical information system

“…Only limited areas in eastern Norway are affected by a C TP-ELA drop of 1000 m based on the present atmospheric circulation pattern, and larger-scale glacierization is initiated along the main watershed towards Trøndelag and along the watershed between Gudbrandsdalen and Østerdalen only with a C TP-ELA lowering of 1500 m ( Figure 5). An asymmetric icesheet buildup is hence likely based on the evaluation of modern ELA-related terms, being in accordance with recent models of the Fennoscandian ice sheet (e.g., Boulton et al, 2001;Arnold and Sharp, 2002). It is therefore necessary to foresee a major change in circulation patterns to explain a large-scale ice-sheet buildup localized in central southern Norway without previous large-scale buildup from the western mountains.…”

Modelling water flow under glaciers and ice sheets

“…While surface water is discussed as a potential source term in some of these studies, it was not explicitly included in ice-sheet drainage models until the work of Arnold & Sharp [58] (see §6). A surface-to-bed hydraulic connection is generally assumed to transmit water in sufficiently large quantities that some efficient drainage system at the ice-bed interface would be required for its evacuation.…”

“…Although similar in its aims, the model of Arnold & Sharp [58,168] (figure 7b) attempts to represent efficient and inefficient drainage beneath the Scandinavian ice sheet, as well as allow for surface water as a source to the basal drainage system. The latter is computed and routed over the ice-sheet surface, whereupon it is injected directly to the bed if a prescribed threshold discharge Q crit is reached and the bed is temperate.…”

Modelling Late Weichselian evolution of the Eurasian ice sheets forced by surface meltwater-enhanced basal sliding

“…The influence of the SME on the development of the Eurasian ice sheets has previously been investigated in oneand two-dimensional models (Arnold and Sharp, 1992Sharp, , 2002. Using a map-plane model, Arnold and Sharp (2002) applied a water-pressure-dependent sliding law to derive velocity changes on the Scandinavian ice sheet in response to subglacial configuration and varying sensitivity to supraglacial meltwater discharge.…”