Implications of increased Greenland surface melt under global-warming scenarios: ice-sheet simulations

Parizek, B. R.; Alley, Richard B.

doi:10.1016/j.quascirev.2003.12.024

Cited by 204 publications

(194 citation statements)

References 47 publications

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“…This inference may be used to better constrain dynamic models of ice sheets, which currently do not use quantified small-scale roughness parameters (e.g. Parizek and Alley, 2004). …”

Section: Implications For Sub-glacial Bed Roughness Under Modern Ice mentioning

confidence: 99%

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Krabbendam

Bradwell

2014

Quaternary Science Reviews

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Vast areas previously covered by Pleistocene ice sheets consist of rugged bedrock-dominated terrain of innumerable knolls and lake-filled rock basins -the 'cnoc-and-lochan' landscape or 'landscape of areal scour'. These landscapes typically form on gneissose or granitic lithologies and are interpreted (1) either to be the result of strong and widespread glacial erosion over numerous glacial cycles; or (2) formed by stripping of a saprolitic weathering mantle from an older, deeply weathered landscape.We analyse bedrock structure, erosional landforms and weathering remnants and within the 'cnoc-andlochan' gneiss terrain of a rough peneplain in NW Scotland and compare this with a geomorphologically similar gneiss terrain in a non-glacial, arid setting (Namaqualand, South Africa). We find that the topography of the gneiss landscapes in NW Scotland and Namaqualand closely follows the old bedrock-saprolite contact (weathering front). The roughness of the weathering front is caused by deep fracture zones providing a highly irregular surface area for weathering to proceed. The weathering front represents a significant change in bedrock physical properties. Glacial erosion (and aeolian erosion in Namaqualand) is an efficient way of stripping saprolite, but is far less effective in eroding hard, unweathered bedrock. Significant glacial erosion of hard gneiss probably only occurs beneath palaeo-ice streams.We conclude that the rough topography of glaciated 'cnoc-and-lochan' gneiss terrains is formed by a multistage process: 1) Long-term, pre-glacial chemical weathering, forming deep saprolite with an irregular weathering front;2) Stripping of weak saprolite by glacial erosion during the first glaciation(s), resulting in a rough land surface, broadly conforming to the pre-existing weathering front ('etch surface');3) Further modification of exposed hard bedrock by glacial erosion. In most areas, glacial erosion is limited, but can be significant beneath palaeo-ice stream. The roughness of glaciated gneiss terrains is crucial for modelling of the glacial dynamics of present-day ice sheets. This roughness is shown here to depend on the intensity of pre-glacial weathering as well as glacial erosion during successive glaciations.

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“…This inference may be used to better constrain dynamic models of ice sheets, which currently do not use quantified small-scale roughness parameters (e.g. Parizek and Alley, 2004). …”

Section: Implications For Sub-glacial Bed Roughness Under Modern Ice mentioning

confidence: 99%

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Krabbendam

Bradwell

2014

Quaternary Science Reviews

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“…Coupling between glacier hydrology and ice flow may hasten glacier melting in response to projected 'greenhouse' warming by accelerating the transfer of ice to lower elevations where surface melting and/or calving remove mass (Meier, 1993;Fountain and Walder, 1998;Zwally et al, 2002;Parizek and Alley, 2004). The issue is especially pertinent in the High Arctic (>75°N) where recent climate models predict exceptional warming over the next century (Manabe et al, 1991;Cattle and Crossley, 1995;Houghton et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Hydrology and dynamics of a polythermal (mostly cold) High Arctic glacier

Bingham

Nienow

Sharp

et al. 2006

Earth Surf Processes Landf

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To improve our understanding of the interactions between hydrology and dynamics in mostly cold glaciers (in which water flow is limited by thermal regime), we analyse short-term (every two days) variations in glacier flow in the ablation zone of polythermal John Evans Glacier, High Arctic Canada. We monitor the spatial and temporal propagation of highvelocity events, and examine their impacts upon supraglacial drainage processes and evolving subglacial drainage system structure. Each year, in response to the rapid establishment of supraglacial-subglacial drainage connections in the mid-ablation zone, a 'spring event' of high horizontal surface velocities and high residual vertical motion propagates downglacier over two to four days from the mid-ablation zone to the terminus. Subsequently, horizontal velocities fall relative to the spring event but remain higher than over winter, reflecting channelization of subglacial drainage but continued supraglacial meltwater forcing. Further transient high-velocity events occur later in each melt season in response to melt-induced rising supraglacial meltwater inputs to the glacier bed, but the dynamic response of the glacier contrasts with that recorded during the spring event, with the degree of spatial propagation a function of the degree to which the subglacial drainage system has become channelized.

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“…Moreover, the representation of an evolving subglacial drainage system in numerical models is challenging, and currently necessitates major simplifications such as reduced spatial dimensions 23,[25][26][27][28] , application on idealized domains 25,29 or disregarding feedbacks on ice flow 30 . Significantly, these dynamic processes are yet to be realistically incorporated into studies aiming to forecast future sea-level rise [31][32][33] . In addition, by focusing explicitly on the character of the hydrological system, previous work has inherently assumed that the ice-bed interface consists of hard bedrock.…”

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confidence: 99%

Sensitive response of the Greenland Ice Sheet to surface melt drainage over a soft bed

et al. 2014

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The dynamic response of the Greenland Ice Sheet (GrIS) depends on feedbacks between surface meltwater delivery to the subglacial environment and ice flow. Recent work has highlighted an important role of hydrological processes in regulating the ice flow, but models have so far overlooked the mechanical effect of soft basal sediment. Here we use a threedimensional model to investigate hydrological controls on a GrIS soft-bedded region. Our results demonstrate that weakening and strengthening of subglacial sediment, associated with the seasonal delivery of surface meltwater to the bed, modulates ice flow consistent with observations. We propose that sedimentary control on ice flow is a viable alternative to existing models of evolving hydrological systems, and find a strong link between the annual flow stability, and the frequency of high meltwater discharge events. Consequently, the observed GrIS resilience to enhanced melt could be compromised if runoff variability increases further with future climate warming.

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Implications of increased Greenland surface melt under global-warming scenarios: ice-sheet simulations

Cited by 204 publications

References 47 publications

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Quaternary evolution of glaciated gneiss terrains: pre-glacial weathering vs. glacial erosion

Hydrology and dynamics of a polythermal (mostly cold) High Arctic glacier

Sensitive response of the Greenland Ice Sheet to surface melt drainage over a soft bed

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