Sheng Fan

Flow laws for ice predict rates of deformation (strain) and are fundamental to modelling glacier and ice-sheet dynamics. Here we apply Bayesian inference to laboratory measurements accumulated over 70 years to constrain flow laws for ice-sheet modelling. At low strains, commonly used flow laws—derived from individual experimental datasets with narr...

Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To better understand grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples of similar starting grain sizes that were annealed at the solidus temperature (0 ∘C) f...

Strain weakening leads to the formation of high‐strain shear zones and strongly influences terrestrial ice discharge. In glacial flow models, strain weakening is assumed to arise from the alignment of weak basal planes—the development of a crystallographic preferred orientation, CPO—during flow. However, in experiments, ice strain weakening also co...

Dynamic recrystallization is an important mechanical weakening mechanism during the deformation of ice, yet we currently lack robust quantitative tools for identifying recrystallized grains in the “migration” recrystallization regime that dominates ice deformation at temperatures close to the ice melting point. Here, we propose grain boundary irreg...

In order to better understand ice deformation mechanisms, we document the microstructural evolution of ice with increasing strain. We include data from experiments at relatively low temperatures (-20 and -30 ∘C), where the microstructural evolution with axial strain has never before been documented. Polycrystalline pure water ice was deformed under...

Plastic deformation of polycrystalline hexagonal ice (ice Ih) induces crystallographic preferred orientations (CPOs), which give rise to anisotropy in the viscosity of ice, thereby exerting a strong influence on the flow of glaciers and ice sheets. The development of CPOs is governed by the relative importance of two pivotal recrystallization mecha...

Flow laws for ice predict rates of deformation (strain) and are fundamental to modelling glacier and ice-sheet dynamics. Here, we apply Bayesian inference to laboratory measurements accumulated over seventy years to constrain flow laws for ice-sheet modelling. At low strains, commonly used flow laws—derived from individual experimental datasets wit...

Plastic deformation of polycrystalline ice 1 h induces crystallographic preferred orientations (CPOs), which give rise to anisotropy in the viscosity of ice, thereby exerting a strong influence on the flow of glaciers and ice sheets. The development of CPOs is governed by two pivotal mechanisms: recrystallization dominated by subgrain/lattice rotat...

The grain size of polycrystalline ice affects key parameters related to the dynamics of ice masses, such as the rheological and dielectric properties of terrestrial ice as well as the ice shells of icy satellites. To investigate the effect of soluble impurities on the grain-growth kinetics of polycrystalline ice, we conducted annealing experiments...

The grain size of polycrystalline ice affects key parameters related to the dynamics of ice masses, such as the rheological and dielectric properties of terrestrial ice flow as well as the ice shells of icy satellites. To investigate the effect of soluble impurities on the grain-growth kinetics of polycrystalline ice, we conducted annealing experim...

Grain growth can modify the microstructure of natural ice, including the grain size and crystallographic preferred orientation (CPO). To understand better grain-growth processes and kinetics, we compared microstructural data from synthetic and natural ice samples that were annealed at ice-solidus temperature (0ºC) to successfully long durations. Th...

Crystallographic preferred orientations (CPOs) are particularly important in controlling the mechanical properties of glacial shear margins. Logistical and safety considerations often make direct sampling of shear margins difficult, and geophysical measurements are commonly used to constrain the CPOs. We present here the first direct comparison of...

During plastic deformation, strain weakening can be achieved, in part, via strain energy reduction associated with intragranular boundary development and grain boundary formation. Grain boundaries (in 2D) are segments between triple junctions, that connect to encircle grains; every boundary segment in the encircling loop has a high (>10°) misorient...

Ice and other minerals usually develop widespread boundaries within grains. Laboratory experiments show these intragranular boundaries are the manifestation of crystalline defects (“dislocations”). During deformation, intragranular boundaries will develop from low-angle to high-angle via a continuous input of dislocations, and they might enclose an...

Crystallographic preferred orientations (CPOs) are particularly important in controlling the mechanical properties of glacial shear margins. Logistical and safety considerations often make direct sampling of shear margins difficult and geophysical measurements are commonly used to constrain the CPOs. We present here the first direct comparison of s...

A 58 m long azimuthally oriented ice core has been collected from the floating lateral sinistral shear margin of the lower Priestley Glacier, Terra Nova Bay, Antarctica. The crystallographic preferred orientations (CPO) and microstructures are described in order to correlate the geometry of anisotropy with constrained large-scale kinematics. Cryoge...

Quartz and ice both exhibit distinctive microstructures when deformed at low stress and high homologous temperature, known as grain-boundary migration (GBM) microstructures. These are difficult to reproduce experimentally in silicate minerals, and no correlation has been established between quantifiable aspects of the microstructure and deformation...

The strength of ice and other minerals becomes weakened during the deformation, and such material characteristic plays a key role in shaping the earth, such as the formation of shear zones. In this study, we deform ice samples to progressively higher strains. The microstructural data of ice samples are used to predict the strength of ice. The resul...

Kinking is an important strain-accommodating process during crystal plastic deformation under relatively large stresses and may influence the mechanical properties of the Earth's lithosphere and planetary cryosphere. To better understand the origins, mechanisms, and microstructural effects of kinking, we present detailed microstructural analyses of...

Kinking can accommodate significant amounts of strain during crystal plastic deformation under relatively large stresses and may influence the mechanical properties of cold planetary cryosphere. To better understand the origins, mechanisms, and microstructural effects of kinking, we present detailed microstructural analyses of coarse-grained ice (~...

It is vital to understand the mechanical properties of flowing ice to model the dynamics of ice sheets and ice shelves and to predict their behaviour in the future. We can increase our understanding of ice physical properties by performing deformation experiments on ice in laboratories and examining its mechanical and microstructural responses. How...

Microstructures provide key insights into understanding the mechanical behavior of ice. Crystallographic preferred orientation (CPO) develops during plastic deformation as ice deforms dominantly by dislocation glide on the basal plane, modified and often intensified by dynamic recrystallization. CPO patterns in fine-grained ice have been relatively...

Dynamic recrystallization is an important mechanical weakening mechanism during the deformation of ice, yet we currently lack robust quantitative tools for identifying recrystallized grains in the “migration” recrystallization regime that dominates ice deformation at temperatures close to the ice melting point. Here, we propose grain boundary irreg...

Anisotropy in the form of a crystallographic preferred orientation (CPO) develops during plastic deformation and modifies the rheological properties of ice, influencing dynamic feedbacks and large-scale flow rates that impact glacial discharge. Warm (T>-10° C), coarse-grained (>20mm) ice, common deep in ice sheets, valley glaciers and polar outlet...

It is vital to understand the mechanical properties of flowing ice to model the dynamics of ice sheets and ice shelves, and to predict their behaviour in the future. We can do this by performing deformation experiments on ice in laboratories, and examining its mechanical and microstructural responses. However, natural conditions in ice sheets and i...

The glacio-fluvial sediments of the Whataroa Valley on the west coast of New Zealand’s South Island contain a record of environmental change since the Last Glacial Maximum. The valley is cut by the Australia–Pacific plate-bounding Alpine Fault, the position of which is obscured by recent glacio-fluvial outwash deposits. Five seismic profiles collec...

Observations of ice shelf anisotropy on borehole seismic data are presented. Hot‐water‐drilledboreholes were made by the Aotearoa New Zealand Ross Ice Shelf Programme through a grounding‐line proximal site at Windless Bight and the central Ross Ice Shelf site HWD‐2. The boreholes were used to freeze seismometers into the ice at different depths. Se...

Microstructures provide key insights into understanding the mechanical behavior of ice. Crystallographic preferred orientation (CPO) develops during plastic deformation as ice dynamically recrystallizes, with the dominance of intracrystalline glide on the basal plane. CPO patterns in fine-grained ice have been relatively well characterized and unde...

Understanding ice deformation mechanisms is crucial for understanding the dynamic evolution of terrestrial and planetary ice flow. To understand better the deformation mechanisms, we document the microstructural evolution of ice with increasing strain. We include data from deformation at relatively low temperature (-20 and -30 °C) where the microst...

The flow behaviour of natural ice is fundamentally influenced by the ice crystallography because dislocation glide on the ice basal-plane is much easier than on other planes. Consequently, an anisotropic crystallographic preferred orientation (CPO) will develop as the c-axes of polycrystalline ice keep rotating and lining up under stress. The CPO r...

Synthetic polycrystalline ice was sheared at temperatures of -5, -20 and -30 ∘C, to different shear strains, up to γ=2.6, equivalent to a maximum stretch of 2.94 (final line length is 2.94 times the original length). Cryo-electron backscatter diffraction (EBSD) analysis shows that basal intracrystalline slip planes become preferentially oriented pa...

We sheared synthetic polycrystalline ice at temperatures of −5, −20 and −30°C, to different shear strains, up to γ=2.6 (equivalent strain of 1.5). Cryo-electron backscatter diffraction (EBSD) shows that basal intra-crystalline slip planes become preferentially oriented parallel to the shear plane, in all experiments. This is visualized as a primary...

Ice deformation

The character of the lithospheric mantle of the northern Siberian craton is not well established; nearly all published data are for mantle xenoliths from a single kimberlite in the center of the craton (Udachnaya). We report major elements of the whole rock, trace elements data of clinopyroxene and Re-Os isotope and PGE concentration of mantle xeno...

There are significant differences between the foreland craton and the incretionary wedge of "orogenic zone" in crustal structure, mechanical property,, et al. Compression makes the lateral variation of basin-mountain crust manifested by tectonic deformation. We set the sandbox modeling experiments of "craton " with two detachment layers directly co...

The basic deformation characteristic of the Kuqa Depression, Tarim Basin is delaminate contractional structure. The middle part of Kuqa Depression can be divided into four layers from the depth to shallow part: basement layer, subsalt layer, salt layer and post-salt layer. Based on the analysis of structural deformation features and tectonic evolut...