Dynamic Ice Model Research Articles

Numerical modeling of ice control on the Albany River, Ontario, Canada

The Kashechewan First Nation (KFN) community is located on a floodplain of the north branch of the Albany River, on the west coast of James Bay. Each spring, the community faces the uncertain prospect of evacuation due to ice-jam flooding, the most severe of which occurred in 2006. A study was conducted to develop long-term options for reducing the flood risk to the community, which included dams, dykes, pier and weir type ice-control structures, and conveyance channels. This paper presents a numerical model study on the Albany River in Ontario, Canada to develop ice control as a potential means for mitigating ice-jam flooding at the KFN community using the two-dimensional ice dynamics model DynaRICE. A method was developed to simulate pier type ice-control structures within the model such that the physical channel conditions, flow conditions, and combinations of ice control could be evaluated. The model allowed detailed simulation of ice retention, resulting inundation, and the forces on the individual piers. To optimize the design of the piers, including pier spacing, height, and size, various combinations of ice, flow, and pier conditions were simulated. Numerical modeling facilitated a comparative examination of flood risk reduction to the community from the various ice control options.

Using specularity content to evaluate eight geothermal heat flow maps of Totten Glacier

Abstract. Geothermal heat flow (GHF) is the dominant factor affecting the basal thermal regime of ice sheet dynamics. But it is poorly defined for the Antarctic ice sheet. We compare the basal thermal state of the Totten Glacier catchment as simulated by eight different GHF datasets. We use a basal energy and water flow model coupled with a 3D full-Stokes ice dynamics model to estimate the basal temperature, basal friction heat and basal melting rate. In addition to the location of subglacial lakes, we use specularity content of the airborne radar returns as a two-sided constraint to discriminate between local wet or dry basal conditions and compare the returns with the basal state simulations with different GHFs. Two medium magnitude GHF distribution maps derived from seismic modelling rank well at simulating both cold- and warm-bed regions, the GHFs from Shen et al. (2020) and Shapiro and Ritzwoller (2004). The best-fit simulated result shows that most of the inland bed area is frozen. Only the central inland subglacial canyon, co-located with high specularity content, reaches the pressure melting point consistently in all the eight GHFs. Modelled basal melting rates in the slow-flowing region are generally 0–5 mm yr−1 but with local maxima of 10 mm yr−1 at the central inland subglacial canyon. The fast-flowing grounded glaciers close to the Totten ice shelf are lubricating their bases with meltwater at rates of 10–400 mm yr−1.

Automatic Extraction of the Calving Front of Pine Island Glacier Based on Neural Network

Calving front location plays a crucial role in studying ice–ocean interaction, mapping glacier area change, and constraining ice dynamic models. However, relying solely on visual interpretation to extract annual changes in the calving front of ice shelves is a time-consuming process. In this study, a comparative analysis was conducted on the segmentation obtained from fully convolutional networks (FCN), U-Net, and U2-Net models, revealing that U2-Net exhibited the most effective classification. Notably, U2-Net outperformed the other two models by more than 30 percent in terms of the F1 parameter. Therefore, this paper introduces an automated approach that utilizes the U2-Net model to extract the calving front of ice shelves based on a Landsat image, achieving an extraction accuracy of 58 m. To assess the model’s performance on additional ice shelves in the polar region, the calving front of the Totten and Filchner ice shelves were also extracted for the past decade. The findings demonstrated that the ice velocity of the Filchner ice shelf exceeded that of the Totten ice shelf. Between February 2014 and March 2015, the majority of the calving fronts along the Filchner Ice Shelf showed an advancing trend, with the fastest-moving front measuring 3532 ± 58 m/yr.

Polarimetric airborne scientific instrument, mark 2, an ice‐sounding airborne synthetic aperture radar for subglacial 3D imagery

AbstractPolarimetric Airborne Scientific INstrument, mark 2 (PASIN2) is a 150 MHz coherent pulsed radar with the purpose of deep ice sounding for bedrock, subglacial channels and ice‐water interface detection in Antarctica. It is designed and operated by the British Antarctic Survey from 2014. With multiple antennas, oriented along and across‐track, for transmission and reception, it enables polarimetric 3D estimation of the ice base with a single pass, reducing the gridding density of the survey paths. The off‐line data processing stream consists of channel calibration; 2D synthetic aperture radar (SAR) imaging based on back‐projection, for along‐track and range dimensions; and finally, a direction of arrival estimation (DoA) of the remaining across‐track angle, by modifying the non‐linear MUSIC algorithm. Calibration flights, during the Antarctic Summer campaigns in 16/17 and 19/20 seasons, assessed and validated the instrument and processing performances. Imaging flights over ice streams and ice shelves close to grounding lines demonstrate the 3D sensing capabilities. By resolving directional ambiguities and accounting for reflector across‐track location, the true ice thickness and bed elevation are obtained, thereby removing the error of the usual assumption of vertical DoA, that greatly influence the output of flow models of ice dynamics.

Highly variable friction and slip observed at Antarctic ice stream bed

The slip of glaciers over the underlying bed is the dominant mechanism governing the migration of ice from land into the oceans, with accelerating slip contributing to sea-level rise. Yet glacier slip remains poorly understood, and observational constraints are sparse. Here we use passive seismic observations to measure both frictional shear stress and slip at the bed of the Rutford Ice Stream in Antarctica using 100,000 repetitive stick-slip icequakes. We find that basal shear stresses and slip rates vary from 104 to 107 Pa and 0.2 to 1.5 m per day, respectively. Friction and slip vary temporally over the order of hours, and spatially over 10s of metres, due to corresponding variations in effective normal stress and ice–bed interface material. Our findings suggest that the bed is substantially more complex than currently assumed in ice stream models and that basal effective normal stresses may be significantly higher than previously thought. Our observations can provide constraints on the basal boundary conditions for ice-dynamics models. This is critical for constraining the primary contribution of ice mass loss in Antarctica and hence for reducing uncertainty in sea-level rise projections.

SIMUG – finite element model of sea ice dynamics on triangular grid in local Cartesian basis

Abstract The paper presents the dynamical core of the new sea ice model SIMUG (Sea Ice Model on Unstructured Grid) on the A- and CD-types of unstructured triangular grids in the local-element basis on sphere. Three standardized box tests to reproduce the Linear Kinematic Features (LKFs), and the short-term forecast in the real Arctic Ocean geometry with the realistic atmosphere and ocean forcing demonstrate the model quality compared to other sea ice models like CICE, FESOM, MITgcm, and ICON-O. The distinctive features of the model presented are a wide choice of transport schemes, and the new numerical implementation with the serial and parallel C++ coding and INMOST, Ani2D, and Ani3D packages to deal with unstructured grids. Code profiling and scalability assessment are carried out. In general, the A-version of the ice drift model works faster, but has fewer degrees of freedom on the same grid. Due to the increase in the degrees of freedom, the model on the CD grid gives ultra-resolution of LKFs, but requires more strict conditions for stability.

Improving numerical accuracy for the viscous-plastic formulation of sea ice

Accurate modeling of sea ice dynamics is critical for predicting environmental variables and is important in applications such as navigating ice breaker ships, and as such there have been numerous investigations on modeling sea ice dynamics. The 1979 viscous-plastic (VP) sea ice model introduced by W.D. Hibler remains the most widely accepted. Due to its highly nonlinear features, the Hibler model is intrinsically challenging for computational solvers. This study therefore focuses on improving the numerical accuracy of the VP sea ice model. Since the poor convergence observed in existing numerical simulations stems from the nonlinear nature of the VP formulation, this investigation proposes using the celebrated weighted essentially non-oscillatory (WENO) scheme – as opposed to the frequently employed centered difference (CD) scheme – for the spatial derivatives in the VP sea ice model. We then proceed to numerically demonstrate that WENO yields higher-order convergence for smooth solutions, and that furthermore it is able to resolve the discontinuities in the sharp features of sea ice covers – something that is not possible using CD methods. Finally, our proposed framework introduces a potential function method that utilizes the phase field method that naturally incorporates the physical restrictions of ice thickness and ice concentration in transport equations, resulting in modified transport equations which include additional forcing terms. Our method does not require post-processing, thereby avoiding the possible introduction of discontinuities and corresponding negative impact on the solution behavior. Numerical experiments are provided to demonstrate the efficacy of our new methodology.

Geothermal Heat Flow and Thermal Structure of the Antarctic Lithosphere

AbstractHigh‐quality maps of Geothermal heat flow (GHF) are crucial when modeling ice dynamics, shape, and mass loss of the Antarctic Ice Sheet, which is one of the largest potential contributors to sea level rise. The determination of GHF remains challenging, as in situ data are sparse and geophysical models exhibit large discrepancies in amplitude and resolution, especially on regional scales. Using a novel approach implementing a joint inversion of gravity and seismic tomography data with various geophysical and mineral physics information, we estimate the 3D thermal lithospheric structure and present a new GHF map. The resulting surface heat flow correlates with the location of subglacial volcanism and can represent a boundary condition for accurate ice dynamics models that can explain observed acceleration in the ongoing ice mass loss. Absolute values are within the range of other seismology‐based methods and are much lower than those obtained using for example, magnetic data. High uncertainties remain in the parametrization of the upper crustal structure and thermal parameters.

Sea Ice Elevation in the Western Weddell Sea, Antarctica: Observations From Field Campaign

AbstractSea ice elevation is crucial in the characterization of three‐dimensional (3D) sea ice patterns, providing physical insights to advance sea ice dynamic models. Moreover, how sea ice elevation may be related to the ocean geophysical environment is still a significant knowledge gap, especially in Antarctica. A radar theory relating electromagnetic scattering mechanisms to sea ice elevation over old and deformed rough ice has been reported in a prior companion paper. This follow‐up paper presents the validated model function and synthetic aperture radar (SAR)‐retrieved sea ice elevations based on the field data acquired during the Operation IceBridge and TanDEM‐X Antarctic Science Campaign. A high‐resolution sea ice digital elevation model (DEM) is generated extensively over a 19 × 450 km sector in the Western Weddell Sea, achieving a good accuracy with a low root‐mean‐square error of 0.23 m. From the SAR‐retrieved sea ice DEM, 3D sea ice patterns including roughness height, auto‐correlation lengths, correlation ellipticity, and orientation angles are calculated over the old and deformed rough sea ice. The 3D sea ice patterns give a comprehensive characterization of sea ice topography in the Western Weddell Sea and show the potential to be used for understanding sea ice formation processes in the Antarctic.

Groundwater flows deep under Antarctic ice

Ice-dynamics models must be updated now that researchers have observed a thick layer of salty water in sediments beneath the West Antarctic Ice Sheet.

Rigorous Analysis and Dynamics of Hibler’s Sea Ice Model

This article develops for the first time a rigorous analysis of Hibler’s model of sea ice dynamics. Identifying Hibler’s ice stress as a quasilinear second-order operator and regarding Hibler’s model as a quasilinear evolution equation, it is shown that a regularized version of Hibler’s coupled sea ice model, i.e., the model coupling velocity, thickness and compactness of sea ice, is locally strongly well-posed within the L_q-setting and also globally strongly well-posed for initial data close to constant equilibria.

Catastrophic ice shelf collapse along the NW Laurentide Ice Sheet highlights the vulnerability of marine-based ice margins

We document the unparalleled depositional and chronological record of an 80,000 km2 ice shelf from the former Laurentide Ice Sheet whose advance and retreat spanned only ∼400 years (11.6–11.2 cal ka BP). Its catastrophic breakup (∼150 years; 11.3–11.2 cal ka BP) coincided with a rapidly warming atmosphere and ocean, paralleling reported conditions impacting the ongoing evolution of marine-based margins of Antarctica and Greenland. Our record highlights the instability of the NW Laurentide Ice Sheet whose marine-based ice streams and ice shelves retreated in channels of intermediate depth (400–600 m) that lack reverse slopes, suggesting that current ice dynamics models may underestimate the sensitivity of similar margins in Antarctica to ongoing global warming. Our reconstruction is based on > 700 km of coastal field surveys complemented by radiocarbon dates stratigraphically encompassing the full lifespan of the former Viscount Melville Sound Ice Shelf. Notably, this detailed record demonstrates that large ice shelves can be removed rapidly, cautioning against dismissing predictions of possible 21st century mean-sea-level rise >1 m derived from the ongoing retreat of marine-based ice sheets. We emphasize that during the last deglaciation of the western Canadian Arctic Archipelago, prominent ice streams transitioned into ice shelves whose depositional landforms are pervasive, demonstrating their pivotal role in the evisceration of the NW Laurentide Ice Sheet. The VMSIS provides an exceptionally detailed geological record whose tightly constrained chronology of growth, maintenance and breakup serves as an instructive example for those modern marine-based margins whose instability is being investigated to address estimates of possible future sea level rise.

Testing a proposed new chronology for the Jasmund Glacitectonic Complex (SW Baltic Sea): No indication of incipient deformation during MIS 3

Weichselian advances of the Scandinavian Ice Sheet have generated several glacitectonically deformed structures in the southwestern Baltic Sea area. One example is the 100 km 2 large Jasmund Glacitectonic Complex (JGC), which was formed proglacially and consists of two subparallel-orientated sets of composite ridges that represent a northern and southern structural complex. The two-part morphological structure of the JGC suggests a formation by two ice advances, one approaching from NE and one from SE direction. So far, this divided structure has been assumed to have been formed by short-time ice-front oscillations during an MIS 2 ice advance. However, based on their recently published ice dynamic model for MIS 3 and the available age data from Jasmund, lüthgens et al. (2020) propose a chronological reinterpretation of the JGC development, according to which two distinct ice advances during early and late MIS 3 formed the JGC. In order to test this novel stratigraphical model for the JGC formation, five OSL samples were taken from fluvial and lacustrine deposits at a key section near Glowe (NW Jasmund). The investigated succession is divided into pre-kinematic sediments, deposited before the glacitectonic deformation, and post-kinematic sediments, deposited after the deformation. Our results show that the youngest dated pre-tectonic sediment has a burial age between ∼40 and 34 ka, which rules out a glacitectonic deformation during an early MIS 3 ice advance (∼60–50 ka). In addition, by reviewing the existing age data set, a development of the JGC during an early and late MIS 3 advance of the SIS must be rejected. Instead, our data confirm the genesis of the JGC during MIS 2.

A numerical model for river ice dynamics based on discrete element method

In this study, a numerical model for river ice dynamics (DEMRICE) based on the discrete element method is developed. The ice dynamic component of this model considers moving surface ice floes as discrete elements. It uses a three-dimensional dilated polyhedral discrete element method to resolve contact and external forces on individual ice floes. The hydrodynamic component uses a streamline upwind Petrov–Galerkin (SUPG) finite-element method to solve the two-dimensional unsteady hydraulic equations. The model is validated with the analytical solution for equilibrium ice jams and the DynaRICE model. The ice jam evolution in a straight rectangular channel and the corresponding flow condition changes are simulated and discussed. Finally, the model is applied to simulate the ice transport and cover development in a reach of the Yellow River near Shisifenzi, Inner Mongolia.

Improving Numerical Accuracy for the Viscous-Plastic Formulation of Sea Ice

Accurate modeling of sea ice dynamics is critical for predicting environmental variables and is important in applications such as navigating ice breaker ships. Research for both modeling and simulating sea ice dynamics is ongoing, with the most widely accepted model based on the viscous-plastic (VP) formulation introduced by Hibler in 1979. Due to its highly nonlinear features, this model is intrinsically challenging for computational solvers. In particular, sea ice simulations often significantly differ from satellite observations. This study therefore focuses on improving the numerical accuracy of the VP sea ice model. Since the poor convergence observed in existing numerical simulations stems from the nonlinear nature of the VP formulation, this investigation proposes using the celebrated weighted essentially non-oscillatory (WENO) scheme -- as opposed to the frequently employed centered difference (CD) scheme -- for the spatial derivatives in the VP sea ice model. We then proceed to numerically demonstrate that WENO yields higher-order convergence for smooth solutions, and that furthermore it is able to resolve the discontinuities in the sharp features of sea ice covers -- something that is not possible using CD methods. Finally, our proposed framework integrates a potential function method that utilizes the phase field method to naturally incorporates the physical restrictions of ice thickness and ice concentration in transport equations, resulting in a modified transport equations which includes additional forcing terms. Our method does not require post-processing, thereby avoiding the possible introduction of discontinuities and corresponding negative impact on the solution behavior. Numerical experiments are provided to demonstrate the efficacy of our new methodology.

Deformation of an ice pack influenced by waves and topographic enhancement of tidal motion near Hopen Island in the Barents Sea

Understanding the physical mechanisms behind the deformation of pack ice floes is important for understanding the dynamics of the local ice regime, and for the calibration and validation of ice dynamics models. In April 2017, six Iridium satellite-tracking beacons were deployed on six pack ice floes in the Barents Sea south of Svalbard in the Norwegian Arctic. The ice tracker deployment was performed as part of an offshore research expedition carried out onboard the Research Vessel (RV) Polarsyssel to characterize the local sea ice environment. In addition to the ice tracker deployments, an anemometer beacon, a wave beacon, and an Acoustic Doppler Current Profiler (ADCP) were deployed on a drifting ice floe to which the vessel was moored for nearly three days, and extensive thickness, salinity, and density measurements were made. The wave beacon recorded the vertical acceleration of the floe so that wave forcing on the floe drift could be estimated. The in-situ wind, ocean current, wave, and ice thickness and density measurements permitted the estimation of met-ocean forcings on the acceleration of the ice floe. On April 28, two days after the last ice tracker was deployed on April 26, the six tracked ice floes rapidly dispersed just to the west-southwest of Hopen Island. The dispersion of the ice floes was dominated by strong shearing within the local ice pack, coinciding with a rapid increase in the speeds of the local tidal currents, which was soon followed by a rapid increase in the wave energy. Each of the six tracked ice floes increased their observed drift speeds in sync with the increase in the local tidal current speeds at different times for each floe, but at approximately the same decrease in water depth as they reached the northern edge of Spitsbergen Bank. The rapid increase in the tidal currents was linked to the topographic enhancement of tidal motion near Hopen Island in the shallower waters of Spitsbergen Bank. The wind and wave measurements made by the anemometer and wave beacons and ice tracker left on the ice floe to which the vessel was moored allowed for an estimate of the relative strength of the wind, tidal, and wave forcings on the local ice field. The results showed that the tidal currents initially dominated the dynamic response of the local ice field compared to the wind, which led to the conclusion that the enhanced tidal current was ultimately the dominant cause of the initial dispersion of the local pack ice field on April 28, and the dispersion was then further enhanced by the increase in wave energy.

Transition to marine ice cliff instability controlled by ice thickness gradients and velocity.

Portions of ice sheets grounded deep beneath sea level can disintegrate if tall ice cliffs at the ice-ocean boundary start to collapse under their own weight. This process, called marine ice cliff instability, could lead to catastrophic retreat of sections of West Antarctica on decadal-to-century time scales. Here we use a model that resolves flow and failure of ice to show that dynamic thinning can slow or stabilize cliff retreat, but when ice thickness increases rapidly upstream from the ice cliff, there is a transition to catastrophic collapse. However, even if vulnerable locations like Thwaites Glacier start to collapse, small resistive forces from sea-ice and calved debris can slow down or arrest retreat, reducing the potential for sustained ice sheet collapse.

Fuzzy Neural Network-Based Evaluation Algorithm for Ice and Snow Tourism Competitiveness

This paper researches and analyzes the evaluation of the competitiveness of ice and snow tourism, uses the improved fuzzy neural network algorithm to process the system flow diagram of ice and snow tourism development through the function and characteristics of the power system of ice and snow tourism, and finally selects more than 40 indicators of the three subsystems of resources, economy, and culture. Based on the construction of cloud fuzzy neural network model, the above method is used for experimental comparison analysis, and experiments are conducted through University of California Irvine (UCI) dataset and engineering examples to compare with the traditional cloud model, fuzzy neural network, and BP neural network to analyze the operation efficiency, accuracy rate, and several rules of the algorithm. Through the experimental comparative analysis, the cloud fuzzy neural network can fully take into account the randomness and fuzziness of the data, optimize the generation of cloud rules, avoid multidimensional rule disasters, and ensure the operational efficiency of the algorithm; the accuracy rate of the algorithm is improved relative to that of the traditional technology, and it applies to a variety of datasets. And the software is used to test the ice and snow tourism industry system dynamics model to realize the correctness and robustness testing of the model. After the constructed model can reflect the real situation within the error range, the final policy simulation of the model is carried out.

Ice thickness and volume of the Renland Ice Cap, East Greenland

Abstract To assess the amount of ice volume stored in glaciers or ice caps, a method to estimate ice thickness distribution is required for glaciers where no direct observations are available. In this study, we use an existing inverse method to estimate the bedrock topography and ice thickness of the Renland Ice Cap, East Greenland, using satellite-based observations of the surface topography. The inverse approach involves a procedure in which an ice dynamical model is used to build-up an ice cap in steady state with climate forcing from a regional climate model, and the bedrock is iteratively adjusted until the modelled and observed surface topography match. We validate our model results against information from airborne radar data and satellite observed surface velocity, and we find that the inferred ice thickness and thereby the stored total volume of the ice cap is sensitive to the assumed ice softness and basal slipperiness. The best basal model parameters for the Renland Ice Cap are determined and the best estimated total ice volume of 384 km3 is found. The Renland Ice Cap is particularly interesting because of its location at a high elevation plateau and hence assumed low sensitivity to climate change.

The Framework For Ice Sheet–Ocean Coupling (FISOC) V1.1

Abstract. A number of important questions concern processes at the margins of ice sheets where multiple components of the Earth system, most crucially ice sheets and oceans, interact. Such processes include thermodynamic interaction at the ice–ocean interface, the impact of meltwater on ice shelf cavity circulation, the impact of basal melting of ice shelves on grounded ice dynamics and ocean controls on iceberg calving. These include fundamentally coupled processes in which feedback mechanisms between ice and ocean play an important role. Some of these mechanisms have major implications for humanity, most notably the impact of retreating marine ice sheets on the global sea level. In order to better quantify these mechanisms using computer models, feedbacks need to be incorporated into the modelling system. To achieve this, ocean and ice dynamic models must be coupled, allowing runtime information sharing between components. We have developed a flexible coupling framework based on existing Earth system coupling technologies. The open-source Framework for Ice Sheet–Ocean Coupling (FISOC) provides a modular approach to coupling, facilitating switching between different ice dynamic and ocean components. FISOC allows fully synchronous coupling, in which both ice and ocean run on the same time step, or semi-synchronous coupling in which the ice dynamic model uses a longer time step. Multiple regridding options are available, and there are multiple methods for coupling the sub-ice-shelf cavity geometry. Thermodynamic coupling may also be activated. We present idealized simulations using FISOC with a Stokes flow ice dynamic model coupled to a regional ocean model. We demonstrate the modularity of FISOC by switching between two different regional ocean models and presenting outputs for both. We demonstrate conservation of mass and other verification steps during evolution of an idealized coupled ice–ocean system, both with and without grounding line movement.