References Flashcards

1
Q

ELA = where over one year accumulation of snow = ablation

A

Benn and Lehmkuhl 2000

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2
Q

Former ELAs = powerful method of quantifying palaeoclimates if e.g. other evidence is lacking

A

Benn and Lehmkuhl 2000

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3
Q

Knowledge of glacier ELAs = palaeoclimatic data = predict future glacier response to climatic change

A

Maisch 1995

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4
Q

Mass balance characteristics of glaciers in high-mountain environments complicate the relationship between ELAs and precipitation/air T
- avalanches/debris cover/topographic effects

A

Benn and Lehmkuhl 2000

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5
Q

Study of glacier mass balance 1946-1995 for 246 glaciers

Western Europe, North America and USSR

Biased towards wetter conditions

A

Braithwaite 2002

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6
Q

Direct stakes/snowpits method - recognised integration with geodetic/remote sensing would be more useful

A

Braithwaite 2002

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7
Q

Glaciers mainly gain mass (accumulation) as snow and mostly lose mass (ablation) by melting and iceberg calving

A

Braithwaite 2002

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8
Q

Local importance of glaciers to societies e.g. HEP or irrigation, or hazards

A

Braithwaite 2002

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9
Q

Modelling ice/snow melt important for issues e.g. water resource management, avalanche forecasting, glacier dynamics, hydrology/hydrochemistry, climate change

A

Hock 2005

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10
Q

Modelling of turbulent fluxes and spatial/temporal variability in albedo = major uncertainties

A

Hock 2005

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11
Q

Typical characteristics of glacier runoff = melt-induced diurnal cyclicality and concentration of annual flow during melt season

A

Hock 2005

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12
Q

Modelling: High temporal resolution essential for predicting peak flows in glacierised/snow-covered basins
High spatial resolution needed to account for large spatial heterogeneity w.r.t. ice/snow melt due to topography

A

Hock 2005

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13
Q

Energy balance melt models more properly describe physical processes at glacier surface than temperature-index methods but require much more data

A

Hock 2005

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14
Q

Further research needed in modelling to focus on links between different energy fluxes and synoptic weather pattern, and investigate potential for operational use in melt forecasting

A

Hock 2005

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15
Q

Glaciers/ice caps = important contributors to global mean SLR

A

Jacob et a 2012

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16
Q

Monthly GRACE method from Jan 2003-Dec 2010 for inversion of mass change over all ice-covered regions larger than 100km2

Results:

  • GIC excluding Greenland and Antarctica peripheral glaciers and ice caps contributed 0.41+/-0.08mm/yr
  • with G/A = 1.06+/-0.19mm/yr

Total agreed with independent estimates within error bars

A

Jacob et al 2012

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17
Q

Ablation under a debris layer could be estimated from meteorological variables if surface T data (estimation of thermal resistance) of layer is available

Generally good method but surface roughness (large at stagnant areas near glacier terminus) should be noted with care

A

Nakawo and Young 1982

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18
Q

Understanding water movement through glacier is fundamental to e.g. glacier dynamics/glacier-induced floods/runoff predictions

A

Fountain and Walder 1998

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19
Q

Firn temporarily stores water and smooths out variations in supply rate (accumulation zone)

In ablation zone, flux of water depends directly on rate of surface melt/rainfall = varies greatly

A

Fountain and Walder 1998

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20
Q

Describes water flow in a “nonarborescent network”, poorly connected to a well-connected aborescent channel network

A

Fountain and Walder 1998

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21
Q

Stored water may be released abruptly and catastrophically in the form of outburst floods

A

Fountain and Walder 1998

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22
Q

Episodic surging of some glaciers due to temporal changes in subglacial hydrology

A

Fountain and Walder 1998

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23
Q

Near-surface, englacial and subglacial water flow are coupled

A

Fountain and Walder 1998

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24
Q

Hydrological system components = snow, firn, surface streams; crevasses, moulins and other englacial passages; and basal channels, cavities and till

A

Fountain and Walder 1998

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25
Q

Mapped 8.25km of passage in 27 distinct englacial conduits in temperate, polythermal, cold-based and debris-covered glaciers between 2005 and 2009 using speleological techniques

In all cases = single unbranching conduit

Morphologies intimately linked to orientation of glacier’s principal stresses or presence of pre-existing lines of high hydraulic conductivity

Shreve-type englacial drainage systems do not exist - englacial conduits can only penetrate through thick ice to recharge the bed where supra glacial bodies intersect/advect through zones of acceleration

A

Gulley and Benn 2009

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26
Q

Used dye tracing techniques for glacier-wide changes in englacial/subglacial system of Haut Glacier d’Arolla 1990-1991

A

Nienow et al 1998

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27
Q

Removal of snow (high albedo and water storage) increases runoff into moulins

A

Nienow et al 1998

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28
Q

Removal of snow (high albedo and water storage) increases runoff into moulins

A

Nienow et al 1998

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29
Q

Three factors control evolution of subglacial drainage over summer melt season (1) weather conditions (2) pattern of snowline retreat (3) distribution of moulins and crevasses

A

Nienow et al 1998

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30
Q

Uncrevassed glaciers with a surface layer permanently below melting point, surface melt may never reach glacier bed

A

Nienow et al 1998

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31
Q

Focus in the Tien Shan, Central Asia
Regions with little summer precipitation = glaciers important role in streamflow regimes

At first shrinking glaciers supply increased glacial runoff but ultimately will result in decrease

= ecological problems and political instability

A

Sorg et al 2012

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32
Q

Greenland Ice Sheet (GIS)

Ice motion across land-terminating region in west gIS slower in 2007-2014 compared with 1985-1994 despite 50% increase in meltwater production

i.e. these sectors of the ice sheet are more resilient to the dynamic impacts on enhanced meltwater production than previously though

A

Nienow et al 2015

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33
Q

Glacial sliding is enhanced by rapid migration of surface meltwater to the ice-bedrock interface

A

Zwally et al 2002

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34
Q

Floating glacier tongues and Antarctic ice shelves respond quickly. in contrast to the flow of grounded ice

A

Zwally et al 2002

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35
Q

GIS grounded above SL and generally believed to respond gradually to climate warming

A

Zwally et al 2002

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36
Q

WAIS

  • radar sounding = wet bed
  • most ice-stream velocity arises at bed
  • deformation within the till is the primary mechanism by which the ice stream moves
A

Alley et al 1986

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37
Q

90% of AIS is drained through ice-streams

A

Bamber et al 2000

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38
Q

Stake method used to measure basal sliding in Ice Stream B, WAIS

Basal sliding rate is 83% of total motion
- may include contribution from shear deformation of till

A

Engelhardt and Kamb 1998

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39
Q

Mechanism of rapid ice stream motion concentrated at/near top of till rather than spread throughout thickness of till layer

A

Engelhardt and Kamb 1998

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40
Q

Climate and weather affect surge initiation, termination and magnitude

A

Harrison and Post 2003

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41
Q

Till deformation processes dominate glacier motion in quiescence

A

Harrison and Post 2003

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42
Q

Non-random geographic distribution of surge-type glaciers but poorly understood - would be useful for constraints on mechanism of surging

A

Harrison and Post 2003

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43
Q

Distributed systems exist seasonally under parts of Variegated Glacier during quiescent phase and discrete system below surge front during surge

A

Harrison and Post 2003

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44
Q

Hypothesis for winter initiation of surges = presence of englacial water trapped late in melt season

A

Harrison and Post 2003

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45
Q

Surging-type glaciers speed up for relatively short time to flow rates as much as a hundred times the normal rate then drops back to normal flow state

A

Kamb et al 1985

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46
Q

1982-1983 Variegated Glacier surge caused by build up of high water pressure in basal passageway system

A

Kamb et al 1985

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47
Q

Highest densities of surge-type glaciers occur within an optimal climatic envelope with T and precipitation thresholds
= intermediate conditions

A

Sevestre and Benn 2015

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48
Q

Two superclusters of surging-type glaciers:
1) Arctic Ring

2) High Mountain Asia

A

Sevestre and Benn 2015

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49
Q

Sticky spots = localised patches of basal friction

A

Stokes et al 2007

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50
Q

4 primary causes of sticky spots
1) bedrock bumps

2) till-free areas
3) areas of ‘strong’ (well-drained) till
4) freeze-on of subglacial meltwater

Act together or in isolation

A

Stokes et al 2007

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51
Q

Future SL rise related to continuing build up of atmospheric GHG concentrations

A

Alley et al 2005

52
Q

Freshwater fluxes from GIS and AIS may affect oceanic circulation, contributing to climate change

A

Alley et al 2005

53
Q

Heavy concentration of population live along coastlines = substantial societal and economic impacts

  • coastal erosion
  • increased susceptibility to storm surges
  • groundwater contamination by salt intrusion
A

Alley et al 2005

54
Q

EAIS actually likely to grow (increased accumulation if warmings don’t exceed 5’C

A

Alley et al 2005

55
Q

Warming has increased mass loss from coastal areas more than it has increased mass gain from snowfall in cold central regions

A

Alley et al 2005

56
Q

Calving rates increase dramatically in response to increases in velocity +/ retreat of the glacier margin

A

Benn et al 2007a

57
Q

Calving and related dynamic processes poorly represented in current ice sheet models

A

Benn et al 2007a

58
Q

1st order control on calving = strain rate determining location and depth of surface crevasses

A

Benn et al 2007a

59
Q

Large icebergs have a cooling effect on oceans through latent and sensible heat exchanges

A

Benn et al 2007a

60
Q

Much of the grounded ice in W Antartica lies on a bed that deepens inland and extents well below SL = thinning could ultimately float much of the ice sheet’s interior

A

Joughin and Alley 2011

61
Q

Mass loss for WAIS ranges from 100 to 200Gt/yr, dominated from draining of Amundsen Sea sector

A

Joughin and Alley 2011

62
Q

Collapse of the marine ice sheet in West Antarctica would raise SL by more than 3m over the course of several centuries or less

A

Joughin and Alley 2011

63
Q

West Antarctic losses increased by 70% in the last decade and earlier volume gain by EAIS ceasedP

A

Paolo and Padman 2015

64
Q

Antarctica: In the Amundsen and Bellingshausen regions some ice shelves have lost up to 18% of their thickness in less than two decades

A

Paolo and Padman 2015

65
Q

The (grounded) Pine Island Glacier transports 69 km3 of ice each year from ~10% of WAIS
Retreat may accelerate ice discharge from WAIS interior

A

Shepherd et al 2001

66
Q

Numerical ice-flow model for Helheim Glacier, one of Greenland’s largest outlet glaciers
Ice acceleration, thinning and retreat begins at calving terminus then propagates upstream through dynamic coupling along glacier - likely caused by basal lubrication through surface melt propagating to glacier bed

A

Nick et al 2009

67
Q

Tidewater outlet glaciers adjust extremely rapidly to changing boundary conditions at the calving terminus

A

Nick et a 2009

68
Q

Shallow Ice Approximation = ice deformation is due to shearing close to bed

A

Pattyn 2018

69
Q

MISI is based on observation that since ice flux increases with ice thickness, the location of a grounding line on a bed sloping inwards is unstable

A

Pattyn 2018

70
Q

Increase in computational efficiency enabling high spatial resolution modelling, high resolution datasets of bedrock topography and surface velocity, longer time series on ice sheet changes and the improved initialisation of ice sheet models = move towards robust predictions on decadal time scales, hindcastidg and potentially reanalysis

A

Pattyn 2018

71
Q

Focus on three important subglacial erosional processes:

1) abrasion of bed by debris embedded in glacier sole
2) crushing of subglacial bedrock due to pressure fluctuation produced by glacier flow over bedrock hummock
3) removal by plucking by above

A

Boulton 1974

72
Q

Glacial erosion involves removal and transport of bedrock and/or sediment by glacial quarrying, glacial abrasion and glacial meltwater

A

Glasser and Bennett 2004

73
Q

All landforms of glacial erosion provide evidence for the release of subglacial meltwater and the existence of warm-based ice

A

Glasser and Bennett 2004

74
Q

Landforms dominated by glacial abrasion are created when there is no ice-bed separation

A

Glasser and Bennett 2004

75
Q

Exposure dating techniques including cosmogenic isotope dating of bedrock surface = important for increasing understand of age/chronological significance of landforms

A

Glasser and Bennett 2004

76
Q

Topographic form of areal scouring relates closely to bedrock structure (strike/dip of bedding planes, layering, joins, structural weaknesses)

A

Gordon 1981

77
Q

Asymmetric roche moutonnée-type forms generally exist in sympathy of bedrock structure regardless of ice movement direction

A

Gordon 1981

78
Q

Basal ice is debris-laden so friction exists between the substratum and rock particles embedded in the basal ice

A

Schweizer and Iken 1992

79
Q

Relative weathering of landscape surfaces has often been used to define the former location of landscape surfaces - highly weathered landscapes took a long time to form and thus must have escaped RECENT glaciation

BUT presence of pseudo-erratics on high-elevation weathered surfaces (Arctic Canada) = non erosive ice covered these

A

Briner et al 2003

80
Q

Ice sheet model (GLIMMER) with erosion component, modelling evolution of landscapes under ice sheets over long time scales in hypothetical conditions

Results: bed morphology exerts a greater influence under low basal slip conditions because ice cannot respond readily to thermal instabilities

A

Jamieson et al 2008

81
Q

Ullapool area NW Scotland shows large-scale megagrooves and streamlined bedrock forms in a well-defined ~20km wide zone interpreted as signature of fast-flowing tributary that once fed a palaeo-ice stream

A

Bradwell et al 2008

82
Q

Elongation ratios <5:1 and >5:1 represent transition from potentially cold-based slow flow to warm-based fast flow

A

Bradwell et al 2008

83
Q

Rapid spatial bedform evolution reflects an increase in subglacial erosive power that may be diagnostic of paleo-ice sheet thermal boundaries (i.e. cold to warm based)

A

Bradwell et al 2008

84
Q

Reference for definitions of glacitectonite, subglacial traction till, melt-out till

A

Evans et al 2006

85
Q

Deformation, flow, sliding, lodgement and ploughing co-exist at the base of temperate glacier ice and act to mobilise, transport and deposit sediment

A

Evans et al 2006

86
Q

Till/till sequences may contain a superimposed signature of former transportation/deposition at the ice-bed interface

A

Evans et al 2006

87
Q

Glacitectonite = rock/sediment deformed by subglacial shearing/deformation but retains some of structural characteristics of parent material

A

Evans et al 2006

88
Q

Subglacial traction till = sediment deposited by a glacier sole either sliding over +/ deforming its bed, with sediment directly released from ice by pressure melting +/liberated from substrate then disaggregated and completely/largely homogenised by shearing

A

Evans et al 2006

89
Q

Melt-out till = sediment released by melting of stagnant/slowly moving debris-rich glacier ice and directly deposited without subsequent transport or deformation

A

Evans et al 2006

90
Q

Laminated glacimarine sediments form by e.g. suspension settling from turbid overflow plumes, turbidity current deposition and contour current activity

Subglacial deformation of pre-existing sediments may also produce laminated deposits in the forms of glacitectonite/deformation till
= discrimination important for reconstruction

A

O Cofaigh and Dowdeswell 2001

91
Q

Flux of glacially transported sediment is related to ice flux = inner zone of ice sheet predominantly one of erosion and outer zone of deposition

A

Boulton 1996a

92
Q

Extensive subglacial aquifers drain the glacier bed and inhibit deformation processes = reduce rates of erosion/deposition

A

Boulton 1996a

93
Q

Fine-grained sediments on glacier bed are eroded/transported more readily = contribute preferentially to till

A

Boulton 1996a

94
Q

Subglacial bedrooms are emergent phenomena arising from self-organisation in the coupled flow of ice, sediment and water; patterning of bedforms due to naturally arising flow instability

A

Clark 2010

95
Q

Subglacial bedforms have recently been discovered beneath the Antarctic Ice Sheet

A

Clark 2010

King et al 2007

96
Q

Rogen moraines should be called Subglacial Ribs because they are not actually moraines

A

Clark 2010

97
Q

Drumlins form by coupled interaction between ice flow and flow of soft underlying substrate (instability theory)

A

Clark 2010

98
Q

Scepticism of instability theory: combat by thinking about smoothing surface of dry sand on a beach - ripples will appear = analogous

A

Clark 2010

99
Q

Note: instability theory cannot make prediction of internal structures and sediment properties, it is a simple conceptual model with potential

A

Clark 2010

100
Q

Pro instability theory; first paper to assess if compatibility with sediments found within drumlins

A

Stokes et al 2013

101
Q

Results: one would expect a diverse range of constituents in drumlins depending on:

1) inheritance of sediments that pre-date drumlin formation
2) duration/variability of ice flow
3) balance between erosion and deposition at the ice-bed interface

= instability theory is compatible

A

Stokes et al 2013

102
Q

Moraine asymmetry correlated with distribution of free faces in valleys

A

Benn 1989

103
Q

Within valley asymmetry of moraines is interpreted as one aspect of long-term asymmetric landscape evolution

A

Benn 1989

104
Q

Controlled moraines = supra glacial debris concentrations that become hummocky moraine upon deicing and possess clear linearity due to inheritance of former pattern of debris-rich folia in parent ice

A

Evans 2009

105
Q

Sediment in an esker in Lanark, Ontario, Canada

Mainly coarse grained, varies from boulders with fine-sand matrix (max discharge) to diamicton (low discharge)

A

Gorrell and Shaw 1991

106
Q

Small scale fining upwards sequence in fans and beads (eskers) indicates deposition by large no. of flow events

A

Gorrell and Shaw 1991

107
Q

Fan and bead environments are areas of ice-bed decoupling, at least during high flow conditions (eskers)

A

Gorrell and Shaw 1991

108
Q

Sedimentary architecture of glacial landforms helps to explain genesis and provide better understanding of the pale-glaciology of ice sheets

A

Carlson et al 2005

109
Q

Kettle Moraine in Wisconsin = single, ~3km wide hummocky ridge for ~90% of its 200km extent with double ridge at beginning - due to extensive underlying ice with thin debris cover between supraglacial fluvial deposits at the time of deposition

A

Carlson et al 2005

110
Q

Brampton kame belt in Cumbria = one of largest glaciofluvial complexes within the UK (over 44km2)

A

Livingstone et al 2010

111
Q

Represents major depositional episode during advanced stages of recession of Late Devensian BIIS in Solway Lowlands = critical for reconstructing deglaciation style

A

Livingstone et al 2010

112
Q

Lack of supraglacial sediment in active temperate glaciers precludes the widespread development of chaotic hummocky moraine

A

Evans and Twigg 2002

113
Q

Active temperate landsystem in Bredamerkurjökull and Fjallsjökull, Iceland

1) areas of extensive, low amplitude marginal dump, push and squeeze moraines often recording annual recession of active ice
2) incised and terraced glacifluvial forms e.g. recessional ice-contact fans and hochsandur fans/eskers/pitted outwash
3) subglacial landforms assemblages; flutes/drumlins/overridden push moraines between ice marginal glacifluvial depo-centres

A

Evans and Twigg 2002

114
Q

Active temperate landsystem in Bredamerkurjökull and Fjallsjökull, Iceland

Subtle surge signatures present = illustrates danger of employing landform-sediment associations from restricted study areas for entire glaciated terrain

A

Evans and Twigg 2002

115
Q

Snaefelljokull volcano-centred ice cap landsystem, W Iceland

Rapidly thinning and receding from its historical Little Ice Age maximum limit

Profound effects on generation of freshwater for surrounding communities

A

Evans et al 2016

116
Q

Snaefelljokull volcano-centred ice cap landsystem, W Iceland

Provides landsystem signature for independent volcano-centred ice caps

  • outer zone of ice-cored moraine
  • in front = locally developed set of proglacially thrust pumice deposits
  • ice-cored moraine passes proximally into bouldery drift and push moraine
  • then large area of flutings/glacially abraded rock (indicative of temperate basal ice conditions)

This landsystem is an exemplar relevant specifically to Icelandic landscape but also more widely relevant to glaciered volcanic terrains globally

A

Evans et al 2016

117
Q

Marine-terminating outlet glaciers can undergo dramatic dynamic change at annual timescales

A

Carr et al 2013

118
Q

3 primary climatic/oceanic controls on outlet glacier dynamics;

1) air T
2) ocean T
3) sea-ice concentrations

A

Carr et al 2013

119
Q

Uncertainties on controls on outlet glacier dynamics:

  • spatial variation in relative importance of each factor
  • contribution of glacier-specific factors to glacier dynamics
  • limitations in accurate modelling
A

Carr et al 2013

120
Q

There is a danger in extrapolating rates of mass loss from a small sample of study glaciers

A

Carr et al 2013

121
Q

Arctic warming expected 4-7’C by 2100

A

Carr et al 2013

122
Q

Greenland Ie Sheet contributed 0.46mm/a to SL rise between 2000 and 2008

A

Carr et al 2013; van den Broeke et al 2009

123
Q

Marine-terminating outlet glacier = channel of fast-moving ice that drains an ice cap or ice sheet and terminates in the ocean at either a floating or grounded margin (Benn and Evans 2010)

A

Carr et al 2013

124
Q

Reverse bed slopes pose instability

A

Carr et al 2013

125
Q

Meltwater-enhanced basal sliding contributes to marine-terminating outlet glacier velocities at seasonal scales but capacity of subglacial hydrological system to evolve limits effect on inter annual behaviour

A

Carr et al 2013