Clinton Phillips Conrad

• Ramirez, Florence; Selway, Kate; 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(107178). doi: https:/doi.org/10.1016/j.pepi.2024.107178.
• 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. ISSN 1525-2027. 25. doi: 10.1029/2023GC011380.
• Ramirez, Florence D.C.; 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.
• 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. ISSN 1525-2027. 24(3). doi: 10.1029/2022GC010813. Full text in Research Archive
• 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
• 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
• 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.

• 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
• 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
• 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.

• Karlsen, Krister Stræte; Conrad, Clinton Phillips; Domeier, Mathew & Trønnes, Reidar G (2021). Spatiotemporal Variations in Surface Heat Loss Imply a Heterogeneous Mantle Cooling History. Geophysical Research Letters. ISSN 0094-8276. 48(6). doi: 10.1029/2020GL092119. Full text in Research Archive Show summary

  Earth's heat budget is strongly influenced by spatial and temporal variations in surface heat flow caused by plate tectonic cycles. Here, we use a novel set of paleo‐seafloor age grids extending back to the mid‐Paleozoic to infer spatiotemporal variations in surface heat loss. The time‐averaged oceanic heat flow is 36.6 TW, or ∼25% greater than at present‐day. Our thermal budget for the mantle indicates that 149 K/Gyr of cooling occurred over this period, consistent with geochemical estimates of mantle cooling for the past 1 Gyr. Our analysis also suggests sustained rapid cooling of the Pacific mantle hemisphere, which may have cooled ∼50 K more than its African counterpart since 400 Ma. The extra heat released from the Pacific mantle may have been trapped there by the earlier long‐lived supercontinent Rodinia (∼1.1–0.7 Ga), and the Pacific mantle may still be hotter than the African mantle today.

• Kiraly, Agnes; Conrad, Clinton Phillips & Hansen, Lars N. (2020). Evolving Viscous Anisotropy in the Upper Mantle and Its Geodynamic Implications. Geochemistry Geophysics Geosystems. ISSN 1525-2027. 21(10). doi: 10.1029/2020GC009159. Full text in Research Archive Show summary

  Asthenospheric shear causes some minerals, particularly olivine, to develop anisotropic textures that can be detected seismically. In laboratory experiments, these textures are also associated with anisotropic viscous behavior, which should be important for geodynamic processes. To examine the role of anisotropic viscosity for asthenospheric deformation, we developed a numerical model of coupled anisotropic texture development and anisotropic viscosity, both calibrated with laboratory measurements of olivine aggregates. This model characterizes the time‐dependent coupling between large‐scale formation of lattice‐preferred orientation (i.e., texture) and changes in asthenospheric viscosity for a series of simple deformation paths that represent upper mantle geodynamic processes. We find that texture development beneath a moving surface plate tends to align the a axes of olivine into the plate motion direction, which weakens the effective viscosity in this direction and increases plate velocity for a given driving force. Our models indicate that the effective viscosity increases for shear in the horizontal direction perpendicular to the a axes. This increase should slow plate motions and new texture development in this perpendicular direction and could impede changes to the plate motion direction for tens of millions of years. However, the same well‐developed asthenospheric texture may foster subduction initiation perpendicular to the plate motion and deformations related to transform faults, as shearing on vertical planes seems to be favored across a sublithospheric olivine texture. These end‐member cases examining shear deformation in the presence of a well‐formed asthenospheric texture illustrate the importance of the mean olivine orientation, and its associated viscous anisotropy, for a variety of geodynamic processes.

View all works in Cristin

• 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.
• Kiraly, Agnes; Conrad, Clinton Phillips; Hansen, Lars; Wang, Yijun & Mather, Ben (2024). Direct estimation of anisotropic viscosity parameters using texture scores of olivine polycrystals.
• Conrad, Clinton Phillips & Ramirez, Florence Dela Cruz (2024). Sensitivity of Long-Wavelength Dynamic Topography and Free-Air Gravity to Lateral Variations in Lower Mantle Viscosity.
• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2024). Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle.
• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2024). Prolonged multi-phase volcanism in the Arctic induced by plume-lithosphere interaction.
• 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.
• Conrad, Clinton Phillips & Ramirez, Florence Dela Cruz (2024). Sensitivity of long-wavelength dynamic topography and free-air gravity to lateral variations in lower mantle viscosity.
• Conrad, Clinton Phillips (2024). Geodynamic implications of lateral viscosity variations in the mantle.
• Heyn, Björn Holger & Conrad, Clinton Phillips (2023). Development and implications of a free base for numerical models.
• Heyn, Björn Holger; Conrad, Clinton Phillips & Shephard, Grace (2023). Plume-lithosphere interaction and continental plume tracks.
• 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.
• Ramirez, Florence Dela Cruz & Conrad, Clinton Phillips (2023). Long wavelength topography: Effect of lateral and radial viscosity variations in the mantle.
• Conrad, Clinton Phillips & Ramirez, Florence Dela Cruz (2023). Dynamic topography and admittance.
• Conrad, Clinton Phillips & Ramirez, Florence Dela Cruz (2023). Long wavelength dynamic topography.
• 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.
• Conrad, Clinton Phillips & Ramirez, Florence Dela Cruz (2023). Effect of Lateral Viscosity Variations in the Mantle on Earth’s Long-Wavelength Dynamic Topography and Free-Air Gravity.
• Kiraly, Agnes; Conrad, Clinton Phillips; Hansen, Lars & Wang, Yijun (2023). Deriving anisotropic viscosity parameters directly from texture scores of olivine polycrystals.
• Weerdesteijn, Maaike Francine Maria & Conrad, Clinton Phillips (2023). Rapid Earth uplift in southeast Greenland driven by recent ice melt above low-viscosity upper mantle.
• Wang, Yijun; Kiraly, Agnes; Conrad, Clinton Phillips; Fraters, Menno & Hansen, Lars (2023). Anisotropic Viscosity in Subduction Models.
• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2023). Locally amplified plume-lithosphere interaction and multiple melting events for 2-phase flow models.
• 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.
• 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.
• Åkesson, Henning; Etzelmüller, Bernd; Lund, Erik Martin; Conrad, Clinton Phillips & Lilleøren, Karianne Staalesen (2023). Arven etter Esmark - GeoOnsdag Spesial. 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). Imagining Esmark's Lost Scandinavian Ice.
• Conrad, Clinton Phillips (2023). Sea Level and the Solid Earth.
• Wang, Yijun; Kiraly, Agnes; Conrad, Clinton Phillips; Hansen, Lars & Fraters, Menno (2023). Effect of olivine anisotropic viscosity in advancing and retreating subduction settings. Show summary

  Lattice preferred orientation (LPO) of olivine crystals occurs due to deformation in the mantle. Different parts of the upper mantle can undergo a large variety of deformation paths. During simple processes, such as simple shearing below oceans due to the movement of tectonic plates, the LPO will reflect the direction of the movement of tectonic plates. On the other hand, in areas, such as around subduction zones, the mantle undergoes more complex deformation paths, resulting in a less easily predictable LPO. Seismic anisotropy has been used as a proxy for mantle flows and the LPO formed in the mantle. To interpret the seismic anisotropy observations more accurately, we need to understand how LPO forms in different regions of subduction. LPO has been implemented in many numerical modelling tools to predict seismic anisotropy, which places constraints on mantle dynamics. However, a few recent studies have linked olivine texture development to viscous anisotropy, resulted from the summed effect of individual crystals that are deforming anisotropically. Anisotropic viscosity can affect deformation and in turn the resulting LPO. To study the effect of anisotropic viscosity (AV) and LPO evolution in geodynamics processes, it is important to know the role of AV on LPO and the differences between the numerical methods that calculate them. We choose three methods of olivine texture development to examine in this study. D-Rex is a polycrystal LPO model that is relatively balanced in computational efficiency and accuracy. From previous studies, D-Rex has been shown to produce faster texture development and stronger texture compared to other methods, including our second choice, the modified director method (MDM). The MDM parameterizes the olivine LPO formation as relative rotation rates along the slip systems that participate in the rotation of olivine grains due to finite deformation. We also couple the MDM with a micromechanical model for olivine AV (which makes our third choice MDM+AV), to allow the anisotropic texture to modify the viscosity and in turn affect the formation of LPO. Here we compare the LPO evolution under subduction settings with a slowly advancing trench and a retreating trench, with and without the effect of AV. Since the mantle flow pattern in subduction zones is not homogeneous, different particles experience a variety of deformation paths. We place 60 particles in each subduction model around the slab to track the deformation and resulting olivine texture. We compute olivine texture using the above-mentioned three different methods (D-Rex, MDM, MDM+AV). With the particles, we can identify characteristic textures developed in key regions such as the mantle wedge, sub-slab area, and lateral slab edge. We then run a statistical analysis on the texture parameter and anisotropic properties of the particles from both retreating and advancing subduction models, to study where anisotropic viscosity has the largest effect on the mantle flow. We expect AV to have a larger effect in a retreating slab setting since the mantle flows feeding material to the sub-slab region is more intensive.

• Kiraly, Agnes; Wang, Yijun; Conrad, Clinton Phillips; Hansen, Lars N. & Mather, Ben (2023). Modelling anisotropic viscosity. Show summary

  Many of Earth’s layers – from the crust to the inner core – are mechanically anisotropic. Anisotropic (i.e. direction-dependent) behaviour of rocks can derive from intrinsic properties of rock forming minerals or from microscopic or macroscopic layering of rocks and/or melts with different composition (extrinsic anisotropy). The Earth Science community often discusses the phenomena of seismic anisotropy, which results from the direction dependent propagation of seismic waves. However, materials that are characterized by elastic (seismic) anisotropy often exhibit viscous anisotropy as well, which is less explored. In geodynamics we are primarily interested in anisotropic viscosity in the crust and the mantle, where both intrinsic and extrinsic anisotropy are present. To model anisotropic viscous behaviour, we have to handle the viscosity as a 4th order tensor while also thinking about the re-orientation of anisotropy (or evolution of texture) in time. In the upper mantle the main source of anisotropy derives from the lattice preferred orientation (LPO) of olivine. Under deformation olivine grains rotate into the deformation direction (we often refer to this as texture evolution), resulting in a texture where some – or many – olivine grains are aligned with each other. Furthermore, because single olivine crystals are mechanically anisotropic – which means they deform more easily along some slip systems than others – then LPO that is developed in the upper mantle will yield anisotropic viscosity on a macroscopic scale. The foundation of our modelling approach is the Modified Director Method, which includes texture evolution and micromechanical models, both deriving from rock mechanic laboratory experiments on olivine aggregates (Hansen et al., 2016a, 2016b). The micromechanical model allows us to calculate the stress needed to achieve a certain strain rate on an aggregate, while the texture evolution model calculates the rotation of grains under a given deformation. To integrate these models into a geodynamic code, or use it to model the evolution of texture and anisotropic viscosity under specific deformation paths, we have to characterize our texture with a rank 4 viscosity or fluidity tensor (Király et al., 2020). It has been shown that the anisotropy related to olivine textures can be characterized by the Hill coefficients (Hill, 1948; Signorelli et al., 2021). Here we show that by building a large database of different textures derived from geodynamic models, we can define a linear model between simple texture parameters and the Hill coefficients with a reasonable cost. This is advantageous for integrating anisotropic viscosity into 4D geodynamic models because it allows for a direct determination of the viscosity tensor from the evolving rock texture, saving a large amount of computational time.

• Heyn, Björn Holger; Shephard, Grace & Conrad, Clinton Phillips (2023). Amplification of sub-lithospheric dynamics by melt migration during plume-lithosphere interaction.
• 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).
• Conrad, Clinton Phillips (2022). The first magnetotelluric survey of the interior of Greenland. [Business/trade/industry journal]. https://eu-polarnet.eu/newsletter-october-2022/.
• Conrad, Clinton Phillips (2022). Deep down temperature shifts give rise to eruptions. [Newspaper]. https://www.esa.int/Applications/Observing_the_Earth/FutureE.
• Wessel, Paul; Chase, Andrew; Frazer, L.N. & Conrad, Clinton Phillips (2022). A method for examining recent drifts of Pacific hotspots.
• Paul, Jyotirmoy; Conrad, Clinton Phillips; Becker, Thorsten W. & Ghosh, Attreyee (2022). Self-induced craton compression: Potential implications for craton stability.
• Robert, Boris; Conrad, Clinton Phillips; Steinberger, Bernhard & Domeier, Mathew Michael (2022). Linking plate kinematics and true polar wander over the last 250 Myrs.
• Wang, Yijun; Kiraly, Agnes; Fraters, Menno; Gassmoeller, Rene; Dannberg, Juliane & Hansen, Lars [Show all 7 contributors for this article] (2022). Olivine texture evolution under a simple deformation scheme: Comparing different numerical methods of LPO calculations.
• Kiraly, Agnes; Wang, Yijun; Fraters, Menno; Gassmoeller, Rene; Dannberg, Juliane & Hansen, Lars [Show all 7 contributors for this article] (2022). Incorporating olivine CPO-related anisotropic viscosity into 3D geodynamics simulations.
• Wang, Yijun; Kiraly, Agnes; Conrad, Clinton Phillips; Fraters, Menno & Hansen, Lars (2022). Olivine texture evolution under simple deformation: Comparing different numerical methods for calculating LPO and anisotropic viscosity.
• Heyn, Björn Holger & Conrad, Clinton Phillips (2022). Basal erosion and surface heat flux anomalies associated with plume-lithosphere interaction beneath continents.
• 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.
• Root, B.; Conrad, Clinton Phillips; Ebbing, J.; Fullea, J. & Lebedev, S. (2022). 4D Deep Dynamic Earth project: Recommendations for future research.
• Ebbing, J.; Fullea, J.; Root, B.; Conrad, Clinton Phillips & 3D Earth Study Team, The (2022). 3D Earth – Towards a digital twin for the geosphere.
• Shephard, Grace; Gaina, Carmen; Heyn, Björn Holger; Conrad, Clinton Phillips; Anfinson, Owen & Schaeffer, Andrew [Show all 7 contributors for this article] (2022). Exploring potential lower mantle structures and interactions for the origins of HALIP.
• Wang, Yijun; Kiraly, Agnes; Conrad, Clinton Phillips; Hansen, Lars N. & Fraters, Menno (2022). Olivine texture evolution under simple deformation: Comparing different numerical methods for calculating LPO and anisotropic viscosity. Show summary

  The development of olivine texture, or lattice preferred orientation (LPO), has been implemented in many numerical modelling tools to predict seismic anisotropy, which places constraints on mantle dynamics. However, a few recent studies have linked olivine texture development to its mechanical anisotropy, which in turn can affect deformation rates and also the resulting texture. To study the effect of anisotropic viscosity (AV) and LPO evolution in geodynamics processes, it is important to know the role of AV and LPO and the differences between the numerical methods that calculate them. The modified director method parameterizes the olivine LPO formation as relative rotation rates along the slip systems that participate in the rotation of olivine grains due to finite deformation. When it is coupled with a micromechanical model for olivine AV, it allows the anisotropic texture to modify the viscosity. We compare the olivine textures predicted by the modified director method both with and without a coupled micromechanical model and textures predicted by the D-Rex LPO evolution model. To do this, we recalculate the texture observed in simple 3D models such as a shear box model and two other well-understood models: a corner flow model and a subduction model. In general, we observed that the D-Rex models predict a stronger anisotropic texture compared to the texture predicted by the modified director method both with and without the micromechanical model, in agreement with previous studies. When including the micromechanical model, the anisotropic texture changes the observed strain rates, which allows for a slightly faster texture evolution that is more similar to the D-Rex predictions than it is to those produced by the modified director method alone. We found that even for the simplest settings there is an increase of 10~15% in strain rate during deformation until a strain of 2.5. When shearing the asthenosphere over ~10 Myr, such anisotropy could modify the effective viscosity of the mantle,causing an up to 40% increase in plate velocity for the same applied stress. The anisotropy can also induce deformation in planes other than the initial shear plane, which can change the direction of the primary deformation. Our ultimate goal is to understand the role of AV and LPO evolution in geodynamic processes by looking at deformation paths predicted by geodynamic models in ASPECTWith this initial test, we will gain a basic understanding of olivine AV behavior and LPO evolution under different deformation settings calculated with different numerical methods, which we will carry onto our next step of implementing anisotropic viscosity of olivine in 3D into ASPECT. How to cite: Wang, Y., Király, Á., Conrad, C. P., Hansen, L., and Fraters, M.: Olivine texture evolution under simple deformation: Comparing different numerical methods for calculating LPO and anisotropic viscosity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7201, https://doi.org/10.5194/egusphere-egu22-7201, 2022.

• Conrad, Clinton Phillips (2021). Sea level in a plastic cup. Show summary

  Eight ways to change the water level in a plastic cup – and global sea level

• Conrad, Clinton Phillips (2021). Global Mantle Flow Patterns and the Time Dependence Dynamic Topography at Earth’s Surface and CMB.
• Conrad, Clinton Phillips (2021). Earth’s History of Changing Sea Level: Billions of Years to Decades .
• Conrad, Clinton Phillips (2021). Tectonic Reconstructions of Past Sea Level, Dynamic Topography and the Deep Water Cycle .
• Conrad, Clinton Phillips (2021). Sea Level and the Solid Earth. 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.

• Heyn, Björn Holger & Conrad, Clinton Phillips (2021). Plume-induced heat flux anomalies and the associated thinning of the continental lithosphere.
• 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.
• 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.
• Paul, Jyotirmoy; Ghosh, Attreyee & Conrad, Clinton Phillips (2020). Erratum to: Traction and strain-rate at the base of the lithosphere: an insight into cratonic survival(Geophysical Journal International DOI: 10.1093/gji/ggz079). Geophysical Journal International. ISSN 0956-540X. 220(1). doi: 10.1093/GJI/GGZ491.
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips & Selway, Kate (2020). Developing an open-source 3D glacial isostatic adjustment modeling code using ASPECT.
• Conrad, Clinton Phillips (2020). Dedikert til forskning på geodynamikk – Clint Conrad er tildelt Evgueni Burov medaljen for 2020 . [Internet]. Geofag nyheter.
• Conrad, Clinton Phillips (2020). Pris til UiO-professor . [Internet]. geoforskning.no.
• Conrad, Clinton Phillips (2020). Forsker på geodynamikk – Clint Conrad har fått Evgueni Burov Medal. [Internet]. Titan.
• Conrad, Clinton Phillips (2020). Korona­krisen vinge­klippet UiO-forskere. [Newspaper]. Universitas.
• Conrad, Clinton Phillips (2020). Slowdown in plate tectonics may have led to Earth’s ice sheets. [Journal]. Science.
• Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). How thermochemical piles initiate plumes at their edges. European Geosci. Union, Gen. Assembly, Geophys. Res. Abstr..
• Conrad, Clinton Phillips (2020). Clint Conrad's Website.
• Conrad, Clinton Phillips (2020). Sea Level and the Solid Earth, Interacting Across Timescales. 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; Selway, Kate; Naliboff, John & Gassmöller, Rene (2020). Developing a 3D glacial isostatic adjustment modeling code using ASPECT.
• Conrad, Clinton Phillips (2020). Earth's History of Changing Sea Level.
• Kiraly, Agnes; Conrad, Clinton Phillips & Hansen, Lars (2020). Evolving viscous anisotropy in the upper mantle and its geodynamic implications.
• 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.
• 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.
• Ramirez, Florence; Selway, Kate & Conrad, Clinton Phillips (2020). Integrating magnetotelluric and seismic geophysical observations to improve upper mantle viscosity estimates beneath polar regions.
• 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.
• Karlsen, Krister Stræte; Conrad, Clinton Phillips & Magni, Valentina (2020). Deep water cycling and sea level change since the breakup of Pangea.
• 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.
• 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?
• 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.
• 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.
• Ramirez, Florence; Selway, Kate & Conrad, Clinton Phillips (2020). Using magnetotelluric and seismic geophysical observations to infer viscosity for Glacial Isostatic Adjustment calculations.
• Heyn, Björn Holger; Conrad, Clinton Phillips & Trønnes, Reidar G (2020). How thermochemical piles initiate plumes at their edges.
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Naliboff, John & Selway, Kate (2020). Developing an open-source 3D glacial isostatic adjustment modeling code using ASPECT.
• Kiraly, Agnes; Conrad, Clinton Phillips; Hansen, Lars & Fraters, Menno RT (2020). The formation of viscous anisotropy in the asthenosphere and its effect on plate tectonics.
• Ramirez, Florence; Selway, Kate & Conrad, Clinton Phillips (2020). Relationship between magnetotelluric and seismic geophysical observations and mantle viscosity.
• 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.
• Conrad, Clinton Phillips; Domeier, Mathew; Selway, Kate & Heyn, Björn Holger (2020). A link between seamount volcanism and thermochemical piles in the deepest mantle.
• Weerdesteijn, Maaike Francine Maria; Conrad, Clinton Phillips; Selway, Kate & Ramirez, Florence (2020). Magnetotelluric Analysis for Greenland and Postglacial Isostatic Evolution (MAGPIE).
• Kiraly, Agnes; Conrad, Clinton Phillips & Hansen, Lars N. (2020). Evolving viscous anisotropy in the upper mantle and its geodynamic implications – Supplementary Materials, Data, and Code [Data set]. Show summary

  This dataset is related to the paper Evolving viscous anisotropy in the upper mantle and its geodynamic implications by Kiraly et al., which is in submission to Geochemistry Geophysics Geosystems (G-cube). Information about the data package can be found in the supplementary material attached to the article.

• Karlsen, Krister Stræte; Domeier, Mathew; Gaina, Carmen & Conrad, Clinton Phillips (2020). Tracer Tectonics. Show summary

  Tracer Tectonics (TracTec) is a Python toolbox for generating seafloor age grids from global plate tectonic reconstructions based on an algorithm developed by Krister S. Karlsen, in collaboration with Mathew Domeier, Carmen Gaina and Clinton P. Conrad, at the Centre for Earth Evolution and Dynamics, University of Oslo, Norway.

• 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. ISSN 1501-7710. 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.

• Wang, Helene; Magni, Valentina & Conrad, Clinton Phillips (2022). Hydrous regions of the mantle transition zone affect patterns of intraplate volcanism. Universitetet i Oslo.
• 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. ISSN 1501-7710. 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.

• Karlsen, Krister Stræte & Conrad, Clinton Phillips (2021). Plate Tectonic Controls on Geodynamic Processes: Earth’s Deep Water Cycle, Sea Level Change and Planetary Cooling Patterns. Universitetet i Oslo. ISSN 1501-7710. Show summary

  The motions of tectonic plates in Earth’s deep past can uncover planetary cycles of water and heat that are important for the evolution of our planet. In this thesis water exchange between Earth’s oceans and deep interior (see figure) was estimated, and there was likely a loss of seawater to the mantle corresponding to ~130 m of sea level drop since ~230 Myr ago. Maps of ancient ocean basins were reconstructed, extending back 400 Myr, and used to infer variations in seafloor depth. The ocean basin volumes estimated from the reconstructions agree well with the paleo-record of global sea level change. Seafloor reconstructions also tell us about past heat loss from Earth’s interior, and the models suggest that the Pacific side of Earth’s interior has been cooling at a much higher rate than its African counterpart during the last 400 Myr. This asymmetry was caused by the assembly of nearly all thick and insulating continental landmasses into the Pangea supercontinent on the African hemisphere, leaving the Pacific side to diffuse heat through relatively thin seafloor. These findings contribute to the understanding of how plate tectonics influences both Earth’s surface (e.g. sea level) and deep interior through geologic time.

• Heyn, Björn Holger & Conrad, Clinton Phillips (2020). Geodynamics of Earth’s Large Low Shear Velocity Provinces Interaction with mantle flow, plume initiation, and core-mantle boundary deformation. Universitetet i Oslo. ISSN 1501-7710. Show summary

  Our planet’s interior is actively convecting like boiling water in a pot, although on significantly larger length and time scales. In some locations, such as Hawaii and Iceland, one consequence of this convection is strong, long-lived volcanism that eventually creates island chains. But where does the erupted material come from, why is the volcano located at this specific spot, and what are the mechanisms to trigger this volcanism? To understand the origins of this Hawaiian-type volcanism, we have to dive deep into the interior of Earth, where the driving forces of convection are located. This doctoral study uses numerical simulations to unravel how continent-sized piles of dense and potentially stiff material, residing about 2900 km beneath our feet, affect the formation of strong upwelling “plumes” that are thought to be associated with Hawaiian-type volcanism. Due to internal deformation, such piles periodically perturb a layer of hot material surrounding them, causing some material to rise and eventually erupt into volcanism. Moreover, this triggering mechanism causes a characteristic depression on the core-mantle boundary that may be used to constrain the properties of the deep Earth, and also locate newly emerging plumes before they erupt to the surface to produce Hawaiian-type volcanoes.

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