Ice Temperature Profiles Research Articles

Microwave Observations of Ganymede's Sub‐surface Ice: 2. Reflected Radiation

AbstractJuno's microwave radiometer experiment (MWR) provided the first spatially resolved observations beneath the surface of Ganymede's ice shell. The results indicate that scattering is a significant component of the observed brightness temperature, which is a combination of the upwelling ice emission and reflected emission from the sky and from Jupiter's synchrotron emission (Brown et al., 2023). Retrieval of the sub‐surface ice temperature profile requires that these confounding signals are estimated and removed to isolate the thermal signature of the ice. We present data analysis and model results to estimate the reflected synchrotron emission component. Our results indicate reflected emission over a broad range of observed angles, due to surface roughness and internal scattering. Based on viewing geometry, direct specular reflection from a smooth surface at a narrow angle is not observed. A microwave‐reflective medium is indicated, that is, a very rough surface and/or non‐homogeneous subsurface.

Development of ANN-Based Algorithm to Estimate Wintertime Sea Ice Temperature Profile Over the Arctic Ocean

Development of ANN-Based Algorithm to Estimate Wintertime Sea Ice Temperature Profile Over the Arctic Ocean

The internal melting of landfast sea ice in Prydz Bay, East Antarctica

Summertime internal melting of Antarctic sea ice is common due to the penetration of solar radiation below the snow and ice surface. We focus on the role of internal melting and heat conduction in generating gap layers within the ice. These often occur approximately 0.1 m below the ice surface. In a small-scale survey over land-fast sea ice in Prydz Bay, East Antarctica, we observed, for the first time, gap layers 0.6–1.0 m below the surface for both first-year ice and multi-year ice. A 1D snow/ice thermodynamic model successfully simulated snow and ice mass balance and the evolution of the gap layers. Their spatial distribution was largely controlled by snow thickness and ice thickness. A C-shaped ice temperature profile with the lowest values in the middle of the ice layer resulted in heat flux convergence causing downward progression of the internal melt layer. Multidecadal (1979–2019) seasonal simulations showed decreasing air temperature favored a postposed internal melting onset, reduced total internal melt, and delayed potential ice breakup, which indicated a higher chance for local coastal ice to be shifted from first-year ice to multi-year ice.

Modeling a class of thermal ice probes for accessing the solar system’s ocean worlds

The subsurface oceans of icy moons in the outer solar system are prime candidates for harboring extra-terrestrial life. Missions to melt through the ice shells of these worlds utilizing an ice probe or “cryobot” to access the oceans have been proposed. To design such a cryobot for a successful mission, the relationship between a cryobot’s heat budget and descent speed within any given environment must be understood. Large uncertainties in the ice shell thickness and temperature profile require that the problem be treated via probabilistic techniques, such as a Monte Carlo simulation. By contrast, the speed of a cryobot descending through ice with specified far-field temperature and material properties can, in principle, be quantified with little uncertainty. A model of cryobot performance that can be computed quickly and accurately will save significant computational time for the broader simulation, and allow for the mission’s basic thermal needs to be understood. The work reported here builds upon an existing analytic thermal model of ice probes that, while suitable for terrestrial conditions, begins to incur potentially problematic errors in extraterrestrial environments. The new model provides improvement to the previous model for flight-relevant probes in extra-terrestrial ice conditions, predicting the total heat budget to within 1.2% of high-fidelity numerical simulations while requiring a small fraction of the computational time. The model can be non-dimensionalized in a compact form, making it suitable for modeling a broad class of cylindrical ice probes in a probabilistic modeling framework for determining the time required to access the sub-surface ocean. Such models can then provide the high-level requirements for cryobot system architectures that will enable successful ocean-access missions.

Observation and modelling of snow and sea ice mass balance and its sensitivity to atmospheric forcing during spring and summer 2007 in the Central

Snow depth and sea ice thickness were observed applying an ice mass balance buoy (IMB) in the drifting ice station Tara during the International Polar Year in 2007. Detailed in situ observations on meteorological variables and surface fluxes were taken during May to August. For this study, the operational analyses and short-term forecasts from two numerical weather prediction (NWP) models (ECMWF and HIRLAM) were extracted for the Tara drift trajectory. We compared the IMB, meteorological and surface flux observations against the NWP products, also applying a one-dimensional thermodynamic sea ice model (HIGHTSI) to calculate the snow and ice mass balance and its sensitivity to atmospheric forcing. The modelled snow depth time series, controlled by NWP-based precipitation, was in line with the observed one. HIGHTSI reproduced well the snowmelt onset, the progress of the melt, and the first date of snow-free conditions. HIGHTSI performed well also in the late August freezing season. Challenges remain to model the “false bottom” observed during the melting season. The evolution of the vertical temperature profiles in snow and ice was better simulated when the model was forced by in situ observations instead of NWP results. During the melting period, the nonlinear ice temperature profile was successfully modelled with both forcing options. During spring and the melting season, total sea ice mass balance was most sensitive to uncertainties in NWP results for the downward longwave radiation, followed by the downward shortwave radiation, air temperature, and wind speed. Citation : Cheng B, Vihma T, Palo T, et al. Observation and modelling of snow and sea ice mass balance and its sensitivity to atmospheric forcing during spring and summer 2007 in the Central Arctic. Adv Polar Sci, 2021, 32(4): 309-323, doi: 10.13679/j.advps.2021.0047

Arctic sea ice state estimation from thermodynamic PDE model

Recent rapid loss of the Arctic sea ice motivates the study of the Arctic sea ice thickness. Global climate model that describes the ice thickness evolution requires an accurate spatial temperature profile of the Arctic sea ice. However, measuring the complete temperature profile is not feasible within and throughout the Arctic icecap. Instead, measuring the ice thickness is doable with the acquisition of data from submarine and satellite devices. In this paper, we develop a backstepping observer algorithm to estimate the temperature profile for the Arctic sea ice model via available measurements of sea ice thickness and sea ice surface temperature. The observer is designed in a rigorous manner to drive the temperature profile estimation error to zero, for a salinity-free sea ice model. Moreover, the proposed observer is used to estimate the temperature profile of the original sea ice model with salinity via numerical simulation. The simulation results illustrate that our observer design achieves a successful estimation of the sea ice temperature profile in three days, which is ten times faster than the straightforward open-loop algorithm.

Empirical prediction of snow and land-fast sea ice temperature from surface meteorology on Pistolet Bay, Northern Newfoundland

Abstract The temperature of sea ice and snow cover on the ice surface is a critical component of thermodynamic models of sea ice. Ice temperature is also an important factor in the sea ice strength and therefore in the potential loads the ice can exert on ships, ports, bridges, and offshore structures. The snow layer, while remaining distinct from the sea ice in its physical properties, can become compacted on the ice and contribute to the effective ice thickness and strength. The temperature of sea ice is governed by the atmospheric energy flux balance at the snow surface and the ocean energy flux at the ice base. In addition, snow cover acts as an insulator to sea ice, buffering it against temperature changes due to changes in surface meteorological conditions. The average internal ice temperature and total thickness (through its impact on ice salinity and brine volume) significantly affect ice strength parameters used in the calculation of loads on engineered structures. In February 2017–2019, three field campaigns were carried out on the land-fast ice on Pistolet Bay, north of St. Anthony, Newfoundland in Atlantic Canada. For approximately five days in 2017 and about four days in 2018–2019, surface air temperatures, wind speeds, and snow and ice temperature profiles were continuously measured. Dew point temperatures were obtained from the North American Regional Reanalysis (NARR) dataset. The datasets from the three field campaigns were used to develop empirical linear regression models of snow and ice surface and depth-mean temperatures as a function of the air temperature alone, and of the air and dew point temperatures and wind speed. In this paper, the meteorological data from the three field campaigns are presented, along with the snow and ice thickness and temperature data. The linear models of snow and ice temperature are presented, tested using the observed field data from the Pistolet Bay campaigns, and compared with results obtained from previously published models of snow and sea ice temperature. The results show that the models of snow and ice temperature as a function of the three meteorological variables are modestly more robust than the models as a function of air temperature alone, with R2 values of up to 0.90. The models presented in this paper have potential usefulness in improved prediction of site-specific snow/ice temperatures and associated temperature-dependent ice properties, such as strength at sites where gridded weather data or in-situ meteorological measurements are available, but in-situ snow/ice temperature measurements are nonexistent.

Simulation of Remote Sensing of Clouds and Humidity From Space Using a Combined Platform of Radar and Multifrequency Microwave Radiometers

AbstractThis study presents a simulated simultaneous retrieval of mass mean cloud ice particle effective diameter, ice water content, water vapor, and temperature profiles using a combination of a 94‐GHz cloud radar and multifrequency (118, 183, 240, 310, 380, 664, and 850 GHz) millimeter‐ and submillimeter‐wave radiometers from a space platform. The retrieval capabilities and uncertainties of the combined radar and microwave radiometers are quantified. We show that this combined active and passive remote sensing approach with SmallSat technologies addresses a gap in the current state‐of‐the‐art remote sensing measurements of ice cloud properties, especially deriving vertical profiles of ice cloud particle sizes in the atmosphere together with the ambient thermodynamic conditions. Therefore, this new approach can serve as a plausible candidate for future missions that target cloud and precipitation processes to improve weather forecasts and climate predictions.

Discrimination Algorithm and Procedure of Snow Depth and Sea Ice Thickness Determination Using Measurements of the Vertical Ice Temperature Profile by the Ice-tethered Buoys.

Snow depth and sea ice thickness in the Polar Regions are significant indicators of climate change and have been measured over several decades by ice-tethered buoys. However, sea ice temperature profiles measured by ice-tethered buoys are rarely used to infer snow depth and sea ice thickness owing to the lack of automatic discrimination algorithms, restricting the use of the data for sea ice thermodynamics studies. In this study, snow depth and sea ice thickness were retrieved through the measurements of sea ice temperature profiles using discrimination algorithms of the change point and the maximum likelihood detection methods. The data measured by 50 ice-tethered buoys were used to evaluate the accuracy of the results determined by the algorithm. Influences on the seasonal sea ice thermodynamic state, vertical interval of temperature sensors on the buoys, and initial ice thickness on the estimation errors were also evaluated. The performance of the discrimination algorithm for the data from the Arctic and Antarctic regions was also compared. There were no identifiable differences between the estimation errors from the Arctic and Antarctica. Increases in both the interval of the temperature sensors and the initial ice thickness enlarged the error for the estimation of ice thickness. A procedure developed in this study strengthens the potential application of measurements from the ice-tethered buoys only with the measurements of the vertical temperature profile of the layer of snow-covered ice, but not the measurements of ice basal and surface positions using acoustic sounding.

Analysing some martian atmospheric characteristics associated with a dust storm over the Lunae Planum region during October 2014

This study analyses the vertical aerosol distribution and associated atmospheric characteristics during a dust storm event in early Martian southern summer. The analysis is based on the observations of the Mars Colour Camera (MCC) onboard the Indian Mars Orbiter Mission during October 11 and October 20, 2014. A local-scale dust storm is found within the north-eastern portion of the Lunae Planum region on October 11, 2014, which is observed to be relatively larger during October 20. The dust storm disappeared in the next image taken over the same region during October 28, 2014, leaving a thick haze over Lunae Planum and the Valles Marineris region. It is observed from the Mars Daily Global Maps of the Mars Color Imager (MARCI) on board the Mars Reconnaissance Orbiter (MRO) that the dust storm was generated in the Acidalia region, moved south and came over Lunae Planum and Tempe Terra. Later on, this northern hemispheric storm sequence crossed the equator and merged with a Hellas sequence over Noachis Terra. An increase in vertically integrated dust opacity derived from the observations of Mars Climate Sounder on board MRO was seen over a large latitudinal extent i.e., 60° S to 60° N. Analysis of dust and water ice opacity and temperature profile is carried out before, during and after the dust storm period as observed by MCC and MARCI images. Dust opacity is found to have increased drastically up to 20 km altitude. An increase of dustiness at the HATDM (High Altitude Tropical Dust Maximum) layer is seen, but with a temporal delay of 2° LS after the dust storm disappearance. The study implicates the variation of convective boundary layer growth in the tenuous Martian atmosphere during the dust storm scenario for this temporal delay in dust lifting. The dust lifting is found to be exclusively responsible for the increase in heating rate at this layer, not cloud radiative heating caused by water ice clouds.

Overview of one year acoustical oceanography measurements on Chukchi shelf during Shallow Water Canada Basin Acoustic Propagation Experiment 2016–2017

A multi-institutional, acoustical oceanography experiment was conducted from October 2016 through November 2017 on the Chukchi continental shelf covering 100–700 m isobaths. Parallel to a deep-water experiment conducted during the same period, the Shallow Water Canada Basin Acoustic Propagation Experiment (SW CANAPE) was designed to assess basin scale acoustic signals on the shelf region while detailed oceanographic dynamic of the shelf break region, particularly the upwelling and other dynamic of the upper 500 m water column, was measured simultaneously. Multiple arrays of oceanographic sensors including upward looking ice profiler, current profiler, temperature, conductivity, and pressure profiles measured temporal and spatial dynamics of 500 m upper ocean in connection with acoustic measurements. Distributed in a 30 km2 area north of Barrow Alaska, vertical line arrays including an L-shaped array, covered upper 200 m of the water column. Two acoustic sources placed at 148 m and 193 m depths on the shelf emitted broadband acoustic signals in frequency bands (700–1100 Hz, and 1400–4000 Hz) along and across the shelf while the sound speed and current profile and surface ice were being measured continuously. Deep water low frequency signals were also recorded. This talk provides an overview of the SW CANAPE experiment and highlights some of the detailed measurements. [Work supported by ONR.]A multi-institutional, acoustical oceanography experiment was conducted from October 2016 through November 2017 on the Chukchi continental shelf covering 100–700 m isobaths. Parallel to a deep-water experiment conducted during the same period, the Shallow Water Canada Basin Acoustic Propagation Experiment (SW CANAPE) was designed to assess basin scale acoustic signals on the shelf region while detailed oceanographic dynamic of the shelf break region, particularly the upwelling and other dynamic of the upper 500 m water column, was measured simultaneously. Multiple arrays of oceanographic sensors including upward looking ice profiler, current profiler, temperature, conductivity, and pressure profiles measured temporal and spatial dynamics of 500 m upper ocean in connection with acoustic measurements. Distributed in a 30 km2 area north of Barrow Alaska, vertical line arrays including an L-shaped array, covered upper 200 m of the water column. Two acoustic sources placed at 148 m and 193 m depths on the shel...

Observations and modelling of first-year ice growth and simultaneous second-year ice ablation in the Prydz Bay, East Antarctica

ABSTRACT The seasonal cycle of fast ice thickness in Prydz Bay, East Antarctica, was observed between March and December 2012. In March, we observed a 0.16 m thickness gain of 0.22 m-thick first-year ice (FYI), while 1.16 m-thick second-year ice (SYI) nearby simultaneously ablated by 0.59 m. A 1-D thermodynamic sea-ice model was applied to identify the factors that led to the simultaneous growth of FYI and melt of SYI. The different evolutions were explained by the difference in the conductive heat flux between the FYI and SYI. As the FYI was thin, there was a large temperature gradient between the ice base and the colder ice surface. This generated an upward conductive heat flux, which was larger than the heat flux from the ocean to the ice base, yielding basal growth of ice. In the case of the thicker SYI the temperature gradient and, hence, the conductive heat flux were smaller, and not sufficient to balance the oceanic heat flux at the ice base, yielding basal ablation. Penetration of solar radiation affected the conductive heat flux in both cases, and the model results were sensitive to the initial ice temperature profile and the uncertainty of the oceanic heat flux.

Application of 3-D ensemble variational data assimilation to a Baltic Sea reanalysis 1989–2013

A 3-D ensemble variational (3DEnVar) data assimilation method has been implemented and tested for oceanographic data assimilation of sea surface temperature (SST), sea surface salinity (SSS), sea ice concentration (SIC), and salinity and temperature profiles. To damp spurious long-range correlations in the ensemble statistics, horizontal and vertical localisation was implemented using empirical orthogonal functions. The results show that the 3DEnVar method is indeed possible to use in oceanographic data assimilation. So far, only a seasonally dependent ensemble has been used, based on historical model simulations. Near-surface experiments showed that the ensemble statistics gave inhomogeneous and anisotropic horizontal structure functions, and assimilation of real SST and SIC fields gave smooth, realistic increment fields. The implementation was multivariate, and results showed that the cross-correlations between variables work in an intuitive way, for example, decreasing SST where SIC was increased and vice versa. The profile data assimilation also gave good results. The results from a 25-year reanalysis showed that the vertical salinity and temperature structure were significantly improved, compared to both dependent and independent data.

Modeling transport phenomena of ice slurry in an ice forming unit

In this article, multiphase convective and solidification transport phenomena of ice slurry is investigated by developing a one-domain macroscopic model to simulate its formation in a rectangular ice forming unit. Convection, sedimentation, interfacial drag, permeability, remelting and viscosity variations are incorporated into this model through the appropriate governing multiphase transport equations. Validation studies with literature data are performed to determine the most suitable drag law by comparing the position of the interface between the coherent and non-coherent zones. After establishing modified Stokes' Law as the best-suited drag model, solidification study of an aqueous ammonium chloride solution is performed. The results for the evolution of ice fraction, species distribution, temperature profile and multiphase velocity field are presented. Solid fraction gradient, due to the generation of ice particles, has a major influence on the density gradient leading to a counter-clockwise flow current resulting in the homogenization of temperature and species in the generated ice slurry.

Freshwater ice thickness apparatus based on differences in electrical resistance and temperature

An apparatus for monitoring freshwater ice thickness using the differences in the electrical resistance and the temperature of air, ice, and water is developed. The principle and components of the apparatus are presented. Using the proposed apparatus, the electrical resistance characteristics of air, ice, and water from 12 to −55°C were studied in the laboratory. Field measurements using this apparatus were conducted in the Wanjiazhai Reservoir in the upper Yellow River for approximately four months during the winter of 2012–2013. The results showed that the recorded ice thickness agreed with the drill-hole measurements. The differences between the recorded and the drill-hole data are between 0 and 0.02m. The new apparatus can continuously and automatically operate in freshwater ice. It provides an effective method for monitoring the ice thickness and temperature profiles in the air, ice and underlying water.

Heat sources within the Greenland Ice Sheet: dissipation, temperate paleo-firn and cryo-hydrologic warming

Abstract. Ice temperature profiles from the Greenland Ice Sheet contain information on the deformation history, past climates and recent warming. We present full-depth temperature profiles from two drill sites on a flow line passing through Swiss Camp, West Greenland. Numerical modeling reveals that ice temperatures are considerably higher than would be expected from heat diffusion and dissipation alone. The possible causes for this extra heat are evaluated using a Lagrangian heat flow model. The model results reveal that the observations can be explained with a combination of different processes: enhanced dissipation (strain heating) in ice-age ice, temperate paleo-firn, and cryo-hydrologic warming in deep crevasses.

Evolution of snow and ice temperature, thickness and energy balance in Lake Orajärvi, northern Finland

The seasonal evolution of snow and ice on Lake Orajärvi, northern Finland, was investigated for three consecutive winter seasons. Material consisting of numerical weather prediction model (HIRLAM) output, weather station observations, manual snow and ice observations, high spatial resolution snow and ice temperatures from ice mass balance buoys (SIMB), and Moderate Resolution Imaging Spectroradiometer (MODIS) lake ice surface temperature observations was gathered. A snow/ice model (HIGHTSI) was applied to simulate the evolution of the snow and ice surface energy balance, temperature profiles and thickness. The weather conditions in early winter were found critical in determining the seasonal evolution of the thickness of lake ice and snow. During the winter season (Nov.–Apr.), precipitation, longwave radiative flux and air temperature showed large inter-annual variations. The uncertainty in snow/ice model simulations originating from precipitation was investigated. The contribution of snow to ice transformation was vital for the total lake ice thickness. At the seasonal time scale, the ice bottom growth was 50–70% of the total ice growth. The SIMB is suitable for monitoring snow and ice temperatures and thicknesses. The Mean Bias Error (MBE) between the SIMB and borehole measurements was −0.7 cm for snow thicknesses and 1.7 cm for ice thickness. The temporal evolution of MODIS surface temperature (three seasons) agrees well with SIMB and HIGHTSI results (correlation coefficient, R=0.81). The HIGHTSI surface temperatures were, however, higher (2.8°C≤MBE≤3.9°C) than the MODIS observations. The development of HIRLAM by increasing its horizontal and vertical resolution and including a lake parameterisation scheme improved the atmospheric forcing for HIGHTSI, especially the relative humidity and solar radiation. Challenges remain in accurate simulation of snowfall events and total precipitation.

Porosity of growing sea ice and potential for oil entrainment

Abstract The pore space in the bottom-most layers of growing sea ice is directly connected to the ocean beneath, allowing for fluid exchange while providing a sheltered environment for sea-ice microbial communities. Because of its role as a habitat and its high porosity and permeability, potential entrainment of oil into this pore space is of broader concern. We estimate the ice volume that can potentially be infiltrated by oil and other buoyant pollutants in surface ocean water evaluating several years of sea ice measurements on undeformed landfast first-year sea ice at Barrow, Alaska. This ice is representative of undeformed sea ice in areas targeted for offshore oil development. The calculated ice volume is related to crude oil entrainment volumes with empirical relationships derived from field and laboratory measurements. We synthesize 12 years of sea-ice core salinity data and 6 years of quasi-continuous sea ice temperature profile measurements to derive the seasonal evolution of ice thickness and temperature gradients in sea ice. Porosity profiles are calculated from temperature and salinity profiles. Based on previous observations, an oil penetration depth is defined by a porosity threshold of 0.1 to 0.15. Ice thickness is found to increase from 0.6 m in January to its maximum of 1.5 m in May, and average temperature gradients at the ice–water interface range from − 15 °C/m in January to − 2 °C/m in May. Depending on ice temperature conditions, derived depths of fluid penetration range from 0.02 to 0.10 m in January to 0.12 to 0.25 m in May for a porosity threshold of 0.10. These penetration depths are approximately halved for a porosity threshold of 0.15. For average temperature conditions, expected entrainment of crude oil is less than 2 L/m2 in January and may be as high as 5 to 10 L/m2 in May. Accessible ice volume and entrainment potential are expected to increase during warm spells and with the opening of brine channel networks in late spring. Considering inhomogeneous spread and pooling of oil under ice, entrainment in warm sea ice is expected to add approximately 20% to previous estimates of the under-ice pooling capacity.

Modelling the liquid-water vein system within polar ice sheets as a potential microbial habitat

Based on the fundamental and distinctive physical properties of polycrystalline ice Ih, the chemical and temperature profiles within the polar ice sheets, and the observed selective partitioning of bacteria into liquid water filled veins in the ice, we consider the possibility that microbial life could survive and be sustained within glacial systems. Here, we present a set of modelled vertical profiles of vein diameter, vein chemical concentration, and vein water volume variability across a range of polar ice sheets using their ice core chemical profiles. A sensitivity analysis of VeinsInIce1.0, the numerical model used in this study shows that the ice grain size and the local borehole temperature are the most significant factors that influence the intergranular liquid vein size and the amount of freeze-concentrated impurities partitioned into the veins respectively. Model results estimate the concentration and characteristics of the chemical broth in the veins to be a potential extremophilic microbial medium. The vein sizes are estimated to vary between 0.3μm to 8μm across the vertical length of many polar ice sheets and they may contain up to 2μL of liquid water per litre of solid ice. The results suggest that these veins in polar ice sheets could accommodate populations of psychrophilic and hyperacidophilic ultra-small bacteria and in some regions even support the habitation of unicellular eukaryotes. This highlights the importance of understanding the potential impact of englacial microbial metabolism on polar ice core chemical profiles and provides a model for similar extreme habitats elsewhere in the universe.

Variation of Sea Ice Temperature from CHINARE 2003 and Its Application on Sea Ice Model Evaluation

AbstractVariation of vertical profiles of sea ice temperature and adjacent atmosphere and ocean temperatures were measured by ice drifting buoys deployed in the northeast Chukchi Sea as part of the 2003 Chinese Arctic Research Expedition. The buoy observations (September 2003 to February 2005) show that the cooling of the ice began in late September, propagated down through the ice, reaching the bottom of the ice in December, and continued throughout the winter. In winter 2003/04, some obvious warmings were observed in the upper portion of the ice in response to major warmings in the overlying atmosphere associated with the periodicity of storms in the northeast Chukchi Sea. It is found that the melt season at the buoy site in 2004 was about 15% longer than normal. The buoy observed vertical ice temperature profiles were used as a diagnostic for sea ice model evaluation. The results show that the simulated ice temperature profiles have large discrepancies as compared with the observations.