The bedrock geology under the Inland Ice: the next major challenge for Greenland mapping

Dawes, P.R

doi:10.34194/geusb.v17.5014

Cited by 49 publications

(75 citation statements)

References 3 publications

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“…Notable uncertainties remain about the hot spot's exact track and timing. The hot spot likely interacted with rifting, contributing to the lava outpourings that built the eastern and western Tertiary flood basalt provinces (e.g., Dawes, ; Henriksen et al, , ) (Figure ). Hot spot‐rifting interactions on the east side of Greenland likely contributed to large, rapid emissions of CO 2 that triggered the Paleocene‐Eocene Thermal Maximum ~56 Ma (e.g., Gutjahr et al, ; Storey et al, ).…”

Section: Geologic Settingmentioning

confidence: 99%

“…The hot spot flow in central regions focused on a preexisting weakness associated with the geologic boundary extending from the east coast (Sleep, ; Sleep et al, ), perhaps slightly to the north of the center of the hot spot track, and further thermally eroded this weak region. Data from beneath the ice sheet remain very sparse (Dawes, ), but there is no compelling evidence of extensive inland flood basalt activity of the type seen in the eastern and western Tertiary basalt provinces, favoring the hypothesis that partial melt associated with the hot spot track was left beneath Greenland rather than breaking through.…”

Section: Geologic Settingmentioning

confidence: 99%

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Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

et al. 2019

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The history of the Greenland Ice Sheet has been influenced by the geodynamic response to ice sheet fluctuations, and this interaction may help explain past deglaciations under modest climate forcing. We hypothesize that when the Iceland hot spot passed beneath north-central Greenland, it thinned the lithosphere and left anomalous heat likely with partially melted rock; however, it did not break through the crust to supply voluminous flood basalts. Subsequent Plio-Pleistocene glacial-interglacial cycles caused large and rapidly migrating stresses, driving dike formation and other processes that shifted melted rock toward the surface. The resulting increase in surface geothermal flux favored a thinner, faster-responding ice sheet that was more prone to deglaciation. If this hypothesis of control through changes in geothermal flux is correct, then the long-term (10 5 to 10 6 years) trend now is toward lower geothermal flux, but with higher-frequency (≤10 4 to 10 5 years) oscillations linked to glacial-interglacial cycles. Whether the geothermal flux is increasing or decreasing now is not known but is of societal relevance due to its possible impact on ice flow. We infer that projections of the future of the ice sheet and its effect on sea level must integrate geologic and geophysical data as well as glaciological, atmospheric, oceanic, and paleoclimatic information.Plain Language Summary The behavior of the Greenland Ice Sheet and its effect on future sea level depends on its geologic history as well as on greenhouse warming. The Iceland hot spot passed beneath Greenland millions of years ago, and left hot, possibly melted rock deep beneath the island. Since then, growth and shrinkage of the ice sheet have changed stresses in the rocks beneath. These stress changes may have shifted the melted rock upward, perhaps all the way to the base of the ice sheet, probably in pulses tied to times of rapid ice sheet change. This would have changed the heat flow from the Earth into the base of the ice, which affects how easily the ice sheet grows and shrinks. The future of the ice sheet depends primarily on how much the climate warms, but better understanding of the interactions between the ice and the rocks beneath will allow better predictions of ice sheet changes.

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Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

et al. 2019

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“…The Summit in central Greenland is 3231 m above sea level (asl); in southern Greenland, the highest elevation is 2873 m asl (Figure S1 in the supporting information) [ Bamber , ]. The geology of the current ice‐free margin has been extensively studied [e.g., Baadsgaard , ; Friend and Nutman , ; Hollis et al ., ; Dawes , ]. Most of the bedrock is Precambrian shield and is mainly composed of granitic gneiss and granitoids [ Dawes , ].…”

Section: Geology Glaciology and Climatementioning

confidence: 99%

Noble gas signatures in Greenland: Tracing glacial meltwater sources

Niu

Castro

Aciego

et al. 2015

Geophysical Research Letters

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This study represents the first comprehensive noble gas study in glacial meltwater from the Greenland Ice Sheet. It shows that most samples are in disequilibrium with surface collection conditions. A preliminary Ne and Xe analysis suggests that about half of the samples equilibrated at a temperature of ~0°C and altitudes between 1000 m and 2000 m, with a few samples pointing to lower equilibration altitudes and temperatures between 2°C and 5°C. Two samples suggest an origin as melted ice and complete lack of equilibration with surface conditions. A helium component analysis suggests that this glacial meltwater was isolated from the atmosphere prior to the 1950s, with most samples yielding residence times ≤ 420 years. Most samples represent a mixture between a dominant atmospheric component originating as precipitation and basal meltwater or groundwater, which has accumulated crustal 4He over time.

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“…The ice sheet prevents direct geological observations within Greenland's interior and as a result, most studies have focused on its margins. The tectonic framework of Greenland's interior remains largely unknown, and tectonic reconstructions are largely based on the integration and extrapolation of near‐coast geological observations (Brooks, ; Dawes, ; Escher & Pulvertaft, ; Henriksen et al, , ; Roberts & Bally, ; St‐Onge et al, ; Surlyk, ; van Gool et al, ) and geophysical experiments (Holbrook et al, , ; Schmidt‐Aursch & Jokat, ; Voss & Jokat, ; Voss et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…Most of Greenland is commonly believed to be a Precambrian shield modified by several orogenic and rifting events and that can be divided into several blocks (Dawes, ; Escher & Pulvertaft, ; Henriksen et al, , ). Tectonics models suggest that most of Greenland's original Archean structure was obliterated in the early Proterozoic.…”

Section: Introductionmentioning

confidence: 99%

High‐Resolution Rayleigh Wave Group Velocity Variation Beneath Greenland

2018

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We present a high‐resolution group velocity model of Greenland from the analysis of fundamental mode Rayleigh waves. Regional and teleseismic events recorded by the Greenland Ice Sheet Monitoring Network seismic network were used and we developed a group velocity correction method to estimate the dispersion within our region of study. The global dispersion model GDM52 from Ekström (2011, https://doi.org/10.1111/j.1365‐246X.2011.05225.x) was used to calculate group delays from the earthquake to the boundaries of our study area. An iterative reweighted generalized least squares approach was then used to invert for the regional group velocity variations between periods of 25 s and 180 s. The group delay correction method helps alleviate the limitations of the sparse Greenland seismic network in a region with poor seismicity. Both the ray coverage and resolution of our model are significantly better than similar studies of Greenland using two‐station methods. Spike tests suggest that features as small as 200 km can be resolved across Greenland. Our dispersion maps are consistent with previous studies and reveal many signatures of known geologic features including known sedimentary basins in Baffin Bay, the West and East Greenland flood basalt provinces, the East and South Greenland Archean blocks. Our model also contains two prominent features: a deep high‐velocity anomaly extending from northwestern to southwestern Greenland that could be the signature of a cratonic root and a low‐velocity anomaly in central eastern Greenland that correlates with the Icelandic plume track and could be associated with lithospheric thinning and upwelling of hot asthenosphere material.

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The bedrock geology under the Inland Ice: the next major challenge for Greenland mapping

Cited by 49 publications

References 3 publications

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet

Noble gas signatures in Greenland: Tracing glacial meltwater sources

High‐Resolution Rayleigh Wave Group Velocity Variation Beneath Greenland

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