Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE)

• Mohn, Chris Erik; Caracas, Razvan & Conrad, Clinton Phillips (2025). Lower mantle water distribution from ab initio proton diffusivity in bridgmanite. Earth and Planetary Science Letters. ISSN 0012-821X. 649. doi: 10.1016/j.epsl.2024.119095. Full text in Research Archive Show summary

  Proton self diffusion coefficients for bridgmanite at lower mantle conditions are calculated from ab initio molecular dynamics simulations. We find that the proton self diffusion coefficient, is nearly constant ∼ 10−8 m2 s−1 along the lower mantle geotherm but increases by nearly one order of magnitude from ∼10−10 m2 s−1 to ∼ 10−9 m2 s−1 along a cold slab geotherm to about 1800 km depth. These rates imply that the proton diffusion length scale is less than 10 km in lower mantle peridotite in the 150-200 million years timescale for slab material to sink through the lower mantle. Cold wet slabs probably lose less than one percent of their total water content to the ambient mantle on their journey through the lower mantle, indicating that recycled water is far from homogeneously distributed since slab delivery is highly heterogeneous. We estimate that 0.1 to 0.3 ocean masses (<100 ppm wt%) of recycled water may be currently stored in slab remnant materials within the lower mantle. This water is likely not entrained by plumes but is instead captured by background mantle flow before returning to the mid-ocean ridges. By contrast, deep-rooted mantle plumes may entrain materials containing primordial-like water from the lowermost mantle or the core, and preserve these anomalies in fairly small-scale heterogeneities. Over the age of the Earth, the proton diffusion length scale is a few tens of km, which places constraints on the size of possible primordial water reservoirs isolated from convective mixing, and indicates little flux of water across the core-mantle boundary.

• Wang, Helene; Magni, Valentina; Conrad, Clinton Phillips & Domeier, Mathew Michael (2025). Hydrous Regions of the Mantle Transition Zone Lie Beneath Areas of Continental Intraplate Volcanism. Geochemistry Geophysics Geosystems. 26(3). doi: 10.1029/2024GC011901. Full text in Research Archive Show summary

  Great volumes of water are carried downward into the mantle transition zone (MTZ, 410–670 km depth) by subducting slabs. If this water is later drawn upward, the resulting mantle melting may generate continental intraplate volcanism (IPV). Despite water's importance, its amount and spatial distribution within the MTZ, and its impact on IPV, are poorly constrained. Here we use plate tectonic reconstructions to estimate the rates and positions of water injection into the MTZ by subducted slabs during the past 400 Myr. This allows us to construct global maps of heterogeneous MTZ hydration, which we then compare to IPV eruption locations from the past 200 Myr. We detect a statistically significant correlation between wet MTZ regions and IPV locations at the surface, but only if slabs sink faster than 1 cm/yr, water remains stored in the MTZ for periods of 30–100 Myr, and IPV eruptions occur 10–30 Myr later. We find that 42%–68% of continental IPV is underlain by wet MTZ, with greater fractions associated with longer MTZ residence time. Hydrous underpinning of continental IPV was highest during the Jurassic, when more extensive slab interaction with the MTZ hydrated a wider area of the MTZ. Since the Cretaceous, continents have been moving over the wet MTZ, increasing IPV possibilities. MTZ regions near the northern Pacific, southern Africa, and western Europe have remained dry by avoiding wet slabs. We suggest that subducted water shapes global patterns of intraplate volcanism, with hydrous upwellings rising from the MTZ to generate continental IPV above wet MTZ regions.

• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2024). Recent ice melt above a mantle plume track is accelerating the uplift of Southeast Greenland. Communications Earth & Environment. 5. doi: 10.1038/s43247-024-01968-6. Full text in Research Archive Show summary

  Around the periphery of the Greenland ice sheet, satellite-based observations of ground uplift record Earth’s response to past and recent unloading of Greenland’s ice mass. On the southeast coast, near the Kangerlussuaq glacier, rapid uplift exceeding 12 mm/yr cannot be explained using current layered Earth deformation models. Here we find that 3D models with a weakened Earth structure, consistent with the passage of Greenland over the Iceland plume, can explain the rapid uplift of Southeast Greenland. This uplift is dominated by a viscous response that is accelerated by the low viscosities of the hot plume track. Recent mass loss, occurring during the last millennium and especially within the past few decades, drives most of the uplift. Holocene indicators recorded similarly rapid uplift following deglaciation that ended the last ice age. Such rapid uplift, occurring beneath marine terminating glaciers, can affect the future stability of entire ice catchment areas and will become increasingly important in the near future as deglaciation accelerates.

• Ramirez, Florence; Selway, Katherine; Conrad, Clinton Phillips; Maupin, Valerie & Smirnov, Maxim (2024). Lateral and radial viscosity structure beneath Fennoscandia inferred from seismic and magnetotelluric observations. Physics of the Earth and Planetary Interiors. ISSN 0031-9201. 351. doi: 10.1016/j.pepi.2024.107178. Full text in Research Archive Show summary

  Fennoscandia is continuously uplifting in response to past deglaciation, termed glacial isostatic adjustment or GIA, and its mantle viscosity is well constrained from ice sheet and sea level data. Here, we compare those GIA-constrained viscosities for the Fennoscandian upper mantle with geophysically-constrained viscosities. We construct the upper mantle viscosity structure of Fennoscandia by inferring temperature and water content from seismic and magnetotelluric (MT) data. Using a 1-D MT model for Fennoscandian cratons together with a global seismic model, we infer an upper mantle viscosity (below 250 km) of ∼1021±2 Pa·s, which encompasses the GIA-constrained viscosities of 1020 − 1021 Pa·s. The GIA viscosities are better matched if the Fennoscandian upper mantle is a wet harzburgite or a dry pyrolite, where pyrolite is ∼10 times more viscous than harzburgite. Using the average temperatures and water contents for harzburgitic upper mantle, the GIA viscosities require 1–4 mm grain sizes indicating a diffusion creep regime. In northwestern Fennoscandia, where a high-resolution 2-D resistivity model is available, greater inferred mantle water content implies viscosities that are 10–100 times lower than those for the Fennoscandian Craton. Our work suggests that the combination of seismic and MT observations can improve upper mantle viscosity estimates, especially for regions with laterally-varying viscosity structures or where GIA constraints are not available. Although our method represents an important step forward, viscosity uncertainty can be further reduced by incorporating additional constraints on rock composition, grain size and mantle stress, as well as more accurate geophysical data, into the viscosity calculation.

• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2024). Prolonged Multi-Phase Magmatism Due To Plume-Lithosphere Interaction as Applied to the High Arctic Large Igneous Province. Geochemistry Geophysics Geosystems. 25(6). doi: 10.1029/2023GC011380. Full text in Research Archive Show summary

  The widespread High Arctic Large Igneous Province (HALIP) exhibits prolonged melting over more than 50 Myr, an observation that is difficult to reconcile with the classic view that large igneous provinces (LIPs) originate from melting in plume heads. Hence, the suggested plume-related origin and classification of HALIP as a LIP have been questioned. Here, we use numerical models that include melting and melt migration to investigate a rising plume interacting with lithosphere of variable thickness, that is, a basin-to-craton setting applicable to the Arctic. Models reveal that melt migration introduces significant spatial and temporal variations in melt volumes and pulses of melt production, including protracted melting for at least about 30–40 Myr, because of the dynamic feedback between migrating melt and local lithosphere thinning. For HALIP, plume material deflected from underneath the Greenland craton can re-activate melting zones below the previously plume-influenced Sverdrup Basin after a melt-free period of about 10–15 Myr, even though the plume is already ∼500 km away. Hence, actively melting zones do not necessarily represent the location of the deeper plume stem at a given time, especially for secondary pulses. Additional processes such as (minor) plume flux variations or local lithospheric extension may alter the timing and volume of HALIP pulses, but are to first order not required to reproduce the long-lived and multi-pulse magmatism of HALIP. Since melting zones are always plume-fed, we would expect HALIP magmatism to exhibit plume-related trace element signatures throughout time, potentially shifting from mostly tholeiitic toward more alkalic compositions.

• Weerdesteijn, Maaike Francine Maria; Naliboff, John B.; Conrad, Clinton Phillips; Reusen, Jesse M.; Steffen, Rebekka & Heister, Timo [Show all 7 contributors for this article] (2023). Modeling Viscoelastic Solid Earth Deformation Due To Ice Age and Contemporary Glacial Mass Changes in ASPECT. Geochemistry Geophysics Geosystems. 24(3). doi: 10.1029/2022GC010813. Full text in Research Archive Show summary

  Abstract The redistribution of past and present ice and ocean loading on Earth's surface causes solid Earth deformation and geoid changes, known as glacial isostatic adjustment. The deformation is controlled by elastic and viscous material parameters, which are inhomogeneous in the Earth. We present a new viscoelastic solid Earth deformation model in ASPECT (Advanced Solver for Problems in Earth's ConvecTion): a modern, massively parallel, open‐source finite element code originally designed to simulate convection in the Earth's mantle. We show the performance of solid Earth deformation in ASPECT and compare solutions to TABOO, a semianalytical code, and Abaqus, a commercial finite element code. The maximum deformation and deformation rates using ASPECT agree within 2.6% for the average percentage difference with TABOO and Abaqus on glacial cycle (∼100 kyr) and contemporary ice melt (∼100 years) timescales. This gives confidence in the performance of our new solid Earth deformation model. We also demonstrate the computational efficiency of using adaptively refined meshes, which is a great advantage for solid Earth deformation modeling. Furthermore, we demonstrate the model performance in the presence of lateral viscosity variations in the upper mantle and report on parallel scalability of the code. This benchmarked code can now be used to investigate regional solid Earth deformation rates from ice age and contemporary ice melt. This is especially interesting for low‐viscosity regions in the upper mantle beneath Antarctica and Greenland, where it is not fully understood how ice age and contemporary ice melting contribute to geodetic measurements of solid Earth deformation.

• Ramirez, Florence Dela Cruz; Conrad, Clinton Phillips & Selway, Katherine (2023). Grain size reduction by plug flow in the wet oceanic upper mantle explains the asthenosphere's low seismic Q zone. Earth and Planetary Science Letters. ISSN 0012-821X. 616. doi: 10.1016/j.epsl.2023.118232. Full text in Research Archive Show summary

  The prominent seismic low-velocity zone (LVZ) in the oceanic low-viscosity asthenosphere is approximately coincident with the low seismic Q zone (LQZ; a zone of high seismic attenuation). Small olivine grain sizes could link these seismic and rheological properties because they reduce viscosity, seismic velocity and seismic Q. Because rock deformation reduces grain sizes, the asthenosphere's seismic properties can place constraints on asthenospheric flow. To determine dominant flow patterns, we develop a self-consistent analytical 1-D channel flow model that accounts for upper mantle rheology and its dependence on flow-modified grain-sizes, water content, and melt fraction, for flow driven by both surface plate motions (Couette flow) and/or horizontal pressure gradients (Poiseuille flow). We find that Couette flow dominates if the upper mantle is dry, and plug flow (a Poiseuille flow for power law rheology) dominates if it is weakened by wet conditions. A plug flow configuration spanning the upper 670 km of the mantle best explains the LQZ in the asthenosphere, and can be attributed to significant grain-size reduction due to extensive shearing across the asthenosphere. This flow configuration also explains high seismic Q values below the asthenosphere associated with minimal shear deformation and large grain sizes above the mantle transition zone. We suggest that the asthenospheric LQZ and LVZ seismic anomalies can be largely explained by grain-size variations associated with plug flow in the wet upper mantle.

• Paul, Jyotirmoy; Conrad, Clinton Phillips; Becker, Thorsten W. & Ghosh, Attreyee (2023). Convective Self-Compression of Cratons and the Stabilization of Old Lithosphere. Geophysical Research Letters. ISSN 0094-8276. 50(4). doi: 10.1029/2022GL101842. Full text in Research Archive Show summary

  Abstract Despite being exposed to convective stresses for much of the Earth's history, cratonic roots appear capable of resisting mantle shearing. This tectonic stability can be attributed to the neutral density and higher strength of cratons. However, the excess thickness of cratons and their higher viscosity amplify coupling to underlying mantle flow, which could be destabilizing. To investigate the stresses that a convecting mantle exerts on cratons that are both strong and thick, we developed instantaneous global spherical numerical models that incorporate present‐day geoemetry of cratons within active mantle flow. Our results show that mantle flow is diverted downward beneath thick and viscous cratonic roots, giving rise to a ring of elevated and inwardly‐convergent tractions along a craton's periphery. These tractions induce regional compressive stress regimes within cratonic interiors. Such compression could serve to stabilize older continental lithosphere against mantle shearing, thus adding an additional factor that promotes cratonic longevity.

• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips & Naliboff, John B. (2022). Solid Earth Uplift Due To Contemporary Ice Melt Above Low-Viscosity Regions of the Upper Mantle. Geophysical Research Letters. ISSN 0094-8276. 49(17). doi: 10.1029/2022GL099731. Full text in Research Archive Show summary

  Glacial isostatic adjustment explains topographic change in formerly and currently glaciated regions, but the role of small (∼100s km) regions of unusually low-viscosity mantle is poorly understood. We developed viscoelastic models with low-viscosity regions in the upper mantle, and measured the effect of these regions on solid earth uplift resulting from contemporary surface ice melt. We found viscous uplift occurring on decadal timescales above the low-viscosity region, at rates comparable to or larger than those from elastic uplift or the viscous response to ice age melting. We find that uplift rates are sensitive to the location, dimensions, and viscosity of the low-viscosity region, and that the largest uncertainty in uplift rates likely comes from the low-viscosity region's horizontal extent. Rapid viscous ground uplift can impact ice dynamics if the low-viscosity region is located close to an ice sheet margin, as for Antarctica and Greenland.

• Heyn, Björn Holger & Conrad, Clinton Phillips (2022). On the Relation Between Basal Erosion of the Lithosphere and Surface Heat Flux for Continental Plume Tracks. Geophysical Research Letters. ISSN 0094-8276. 49(7). doi: 10.1029/2022GL098003. Full text in Research Archive Show summary

  While hotspot tracks beneath thin oceanic lithosphere are visible as volcanic island chains, the plume-lithosphere interaction for thick continental or cratonic lithosphere often remains hidden due to the lack of volcanism. To identify plume tracks with missing volcanism, we characterize the amplitude and timing of surface heat flux anomalies following a plume-lithosphere interaction using mantle convection models. Our numerical results confirm an analytical relationship in which surface heat flux increases with the extent of lithosphere thinning, which is primarily controlled by the viscosity structure of the lower lithosphere and the asthenosphere. We find that lithosphere thinning is greatest when the plate is above the plume conduit, while the maximum heat flux anomaly occurs about 40-140 Myr later. Therefore, younger continental and cratonic plume tracks can be identified by observed lithosphere thinning, and older tracks by an increased surface heat flux, even if they lack extrusive magmatism.

• Ramirez, Florence Dela Cruz; Selway, Katherine; Conrad, Clinton Phillips & Lithgow-Bertelloni, C. (2022). Constraining Upper Mantle Viscosity Using Temperature and Water Content Inferred From Seismic and Magnetotelluric Data. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 127(8). doi: 10.1029/2021JB023824. Full text in Research Archive Show summary

  Mantle viscosity controls a variety of geodynamic processes such as glacial isostatic adjustment (GIA), but it is poorly constrained because it cannot be measured directly from geophysical measurements. Here we develop a method that calculates viscosity using empirical viscosity flow laws coupled with mantle parameters (temperature and water content) inferred from seismic and magnetotelluric (MT) observations. We find that combining geophysical constraints allows us to place significantly tighter bounds on viscosity estimates compared to using seismic or MT observations alone. In particular, electrical conductivity inferred from MT data can determine whether upper mantle minerals are hydrated, which is important for viscosity reduction. Additionally, we show that rock composition should be considered when estimating viscosity from geophysical data because composition directly affects seismic velocity and electrical conductivity. Therefore, unknown composition increases uncertainty in temperature and water content, and makes viscosity more uncertain. Furthermore, calculations that assume pure thermal control of seismic velocity may misinterpret compositional variations as temperature, producing erroneous interpretations of mantle temperature and viscosity. Stress and grain size also affect the viscosity and its associated uncertainty, particularly via their controls on deformation regime. Dislocation creep is associated with larger viscosity uncertainties than diffusion creep. Overall, mantle viscosity can be estimated best when both seismic and MT data are available and the mantle composition, grain size and stress can be estimated. Collecting additional MT data probably offers the greatest opportunity to improve geodynamic or GIA models that rely on viscosity estimates.

• Marcilly, Chloe M.; Torsvik, Trond Helge & Conrad, Clinton Phillips (2022). Global Phanerozoic sea levels from paleogeographic flooding maps. Gondwana Research. ISSN 1342-937X. 110, p. 128–142. doi: 10.1016/j.gr.2022.05.011. Full text in Research Archive Show summary

  The validity of sea level estimates based on stratigraphic correlations has been debated since the 1990 s as relative sea level curves differ between sites due to local tectonics, different deposition rates and changes in dynamic topography. Here, we offer a new eustatic (global) sea level curve for the past 520 million years (Myrs) based on observations of global flooding. We use paleogeographic reconstructions to measure the area of today’s exposed land that was flooded in the past (modern-land flooding). We then apply the modern global hypsometric slope to reconstruct the sea level history. We find minimum sea levels (comparable to today’s level) towards the end of Pangea (210 Ma) and peak levels (∼280 m higher than today) at 80 Ma when Pangea was widely dispersed. A first-order “supercontinent” cycle of 250 million years (Myrs) is recognized but we also document a second-order cycle of 37 Myrs that was previously thought to be undetectable using the hypsometric method. The hypsometric slope is critical for reconstructing past sea levels, and steepening the hypsometric slope during Pangea assembly implies dramatically larger sea level fluctuations. Our new sea level curve shares strong similarities with stratigraphic constraints and correlates with seafloor production proxies throughout the Phanerozoic. Measurements of global flooding represent averages across great continental extents, making them less sensitive than stratigraphic analyses to regional-scale vertical land motion, such as from dynamic topography and hence more reliable for estimating eustatic sea level. This method can also help to identify local deviations caused by regional uplift or subsidence and serves to constrain geodynamic mechanisms for sea level change. Our new sea level reconstruction usefully tracks global variations in Phanerozoic eustatic sea level, but also opens opportunities to estimate such variations in deeper time.

• Hartmann, Robert; Ebbing, Jörg & Conrad, Clinton Phillips (2020). A Multiple 1D Earth Approach (M1DEA) to account for lateral viscosity variations in solutions of the sea level equation: An application for glacial isostatic adjustment by Antarctic deglaciation. Journal of Geodynamics. ISSN 0264-3707. 135. doi: 10.1016/j.jog.2020.101695. Full text in Research Archive Show summary

  The pseudo-spectral form of the sea level equation (SLE) requires the approximation of a radially-symmetric visco-elastic Earth. Thus, the resulting predictions of sea level change (SLC) and glacial isostatic adjustment (GIA) often ignore lateral variations in the Earth structure. Here, we assess the capabilities of a Multiple 1D Earth Approach (M1DEA) applied to large-scale ice load components with different Earth structures to account for these variations. In this approach the total SLC and GIA responses result from the superposition of individual responses from each load component, each computed globally assuming locally-appropriate 1D Earth structures. We apply the M1DEA to three separate regions (East Antarctica, West Antarctica, and outside Antarctica) to analyze uplift rates for a range of Earth structures and different ice loads at various distances. We find that the uplift response is mostly sensitive to the local Earth structure, which supports the usefulness of the M1DEA. However, stresses transmitted across rheological boundaries (e.g., producing peripheral bulges) present challenges for the M1DEA, but can be minimized under two conditions: (1) If the considered time period of ice loading for each component is consistent with the relaxation time of the local Earth structure. (2) If the load components can be subdivided according to the scale of the lateral variations in Earth structure. Overall, our results indicate that M1DEA could be a computationally much cheaper alternative to 3D finite element models, but further work is needed to quantify the relative accuracy of both methods for different resolutions, loads, and Earth structure variations.

• Sames, Benjamin; Wagreich, Michael; Conrad, Clinton Phillips & Iqbal, S. (2020). Aquifer-eustasy as the main driver of short-term sea-level fluctuations during Cretaceous hothouse climate phases. Geological Society Special Publication. ISSN 0305-8719. 498, p. 9–38. doi: 10.1144/SP498-2019-105. Full text in Research Archive Show summary

  A review of short-term (<3 myr: c. 100 kyr to 2.4 myr) Cretaceous sea-level fluctuations of several tens of metres indicates recent fundamental progress in understanding the underlying mechanisms for eustasy, both in timing and in correlation. Cretaceous third- and fourth-order hothouse sea-level changes, the sequence-stratigraphic framework, are linked to Milankovitch-type climate cycles, especially the longer-period sequence-building bands of 405 kyr and 1.2 myr. In the absence of continental ice sheets during Cretaceous hothouse phases (e.g. Cenomanian–Turonian), growing evidence indicates groundwater-related sea-level cycles: (1) the existence of Milankovitch-type humid-arid climate oscillations, proven via intense humid weathering records during times of regression and sea-level lowstands; (2) missing or inverse relationships of sea-level and the marine δ18O archives, i.e. the lack of a pronounced positive excursion, cooling signal during sea-level lowstands; and (3) the anti-phase relationship of sea and lake levels, attesting to high groundwater levels and charged continental aquifers during sea-level lowstands. This substantiates the aquifer-eustasy hypothesis. Rates of aquifer-eustatic sea-level change remain hard to decipher; however, reconstructions range from a very conservative minimum estimate of 0.04 mm a−1 (longer time intervals) to 0.7 mm a−1 (shorter, probably asymmetric cycles). Remarkably, aquifer-eustasy is recognized as a significant component for the Anthropocene sea-level budget.

• Smith-Johnsen, Silje; Fleurian, Basile de; Schlegel, Nicole; Seroussi, Hélène & Nisancioglu, Kerim Hestnes (2020). Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream. The Cryosphere. ISSN 1994-0416. 14(3), p. 841–854. doi: 10.5194/tc-14-841-2020. Full text in Research Archive Show summary

  The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10 % of the Greenland Ice Sheet area and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting heat flux anomalies with various locations and intensities. In our model experiment, a minimum heat flux value of 970 mW m−2 located close to the East Greenland Ice-core Project (EGRIP) is required locally to reproduce the observed NEGIS velocities, giving basal melt rates consistent with previous estimates. The value cannot be attributed to geothermal heat flux alone and we suggest hydrothermal circulation as a potential explanation for the high local heat flux. By including high heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.

View all works in NVA

• Conrad, Clinton Phillips (2025). Impact of Rheology on Glacial Isostatic Adjustment (GIA) Processes in Greenland. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2024). Rapid Earth uplift in Southeast Greenland driven by deglaciation above the Iceland Plume Track. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2024). Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle. Full text in Research Archive
• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2024). Prolonged multi-phase volcanism in the Arctic induced by plume-lithosphere interaction. Full text in Research Archive
• Conrad, Clinton Phillips; Weerdesteijn, Maaike Francine Maria; Ramirez, Florence Dela Cruz & Selway, Kate (2024). Rapid Earth uplift where the Iceland Plume Track Crosses Greenland: GIA modelling and MT Constraints. Full text in Research Archive
• Jaah, Ilyas; Kiraly, Agnes; Shephard, Grace; Conrad, Clinton Phillips & Domeier, Mathew Michael (2024). On the Role of Anisotropic Viscosity on the Motion of the Pacific Plate. Full text in Research Archive
• Conrad, Clinton Phillips (2024). Mantle Heterogeneity Beneath Greenland: Importance for Uplift and Deglaciation. Full text in Research Archive
• Conrad, Clinton Phillips (2024). Rapid Earth Uplift in Greenland above the Iceland Plume Track. Full text in Research Archive
• Conrad, Clinton Phillips (2024). Geodynamic implications of lateral viscosity variations in the mantle. Full text in Research Archive
• Marcilly, Chloe M.; Torsvik, Trond Helge & Conrad, Clinton Phillips (2024). Corrigendum to “Global Phanerozoic sea levels from paleogeographic flooding maps” [Gondwana Res. 110 (2022) 128–142, (S1342937X22001563), (10.1016/j.gr.2022.05.011)]. Gondwana Research. ISSN 1342-937X. 129, p. 367–368. doi: 10.1016/j.gr.2024.01.006. Full text in Research Archive
• Etzelmüller, Bernd; Lilleøren, Karianne Staalesen; Conrad, Clinton Phillips; Åkesson, Henning & Lund, Martin (2023). GeoOnsdag Spesial "Arven etter Esmark" - Sjå opptak frå foredraget. [Internet]. https://www.mn.uio.no/geo/om/organisasjon/geohyd/aktuelt/geo. Full text in Research Archive
• Ramirez, Florence Dela Cruz; Conrad, Clinton Phillips & Selway, Kate (2023). Plug flow and its associated grain-size variation in the oceanic asthenosphere explain the low seismic Q zone. Full text in Research Archive
• Shephard, Grace; Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Prolonged multi-phase magmatism due to plume-lithosphere interaction as applied to the High Arctic Large Igneous Province. Full text in Research Archive
• Ramirez, Florence Dela Cruz; Selway, Kate; Conrad, Clinton Phillips; Smirnov, Maxim & Maupin, Valerie (2023). Lateral and radial viscosity variations beneath Fennoscandia inferred from seismic and MT observations. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2023). Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle. Full text in Research Archive
• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2023). Locally amplified plume-lithosphere interaction and multiple melting events for 2-phase flow models. Full text in Research Archive
• Heyn, Björn Holger; Conrad, Clinton Phillips & Shephard, Grace (2023). Plume-lithosphere interaction and continental plume tracks. Full text in Research Archive
• Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Development and implications of a free base for numerical models. Full text in Research Archive
• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2023). Amplification of sub-lithospheric dynamics by melt migration during plume-lithosphere interaction. Full text in Research Archive
• Shephard, Grace; Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Large-scale volcanism at the top of the world; plume and melt modelling of the High Arctic Large Igneous Province (HALIP). Full text in Research Archive
• Åkesson, Henning; Etzelmüller, Bernd; Lund, Erik Martin; Conrad, Clinton Phillips & Lilleøren, Karianne Staalesen (2023). Arven etter Esmark - GeoOnsdag Spesial. Full text in Research Archive Show summary

  Arven etter Esmark, Bernd Etzelmüller/Karianne Lilleøren Imagining Esmark’s Lost Scandinavian Ice, Clint Conrad Gårsdagens is - fremtidens fasit, Henning Åkesson Wind of change, Martin Lund

• Conrad, Clinton Phillips (2023). Sea Level and the Solid Earth. Full text in Research Archive
• Conrad, Clinton Phillips (2023). Imagining Esmark's Lost Scandinavian Ice. Full text in Research Archive
• Heyn, Björn Holger & Conrad, Clinton Phillips (2022). Basal erosion and surface heat flux anomalies associated with plume-lithosphere interaction beneath continents. Full text in Research Archive
• Conrad, Clinton Phillips (2022). Deep down temperature shifts give rise to eruptions. [Journal]. https://www.esa.int/Applications/Observing_the_Earth/FutureE. Full text in Research Archive
• Heyn, Björn Holger (2022). Forskere har undersøkt to enorme, mystiske strukturer i jordens indre. [Journal]. https://www.forskning.no/geologi/forskere-har-undersokt-to-e. Full text in Research Archive
• Root, B.; Conrad, Clinton Phillips; Ebbing, J.; Fullea, J. & Lebedev, S. (2022). 4D Deep Dynamic Earth project: Recommendations for future research. Full text in Research Archive
• Ramirez, Florence Dela Cruz; Selway, Kate; Conrad, Clinton Phillips & Lithgow-Bertelloni, C. (2022). Constraining Upper Mantle Viscosity Using Temperature and Water Content Inferred from Seismic and Mag-netotelluric Data. Full text in Research Archive
• Ebbing, J.; Fullea, J.; Root, B.; Conrad, Clinton Phillips & Team, The 3D Earth Study (2022). 3D Earth – Towards a digital twin for the geosphere. Full text in Research Archive
• Rolf, Tobias; Crameri, Fabio; Heyn, Björn Holger & Thielmann, Marcel (2022). Testing a (quasi-)free base for modelling core-mantle boundary topography. Full text in Research Archive
• Wessel, Paul; Chase, Andrew; Frazer, L.N. & Conrad, Clinton Phillips (2022). A method for examining recent drifts of Pacific hotspots. Full text in Research Archive
• Robert, Boris; Conrad, Clinton Phillips; Steinberger, Bernhard & Domeier, Mathew Michael (2022). Linking plate kinematics and true polar wander over the last 250 Myrs. Full text in Research Archive
• Paul, Jyotirmoy; Conrad, Clinton Phillips; Becker, Thorsten W. & Ghosh, Attreyee (2022). Self-induced craton compression: Potential implications for craton stability. Full text in Research Archive
• Conrad, Clinton Phillips (2021). Tectonic Reconstructions of Past Sea Level, Dynamic Topography and the Deep Water Cycle. Full text in Research Archive
• Heyn, Björn Holger & Conrad, Clinton Phillips (2021). Plume-induced heat flux anomalies and the associated thinning of the continental lithosphere. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Reusen, J.M.; Steffen, R. & Naliboff, J. (2021). Solid earth uplift due to contemporary ice melting above low-viscosity regions of Greenland’s upper mantle. Full text in Research Archive
• Conrad, Clinton Phillips (2021). Earth’s History of Changing Sea Level: Billions of Years to Decades. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Hollyday, A.; Austermann, J. & Gassmöller, R. (2021). Extending the open-source code ASPECT to solve the sea level equation on a heterogeneous Earth. Full text in Research Archive
• Conrad, Clinton Phillips (2021). Global Mantle Flow Patterns and the Time Dependence Dynamic Topography at Earth’s Surface and CMB. Full text in Research Archive
• Conrad, Clinton Phillips (2021). Sea Level and the Solid Earth. Full text in Research Archive Show summary

  Sea level presents a fundamental boundary on our planet, for geological processes, biological species, and human society. It is therefore important to understand how this boundary changes with time. Since the ice ages, and even recently, major changes in sea level have been driven by changes to the volume of seawater (e.g., via exchange with continental ice). However, this mass transfer from land storage to the oceans also deforms both the land and sea surfaces, inducing large regional variations in sea level that affect projections of sea level change on coastlines. On longer geological timescales, spanning many millions of years, a variety of solid earth deformation processes drive most of the observed sea level change. These processes include ridge volume change, sediment accumulation, seafloor volcanism, dynamic topography, and continental orogeny, and they affect sea level by changing the volume of the ocean basins. One the longest timescales, changes to the volume of seawater are again the most important factor, but it is water exchange with Earth’s deep interior, rather than exchange the continental reservoirs, that controls the sea level. In this seminar I will discuss sea level changes occurring throughout Earth’s history, across timescales ranging from billions of years to decades, and the role that various different solid earth deformation processes play in determining the level of the sea.

• Ramirez, Florence; Selway, Kate & Conrad, Clinton Phillips (2020). Using magnetotelluric and seismic geophysical observations to infer viscosity for Glacial Isostatic Adjustment calculations. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Selway, Kate & Ramirez, Florence (2020). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE). Full text in Research Archive
• Hartmann, Robert; Ebbing, Jörg & Conrad, Clinton Phillips (2020). A Multiple 1D Earth Approach (M1DEA) to account for lateral viscosity variations in solutions of the sea level equation: An application for glacial isostatic adjustment by Antarctic deglaciation. Full text in Research Archive
• Ramirez, Florence; Selway, Kate & Conrad, Clinton Phillips (2020). Relationship between magnetotelluric and seismic geophysical observations and mantle viscosity. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Sea Level and the Solid Earth, Interacting Across Timescales. Full text in Research Archive Show summary

  Sea level presents a fundamental boundary on our planet, for geological processes, biological species, and human society. It is therefore important to understand how this boundary changes with time. Since the ice ages, and even recently, major changes in sea level have been driven by changes to the volume of seawater (e.g., via exchange with continental ice). However, this mass transfer from land storage to the oceans also deforms both the land and sea surfaces, inducing large regional variations in sea level that affect projections of sea level change on coastlines. On longer geological timescales, spanning many millions of years, a variety of solid earth deformation processes drive most of the observed sea level change. These processes include ridge volume change, sediment accumulation, seafloor volcanism, dynamic topography, and continental orogeny, and they affect sea level by changing the volume of the ocean basins. One the longest timescales, changes to the volume of seawater are again the most important factor, but it is water exchange with Earth’s deep interior, rather than exchange the continental reservoirs, that controls the sea level. In this seminar I will discuss sea level changes occurring throughout Earth’s history, across timescales ranging from billions of years to decades, and the role that various different solid earth deformation processes play in determining the level of the sea.

• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Naliboff, John & Selway, Kate (2020). Developing an open-source 3D glacial isostatic adjustment modeling code using ASPECT. Full text in Research Archive
• Conrad, Clinton Phillips; Selway, Kate; Weerdesteijn, Maaike Francine Maria; Smith-Johnsen, Silje; Nisancioglu, Kerim Hestnes & Karlsson, Nanna B (2020). Magnetotelluric Constraints on Upper Mantle Viscosity Structure and Basal Melt Beneath the Greenland Ice Sheet. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Dedikert til forskning på geodynamikk – Clint Conrad er tildelt Evgueni Burov medaljen for 2020. [Internet]. Geofag nyheter. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Forsker på geodynamikk – Clint Conrad har fått Evgueni Burov Medal. [Internet]. Titan. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Pris til UiO-professor. [Internet]. geoforskning.no. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips & Selway, Kate (2020). Developing an open-source 3D glacial isostatic adjustment modeling code using ASPECT. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Korona­krisen vinge­klippet UiO-forskere. [Journal]. Universitas. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Slowdown in plate tectonics may have led to Earth’s ice sheets. [Journal]. Science. Full text in Research Archive
• Selway, Kate; Conrad, Clinton Phillips; Ramirez, Florence; Karlsson, Nanna B; Weerdesteijn, Maaike Francine Maria & Heyn, Björn Holger (2020). How magnetotellurics can aid cryosphere studies: mantle rheology, GIA, surface heat flow, and basal melting. Full text in Research Archive
• Heyn, Björn Holger; Conrad, Clinton Phillips & Selway, Kate (2020). Numerical constraints on heat flux variations and lithospheric thinning associated with passage of the Iceland plume beneath Greenland. Full text in Research Archive
• Ramirez, Florence; Selway, Kate & Conrad, Clinton Phillips (2020). Integrating magnetotelluric and seismic geophysical observations to improve upper mantle viscosity estimates beneath polar regions. Full text in Research Archive
• Conrad, Clinton Phillips (2020). Earth's History of Changing Sea Level. Full text in Research Archive
• Conrad, Clinton Phillips; Selway, Kate; Weerdesteijn, Maaike Francine Maria; Smith-Johnsen, Silje; Nisancioglu, Kerim Hestnes & Karlsson, Nanna B (2020). Magnetotelluric Constraints on Upper Mantle Viscosity Structure and Basal Melt Beneath the Greenland Ice Sheet. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Gassmöller, Rene; Naliboff, John & Selway, Kate (2020). An Open-source 3D Glacial Isostatic Adjustment Modeling Code using ASPECT. Full text in Research Archive
• Gaina, Carmen; Barletta, V.; Conrad, Clinton Phillips; Ebbing, Jörg; Forsberg, R. & Ferraccioli, Fausto [Show all 9 contributors for this article] (2020). Interplay of cryosphere, solid earth and dynamic mantle in the Arctic. Full text in Research Archive
• Selway, Kate; Conrad, Clinton Phillips; Ramirez, Florence & Weerdesteijn, Maaike Francine Maria (2020). How can geophysical imaging help constrain mantle viscosity to improve glacial isostatic adjustment models? Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Selway, Kate; Naliboff, John & Gassmöller, Rene (2020). Developing a 3D glacial isostatic adjustment modeling code using ASPECT. Full text in Research Archive
• Conrad, Clinton Phillips (2019). The MAGPIE Blog. [Internet]. https://magpiegreenland.wordpress.com/. Full text in Research Archive Show summary

  We started the MAGPIE project in April 2019 with funding from Forskningsrådet, which is the Research Council of Norway. Our ultimate goal is to develop better estimates for current and recent melting of the Greenland Ice Sheet. Achieving this will require us to coordinate an international collaboration between many different individuals, each contributing a their own unique expertise. As we work towards our goal, we will learn a great deal about the glacial history of the Greenland Ice Sheet, as well as the deformation patterns of the rocky mantle beneath the ice. We will learn how the Earth beneath Greenland has uplifted as ice has melted during the ice ages, and how it continues to uplift today as a result of current melting.

• Selway, Kate; Conrad, Clinton Phillips; Nisancioglu, Kerim Hestnes; Karlsson, Nanna B & Steinberger, Bernhard (2019). The MAGPIE Project: Magnetotelluric Analysis of Greenland and Postglacial Isostatic Evolution. Full text in Research Archive
• Conrad, Clinton Phillips (2019). Sea level and the Solid Earth. Full text in Research Archive
• Conrad, Clinton Phillips; Selway, Kate; Weerdesteijn, Maaike & Smith-Johnsen, Silje (2019). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE). Full text in Research Archive
• Conrad, Clinton Phillips (2019). Arctic Deglaciation and its Connection to the Deep Earth. Full text in Research Archive
• Weerdesteijn, Maaike; Selway, Kate & Conrad, Clinton Phillips (2019). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE). Full text in Research Archive
• Weerdesteijn, Maaike; Conrad, Clinton Phillips; Selway, Kate & Ramirez, Florence (2019). MAGPIE: Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution. Full text in Research Archive
• Conrad, Clinton Phillips; Selway, Kate; Weerdesteijn, Maaike; Smith-Johnsen, Silje; Nisancioglu, Kerim Hestnes & Karlsson, Nanna B (2019). Magnetotelluric constraints on upper mantle viscosity structure and basal melt beneath the Greenland ice sheet. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Selway, Kate & Ramirez, Florence (2019). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE). Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Selway, Kate & Ramirez, Florence (2019). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE). Full text in Research Archive
• Conrad, Clinton Phillips; Selway, Kate; Weerdesteijn, Maaike Francine Maria; Smith-Johnsen, Silje; Nisancioglu, Kerim Hestnes & Karlsson, Nanna B (2019). Magnetotelluric Constraints on Upper Mantle Viscosity Structure and Basal Melt Beneath the Greenland Ice Sheet. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Selway, Kate & Ramirez, Florence (2019). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE). Full text in Research Archive
• Nisancioglu, Kerim Hestnes (2019). Greenland and Nordic Seas/Arctic Variability. Full text in Research Archive
• Hopper, John R.; Fatah, Rader Abdul; Gaina, Carmen; Geissler, Wolfram H; Funck, Thomas & Kimbell, Geoffrey S [Show all 7 contributors for this article] (2019). Sediment thickness, crustal thickness, and residual topography of the North Atlantic: estimating dynamic topography around Iceland. Full text in Research Archive
• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2023). Solid earth deformation due to glacial mass changes above low-viscosity upper mantle: Model development, importance of contemporary ice melt, and an application to southeast Greenland. Universitetet i Oslo. Full text in Research Archive Show summary

  Changes to Earth’s climate redistribute masses of ice and water on Earth's surface. These loads cause the solid earth to deform, and it is commonly thought that this happens in two ways: ice age ice melting caused a long-term viscous flow that is still occurring, and modern ice melting drives an instantaneous elastic deformation. However, regions in West Antarctica and southeast Greenland are currently uplifting so rapidly that another deformation mechanism must be important. Here we study how confined regions of unusually weak rocks within Earth’s upper mantle can deform viscously, generating rapid surface uplift. This doctoral thesis presents a new viscoelastic earth deformation model that can accommodate large lateral variations in Earth structure. We benchmark this code and use it to investigate the poorly understood role of small (~100s km) regions of unusually low-viscosity mantle beneath rapidly melting ice. We then apply our code to southeast Greenland, a region likely weakened by the Iceland plume ~40 Ma ago. We show that the uplift here is dominated by a viscous response to recent and rapid deglaciation, occurring within the past few decades. This viscous contribution is not usually considered, but will become increasingly important in the future as deglaciation accelerates.

• Ramirez, Florence Dela Cruz & Conrad, Clinton Phillips (2022). Improving upper mantle viscosity estimates: Constraints from seismic and magnetotelluric data, and impacts on asthenospheric flow. Universitetet i Oslo. Full text in Research Archive Show summary

  A simplified Earth’s structure consists of three geological layers: a stiff lithosphere (plates), a mantle and a core. Like for an example your favorite yogurt, the rock in the solid mantle can be flowing, but it requires an enormous amount of force to deform it and a time scale over thousands to millions of years! To quantify how fast the deformation process would be for a certain applied force, the physical quantity “viscosity” is used. For instance, water has lower viscosity than yogurt, which enables you to stir the water faster than the yogurt. For the mantle, viscosity affects how fast the plates can move laterally and vertically. An example for this is Scandinavia (including Norway), which is continuously uplifting as a response to melting of past ice sheet from “siste istid” with up to 3000 meters ice caps, thereby influencing climate and sea level. Unfortunately, mantle viscosity cannot be measured directly, but is commonly estimated from surface deformations. This doctoral study introduces a method for estimating viscosity using geophysical observations (seismic and magnetotelluric), which reflect realistic mantle conditions such as temperature, water content, and partial melt that control viscosity. The method provides useful results for Scandinavia and can be applied in other places as well. Resulting viscosity models can aid in geodynamic studies such as modelling flow patterns below the moving oceanic plates.

• Wang, Helene; Magni, Valentina & Conrad, Clinton Phillips (2022). Hydrous Regions of the Mantle Transition Zone Affect Patterns of Intraplate Volcanism. Universitetet i Oslo. Full text in Research Archive Show summary

  The Earth’s mantle transition zone (MTZ), located between approximately 410-660 km depth, can store an amount of water equivalent to 2-10 oceans of water, which is transported into the deep mantle by subducting oceanic lithosphere. The presence of water is likely to reduce the viscosity of mantle rocks and has the potential to generate melting in the upper mantle that could promote the occurrence of intraplate volcanism (IPV). Therefore, water within the Earth’s interior impacts mantle convection dynamics, plate tectonics and could alter the chemical and thermal evolution of the planet. Despite its importance, the amount and spatial distribution of water within the mantle, and its effect on the origin of volcanism far from plate boundaries, are poorly constrained. Previous modeling studies have estimated rates and volumes of water subducted into the deep mantle based on plate tectonic reconstructions that track the history of subduction through time. In this work, I extend this approach to model the spatial and temporal heterogeneity of water in the MTZ during the past 400 million years (Myr) and compare the predicted regions of wet and dry MTZ with the locations of past and present IPV. I conduct a parametric study where I vary the residence time of water in the MTZ, the slab sinking rate, and the delay period between water in the MTZ and IPV occurrence. Despite the uncertainties associated with the plate tectonic reconstructions and IPV dataset, my models show a remarkable agreement between the hydrated regions of the MTZ and locations of IPV. I find a statistically significant correlation at the 95% confidence level for models where 60-89% of IPV locations occur above wet regions of the MTZ during the past 250 Myr. This confirms the hypothesis that water is transported to the MTZ by subducting slabs and, consequently, causes spatial and temporal mantle heterogeneities. Furthermore, my results show that the MTZ water residence time significantly impacts the distribution of water, with the best fits obtained for residence times of 100 Myr or longer. This implies that MTZ water reservoirs caused by the dehydration of stagnating slabs can remain stable for time periods much longer than the sinking time of a slab. In contrast, the effect of varying the vertical descent rate of slabs and the IPV delay period is modest. However, a delay of 10-50 Myr between water in the MTZ and intraplate eruptions better predicts IPV locations than accounting for no delay. Overall, these findings suggest a link between the formation of volcanism far from plate boundaries and water within the MTZ.

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