The dynamics of forearc - back-arc vertical motion: numerical models and observations from the Mediterranean

The dynamics of oceanic and continental subduction zones is linked to the rise and demise of forearc and backarc basins in the overriding plate. Subsidence and uplift rates of these distinct sedimentary basins are controlled by variations in plate convergence and subduction velocities and determined by lithospheric rheological structure and different lithospheric thicknesses.In this study we conducted a series of high-resolution 2D numerical models applying the thermo-mechanical code 2DELVIS (Gerya and Yuen, 2007). The model, based on finite differences and marker-in-cell techniques, solves the mass, momentum, and energy conservation equations for incompressible media; assumes elasto-visco-plastic rheologies and involves erosion, sedimentation and hydration processes.The models show the evolution of wedge-top basins lying on top of the accretionary wedge and retro-forearc basins in the continental overriding plate, separated by a forearc high. These forearc regions are affected by repeated compression and extension phases. Higher subsidence rates are recorded in the syncline structure of the retro-forearc basin when the slab dip angle is higher and the subduction interface is stronger and before the slab reaches the 660 km discontinuity. This implies the importance of the slab suction force as the main forcing factor creating up to 3-4 km negative dynamics topographic signals.Extensional back-arc basins are either localized along inherited crustal or lithospheric weak zones at large distance from the forearc region or are initiated just above the hydrated mantle wedge. During trench retreat and slab roll-back the older volcanic arc area becomes part of the back-arc region. Back-arc subsidence is primarily governed by crustal and lithospheric thinning controlled by slab roll-back. Onset of continental subduction and soft collision is linked to the rapid uplift of the forearc basins; however, the back-arc region records ongoing extension. Finally, during hard collision the forarc and back-arc basins are ultimately under compression.Our results are compared with the evolution of the Mediterranean and based on the reconstructed plate kinematics, subsidence and heat flow evolution we classify the Western and Eastern Alboran, Paola and Tyrrhenian, Transylvanian and Pannonian Basins to be genetically similar forearc&#8211;backarc basins, respectively.

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A global survey of cloud overlap based on CALIPSO and CloudSat measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-519-2015 ◽

2015 ◽

Vol 15 (1) ◽

pp. 519-536 ◽

Cited By ~ 65

Author(s):

J. Li ◽

J. Huang ◽

K. Stamnes ◽

T. Wang ◽

Q. Lv ◽

...

Keyword(s):

Standard Deviation ◽

Numerical Models ◽

Vertical Motion ◽

Warm Pool ◽

Central Pacific ◽

Cloud Systems ◽

Central Pacific Ocean ◽

Convective Clouds ◽

Vertical Distributions ◽

Global Mean

Abstract. Using 2B-CLDCLASS-LIDAR (radar–lidar) cloud classification and 2B-FLXHR-LIDAR radiation products from CloudSat over 4 years, this study evaluates the co-occurrence frequencies of different cloud types, analyzes their along-track horizontal scales and cloud radiative effects (CREs), and utilizes the vertical distributions of cloud types to evaluate cloud-overlap assumptions. The statistical results show that high clouds, altostratus (As), altocumulus (Ac) and cumulus (Cu) tend to coexist with other cloud types. However, stratus (St) (or stratocumulus, Sc), nimbostratus (Ns) and convective clouds are much more likely to exhibit individual features than other cloud types. On average, altostratus-over-stratus/stratocumulus cloud systems have a maximum horizontal scale of 17.4 km, with a standard deviation of 23.5 km. Altocumulus-over-cumulus cloud types have a minimum scale of 2.8 km, with a standard deviation of 3.1 km. By considering the weight of each multilayered cloud type, we find that the global mean instantaneous net CREs of multilayered cloud systems during the daytime are approximately −41.3 and −50.2 W m−2, which account for 40.1 and 42.3% of the global mean total net CREs at the top of the atmosphere (TOA) and at the surface, respectively. The radiative contributions of high-over-altocumulus and high-over-stratus/stratocumulus (or cumulus) in the all multilayered cloud systems are dominant due to their frequency. Considering the overlap of cloud types, the cloud fraction based on the random overlap assumption is underestimated over vast oceans, except in the west-central Pacific Ocean warm pool. Obvious overestimations mainly occur over tropical and subtropical land masses. In view of a lower degree of overlap than that predicted by the random overlap assumption to occur over the vast ocean, particularly poleward of 40° S, the study therefore suggests that a linear combination of minimum and random overlap assumptions may further improve the predictions of actual cloud fractions for multilayered cloud types (e.g., As + St/Sc and Ac + St/Sc) over the Southern Ocean. The establishment of a statistical relationship between multilayered cloud types and the environmental conditions (e.g., atmospheric vertical motion, convective stability and wind shear) would be useful for parameterization design of cloud overlap in numerical models.

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Determining the Plio-Quaternary uplift of the southern French massif-Central; a new insights for intraplate orogen dynamics

10.5194/se-2019-99 ◽

2019 ◽

Cited By ~ 1

Author(s):

Oswald Malcles ◽

Philippe Vernant ◽

Jean Chéry ◽

Pierre Camps ◽

Gaël Cazes ◽

...

Keyword(s):

Numerical Models ◽

Morphological Evolution ◽

Vertical Motion ◽

French Massif Central ◽

Dynamic Topography ◽

Active Deformation ◽

Massif Central ◽

The North ◽

Cave System ◽

Clay Deposits

Abstract. The evolution of intra-plate orogens is still poorly understood. Yet, this is of major importance for understanding the Earth and plate dynamic, as well as the link between surface and deep geodynamic processes. The French Massif Central is an intraplate orogen with a mean elevation of 1000 m, with the highest peak elevations ranging from 1500 m to 1885 m. However, active deformation of the region is still debated due to scarce evidence either from geomorphological or geophysical (i.e. geodesy and seismology) data. Because the Cévennes margin allows the use of karst sediments geochronology and morphometrical analysis, we study the vertical displacements of that region: the southern part of the French Massif-Central. Geochronology and morphometrical results, helped with lithospheric-scale numerical modelling, allow, then, a better understanding of this intraplate-orogen evolution and dynamic. Using the ability of the karst to durably record morphological evolution, we first quantify the incision rates. We then investigate tilting of geomorphological benchmarks by means of a high-resolution DEM. We finally use the newly quantified incision rates to constrain numerical models and compare the results with the geomorphometric study. We show that absolute burial age (10Be/26Al on quartz cobbles) and the paleomagnetic analysis of karstic clay deposits for multiple cave system over a large elevation range correlate consistently. This correlation indicates a regional incision rate of 83.4 +17.3/−5.4 m Ma−1 during the last ca 4 Myrs (Plio-Quaternary). Moreover, we point out through the analysis of 55 morphological benchmarks that the studied region has undergone a regional southward tilting. This tilting is expected as being due to a differential vertical motion between the north and southern part of the studied area. Numerical models show that erosion-induced isostatic rebound can explain up to two-thirds of the regional uplift deduced from dating technics and are consistent with the southward tilting obtain from morphological analysis. We presume that the remaining part is related to dynamic topography or thermal isostasy due to the Massif Central plio-quaternary magmatism.

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The challenges of representing vertical motion in numerical models

Remote Sensing and Modeling of the Atmosphere, Oceans, and Interactions VII ◽

10.1117/12.2501584 ◽

2018 ◽

Author(s):

Ousmane O. Sy ◽

Derek J. Posselt ◽

Susan C. van den Heever ◽

Ziad S. Haddad ◽

Graeme L. Stephens ◽

...

Keyword(s):

Numerical Models ◽

Vertical Motion

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Enhancing WRF Model Forecasts by Assimilating High-Resolution GPS-Derived Water-Vapor Maps combined with METEOSAT-11 Data

10.5194/egusphere-egu21-4503 ◽

2021 ◽

Author(s):

Yuval Reuveni ◽

Anton Leontiev ◽

Dorita Rostkier-Edelstein

Keyword(s):

Water Vapor ◽

High Resolution ◽

Numerical Models ◽

Eastern Mediterranean ◽

Wrf Model ◽

In Situ Measurements ◽

Suggested Approach ◽

Positioning Systems ◽

The Mediterranean

Improving the accuracy of numerical weather predictions still poses a challenging task. The lack of sufficiently detailed spatio-temporal real-time in-situ measurements constitutes a crucial gap concerning the adequate representation of atmospheric moisture fields, such as water vapor, which are critical for improving weather predictions accuracy. Information on total vertically integrated water vapor (IWV), extracted from global positioning systems (GPS) tropospheric path delays, can enhance various atmospheric models at global, regional, and local scales. Currently, numerous existing atmospheric numerical models predict IWV. Nevertheless, they do not provide accurate estimations compared with in-situ measurements such as radiosondes. In this work, we demonstrate a novel approach for assimilating 2D IWV regional maps estimations, extracted from GPS tropospheric path delays combined with METEOSAT satellite imagery data, to enhance Weather Research and Forecast (WRF) model predictions accuracy above the Eastern Mediterranean area. Unlike previous studies, which assimilated IWV point measurements, here, we assimilate quasi-continuous 2D GPS IWV maps, augmented by METEOSAT-11 data, over Israel and its surroundings. Using the suggested approach, our results show a decrease of more than 30% in the root mean square error (RMSE) of WRF forecasts after assimilation relative to the standalone WRF when verified against in-situ radiosonde measurements near the Mediterranean coast. Furthermore, substantial improvements along the Jordan Rift Valley and Dead Sea Valley areas are achieved when compared to 2D IWV regional maps. Improvements in these areas suggest the importance of the assimilated high resolution IWV maps, in particular when assimilation and initialization times coincide with the Mediterranean Sea Breeze propagation from the coastline to highland stations.

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Arc-trench-back arc systems in the Mediterranean area: examples of extrusion tectonics

Journal of the Virtual Explorer ◽

10.3809/jvirtex.2002.00050 ◽

2002 ◽

Vol 08 ◽

Cited By ~ 23

Author(s):

Enzo Mantovani ◽

Dario Albarello ◽

Daniele Babbucci ◽

Caterina Tamburelli ◽

Marcello Viti

Keyword(s):

Mediterranean Area ◽

The Mediterranean ◽

Back Arc

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Thinning leads to calving-style changes at Bowdoin Glacier, Greenland

10.5194/tc-2020-252 ◽

2020 ◽

Author(s):

Eef C. H. van Dongen ◽

Guillaume Jouvet ◽

Shin Sugiyama ◽

Evgeny A. Podolskiy ◽

Martin Funk ◽

...

Keyword(s):

Mass Loss ◽

Numerical Models ◽

Mass Loss Rate ◽

Ice Sheet ◽

Vertical Motion ◽

Greenland Ice Sheet ◽

Remote Sensing Data ◽

Full Spectrum ◽

Additional Support ◽

Behaviour Changes

Abstract. Ice mass loss from the Greenland Ice Sheet is the largest single contributor to sea-level rise in the 21st century. The mass loss rate has accelerated in recent decades mainly due to thinning and retreat of its outlet glaciers. The diverse calving mechanisms responsible for tidewater glacier retreat are not fully understood yet. Since a tidewater glacier’s sensitivity to external forcings depends on its calving style, a detailed insight into calving processes is necessary to improve projections of ice sheet mass loss by calving. As tidewater glaciers are mostly thinning, their calving styles are expected to change. Here, we study calving behaviour changes under a thinning regime at Bowdoin Glacier, Northwest Greenland, by combining field and remote sensing data from 2015 to 2019. Previous studies showed that major calving events in 2015 and 2017 were driven by hydro-fracturing and melt-undercutting. New observations from UAV imagery and a GPS network installed at the calving front in 2019 suggest ungrounding and buoyant calving have recently occurred, as they show (1) increasing tidal modulation of vertical motion compared to previous years, (2) absence of a surface crevasse prior to calving, and (3) uplift and horizontal surface compression prior to calving. Furthermore, an inventory of calving events from 2015 to 2019 based on satellite imagery provides additional support for a change towards buoyant calving since it shows an increasing occurrence of calving events outside of the melt season. The observed change of calving style could lead to a possible retreat of the terminus, which has been stable since 2013. We therefore highlight the need for high-resolution monitoring to detect changing calving styles and numerical models that cover the full spectrum of calving mechanisms to improve projections of ice sheet mass loss by calving.

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Evaluation of isotopes and elements in planktonic foraminifera from the Mediterranean Sea as recorders of seawater oxygen isotopes and salinity

10.5194/cp-2020-26 ◽

2020 ◽

Author(s):

Linda K. Dämmer ◽

Lennart de Nooijer ◽

Erik van Sebille ◽

Jan Haak ◽

Gert-Jan Reichart

Keyword(s):

Mediterranean Sea ◽

Oxygen Isotopes ◽

Environmental Variability ◽

Sea Water ◽

Numerical Models ◽

Salinity Gradient ◽

Western Mediterranean ◽

Ocean Current ◽

Seawater Salinity ◽

The Mediterranean

Abstract. The Mediterranean Sea is characterized by a relatively strong west to east salinity gradient, which makes it an area suitable to test the effect of salinity on foraminiferal shell geochemistry. We collected living specimens of the planktonic foraminifer Globigerinoides ruber (white) to analyse the relation between element/Ca ratios, stable oxygen isotopes of their shells and surface seawater salinity, isotopic composition and temperature. The oxygen isotopes of sea surface water correlate with salinity in the Mediterranean also during winter, when sampled for this study. Sea water oxygen and hydrogen isotopes are positively correlated in both the eastern and western Mediterranean Sea, though especially in the eastern part the relationship differs from values reported previously for that area. The slope between salinity and seawater oxygen isotopes is lower than previously published. Still, despite the rather modest slope, seawater and foraminiferal carbonate oxygen isotopes are correlated in our dataset although with large residuals and high residual variability. This scatter can be due to either biological variability in vital effects or environmental variability. Numerical models backtracking particles show ocean current driven mixing of particles of different origin might dampen sensitivity and could result in an offset caused by horizontal transport. Results show that Na/Ca is positively correlated to salinity and independent of temperature. Foraminiferal Mg/Ca increases with temperature, as expected, and in line with earlier calibrations, also in the high salinity environment. By using living foraminifera during winter, the previously established Mg/Ca-temperature calibration is extended to temperatures below 18 °C, which is a fundamental prerequisite of using single foraminifera for reconstructing past seasonality.

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Uncertainties in the stability field of UHP hydrous phases (10-A phase and phase E) and deep-slab dehydration: potential implications for fluid migration and water fluxes at subduction zones

10.5194/egusphere-egu2020-4783 ◽

2020 ◽

Author(s):

Nestor G. Cerpa ◽

José Alberto Padrón-Navarta ◽

Diane Arcay

Keyword(s):

Lithospheric Mantle ◽

Subduction Zones ◽

Mantle Wedge ◽

Numerical Models ◽

Stability Field ◽

Fluid Migration ◽

Water Fluxes ◽

Water Release ◽

The Stability ◽

Back Arc

The subduction of water via lithospheric-mantle hydrous phases have major implications for the generation of arc and back-arc volcanism, as well as for the global water cycle. Most of the current numerical models use Perple_X [Connolly et al., 2009] to quantify water release from the slab and subsequent fluid migration in the mantle wedge. At UHP conditions, the phase diagrams generated with this thermodynamic code suggest that the breakdown of serpentine and chlorite leads to the near complete dehydration of the lithospheric mantle before reaching a 200-km depth. Laboratory experiments, however, have observed the stability of the 10-&#197; phase and the phase E in natural bulk compositions, which may hold moderate amounts of water, beyond the stability field of serpentine and chlorite [Fumagalli and Poli, 2005; Maurice et al., 2018]. Here, using 2D thermo-mechanical models, we explore to what extent the presence of these hydrous phases may favor a deeper subduction of water than those predicted by Perple_X.We perform end-member models in terms of slab temperature and thickness of hydrated lithospheric mantle entering at trench. The computed geotherms within the uppermost subducted mantle show that the stability field of mantle hydrous phases around 600-800&#176;C and 6-8 GPa is crucial for predictions of water fluxes. We point out that the lack of systematic experiments at these P-T conditions, as well as the absence of 10-&#197; and E phases in current thermodynamic databases, prevent accurate estimates of deep water transfers. We nonetheless build a phase diagram based on current experimental constraints that includes approximations of their stability field and qualitatively discuss the potential implications for fluid migration in the back-arc mantle wedge and water fluxes.

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Linking subduction dynamics to back-arc deformation

10.5194/egusphere-egu2020-7092 ◽

2020 ◽

Author(s):

Valentina Magni ◽

Manel Prada

Keyword(s):

Boundary Conditions ◽

Numerical Models ◽

Thermal Structure ◽

Oceanic Lithosphere ◽

Lau Basin ◽

Crustal Composition ◽

Lithospheric Extension ◽

Back Arc ◽

Existing Structure ◽

Tyrrhenian Basin

The morphology of back-arc basins shows how complex their formation is and how pre-existing lithospheric structures, rifting and spreading processes, and subduction dynamics all have a role in shaping them. Often, back-arc basins present multiple spreading centres that form one after the other (e.g. Mariana subduction zone), propagate and rotate (e.g., Lau Basin) following trench retreat. Episodes of fast and slow trench retreat can cause rift jumps, migration of magmatism, and pulses of higher crustal production (e.g., Tyrrhenian Basin). The evolution of a back-arc basin is not only tightly linked to subduction dynamics, but it is likely that the composition and the pre-existing structure of the lithosphere play a role in shaping the basin too. In this work, we investigate the interplay between these features with numerical models of lithospheric extension with a visco-plastic rheology. We use the finite element code ASPECT to model the rifting of continental and oceanic lithosphere with boundary conditions that simulate the asymmetric type of extension caused by the trench retreat. We perform a parametric study in which we systematically change key parameters such as crustal composition and thickness, initial thermal structure and rheology of the lithosphere, and rate of extension. These models aim at understanding how pre-existing lithospheric structures affect back-arc rifting and spreading and what processes control spreading centres jumps in back-arc settings. Preliminary results show that time-dependent boundary conditions that simulate episodes of fast trench retreat, thus fast extension, play an important role into the style of lithospheric back-arc deformation. Finally, we will compare our model results with the location and timing of back-arc rifting and spreading in different active and inactive back-arc basins.

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