Surficial glaciology of Jakobshavns Isbræ, West Greenland: Part I. Surface morphology

Echelmeyer, Κ. A.; Clarke, T. S.; Harrison, W. D.

doi:10.1017/s0022143000005803

Cited by 162 publications

(189 citation statements)

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“…Because the most easily observable characteristic of supraglacial lakes is their surface area and not their volume, we relate the mean lake surface diameter to its volume assuming a simple conical lake geometry and a diameter:depth ratio of 100:1. This approximation is consistent with surface slopes and depth-to-diameter relationships observed in 2 lakes south of Jakobshavn Isbrae [Das et al, 2008] and yields depths up to tens of meters for lakes with diameters >1 km, consistent with lake depths reported by previous studies in Greenland [Box and Ski, 2007, Sneed and Hamilton, 2007, Echelmeyer et al, 1991, McMillan et al, 2007.…”

Section: Calculating Lake Drainage Timessupporting

confidence: 91%

Experimental studies of melting and crystallization processes in planetary interiors

Krawczynski¹

2011

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Melting and crystallization processes on the Earth and Moon are explored in this thesis, and the topics of melt generation, transport, and crystallization are discussed in three distinct geologic environments: the Moon's mantle, the Greenland ice sheet, and the Earth's crust. Experiments have been conducted to determine the conditions of origin for two high-titanium magmas from the Moon. The lunar experiments (Chapter 2) were designed to explore the effects of variable oxygen fugacity (f O 2 ) on the high pressure and high temperature crystallization of olivine and orthopyroxene in high-Ti magmas. The results of these experiments showed that the source regions for the high-Ti lunar magmas are distributed both laterally and vertically within the lunar mantle, and that it is critical to estimate the pre-eruptive oxygen fugacity in order to determine true depth of origin for these magmas within the lunar mantle. Chapter 3 models the behavior of water flow through the Greenland ice sheet driven by hydrofracture of water through ice. The results show that melt water in the ablation zone of Greenland has almost immediate access to the base of the ice sheet in areas with up two kilometers of ice. Chapter 4 is an experimental study of two hydrous high-silica mantle melts from the Mt. Shasta, CA region. Crystallization is simulated at H 2 O saturated conditions at all crustal depths, and a new geobarometerhygrometer based on amphibole magnesium number is calibrated. In Chapter 5 I use the new barometer to study a suite of mafic enclaves from the Mt. Shasta region, and apply it to amphiboles in these enclaves. Evidence for pre-eruptive H 2 O contents of up to 14 wt% is presented, and bulk chemical analyses of the inclusions are used to show that extensive magma mixing has occurred at all crustal depths up to 35 km beneath Mt. Shasta. Tim Grove. I can never repay all the knowledge, time, trust, friendship, and guidance that you have freely given to me. You are more than an advisor; you made me feel like family. Your endless energy and passion for petrology has rubbed off on me, and has reinforced my desire to pursue the origins of igneous rocks. The time we spent in the field is the most fun I have ever had, and has taught me that geology necessarily happens in the field as well as the lab. Those experiences will shape the future of my geologic career. In the lab you trusted me to make my own scientific decisions, and then patiently helped me fix all the equipment I broke and set me straight on some of the wacky decisions I made! You read all of the early drafts of this thesis, practiced all my talks over and over with me, and at times I know it was painful, but you shaped me into a scientist. I am truly honored that my thesis will always sit right above your desk, with all of your great students. I hope that someday I will live up to your expectations of me and I promise to pass on the dedication and care to my own students that you have showed me. In the future, stop by for a visit in my thermodynamics/petrology/...

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Section: Calculating Lake Drainage Timessupporting

confidence: 91%

Experimental studies of melting and crystallization processes in planetary interiors

Krawczynski¹

2011

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“…Given the rapid flow of many tidewater glaciers, it is important to resolve whether the volume of meltwater generated by frictional heat is critical to their rapid ice motion [6] and if so, to better incorporate this process effectively in to predictive dynamic ice sheet models.…”

Section: Basal Melt Ratesmentioning

confidence: 99%

“…Prior to the twenty-first century however, the hydrology of the GrIS had received little attention, with the exception of reports in the Rapport Grønlands Geologiske Undersøgelse [5] which remain largely unused by the research community, and studies at Jakobshavn Isbrae [6]. This perhaps reflected in part the view that ice sheets were stable over millennial timescales and that surface meltwaters would not penetrate through the ice to the glacier bed due both to the cold (i.e.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Nienow

Sole

Slater

et al. 2017

Curr Clim Change Rep

105

100

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Purpose of the Review This review discusses the role that meltwater plays within the Greenland ice sheet system. The ice sheet's hydrology is important because it affects mass balance through its impact on meltwater runoff processes and ice dynamics. The review considers recent advances in our understanding of the storage and routing of water through the supraglacial, englacial, and subglacial components of the system and their implications for the ice sheet. Recent Findings There have been dramatic increases in surface meltwater generation and runoff since the early 1990s, both due to increased air temperatures and decreasing surface albedo. Processes in the subglacial drainage system have similarities to valley glaciers and in a warming climate, the efficiency of meltwater routing to the ice sheet margin is likely to increase. The behaviour of the subglacial drainage system appears to limit the impact of increased surface melt on annual rates of ice motion, in sections of the ice sheet that terminate on land, while the large volumes of meltwater routed subglacially deliver significant volumes of sediment and nutrients to downstream ecosystems. Summary Considerable advances have been made recently in our understanding of Greenland ice sheet hydrology and its wider influences. Nevertheless, critical gaps persist both in our understanding of hydrology-dynamics coupling, notably at tidewater glaciers, and in runoff processes which ensure that projecting Greenland's future mass balance remains challenging.

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“…Krawczynski et al (2009) calculated that supraglacial lakes 250 to 800 m across and 2 to 5 m deep contain sufficient water to drive a fracture to the base of kilometre-thick ice. Many lakes on the Greenland Ice Sheet attain this size or larger (Box and Ski, 2007;Echelmeyer et al, 1991;Georgiou et al, 2009), of which a small proportion (13 % between 2005-2009) drain in less than 2 days (Selmes et al, 2011). Surface lakes can drain rapidly into moulins via supraglacial rivers; however, many drain by the in situ propagation of hydraulically driven fractures (e.g.…”

Section: Introductionmentioning

confidence: 99%

Ice tectonic deformation during the rapid in situ drainage of a supraglacial lake on the Greenland Ice Sheet

et al. 2013

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Abstract. We present detailed records of lake discharge, ice motion and passive seismicity capturing the behaviour and processes preceding, during and following the rapid drainage of a ∼ 4 km 2 supraglacial lake through 1.1-km-thick ice on the western margin of the Greenland Ice Sheet. Peak discharge of 3300 m 3 s −1 coincident with maximal rates of vertical uplift indicates that surface water accessed the ice-bed interface causing widespread hydraulic separation and enhanced basal motion. The differential motion of four global positioning system (GPS) receivers located around the lake record the opening and closure of the fractures through which the lake drained. We hypothesise that the majority of discharge occurred through a ∼ 3-km-long fracture with a peak width averaged across its wetted length of ∼ 0.4 m. We argue that the fracture's kilometre-scale length allowed rapid discharge to be achieved by combining reasonable water velocities with sub-metre fracture widths. These observations add to the currently limited knowledge of in situ supraglacial lake drainage events, which rapidly deliver large volumes of water to the ice-bed interface.

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Surficial glaciology of Jakobshavns Isbræ, West Greenland: Part I. Surface morphology

Cited by 162 publications

References 18 publications

Experimental studies of melting and crystallization processes in planetary interiors

Experimental studies of melting and crystallization processes in planetary interiors

Recent Advances in Our Understanding of the Role of Meltwater in the Greenland Ice Sheet System

Ice tectonic deformation during the rapid in situ drainage of a supraglacial lake on the Greenland Ice Sheet

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