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Sea ice dynamics exhibit granular behavior as individual floes and fracture networks become particularly evident at length scales O(10–100) km and smaller. However, climate models do not resolve floes and represent sea ice as a continuum, while existing floe‐scale sea ice models tend to oversimplify floes using discrete elements of predefined simple shapes. The idealized nature of climate and discrete element sea ice models presents a challenge of comparing the model output with floe‐scale sea ice observations. Here we present SubZero, a conceptually new sea ice model geared to explicitly simulate the life cycles of individual floes by using complex discrete elements with time‐evolving shapes. This unique model uses parameterizations of floe‐scale processes, such as collisions, fractures, ridging, and welding, to simulate a wide range of evolving floe shapes and sizes. We demonstrate the novel capabilities of the SubZero model in idealized experiments, including uniaxial compression, the summer‐time sea ice flow through the Nares Strait, and winter‐time sea ice growth. The model naturally reproduces the statistical behavior of the observed sea ice, such as the power‐law appearance of the floe size distribution and the long‐tailed ice thickness distribution. The SubZero model could provide a valuable alternative to existing discrete element and continuous sea ice models for simulations of floe interactions. Plain Language Summary: Sea ice is an inherent part of our climate system that responds rapidly to climate change. It is commonly conceptualized as a collection of many strongly interacting floes (sea ice fragments). However, climate models treat sea ice as a continuum, as resolving the complexity of floe‐scale mechanical and thermodynamical processes is challenging. Here we present a conceptually new sea ice model that can explicitly simulate the life cycle of individual sea ice floes, including collisions, fractures, ridging and rafting, welding, and growth. We demonstrate the novel capabilities of SubZero in idealized experiments, including simulations of summer‐time sea ice flow through a narrow strait and winter‐time sea ice growth. Both experiments were successful in reproducing the statistical behavior of the observed sea ice, specifically the distribution of floe sizes and thicknesses. The unique SubZero capabilities may improve the realism of sea ice modeling. Key Points: A prototype of a conceptually new sea ice model is developed for explicit simulation of floe‐scale dynamicsFloes are modeled as polygons with evolving boundaries subject to parameterized mechanical and thermodynamic processesA set of idealized process studies demonstrated that the new model can mimic the observed floe size and ice thickness distributions [ABSTRACT FROM AUTHOR]

The Southern Patagonian Icefield shows rapid retreat and thinning with variability in magnitude and timing among individual glaciers. To better understand these heterogeneous changes, we estimated the ice thickness distribution within the middle and lower basins of Perito Moreno, Upsala, and Viedma freshwater calving glaciers during the 2017–2018 period. We employed a surface velocity inversion method that incorporates glacier motion through internal deformation and basal slip. Additionally, we applied a directional smoothing filter to estimate surface slope and a calibration process to improve model accuracy. Based on the estimated bed elevation, we introduced an index of relative terminus stability, calculated as the ratio between the height of the ice cliff at the calving front and the water depth at the glacier terminus. Our results show a good performance of model, with a mean RMSE of 77.5 m and correlations >0.89 between observed and modeled ice thickness. Perito Moreno glacier shows ice thickness ranging from 200 to 700 m along its centerline, from the calving front to 15 km upstream. It also displays a stability index four times higher than the other two glaciers, which may explain its relatively stable behavior. In contrast, the Upsala and Viedma glaciers exhibit much thicker ice both at the terminus and higher elevations, with stability indexes close to floating near the calving front. We found that retreat rates of 200 m a−1, coupled with thinning rates of 10 m a−1, can propagate the close to floating conditions of the ice up-glacier. The Upsala and Viedma glaciers have reached these values, which can account for their rapid mass loss. Our results and methodology contribute to the understanding and monitoring of calving glaciers' stability in the region. • Modeling ice thickness is fundamental for expanding data points in Patagonia. • The index of terminus stability, derived from glacier bed topography, enriches our understanding of glacier behavior in the Southern Patagonian Icefield. • Signals of thinning and retreat, linked to flotation processes, can propagate up-glacier, leading to rapid ice mass losses. [ABSTRACT FROM AUTHOR]

Glacial lake formations are currently being observed in the majority of glacierized mountains in the world. Given the ongoing climate change and population increase, studying glacier ice thickness and bed topography is a necessity for understanding the erosive power of glacier activity in the past and lake formation in the future. This study uses the available information to predict potential sites for future lake formation in the Upper Rhône catchment located in the Southwestern Swiss Alps. The study integrates the latest available glacier outlines and high-quality digital elevation models (DEMs) into the Volume and Topography Automation (VOLTA) model to estimate ice thickness within the extent of the glaciers. Unlike the previous ice thickness models, VOLTA calculates ice thickness distribution based on automatically-derived centerlines, while optimizing the model by including the valley side drag parameter in the force equation. In this study, a total ice volume of 37.17 ± 12.26 km3 (1σ) was estimated for the Upper Rhône catchment. The comparison of VOLTA performance indicates a stronger relationship between measured and predicted bedrock, confirming the less variability in VOLTA’s results (r2 ≈ 0.92) than Glacier Bed Topography (GlabTop) (r2 ≈ 0.82). Overall, the mean percentage of ice thickness error for all measured profiles in the Upper Rhône catchment is around ±22%, of which 28 out of 42 glaciers are underestimated. By incorporating the vertical accuracy of free-ice DEM, we could identify 171 overdeepenings. Among them, 100 sites have a high potential for future lake formation based on four morphological criteria. The visual evaluation of deglaciated areas also supports the robustness of the presented methodology, as 11 water bodies were already formed within the predicted overdeepenings. In the wake of changing global climate, such results highlight the importance of combined datasets and parameters for projecting the future glacial landscapes. The timely information on future glacial lake formation can equip planners with essential knowledge, not only for managing water resources and hazards, but also for understanding glacier dynamics, catchment ecology, and landscape evolution of high-mountain regions.

The one-dimensional thermodynamic model adapted to the physiographic conditions of the Kerch Strait was used to study the seasonal evolution of sea ice thickness in the Kerch and Kamysh-Burun bays in the winter of 2007/2008. The dependence of the regional variability of ice thickness on hydrometeorological conditions is analyzed. [ABSTRACT FROM AUTHOR]

The heterogeneity of ocean surface conditions associated with a spatially variable sea ice cover needs to be represented in models in order to represent adequately mixed layer processes and the upper ocean density structure. This study assesses the sensitivity of the ocean-sea ice model NEMO-LIM to a subgrid-scale representation of ice-ocean interactions. The sea ice component includes an ice thickness distribution, which provides heterogeneous surface buoyancy fluxes and stresses. A multi-column ocean scheme is developed to take them explicitly into account, by computing convection and turbulent vertical mixing separately in the open water/lead fraction of grid cells and below each ice thickness category. For the first time in a three-dimensional simulation, the distinct temperature and salinity profiles of the ocean columns are allowed to be maintained over several time steps. It is shown that the model response is highly sensitive to the homogenization time scale between the columns. If the latter are laterally mixed with time scales shorter than 10 h, subgrid-scale effects exist but the mean state is practically unaffected. For longer mixing time scales, in both hemispheres, the main impacts are reductions in under-ice mean mixed layer depths and in the summer melt of sea ice, following decreased oceanic heat flux at the ice base. Large changes in the open water temperature in summer suggest that the scheme could trigger important feedback processes in coupled simulations. [ABSTRACT FROM AUTHOR]

Ice thickness distribution and volume are both key parameters for glaciological and hydrological applications. This study presents VOLTA (Volume and Topography Automation), which is a Python script tool for ArcGIS TM that requires just a digital elevation model (DEM) and glacier outline(s) to model distributed ice thickness, volume and bed topography. Ice thickness is initially estimated at points along an automatically generated centreline network based on the perfect-plasticity rheology assumption, taking into account a valley side drag component of the force balance equation. Distributed ice thickness is subsequently interpolated using a glaciologically correct algorithm. For five glaciers with independent field-measured bed topography, VOLTA modelled volumes were between 26.5% (underestimate) and 16.6% (overestimate) of that derived from field observations. Greatest differences were where an asymmetric valley cross section shape was present or where significant valley infill had occurred. Compared with other methods of modelling ice thickness and volume, key advantages of VOLTA are: a fully automated approach and a user friendly graphical user interface (GUI), GIS consistent geometry, fully automated centreline generation, inclusion of a side drag component in the force balance equation, estimation of glacier basal shear stress for each individual glacier, fully distributed ice thickness output and the ability to process multiple glaciers rapidly. VOLTA is capable of regional scale ice volume assessment, which is a key parameter for exploring glacier response to climate change. VOLTA also permits subtraction of modelled ice thickness from the input surface elevation to produce an ice-free DEM, which is a key input for reconstruction of former glaciers. VOLTA could assist with prediction of future glacier geometry changes and hence in projection of future meltwater fluxes. [ABSTRACT FROM AUTHOR]

The high heterogeneity of sea ice properties implies that its effects on the ocean are spatially variable at horizontal scales as small as a few meters. Previous studies have shown that taking this variability into account in models could be required to simulate adequately mixed layer processes and the upper ocean temperature and salinity structures. Although many advanced sea ice models include a subgrid-scale ice thickness distribution, potentially providing heterogeneous surface boundary conditions, the information is lost in the coupling with a unique ocean grid cell underneath. The present paper provides a thorough examination of boundary conditions at the ocean surface in the NEMO-LIM model, which can be used as a guideline for studies implementing subgrid-scale ocean vertical mixing schemes. Freshwater, salt, solar heat and non-solar heat fluxes are examined, as well as the norm of the surface stress. All of the thermohaline fluxes vary considerably between the open water and ice fractions of grid cells. To a lesser extent, this is also the case for the surface stress. Moreover, the salt fluxes in both hemispheres and the solar heat fluxes in the Arctic show a dependence on the ice thickness category, with more intense fluxes for thinner ice, which promotes further subgrid-scale heterogeneity. Our analysis also points out biases in the simulated open water fraction and in the ice thickness distribution, which should be investigated in more details in order to ensure that the latter is used to the best advantage. [ABSTRACT FROM AUTHOR]

Abstract: A dynamic ice model is presented using a novel approach where the memory of weak directions in the ice cover is stored. The model computes ice motion, ice deformation and the associated dynamic ice production without the need of a full two dimensional computation. The ice dynamics is based on a viscous-plastic approach in a marginal ice zone with both compressive and shear stresses. The method is very computational efficient but is likely restricted to basin scales of semi size with relatively coherent wind forcing over the basin. The model is applied to the Bothnian Bay of the Baltic Sea and coupled with an ocean model. The results show good agreement when compared against measurements of ice velocity from an upward looking ADCP deployed in the center of the Bothnian Bay and observations from ice charts. As a model application, the dynamic ice production that occurs in addition to the pure thermodynamic growth in a deforming ice cover has been computed over the period 1991–2004. The results show that the dynamic ice production typically increases the ice volume with 80% over the simulation period. [Copyright &y& Elsevier]

Abstract: Sea-ice dynamics models play an important role in operational arctic ice forecasting. An essential component of these models is the redistribution of the ice thickness as the ice field undergoes ridging and lead formation resulting from the loads imposed by the wind and water currents. The present paper describes an ice thickness redistribution model that treats such processes. It can be regarded as a development of the Gray and Morland [Gray, J.M.N.T., Morland, L.W., 1994. A two-dimensional model for the dynamics of sea-ice. Philos. Trans. R. Soc. Lond., A 347, 219–290] mixture theory approach that considers two ice components; undeformed level ice, and deformed ridged ice. Equations for the temporal changes in ice thickness and area fraction for both classes of undeformed and ridged ice are formulated for general deformation fields. Sample calculations are performed for various initial conditions of ice thicknesses and area fractions, and for idealized strain rates including pure divergence, pure convergence and simple shear. The subsequent evolutions of ice thickness and area fraction are presented and discussed. Under continued forcing, the model shows that the ridged ice evolves towards a maximum thickness, a behaviour that has been noticed in both field observations and computer simulations of the pressure ridging process. These asymptotic ridged ice thicknesses are used to determine the ridging parameter β that appears in the model and is related to the mass transfer from unridged to ridged ice. [Copyright &y& Elsevier]

Glacial lake formations are currently being observed in the majority of glacierized mountains in the world. Given the ongoing climate change and population increase, studying glacier ice thickness and bed topography is a necessity for understanding the erosive power of glacier activity in the past and lake formation in the future. This study uses the available information to predict potential sites for future lake formation in the Upper Rhône catchment located in the Southwestern Swiss Alps. The study integrates the latest available glacier outlines and high-quality digital elevation models (DEMs) into the Volume and Topography Automation (VOLTA) model to estimate ice thickness within the extent of the glaciers. Unlike the previous ice thickness models, VOLTA calculates ice thickness distribution based on automatically-derived centerlines, while optimizing the model by including the valley side drag parameter in the force equation. In this study, a total ice volume of 37.17 ± 12.26 km3 (1σ) was estimated for the Upper Rhône catchment. The comparison of VOLTA performance indicates a stronger relationship between measured and predicted bedrock, confirming the less variability in VOLTA's results (r2 ≈ 0.92) than Glacier Bed Topography (GlabTop) (r2 ≈ 0.82). Overall, the mean percentage of ice thickness error for all measured profiles in the Upper Rhône catchment is around ±22%, of which 28 out of 42 glaciers are underestimated. By incorporating the vertical accuracy of free-ice DEM, we could identify 171 overdeepenings. Among them, 100 sites have a high potential for future lake formation based on four morphological criteria. The visual evaluation of deglaciated areas also supports the robustness of the presented methodology, as 11 water bodies were already formed within the predicted overdeepenings. In the wake of changing global climate, such results highlight the importance of combined datasets and parameters for projecting the future glacial landscapes. The timely information on future glacial lake formation can equip planners with essential knowledge, not only for managing water resources and hazards, but also for understanding glacier dynamics, catchment ecology, and landscape evolution of high-mountain regions. [ABSTRACT FROM AUTHOR]