Marine ice sheet experiments with the Community Ice Sheet Model

Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law and to the treatment of stresses and melt rates near the grounding line. We study the effects of these numerical choices on marine ice sheet dynamics in the Community Ice Sheet Model (CISM). In the framework of the Marine Ice Sheet Model Intercomparison Project 3d (MISMIP3d), we show that a depth-integrated, higher-order solver gives results similar to a 3D (Blatter–Pattyn) solver. We confirm that using a grounding line parameterization to approximate stresses in the grounding zone leads to accurate representation of ice sheet flow with a resolution of ∼2 km, as opposed to ∼0.5 km without the parameterization. In the MISMIP+ experimental framework, we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice sheet geometry, forcing, or model numerics. In both experimental frameworks, ice flow is sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate and ∼1 km (arguably 2 km) when the connectivity is strong.

SHAPE OF A SLIDING CAPILLARY CONTACT DUE TO THE HYSTERESIS OF CONTACT ANGLE: THEORY AND EXPERIMENT

We consider a classical problem of a capillary neck between a parabolic body and a plane with a small amount of liquid in between. In the state of thermodynamic equilibrium, the contact area between the bodies and the liquid layer has a circular shape. However, if the bodies are forced to slowly move in the tangential direction, the shape will change due to the hysteresis of the contact angle. We discuss the form of the contact area under two limiting assumptions about the friction law in the boundary line. We also present a detailed experimental study of the shape of sliding capillary contact in dependence on the roughness of the contacting surfaces.

Determination of Magnitudes and Orientation of the Paleostress of Bekhme Structure in Shaqlawa area, Northerneastern Iraq

This study presents the determination of the paleostress magnitudes and orientation of Bekhme Structure in Shaqlawa area, northeastern Iraq. Paleostress analysis of slip-fault measurements is performed using Right dihedral, Lisle diagram, and Mohr Circles methods. Depending on Mohr Circles, Bott law, and vertical thickness, the magnitudes of the paleostress at the time of the tectonic activity were determined. Firstly, Georient Software was used to estimate the orientation of the paleostresses (σ1, σ2, and σ3). Secondly, using the rupture –friction law, taking into account the depth of the overburden and the vertical stress (σv),the magnitudes of the paleostresses were calculated (σ1=4500 bars, σ2=1900 bars and σ3=700 bars). The high magnitudes of the principal stress axes may be attributed to the active tectonic events which led to the deformation of the area during the Cretaceous and Tertiary periods. The study area shows that the poles of the measured faults lie in the reactivated area of Mohr circles. This indicates the instability of the study area. The study area is estimated to have high importance, due to the possibility of the existence of deposited hydrocarbons. Fold- Thrust belt marks the deformation fronts of the major orogeny that forms from the collision of the Arabian Plate with the Turkish and Iranian Plates.

Marine ice-sheet experiments with the Community Ice Sheet Model using the MISMIP+ experimental framework.

<p>Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law, and to the treatment of stresses and melt rates near the grounding line. We present the effects of these numerical choices on marine ice-sheet dynamics in the Community Ice Sheet Model (CISM). In the experimental framework of the Marine Ice Sheet Model Intercomparison Project (MISMIP+), we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice-sheet geometry, forcing, or model numerics. In the MISMIP+ framework, the ice flow is also sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate, and ∼1 km (arguably 2 km) when the connectivity is strong.</p>

Friction law for atomic-scale contact assisted by atomistic simulations

Non-empirical law depicting how atomic-scale friction behaves is crucial to facilitate the practical design of tribosystems. However, progress in developing a practically usable friction law has stagnated because atomic-scale friction arises from the continuous forming and rupturing of interfacial chemical bonds and such interfacial chemical reactions are difficult to measure precisely in experiments. Here, we propose a usable friction law for atomic-scale contact by using atomistic simulations to correctly measure the interfacial chemical reactions of a realistic rough surface, and confirm its applicability to predicting how atomic-scale friction varies with temperature, sliding velocity, and load.

Marine ice-sheet experiments with the Community Ice Sheet Model

Ice sheet models differ in their numerical treatment of dynamical processes. Simulations of marine-based ice are sensitive to the choice of Stokes flow approximation and basal friction law, and to the treatment of stresses and melt rates near the grounding line. We study the effects of these numerical choices on marine ice-sheet dynamics in the Community Ice SheetModel (CISM). In the framework of the Marine Ice Sheet Model Intercomparison Project 3d (MISMIP3d), we show that a depth-integrated, higher-order solver gives results similar to a 3D (Blatter-Pattyn) solver. We confirm that using a grounding-line parameterization to approximate stresses in the grounding zone leads to accurate representation of ice sheet flow with a resolution of ∼2 km, as opposed to ∼0.5 km without the parameterization. In the MISMIP+ experimental framework, we compare different treatments of sub-shelf melting near the grounding line. In contrast to recent studies arguing that melting should not be applied in partly grounded cells, it is usually beneficial in CISM simulations to apply some melting in these cells. This suggests that the optimal treatment of melting near the grounding line can depend on ice-sheet geometry, forcing, or model numerics. In both experimental frameworks, ice flow is sensitive to the choice of basal friction law. To study this sensitivity, we evaluate friction laws that vary the connectivity between the basal hydrological system and the ocean near the grounding line. CISM yields accurate results in steady-state and perturbation experiments at a resolution of ∼2 km (arguably 4 km) when the connectivity is low or moderate, and ∼1 km (arguably 2 km) when the connectivity is strong.