Climate‐driven vertical acceleration of Icelandic crust measured by continuous GPS geodesy

Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún

doi:10.1002/2014gl062446

Cited by 41 publications

(33 citation statements)

References 34 publications

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“…Future studies of the relationship between ice cap load variations and magma generation should include the potential feedback effects introduced by tephra deposition and changes in ice surface albedo. Many studies have demonstrated the link between deglaciation, surface uplift, and magma generation [e.g., Jull and McKenzie , ; Pagli and Sigmundsson , ; Schmidt et al ., ], however, no such study has yet included the potential effects of accelerated ice melt due to climate warming [ Compton et al ., ] or the feedback processes introduced by volcanic tephra deposition.…”

Section: Discussionmentioning

confidence: 99%

“…Compton et al . [] showed that cGPS stations in Iceland experience measurable uplift accelerations in the vertical coordinate component. Rather than simultaneously incorporating parameters for initial offsets, velocities, and accelerations in our ice mass inversion scheme, we instead estimated these parameters and used these estimates to reduce the time series such that the residuals exhibit zero mean quasiperiodic motions without secular trends.…”

Section: Cgps Datamentioning

confidence: 99%

“…Our estimates of vertical annual motion from the raw cGPS time series generally agree with previous studies [ Grapenthin et al ., ]. Spatial variation in the amplitudes is similar to the patterns of secular vertical velocities [ Árnadóttir et al ., ; Geirsson et al ., ] and accelerations [ Compton et al ., ] with larger amplitudes in the center of Iceland that decrease toward the coasts. Assuming that seasonal motions are sinusoidal, we estimate amplitudes of vertical peak‐to‐peak periodic displacements as high as 22 mm (18 mm for the reduced data set) in the Central Highlands region of the island between the Vatnajökull and Hofsjökull ice caps (Figure and Table ).…”

Section: Cgps Datamentioning

confidence: 99%

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Short‐term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

Compton

Bennett

Hreinsdóttir

et al. 2017

Geochem Geophys Geosyst

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As the global climate changes, understanding short‐term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak‐to‐peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS‐measured displacements for estimating seasonal and shorter‐term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half‐space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake‐based observations of loading and melting within the 1 σ confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice‐yearly stake measurements.

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Section: Discussionmentioning

confidence: 99%

Section: Cgps Datamentioning

confidence: 99%

Section: Cgps Datamentioning

confidence: 99%

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Short‐term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

Compton

Bennett

Hreinsdóttir

et al. 2017

Geochem Geophys Geosyst

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“…However, the GIA‐uncorrected GPS velocities in 1994–2003 were compared with GIA‐corrected velocities in 2003–2010 (Figure d). It is worth noting that the GIA signal in Iceland is time dependent and was significantly faster during 2003–2010 than in 1994–2003 [ Geirsson et al ., ; Compton et al ., ]. Within the uncertainty limits, GIA‐uncorrected 1994–2003 and corrected 2003–2010 velocities are fairly similar and both follow the model curve that results in ~4 mm yr −1 subsidence at the rift center (Figure e).…”

Section: Geodetic Datamentioning

confidence: 97%

Continuous subsidence in the Thingvellir rift graben, Iceland: Geodetic observations since 1967 compared to rheological models of plate spreading

et al. 2016

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North America‐Eurasia relative plate motion across the Mid‐Atlantic Ridge in south Iceland is partitioned between overlapping ridge segments, the Western Volcanic Zone (WVZ) and the Eastern Volcanic Zone. The Thingvellir graben, a 4.7 km wide graben, lies along the central axis of the WVZ and has subsided >35 m during the Holocene. An ~8 km long leveling profile across the graben indicates a subsidence rate of ~1 mm yr−1 from 1990 to 2007, relative to the first (westernmost) benchmark. Modeled GPS velocities from 1994 to 2003 estimate a spreading rate of 6.7 ± 0.5 mm yr−1 or 35% of the full plate motion rate and up to 6.0 mm yr−1 subsidence. The combined geodetic observations show that the deformation zone is 10 times wider than the graben width. We utilize these geodetic observations to test the effects of ridge thermal structure on the kinematics across divergent boundaries. We apply a nonlinear rheology, thermomechanical model implemented in a finite element model. A 700°C isotherm is applied for the brittle to ductile transition in the crust, representing a dry olivine rheology. We adjust the depth of this isotherm to solve for the best fit model. The best fit model indicates that the 700°C isotherm is at 8 km depth below the ridge axis, which results in an average thermal gradient of 87.5°C km−1 in the upper crust. The thermomechanical model predicts a subsidence rate of 4 mm yr−1, comparable to our geodetic observations.

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“…However, this model is based on InSAR and GPS observations mostly prior to our study period. It also does not account for the observed relatively rapid acceleration of GIA with time [ Compton et al , ]. We find that it underestimates the horizontal and vertical GIA signal in our data.…”

Section: Modelingmentioning

confidence: 99%

Deformation in the Northern Volcanic Zone of Iceland 2008–2014: An interplay of tectonic, magmatic, and glacial isostatic deformation

et al. 2017

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GPS measurements spanning 2008 to 2014 are used to derive the surface velocity field across the Northern Volcanic Zone (NVZ) of Iceland, a subaerial part of the divergent boundary between the North American and Eurasian plates. No volcanic activity nor magmatic intrusions were detected in the zone during this time period. We infer an extensional rate of 17.4 −0.3+0.2 mm/yr in direction 292.0 −0.6+0.5°, consistent with the results of previous studies and current plate motion models including MORVEL2010 and GEODVEL2010. The horizontal velocity field reveals about 50 km wide stretching zone caused by the divergent plate movements. Glacial isostatic adjustment (GIA) induces uplift of over 20 mm/yr at the northern edge of Vatnajökull ice cap and 3–4 mm/yr horizontal motion directed away from the ice cap. Deformation in the NVZ between 2008 and 2014 can be reproduced by a combination of models relating to several different processes: (i) Mogi sources for volcanic and geothermal deformation at the Askja and Krafla volcanoes, (ii) scaled version of a velocity field derived from a glacial isostatic model, and (iii) simple arctangent‐based model for secular plate spreading. We find the approximate location of the plate boundary spreading axis as well as its locking depth. The spreading axis lies through the Krafla, Fremrinámar, and Askja central volcanoes, the most active ones in the NVZ. It does not appear to follow the general direction of each fissure swarm but rather to change direction at the central volcanoes. The locking depth is on average within the 7–9 km range.

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Climate‐driven vertical acceleration of Icelandic crust measured by continuous GPS geodesy

Cited by 41 publications

References 34 publications

Short‐term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

Short‐term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

Continuous subsidence in the Thingvellir rift graben, Iceland: Geodetic observations since 1967 compared to rheological models of plate spreading

Deformation in the Northern Volcanic Zone of Iceland 2008–2014: An interplay of tectonic, magmatic, and glacial isostatic deformation

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