Lithospheric Structure of Greenland From Ambient Noise and Earthquake Surface Wave Tomography

Pourpoint, M.; Anandakrishnan, S.; Ammon, Charles J.; Alley, Richard B.

doi:10.1029/2018jb015490

Cited by 22 publications

(41 citation statements)

References 117 publications

(268 reference statements)

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“…In this section, we review results of previous seismological studies of the crust and upper mantle structure beneath Greenland and surrounding regions, focusing mainly on seismic tomography studies. The structure has been investigated using several tomographic methods with various spatial scales, including regionalscale surface wave tomography (Antonijevic & Lees, 2018;Darbyshire et al, 2004Darbyshire et al, , 2018Levshin et al, 2017;Mordret, 2018;Pourpoint et al, 2018), surface wave tomography of the North Atlantic region (Pilidou et al, 2004), body wave tomography of the whole Arctic region (Jakovlev et al, 2012), full waveform tomography of the North Atlantic region (Rickers et al, 2013), full waveform tomography of the whole Arctic region (Lebedev et al, 2017), and global tomography (e.g., Hosseini et al, 2020;Lei et al, 2020;Zhao, 2001Zhao, , 2004Zhao et al, 2013).…”

Section: Previous Studiesmentioning

confidence: 99%

“…Such discrepancies are also prominent in the lower crust. Darbyshire et al (2018) and Pourpoint et al (2018) showed a nearly homogeneous velocity structure as it approaches the Moho; Levshin et al (2017) imaged almost the same velocity pattern as in the upper crust, while Mordret (2018) imaged reversed patterns in the upper and lower crust beneath southern Greenland. Lebedev et al (2017) showed only the lower crustal structure, but included low-V regions in northern Greenland and in the southern Archean block, which display similarities to the upper crustal structure of other models (Darbyshire et al, 2018;Mordret, 2018).…”

Section: Crustal Structurementioning

confidence: 99%

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P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

2020

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We study the 3-D P wave velocity (Vp) structure of the crust and upper mantle beneath Greenland and surrounding regions using the latest P wave arrival time data. The Greenland Ice Sheet Monitoring Network (GLISN), initiated in 2009, is an international project for seismic observation in these regions using 34 stations. We use a regional seismic tomography method to simultaneously invert P wave arrival times of local earthquakes and P wave relative traveltime residuals of teleseismic events. These data are extracted from the ISC-EHB catalog; however, for the teleseismic data, we picked new arrival times from seismograms using a cross-correlation method. Our tomographic results clearly reveal the Iceland plume, the Jan Mayen plume, and a newly discovered "Svalbard plume," which merge together in the mantle transition zone. A high-Vp body exists beneath the Greenland Sea, which might act as an obstacle against the rising Svalbard plume. Furthermore, our results reveal a remarkable low-Vp anomaly elongated in the NW-SE direction at depths ≤250 km beneath central Greenland, which is connected with the Iceland and Jan Mayen hotspots. Although previous studies have suggested a similar feature, our result is the first to show the low-Vp zone existing at all depths in the Greenland lithosphere, and its spatial distribution coincides with a high heat flux region. These characteristics indicate that the low-Vp zone reflects residual heat from the Iceland plume when the Greenland lithosphere passed over this plume at~80-20 Ma. Our results also indicate the possible existence of residual heat from the Jan Mayen plume. Plain Language Summary Greenland is a stable land mass that has preserved~4 Gyr of Earth's history. In its vicinity, there are the Mid-Atlantic Ridge, the Iceland and Jan Mayen hotspots, and a geothermal area in Svalbard, which indicate the complexity of this region. We apply seismic tomography to analyze the latest data recorded by a new seismograph network, and we obtain detailed 3-D images of the crust and upper mantle. Our results clearly image the conduit-like Iceland plume, the Jan Mayen plume, and a newly discovered "Svalbard plume," which merge together in the mantle transition zone. These new findings will improve our understanding of the tectonic and thermal evolution of this region. We also find a low seismic velocity zone running in the NW-SE direction beneath central Greenland, which is connected with the Iceland and Jan Mayen hotspots. This zone is located within the Greenlandic plate, and its spatial distribution agrees well with an area of high geothermal heat flux. These results suggest that the low-velocity zone reflects residual heat from the Iceland plume when the Greenlandic plate passed over the plume at~80-20 Ma. Our model further suggests a possible heat track left by the Jan Mayen plume.

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Section: Previous Studiesmentioning

confidence: 99%

Section: Crustal Structurementioning

confidence: 99%

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

2020

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“…Seismic tomography and related data indicate a thick, high‐seismic‐velocity cratonic keel extending north‐south under central‐west Greenland, transected by a broad zone of lower seismic velocity approximately connecting the eastern and western Tertiary basalt provinces (Jakovlev et al, ; Lebedev et al, ; Pourpoint et al, ; Pourpoint et al, ; Rickers et al, ; Rogozhina et al, ; Figure ). The location of this low‐velocity zone is close to, or slightly north of, the majority of reconstructed tracks of the Iceland hot spot as summarized by Rogozhina et al ().…”

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 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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“…We then test the plausibility of this mechanism by applying computationally efficient simulations to estimate deviatoric stress fields during glacial/interglacial cycling of the GrIS, finding widespread stresses similar to those estimated to cause dike propagation in magmatic systems. Together, these support our hypothesis that ice‐sheet processes might have contributed to anomalous GHF, and we argue that more targeted geophysical studies [e.g., Pourpoint et al ., ] informing higher‐order modeling are required to advance this work.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of volcanism and geothermal heat flux by ice‐age cycling: A stress modeling study of Greenland

2016

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Ice‐age cycling of the Greenland ice sheet likely contributed to locally elevated subglacial geothermal heat fluxes (GHFs), based on recent thermal modeling. Borehole and geophysical data indicate higher GHF in some areas than suggested by current knowledge of underlying geology, particularly at the head of the Northeast Greenland Ice Stream. Changes in lithospheric loading during ice‐sheet growth and decay cycles produce large and geologically rapid changes in the effective stress state beneath and near the ice sheet. Oscillations in melt fraction from cyclic loading through multiple ice‐age cycles will enhance upward magma migration through the nonlinear increase of melt migration velocity with melt fraction. We simulate periodic ice‐sheet loading scenarios along an east‐west transect across central Greenland on an Elastic Lithosphere, Relaxed Asthenosphere Earth model. Under likely parameter ranges, deviatoric stresses in the elastic lithosphere across widespread regions are sufficiently high to meaningfully enhance dike emplacement and also allow vug‐wave propagation in some scenarios. Stress patterns migrate laterally in response to ice‐sheet dynamics, favoring multistage magma ascent. If melt occurs at depth, our modeling suggests that ice‐age cycling could help it migrate upward to shallow depth or erupt, contributing to the high observed GHF. Furthermore, shallow magma emplacement might feed hydrothermal systems exploiting enhanced faulting or fracturing from ice‐age cycling, adding to elevated GHF. The preglacial passage of the Iceland‐Jan Mayen hot spot could have sourced such magmas. Direct observations of these lithospheric processes needed to further constrain our models are limited, highlighting the value of more targeted geophysical studies informing future modeling.

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Lithospheric Structure of Greenland From Ambient Noise and Earthquake Surface Wave Tomography

Cited by 22 publications

References 117 publications

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

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

Enhancement of volcanism and geothermal heat flux by ice‐age cycling: A stress modeling study of Greenland

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