Surface Melting Of Ice Research Articles

A hydrophobic electroless copper-nickel fabric with dual drive energy conversion for all-weather anti-icing/icephobic and deicing

Ice can lead to inconvenience and disasters in human activities, making it a widely concern for researchers to find solutions to prevent icing. Hydrophobic materials have been developed for passive anti-icing with a long time, but without active deicing effect. Recently, researchers have explored hydrophobic photothermal materials with passive anti-icing and active deicing ability, which are limited on cloudy days and the night. Consequently, developing materials with anti-icing/icephobic and deicing capabilities for all-weather use has emerged as an innovative strategy. This paper develops hydrophobic PDMS/Cu-Ni@PET with photo/electric thermal properties to support all-weather anti-icing/icephobic and deicing, which is synthesized using copper-nickel and hydrophobic polydimethylsiloxane (PDMS). The PDMS/Cu-Ni@PET exhibits an outstanding anti-icing performance with a delayed icing time of 1224 s at -10 °C, and achieves a surface equilibrium temperature of 68.9 °C under 1 sunlight intensity, enabling the melting of surface ice particles within 614 ± 118 s. When a voltage is applied to both sides of the fabric, the equilibrium temperature can be reached within 60 s, and attained 158 °C at 6 V, enabling the melting of surface ice within 97 s. It provides a novel approach for developing photo/electric thermal superhydrophobic coatings that can maintain all-weather deicing performance.

The Effects of Summer Snowfall on Arctic Sea Ice Radiative Forcing

AbstractSnow is the most reflective natural surface on Earth. Since fresh snow on bare sea ice increases the surface albedo, the impact of summer snow accumulation can have a negative radiative forcing effect, which would inhibit sea ice surface melt and potentially slow sea‐ice loss. However, it is not well known how often, where, and when summer snowfall events occur on Arctic sea ice. In this study, we used in situ and model snow depth data paired with surface albedo and atmospheric conditions from satellite retrievals to characterize summer snow accumulation on Arctic sea ice from 2003 to 2017. We found that, across the Arctic, ∼2 snow accumulation events occurred on initially snow‐free conditions each year. The average snow depth and albedo increases were ∼2 cm and 0.08, respectively. 16.5% of the snow accumulation events were optically thick (>3 cm deep) and lasted 2.9 days longer than the average snow accumulation event (3.4 days). Based on a simple, multiple scattering radiative transfer model, we estimated a −0.086 ± 0.020 W m−2 change in the annual average top‐of‐the‐atmosphere radiative forcing for summer snowfall events in 2003–2017. The following work provides new information on the frequency, distribution, and duration of observed snow accumulation events over Arctic sea ice in summer. Such results may be particularly useful in understanding the impacts of ephemeral summer weather on surface albedo and their propagating effects on the radiative forcing over Arctic sea ice, as well as assessing climate model simulations of summer atmosphere‐ice processes.

On the effects of the timing of an intense cyclone on summertime sea-ice evolution in the Arctic

Abstract This study investigates the impacts of the timing of an extreme cyclone that occurred in August 2012 on the sea-ice volume evolution based on the Arctic Ice Ocean Prediction System (ArcIOPS). By applying a novel cyclone removal algorithm to the atmospheric forcing during 4–12 August 2012, we superimpose the derived cyclone component onto the atmospheric forcing one month later or earlier. This study finds that although the extreme cyclone leads to strong sea-ice volume loss in all runs, large divergence occurs in sea-ice melting mechanism in response to various timing of the cyclone. The extreme cyclone occurred in August, when enhanced ice volume loss is attributed to ice bottom melt primarily and ice surface melt secondarily. If the cyclone occurs one month earlier, ice surface melt dominates ice volume loss, and earlier appearance of open water within the ice zone initiates positive ice-albedo feedback, leading to a long lasting of the cyclone-induced impacts for approximately one month, and eventually a lower September ice volume. In contrast, if the cyclone occurs one month later, ice bottom melt entirely dominates ice volume loss, and the air-open water heat flux in the ice zone tends to offset ice volume loss.

Present‐Day Regional Antarctic Sea Ice Response to Extratropical Cyclones

AbstractBoth atmospheric warming and poleward moisture transport increase the likelihood of sea ice surface melt. In the Southern Hemisphere, short‐lived extratropical cyclones (ETCs) are responsible for a bulk of total heat and moisture transport toward high latitudes. Although these storms form ubiquitously in the midlatitudes, moisture availability and temperature characteristics vary by source region. In this study, we assess atmospheric, oceanic, and sea ice concentration (SIC) anomalies associated with austral winter ETCs over different Antarctic regions using ERA5 reanalysis data. Between 1990 and 2019, we find a total of 514 ETCs, with greater storm frequency in the eastern hemisphere groups. Compared to the climatology, sea ice melts (grows) behind the warm (cold) front of each system and is negatively correlated with atmospheric poleward moisture transport, temperature, meridional winds, and sea surface temperature for all ETCs. We find that Bellingshausen storms move moisture and warm air furthest poleward over their lifespan. However, East Weddell and East Antarctic ETCs are responsible for greater absolute poleward moisture transport than Bellingshausen and Ross systems. More intense ETCs correspond to greater SIC through Day 1, suggesting that SIC impacts ETC strength, regardless of ETC region. From cyclogenesis to cyclolysis, sea ice extent declines underneath composite ETCs, trends are generally not significant. Overall, while sea ice response produced by ETC‐induced atmospheric and oceanic changes varies regionally, the long‐term impacts of ETCs on regional sea ice are negligible over the study period.

Observing the evolution of summer melt on multiyear sea ice with ICESat-2 and Sentinel-2

Abstract. We investigate sea ice conditions during the 2020 melt season, when warm air temperature anomalies in spring led to early melt onset, an extended melt season, and the second-lowest September minimum Arctic ice extent observed. We focus on the region of the most persistent ice cover and examine melt pond depth retrieved from Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) using two distinct algorithms in concert with a time series of melt pond fraction and ice concentration derived from Sentinel-2 imagery to obtain insights about the melting ice surface in three dimensions. We find the melt pond fraction derived from Sentinel-2 in the study region increased rapidly in June, with the mean melt pond fraction peaking at 16 % ± 6 % on 24 June 2020, followed by a slow decrease to 8 % ± 6 % by 3 July, and remained below 10 % for the remainder of the season through 15 September. Sea ice concentration was consistently high (>95 %) at the beginning of the melt season until 4 July, and as floes disintegrated, it decreased to a minimum of 70 % on 30 July and then became more variable, ranging from 75 % to 90 % for the remainder of the melt season. Pond depth increased steadily from a median depth of 0.40 m ± 0.17 m in early June and peaked at 0.97 m ± 0.51 m on 16 July, even as melt pond fraction had already started to decrease. Our results demonstrate that by combining high-resolution passive and active remote sensing we now have the ability to track evolving melt conditions and observe changes in the sea ice cover throughout the summer season.

Modelling the development and decay of cryoconite holes in northwestern Greenland

Abstract. Cryoconite holes (CHs) are water-filled cylindrical holes with cryoconite (dark-coloured sediment) deposited at their bottoms, forming on ablating ice surfaces of glaciers and ice sheets worldwide. Because the collapse of CHs may disperse cryoconite on the ice surface, thereby decreasing the ice surface albedo, accurate simulation of the temporal changes in CH depth is essential for understanding ice surface melt. We established a novel model that simulates the temporal changes in CH depth using heat budgets calculated independently at the ice surface and CH bottom based on hole-shaped geometry. We evaluated the model with in situ observations of the CH depths on the Qaanaaq ice cap in northwestern Greenland during the 2012, 2014, and 2017 melt seasons. The model reproduced the observed depth changes and timing of CH collapse well. Although earlier models have shown that CH depth tends to be deeper when downward shortwave radiation is intense, our sensitivity tests suggest that deeper CH tends to form when the diffuse component of downward shortwave radiation is dominant, whereas CHs tend to be shallower when the direct component is dominant. In addition, the total heat flux to the CH bottom is dominated by shortwave radiation transmitted through ice rather than that directly from the CH mouths when the CH is deeper than 0.01 m. Because the shortwave radiation transmitted through ice can reach the CH bottom regardless of CH diameter, CH depth is unlikely to be correlated with CH diameter. The relationship is consistent with previous observational studies. Furthermore, the simulations highlighted that the difference in albedo between ice surface and CH bottom was a key factor for reproducing the timing of CH collapse. It implies that lower ice surface albedo could induce CH collapse and thus cause further lowering of the albedo. Heat component analysis suggests that CH depth is governed by the balance between the intensity of the diffuse component of downward shortwave radiation and the turbulent heat transfer. Therefore, these meteorological conditions may be important factors contributing to the recent surface darkening of the Greenland ice sheet and other glaciers via the redistribution of CHs.

Experimental study of ice melting of concrete permeable brick sidewalks using embedded carbon fibre heating wire

Electric heating methods have been proven to be effective means to melt ice on sidewalks and bridge decks. However, sidewalks are covered with permeable concrete bricks separated by gaps, which differ from surfaces of roads and bridge decks. Therefore, it is necessary to study methods of melting ice on sidewalks. In this paper, a method for melting ice on sidewalks based on carbon fibre heating wire (CFHW) is proposed. The experiments compare the effects of various environment temperatures, wind speeds, and energising voltages and spacings of CFHW on the surface temperature and melting of ice on sidewalk specimens. The transfer law of heat energy produced by CFHW inside the specimen and the effect of sealing concrete brick holes with a thermal conductive silicone grease in ice melting sidewalks are analysed. The results show that the proposed method has good ice melting performance on sidewalks.

Patterns and drivers of glacier debris-cover development in the Afghanistan Hindu Kush Himalaya

AbstractDebris-covered ice is widespread in mountain regions with debris an important control on surface ice melt and glacier retreat. Quantifying debris cover extent and its evolution through time over large regions remains a challenge. This study develops two Normalized Difference Supraglacial Debris Indices for mapping debris-covered ice based on thermal and near Infrared Landsat 8 bands. They were calibrated with field data. Validation suggests that they have a high level of accuracy. They are then applied to Landsat data for 2016 to produce the first detailed glacier inventory of the Afghanistan Hindu Kush Himalaya that includes debris cover. 3408 glaciers were identified which, for those ⩾0.01 km2 in area, gives an ice cover of 2,222 ± 11 km2 and a debris cover of 619 ± 40 km2. Principal components analysis was used to identify the most influential drivers of debris-covered ice extent. Lower proportions of debris cover were associated with glaciers with a higher elevation range, that were larger, longer and wider. These relations were statistically clearer when the dataset was broken down into climate and geological zones. A glaciers continue to shrink, the proportion of debris cover will become higher, making it more important to map debris cover reliably.

Asymmetric distribution of Pan-Antarctic snowmelt under changing Climate: In perspective of natural climatic events and marine biology

Understanding global climatic changes resulting from global warming and their impact on polar snowmelt and ocean biogeochemistry requires an assessment of the spatio-temporal variability of surface ice melt over the Antarctica region. Even though various studies have been carried out on the ice melts in the Antarctica region, there is a lack of studies related to biophysical (temperature and chlorophyll-a) parameters and El Niño-Southern Oscillation (ENSO) influences in the Antarctica region. To address this problem, the present study assessed the ice melt and its impact on the Antarctica region from 2002 to 2021 using satellite-derived products of sea surface temperature (SST), chlorophyll-a (Chl), and snowmelt. After analyzing the data, it shows that larger ice shelves like Larsen, George VI, Brunt, Riiser-Larsen on the western side and Shackleton, West, and Totten on the eastern side are showing higher snowmelt than usual in a strong La Niña year (2010–2011) (ENSO index greater than −1.5 for austral summer months), while other ice shelves are showing a reduction in snowmelt. The Abbott ice shelf and parts of the Larsen and Ross ice shelves on the western side experienced higher snowmelt during a strong El Niño year (2015–2016) (ENSO index greater than + 1.5 for austral summer months). In contrast, inner land areas adjacent to the ice shelves experienced higher than usual snowmelt. Also, results revealed a significant increase in Chl from the open ocean towards the Antarctica continental shelf, where SST values are decreasing towards the shelf.Moreover, the present study provides critical information on the effect of ENSO on snowmelt and the impact of snowmelt on Chl and SST under changing climate conditions.

Thermodynamical and Dynamical Impacts of an Intense Cyclone on Arctic Sea Ice

AbstractThis study investigates the thermodynamical and dynamical influences of the intense cyclone in the Arctic Ocean in August 2012 on the synoptic‐scale sea ice evolution, using the Arctic Ice Ocean Prediction System (ArcIOPS). As it is hard to fully isolate sea ice loss owing to extreme cyclone from that owing to background atmospheric state in most previous studies on this topic, this study introduces a newly developed algorithm to remove the cyclone component in atmospheric forcing, and conducts sea ice and heat budget analyses in two simulations driven by atmospheric forcing with and without the cyclone. Strong impact of the intense cyclone on sea ice locates on the east side of the cyclone's path, that is, Pacific Arctic for this case. The cyclone affects sea ice in two ways. First, cyclone‐induced enhancement in ice‐ocean interaction leads to increased sea ice basal melt in the Pacific Arctic and part of the Atlantic Arctic, which induces strong sea ice area and volume loss when the cyclone's intensity peaks. Second, as the cyclone strengthens, the increases in air temperature, humidity and wind speed accelerate turbulent heat exchange at the air‐ocean and air‐ice interfaces, leading to enhanced local sea ice surface melt in the Chukchi Sea and northern Beaufort Sea. The cyclone‐induced strong winds stir sea ice leading to enhanced gradients in sea ice velocity field and thus increased sea ice deformation, which further induces strong sea ice area loss. This study also demonstrates a precise atmospheric forcing field is essential for sea ice modeling.

Foehn Winds at Pine Island Glacier and their role in Ice Shelf Sublimation and Surface Melt

Foehn Winds at Pine Island Glacier and their role in Ice Shelf Sublimation and Surface Melt

Foehn winds at Pine Island Glacier and their role in ice shelf sublimation and surface melt

Foehn winds at Pine Island Glacier and their role in ice shelf sublimation and surface melt

Solid Earth Uplift Due To Contemporary Ice Melt Above Low‐Viscosity Regions of the Upper Mantle

AbstractGlacial isostatic adjustment explains topographic change in formerly and currently glaciated regions, but the role of small (∼100s km) regions of unusually low‐viscosity mantle is poorly understood. We developed viscoelastic models with low‐viscosity regions in the upper mantle, and measured the effect of these regions on solid earth uplift resulting from contemporary surface ice melt. We found viscous uplift occurring on decadal timescales above the low‐viscosity region, at rates comparable to or larger than those from elastic uplift or the viscous response to ice age melting. We find that uplift rates are sensitive to the location, dimensions, and viscosity of the low‐viscosity region, and that the largest uncertainty in uplift rates likely comes from the low‐viscosity region's horizontal extent. Rapid viscous ground uplift can impact ice dynamics if the low‐viscosity region is located close to an ice sheet margin, as for Antarctica and Greenland.

Seasonality of Glacial Snow and Ice Microbial Communities.

Blooms of microalgae on glaciers and ice sheets are amplifying surface ice melting rates, which are already affected by climate change. Most studies on glacial microorganisms (including snow and glacier ice algae) have so far focused on the spring and summer melt season, leading to a temporal bias, and a knowledge gap in our understanding of the variations in microbial diversity, productivity, and physiology on glacier surfaces year-round. Here, we investigated the microbial communities from Icelandic glacier surface snow and bare ice habitats, with sampling spanning two consecutive years and carried out in both winter and two summer seasons. We evaluated the seasonal differences in microbial community composition using Illumina sequencing of the 16S rRNA, 18S rRNA, and ITS marker genes and correlating them with geochemical signals in the snow and ice. During summer, Chloromonas, Chlainomonas, Raphidonema, and Hydrurus dominated surface snow algal communities, while Ancylonema and Mesotaenium dominated the surface bare ice habitats. In winter, algae could not be detected, and the community composition was dominated by bacteria and fungi. The dominant bacterial taxa found in both winter and summer samples were Bacteriodetes, Actinobacteria, Alphaproteobacteria, and Gammaproteobacteria. The winter bacterial communities showed high similarities to airborne and fresh snow bacteria reported in other studies. This points toward the importance of dry and wet deposition as a wintertime source of microorganisms to the glacier surface. Winter samples were also richer in nutrients than summer samples, except for dissolved organic carbon—which was highest in summer snow and ice samples with blooming microalgae, suggesting that nutrients are accumulated during winter but primarily used by the microbial communities in the summer. Overall, our study shows that glacial snow and ice microbial communities are highly variable on a seasonal basis.

Influence of Supraglacial Debris Thickness on Thermal Resistance of the Glaciers of Chandra Basin, Western Himalaya

A large number of glaciers in the Hindu-Kush Himalaya are covered with debris in the lower part of the ablation zone, which is continuously expanding due to enhanced glacier mass loss. The supraglacial debris transported over the melting glacier surface acts as an insulating barrier between the ice and atmospheric conditions and has a strong influence on the spatial distribution of surface ice melt. We conducted in-situ field measurements of point-wise ablation rate, supraglacial debris thickness, and debris temperature to examine the thermal resistivity of the debris pack and its influence on ablation over three glaciers (Bara Shigri, Batal, and Kunzam) in Chandra Basin of Western Himalaya during 2016–2017. Satellite-based supraglacial debris cover assessment shows an overall debris covered area of 15% for Chandra basin. The field data revealed that the debris thickness varied between 0.5 and 326 cm, following a spatially distributed pattern in the Chandra basin. The studied glaciers have up to 90% debris cover within the ablation area, and together represent ∼33.5% of the total debris-covered area in the basin. The supraglacial debris surface temperature and near-surface air temperature shows a significant correlation (r = > 0.88, p = < 0.05), which reflects the effective control of energy balance over the debris surface. The thermal resistivity measurements revealed low resistance (0.009 ± 0.01 m2°C W−1) under thin debris pack and high resistance (0.55 ± 0.09 m2°C W−1) under thick debris. Our study revealed that the increased thickness of supraglacial debris significantly retards the glacier ablation due to its high thermal resistivity.

Response of supraglacial rivers and lakes to ice flow and surface melt on the northeast Greenland ice sheet during the 2017 melt season

Fast ice flow and substantial surface runoff form distinct and extensive supraglacial rivers and lakes on the northeast Greenland Ice Sheet (GrIS). These supraglacial rivers and lakes play an important role in controlling surface meltwater routing and storage. However, the hydromorphology of these complex supraglacial features remains poorly quantified. In this study, we mapped the multi-temporal supraglacial rivers and lakes on the northeast GrIS (area ~ 3 × 104 km2) using sixty-five 10 m Sentinel-2 multispectral satellite images acquired during the 2017 summer, and quantified their primary hydromorphology, including meltwater area fraction, meltwater volume, supraglacial river length, river sinuosity, river depth, supraglacial lake area, lake shape, and lake depth. The quantified hydromorphology was compared with variable ice flow regimes and regional climate model (RCM) runoff. The results indicate that widespread supraglacial rivers and lakes maximally cover 5.3% of the northeast GrIS, which is more than double the previous estimates and only slightly lower than that for the strongly melting southwest GrIS (~7.0%). As the surface runoff increases and the snowline retreats, supraglacial rivers and lakes migrate from the ice sheet margin (~400 m) to high elevations (~1400 m). The satellite-mapped surface meltwater area fraction for the entire study area is positively correlated with the RCM surface runoff before the timing of peak melt (August 1), but decreases relatively slowly (by 32–45%) compared to the rapidly decreasing runoff (by 84–96%) in August. Large elevational variations were found for the peak magnitude and timing of the meltwater extent and volume. High (800–1400 m) elevation bands achieve peak values over two weeks later than low (400–800 m) elevation bands, and the 800–1000 m elevation band yields maximum peak values due to the wide distribution of supraglacial rivers. Furthermore, the supraglacial drainage patterns vary with different ice flow regimes. There are long rivers and few lakes in areas where ice deformation controls the ice flow velocity while there are short rivers and large, narrow lakes in areas where basal sliding is a major component of the ice flow. Meanwhile, long, sinuous rivers and small lakes form on the floating ice. In general, this study conducts a preliminary investigation of supraglacial rivers and lakes on the poorly-studied northeast GrIS and reveals that surface melt and ice flow control the hydromorphology of supraglacial rivers and lakes.

Modeling turbulent heat fluxes over Arctic sea ice using a maximum-entropy-production approach

Recently, an algorithm of surface turbulent heat fluxes over snow/sea ice has been developed based on the theory of maximum entropy production (MEP), which is fundamentally different from the bulk flux algorithm (BF) that has been used in sea ice models for a few decades. In this study, we first assess how well the MEP algorithm captures the observed variations of turbulent heat fluxes over Arctic sea ice. It is found that the calculated heat fluxes by the MEP method are in good agreement with in-situ observations after considering the absorption of incoming radiation in a snow/ice surface layer with infinitesimal depth. We then investigate the effects of two different schemes (MEP vs. BF) in the sea ice model of CICE6 on simulated turbulent heat fluxes and sea ice processes in the Arctic Basin. Our results show that the two different schemes give quite different representations of seasonal variations of heat fluxes, particularly for sensible heat fluxes in summer. The heat fluxes simulated by the MEP produce weak cooling effect on the ice surface in summer, whereas the BF generates a warming effect. As a result, compared to the BF, the MEP leads to a reduced seasonal cycle of Arctic sea ice mass flux by modulating snow-to-ice conversion, basal ice growth, surface ice melt and basal ice melt.

Quantifying Mobility Scooter Performance in Winter Environments

ObjectivesTo quantify mobility scooter performance when traversing snow, ice, and concrete in cold temperatures and to explore possible performance improvements with scooter winter tires. DesignCross-sectional. SettingHospital-based research institute. ParticipantsTwo drivers (50 and 100 kg) tested 8 scooter models (N=8). Two mobility scooters were used for winter tire testing. InterventionsScooters were tested on 3 different conditions in a random sequence (concrete, 2.5-cm depth snow, bare ice). Ramp ascent and descent, as well as right-angle cornering up to a maximum of 10° slopes on winter conditions, were observed. Winter tire testing used the same slopes with 2 scooters on bare and melting ice surfaces. Main Outcome MeasuresMaximum achievable angle (MAA) and tire traction loss for ramp ascent and descent performance. The ability to steer around a corner on the ramp. ResultsAll scooters underperformed in winter conditions, specifically when traversing snow- and ice-covered slopes (χ2 [2, N=8]=13.87-15.55, P<.001) and corners (χ2 [2, N=8]=12.25, P<.01). Half of the scooters we tested were unable to climb a 1:12 grade (4.8°) snow-covered slope without losing traction. All but 1 failed to ascend an ice-covered 1:12 grade (4.8°) slope. Performance was even more unsatisfactory for the forward downslopes on both snow and ice. Winter tires enhanced the MAA, permitting 1:12 (4.8°) slope ascent on ice. ConclusionsMobility scooters need to be designed with winter months in mind. Our findings showed that Americans with Disabilities Act–compliant built environments, such as curb ramps that conform to a 1:12 (4.8°) slope, become treacherous or impassible to mobility scooter users when covered in ice or snow. Scooter manufacturers should consider providing winter tires as optional accessories in regions that experience ice and snow accumulation. Additional testing/standards need to be established to evaluate winter mobility scooter performance further.

Retrieval of Summer Sea Ice Concentration in the Pacific Arctic Ocean from AMSR2 Observations and Numerical Weather Data Using Random Forest Regression

The Arctic sea ice concentration (SIC) in summer is a key indicator of global climate change and important information for the development of a more economically valuable Northern Sea Route. Passive microwave (PM) sensors have provided information on the SIC since the 1970s by observing the brightness temperature (TB) of sea ice and open water. However, the SIC in the Arctic estimated by operational algorithms for PM observations is very inaccurate in summer because the TB values of sea ice and open water become similar due to atmospheric effects. In this study, we developed a summer SIC retrieval model for the Pacific Arctic Ocean using Advanced Microwave Scanning Radiometer 2 (AMSR2) observations and European Reanalysis Agency-5 (ERA-5) reanalysis fields based on Random Forest (RF) regression. SIC values computed from the ice/water maps generated from the Korean Multi-purpose Satellite-5 synthetic aperture radar images from July to September in 2015–2017 were used as a reference dataset. A total of 24 features including the TB values of AMSR2 channels, the ratios of TB values (the polarization ratio and the spectral gradient ratio (GR)), total columnar water vapor (TCWV), wind speed, air temperature at 2 m and 925 hPa, and the 30-day average of the air temperatures from the ERA-5 were used as the input variables for the RF model. The RF model showed greatly superior performance in retrieving summer SIC values in the Pacific Arctic Ocean to the Bootstrap (BT) and Arctic Radiation and Turbulence Interaction STudy (ARTIST) Sea Ice (ASI) algorithms under various atmospheric conditions. The root mean square error (RMSE) of the RF SIC values was 7.89% compared to the reference SIC values. The BT and ASI SIC values had three times greater values of RMSE (20.19% and 21.39%, respectively) than the RF SIC values. The air temperatures at 2 m and 925 hPa and their 30-day averages, which indicate the ice surface melting conditions, as well as the GR using the vertically polarized channels at 23 GHz and 18 GHz (GR(23V18V)), TCWV, and GR(36V18V), which accounts for atmospheric water content, were identified as the variables that contributed greatly to the RF model. These important variables allowed the RF model to retrieve unbiased and accurate SIC values by taking into account the changes in TB values of sea ice and open water caused by atmospheric effects.

Collapse of the Last Eurasian Ice Sheet in the North Sea Modulated by Combined Processes of Ice Flow, Surface Melt, and Marine Ice Sheet Instabilities

AbstractThe record of the confluence and collapse of the British‐Irish Ice Sheet and the Fennoscandian Ice Sheet is obscured by the North Sea, hindering reconstructions of the glacial dynamics of this sector of the Eurasian Ice Sheet complex during the last glacial cycle. Previous numerical simulations of the deglaciation of the North Sea have also struggled to capture the confluence and separation of the British‐Irish and Fennoscandian Ice Sheets. We ran an ensemble of 70 experiments simulating the deglaciation of the North Sea between 23 and 18 ka BP using the BISICLES ice sheet model. A novel suite of quantitative model‐data comparison tools was used to identify plausible simulations of deglaciation that match empirical data for ice flow, margin position, and retreat ages, allowing comparisons to large amounts of empirical data. In ensemble members that best match the empirical data, the North Sea deglaciates through the collapse of the marine‐based Norwegian Channel Ice Stream, unzipping the confluence between the British‐Irish Ice Sheet and the Fennoscandian Ice Sheet. Thinning of the Norwegian Channel Ice Stream causes surface temperature feedbacks, rapid grounding line retreat, and ice stream acceleration, further driving separation of the British‐Irish and the Fennoscandian Ice Sheets. These simulations of the North Sea deglaciation conform with the majority of empirical evidence, and therefore provide physically plausible insights that are consistent with reconstructions based on the empirical evidence, and permit a quantitative comparison between model and data.