Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

Khan, Shfaqat Abbas; Sasgen, Ingo; Bevis, Michael; Dam, Tonie van; Bamber, Jonathan; Wahr, John; Willis, M. J.; Kjær, Kurt H.; Wouters, Bert; Helm, Veit; Csathó, B. M.; Fleming, Kevin; Bjørk, Anders A.; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers

doi:10.1126/sciadv.1600931

Cited by 125 publications

(235 citation statements)

References 57 publications

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“…The viscosity inferred in this region is several orders of magnitude lower than the surrounding cratonic areas (Figure b). The median value of ∼10 20 Pa s at 180‐km depth (Figures c and b) is in good agreement with a revised GIA model obtained from geodetic data (Khan et al, ).…”

Section: Discussionsupporting

confidence: 88%

Uncovering the Iceland Hot Spot Track Beneath Greenland

Mordret

2018

JGR Solid Earth

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During the past 120 Ma, the Greenland craton drifted over the Iceland hot spot; however, uncertainties in geodynamic modeling and a lack of geophysical evidence prevent an accurate reconstruction of the hot spot track. I image the Greenland lithosphere down to 200‐km depth with both group and phase velocity seismic noise tomography. The 3‐D shear wave velocity model obtained using 4–5 years of continuous seismic records from the Greenland Ice Sheet Monitoring Network is well resolved for most of the Greenland main island. The crustal part of the model clearly shows different tectonic units. The hot spot track is observed as a linear high‐velocity anomaly in the middle and lower crust associated with magmatic intrusions. In the upper mantle, a pronounced low‐velocity anomaly below the east coast might be due to the remnant effect of the Iceland hot spot when it was at its maximum intensity. Thermomechanical modeling suggests that this area has higher temperature and lower viscosity than the surrounding cratonic areas and experiences a higher than average surface heat flow. This new detailed picture of the Greenland lithosphere will drive more accurate geodynamic reconstructions of tectonic plate motions and help to better understand the North Atlantic tectonic history. Models of Greenland glacial isostatic adjustment will benefit from the 3‐D upper‐mantle viscosity model, which in turn will enable more precise estimations of the Greenland ice sheet mass balance.

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Section: Discussionsupporting

confidence: 88%

Uncovering the Iceland Hot Spot Track Beneath Greenland

Mordret

2018

JGR Solid Earth

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“…The low‐velocity anomalies from CE Greenland are consistent with previous P and S waves tomography (Jakovlev et al, ; Lebedev et al, ; Mordret, ; Rickers et al, ; Schaeffer & Lebedev, , ) and with indications of lithospheric thinning in this region (Kumar et al, ; Schiffer et al, ). The presence of this mantle low‐velocity anomaly in a region of documented postrift uplift (Anell et al, ; Døssing et al, ; Japsen & Chalmers, ) and unusually high GIA uplift rates (e.g., +10 mm/year; Khan et al, ) could also be an evidence of low upper mantle viscosity and explain the mechanism for isostatic compensation in a region with no deep crustal roots. The lack of a similar velocity low beneath the western Tertiary Basalt Province in this depth range could indicate limited lithospheric modifications from the failed rifting of the Labrador Sea.…”

Section: Resultsmentioning

confidence: 96%

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

Pourpoint¹,

Anandakrishnan

Ammon

et al. 2018

JGR Solid Earth

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We present a high‐resolution shear wave velocity model of Greenland's lithosphere from regional and teleseismic Rayleigh waves recorded by the Greenland Ice Sheet Monitoring Network supplemented with observations from several temporary seismic deployments. To construct Rayleigh wave group velocity maps, we integrated signals from regional and teleseismic earthquakes with several years of ambient seismic noise and used the dispersion to constrain crustal and upper‐mantle seismic shear wave velocity structure. Specifically, we used a Markov Chain Monte Carlo technique to estimate 3‐D shear wave velocities beneath Greenland to a depth of 200 km. Our model reveals four prominent anomalies: a deep high‐velocity feature extending from southwestern to northwestern Greenland that may be the signature of a thick cratonic keel, a corridor of relatively low upper‐mantle velocity across central Greenland that could be associated with lithospheric modification from the passage of the Iceland plume beneath Greenland or interpreted as a tectonic boundary between cratonic blocks, an upper‐crustal southwest‐northeast trending boundary separating Greenland into two regions of contrasting tectonic and crustal properties, and a midcrustal low‐velocity anomaly beneath northeastern Greenland. The nature of this midcrustal anomaly is of particular interest given that it underlies the onset of the Northeast Greenland Ice Stream and raises interesting questions regarding how deeper processes may impact the ice stream dynamics and the evolution of the Greenland Ice Sheet.

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“…Because the observed rates of land motion have been corrected for elastic deformation associated with ice loading over the GPS monitoring period (24), the elastic contribution was removed from the model output. Comparing observed and modeled rates in Table S1 indicates that the revised model is an improvement at all sites except those in the northeast (JGBL, KMJP, LEFN, NORD).…”

Section: Methodsmentioning

confidence: 99%

“…In a recent study (24), the component of this motion associated with past ice-sheet changes was isolated by estimating and removing the signal caused by ice-sheet changes and the corresponding elastic earth deformation during the GPS monitoring period. Table S1 provides a comparison of observed and modeled uplift rates that includes values for both Huy3 and the revised model.…”

Section: Implications Of Agassiz δ 18 O Temperature Reconstruction Fomentioning

confidence: 99%

High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution

Lecavalier

Fisher

Milne

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

183

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We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4-5°C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800-7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland.ice core | temperature reconstruction | Holocene climate | Greenland ice sheet I nstrumented records of temperature and environmental change extend for a few centuries at most. Although these records provide evidence of climate warming, the time span covered is relatively short compared with the centuries to millennia response times of some climate system components (1). In this respect, reconstructions of temperature and environmental changes obtained from climate proxies (e.g., sediment cores, ice cores) play a complementary role to the instrumented records by providing a longer temporal context within which to interpret the magnitude and rate of recent changes (2). Furthermore, the relatively large spatial and temporal variability captured in these reconstructions represents a useful dataset to test models of the climate system (3). Of particular interest are periods during Earth's history when the climate was warmer than at present, as these provide information that is potentially more relevant to changes in the future.In this study, we focus on the reconstruction of past climate using ice cores from the Agassiz ice cap, located on Ellesmere Island in the Canadian Arctic Archipelago (Fig. 1A). This site is of particular interest as it is located in the high Arctic, and temperature reconstructions can be compared with those from more southerly locations to estimate polar amplification of climate in the past (4). Furthermore, it is located proximal to the Greenland ice sheet, and so can be used to better constrain the climate forcing used to model the past evolution of this ice sheet.In a recent study (5), δ 18 O measurements in ice from the Agassiz (81°N) and Renland (70°N) ice caps (Fi...

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Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

Abstract: Present destabilization of marine-based sectors in Greenland may increase sea level for centuries to come.

Cited by 125 publications

References 57 publications

Uncovering the Iceland Hot Spot Track Beneath Greenland

Uncovering the Iceland Hot Spot Track Beneath Greenland

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

High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution

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