Snow Ice Research Articles

Temporal evolution of decaying summer first-year sea ice in the Western Weddell Sea, Antarctica

The evolution of the main physico-chemical properties of the unflooded 90-cm-thick first-year sea-ice cover at the Ice Station POLarstern (ISPOL) “clean site” is described. ISPOL was an international experiment of the German research icebreaker R.V. Polarstern. The vessel was anchored to an ice floe for an observation period of 5 weeks, during the early summer melt onset in the Western Weddell Sea. The “clean site” was specially designed and accessed so as to prevent any trace metal contamination of the sampling area. Observations were made at 5-day intervals during December 2004 in the central part of the main floe. Results show the succession of two contrasting phases in the behavior of the brine network (brine channels, pockets, and tubes). Initially, brine salinity was higher than that of sea-water, leading to brine migration and a decrease in the mean bulk salinity of the ice cover. This process is highly favored by the already high bulk porosity (14%), which ensures full connectivity of the brine network. Gravity drainage rather than convection seems to be the dominant brine transfer process. Half-way through the observation period, the brine salinity became lower than that of the sea-water throughout the ice column. The brine network therefore switched to a “stratified” regime in which exchange with sea-water was limited to molecular diffusion, strongly stabilizing the bulk mean sea-ice salinity. During the transition between the two regimes, and in areas closer to ridges, slush water (resulting from a mixture of snow meltwater and sea water accumulated at the snow–ice interface) penetrated through the growing “honeycomb-like structure” and replaced the downward draining brines. This resulted in a slight local replenishment of nutrients (as indicated by dissolved silicic acid). However, as a whole, the described decaying regime in this globally unflooded location with limited snow cover should be unfavorable to the development of healthy and active surface and internal microbial communities. The switch from gravity to diffusion controlled transport mechanisms within the ice column also should affect the efficiency of gas exchange across the sea-ice cover. The observed late build-up of a continuous, impermeable, superimposed ice layer should further significantly hamper gas exchange. Statistical estimates of the evolution of the ice thickness during the observation period and salinity trends of the under-ice water salinity down to 30 m corroborate model predictions of a moderate bottom melting (5–10 cm) from ocean heat fluxes.

Antarctic sea ice thickness and snow‐to‐ice conversion from atmospheric reanalysis and passive microwave snow depth

Passive microwave snow depth, ice concentration, and ice motion estimates are combined with snowfall from the European Centre for Medium‐Range Weather Forecasting (ECMWF) reanalysis (ERA‐40) from 1979–2001 to estimate the prevalence of snow‐to‐ice conversion (snow‐ice formation) on level sea ice in the Antarctic for April–October. Snow ice is ubiquitous in all regions throughout the growth season. Calculated snow‐ice thicknesses fall within the range of estimates from ice core analysis for most regions. However, uncertainties in both this analysis and in situ data limit the usefulness of snow depth and snow‐ice production to evaluate the accuracy of ERA‐40 snowfall. The East Antarctic is an exception, where calculated snow‐ice production exceeds observed ice thickness over wide areas, suggesting that ERA‐40 precipitation is too high there. Snow‐ice thickness variability is strongly controlled not just by snow accumulation rates, but also by ice divergence. Surprisingly, snow‐ice production is largely independent of snow depth, indicating that the latter may be a poor indicator of total snow accumulation. Using the presence of snow‐ice formation as a proxy indicator for near‐zero freeboard, we examine the possibility of estimating level ice thickness from satellite snow depths. A best estimate for the mean level ice thickness in September is 53 cm, comparing well with 51 cm from ship‐based observations. The error is estimated to be 10–20 cm, which is similar to the observed interannual and regional variability. Nevertheless, this is comparable to expected errors for ice thickness determined by satellite altimeters. Improvement in satellite snow depth retrievals would benefit both of these methods.

Properties of sea ice and overlying snow in the Southern Sea of Okhotsk

The general properties of sea ice and overlying snow in the southern Sea of Okhotsk were examined during early February of 2003 to 2005 with the P/V “Soya”. Thin section analysis of crystal structure revealed that frazil ice (48% of total core length) was more prevalent than columnar ice (39%) and that stratigraphic layering was prominent with a mean layer thickness of 12 cm, indicating that dynamic processes are essential to ice growth. The mean thickness of ice blocks and visual observations suggest that ridging dominates the deformation process above thicknesses of 30 to 40 cm. As for snow, it was found that faceted crystals and depth hoar are dominant (78%), as which is also common in the Antarctic sea ice, and is indicative of the strong vertical temperature gradients within the snow. Stable isotope measurements (δ18O) indicate that snow ice occupies 9% of total core length and that the mass fraction of meteoric ice accounts for 1 to 2% of total ice volume, which is lower than the Antarctic sea ice. Associated with this, the effective fractionation coefficient during the freezing of seawater was also derived. Snow ice was characterized by lower density, higher salinity, and nearly twice the gas content of ice of seawater origin. In addition, it is shown that the surface brine volume fraction and freeboard are well correlated with ice thickness, indicating some promise for remote sensing approaches to the estimation of ice thickness.

Diatom‐induced silicon isotopic fractionation in Antarctic sea ice

In this study, we measure the silicon‐isotopic composition δ29Si,‰, relative to NBS28 quartz standard) of dissolved silicon and biogenic silica collected by sequential melting from spring Antarctic pack ice collected near 117°E‐64.5°S. This work aims to investigate the use of Si isotopes to quantify the activity of sea‐ice diatoms in the different brine structures and the influence of sea‐ice diatoms on the spring ice edge blooms. From three cores with contrasted physico‐chemical characteristics, we report significant isotopic fractionations linked to diatom activity with distinct silicon biogeochemical dynamics between different brine structures. The diatoms in snow ice and in brine pockets of frazil or congelation ice have the heavier silicon‐isotopic composition (+0.53 to +0.86‰), indicating that they grow in a closed system and use a significant fraction of the small dissolved silicon pool available. In the brine channels and skeletal layer, diatoms display a relatively lower silicon‐isotopic composition (+0.41 to +0.70‰), although it is still relatively positive compared to expected equilibrium fractionation. This suggests that the diatoms have grown in a semi‐closed system where the dissolved silicon pool (i.e., brine) is partially replenished. The silicon‐isotopic composition (+0.63‰) of the sea‐ice diatoms is much heavier than the one of biogenic silica in the seasonal ice zone mixed layer (+0.09‰). Our results suggest that sea‐ice diatoms either contribute to an insignificant part of the whole diatom biomass in the upper water layer, or that they are directly exported below the mixed layer.

Structure, salinity and isotopic composition of multi-year landfast sea ice in Nella Fjord, Antarctica

The structural, salinity and stable oxygen-isotopic properties of multi-year landfast sea-ice samples collected from Nella Fjord, East Antarctica were used to determine the ice formation process and the fractional contribution of snow, in both snow ice and superimposed ice, to the total sea-ice thickness. The textural analysis of the sea-ice cores revealed a general structure of a granular surface layer, horizontal c-axis in the columnar ice and, in some cases, a “buried” granular-ice layer at depth between two columnar-ice layers. The textural and isotopic properties of the ice core samples indicate that thermodynamic mechanisms alone are responsible for the development of the multi-year fast ice in the region investigated. Superimposed ice contributed 5% to the ice thickness at some sites. Using a mid-range isotopic criterion to distinguish between snow ice and frazil ice in the granular layers, we estimate that snow-ice layers contributed 38% of the total ice thickness in the samples. The actual fraction of snow in the granular-ice layers in different cores was from 1% to 24% of the total sea-ice thickness.

Physical characterization of air inclusions in river ice

The physical characteristics of air inclusions embedded in the ice covers of the Saint Francois River (Quebec, Canada) and the Athabasca River (Alberta, Canada) are studied because of the importance of such inclusions to the analysis and interpretation of Synthetic Aperture Radar satellite images used to characterize river ice. Studies of ice cores sampled from these two rivers show that the concentration of air inclusions in the ice cover is highly dependent on both the ice type as well as the rate of freezing. When this rate is slow, the ice cover will have few air inclusions. However, when it is rapid and sustained in duration, the amount and cross sectional diameter of these inclusions increase. Air inclusions in the snow ice were found to be spherical and ranging in size from just a few millimetres up to about a centimetre. Generally, air inclusions formed in the sampled columnar ice were sparse and either spherical or tubular in shape. Air inclusions in the frazil ice were found to present a different structure from those formed in the other ice types. In most cases, their shape were irregular and their distribution was inhomogeneous. The study of these inclusions under a microscope showed them to have angular boundaries with a whitish appearance. These results will be valuable to the development of radar backscatter analysis algorithms for river ice characterization.

Some aspects of ice phenology on ponds in central Alaska, USA

AbstractIce phenology (freeze-up, break-up and duration) was monitored for five seasons between autumn 2001 and spring 2006 at 11 small, shallow ponds in the boreal forest of central Alaska, USA. The sequence in which freeze-up (FU; day of 100% ice cover) and break-up (BU; day of zero ice cover) occurred at the 11 ponds showed moderately high to very high coherence each season. This was probably due to FU and BU being poorly correlated with pond morphometry (area, depth). BU is strongly correlated with April mean air temperature; a ±1˚C change in mean April air temperature is equivalent to a ±1.86 day change in BU. FU and air-temperature relationships are inconclusive, primarily because post-FU warm intervals in two autumns cause an anticorrelation between mean September air temperature and FU. Mean ice duration varies between 205 and 225 days, and is strongly correlated with maximum ice thickness through its effect on BU. A ±10mm change in maximum ice thickness will cause a ±0.6 day change in ice duration. Maximum ice thickness and ice composition (snow ice, congelation ice) also have a strong influence on break-up when all data from all ponds and all years are considered. The predictability of FU and BU sequence, the minor role of morphometry in FU and BU, the strong role of April mean air temperature in BU, and the role of maximum ice thickness in duration suggests that these ponds would be good sites for continued long-term observation of phenology and the influence of weather/climate variation and change, and for freeze-up/break-up process studies, particularly the role of ice composition and albedo.

Characteristics and climatic sensitivities of runoff from a cold‐type glacier on the Tibetan Plateau

AbstractModel calculations are made in order to understand the characteristics and response to climate change of runoff from a cold glacier on the Tibetan Plateau. Some 20% of meltwater is preserved at the snow–ice boundary due to refreezing, since the glaciers in mid to northern Tibet are sufficiently cooled during the previous winter.Sensitivity to alterations in meteorological parameters has revealed that a change in air temperature would cause not only an increase in melting by sensible heat, but also a drastic increase in melting due to lowering of the albedo, since some of the snowfall changes to rainfall. In addition, it was suggested that a decrease in precipitation would cause a lowering of the surface albedo, with a resulting increase in the contribution of glacier runoff to the total runoff of river water. This study shows the first quantitative evaluation of the above effects, though they have been suggested qualitatively. The seasonal sensitivity of glacier runoff was examined by changing the dates given for a meteorological perturbation for a period of only 5 days. It was revealed that changes in both air temperature and precipitation during the melting season strongly affected glacier runoff by changing the surface albedo, though these perturbations only slightly altered the annual averages. Copyright © 2006 John Wiley & Sons, Ltd.

Growth and Decay of Estuary Ice Cover

This paper presents a new vertical 1D finite-element model to simulate the growth and decay of an ice cover (columnar ice, snow ice, slush, and snow cover consolidation) over a winter season in a partially mixed mesotidal estuary. In this study, we present, discuss, and validate boundary conditions as well as test and optimize the numerical model. Predictions from the model were assessed against field observations of ice thicknesses and internal temperatures taken over 3 years . This paper explains why ice in the estuary is almost completely composed of freshwater. We demonstrate how a columnar ice sheet grows over the first half of the winter season and is then melted from underneath during the second half of winter, especially where currents are strong. We also demonstrate that significant snow ice may form over the second half of winter if the ice cover survives long enough by resisting mechanical breakup of spring tides in March.

Traversing grounded rubble fields by foot — Implications for evacuation

A field program was carried out in the Canadian Beaufort Sea to obtain quantitative details of the time required to traverse a variety of ice rubble conditions, typical of those that may surround an offshore structure in landfast ice. The results indicate that the time required to cross rubble fields increases rapidly with increasing rubble severity, determined by factors such as rubble height, ice block size and snow depth. The quantitative findings have implications for emergency evacuation from an offshore structure when an on-ice Evacuation Shelter is identified in the EER strategy for the structure. The results and analysis show that preparing and maintaining a suitable egress path across ice rubble is essential for safe evacuation from an offshore structure surrounded by landfast ice and a grounded rubble field. The implications for an offshore structure in a variety of ice conditions are presented.

Extreme Anomalous Atmospheric Circulation in the West Antarctic Peninsula Region in Austral Spring and Summer 2001/02, and Its Profound Impact on Sea Ice and Biota*

AbstractExceptional sea ice conditions occurred in the West Antarctic Peninsula (WAP) region from September 2001 to February 2002, resulting from a strongly positive atmospheric pressure anomaly in the South Atlantic coupled with strong negative anomalies in the Bellingshausen–Amundsen and southwest Weddell Seas. This created a strong and persistent north-northwesterly flow of mild and moist air across the WAP. In situ, satellite, and NCEP–NCAR Reanalysis (NNR) data are used to examine the profound and complex impact on regional sea ice, oceanography, and biota. Extensive sea ice melt, leading to an ocean mixed layer freshening and widespread ice surface flooding, snow–ice formation, and phytoplankton growth, coincided with extreme ice deformation and dynamic thickening. Sea ice dynamics were crucial to the development of an unusually early and rapid (short) retreat season (negative ice extent anomaly). Strong winds with a dominant northerly component created an unusually compact marginal ice zone and a major increase in ice thickness by deformation and over-rafting. This led to the atypical persistence of highly compact coastal ice through summer. Ecological effects were both positive and negative, the latter including an impact on the growth rate of larval Antarctic krill and the largest recorded between-season breeding population decrease and lowest reproductive success in a 30-yr Adélie penguin demographic time series. The unusual sea ice and snow cover conditions also contributed to the formation of a major phytoplankton bloom. Unexpectedly, the initial bloom occurred within compact sea ice and could not be detected in Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) ocean color data. This analysis demonstrates that sea ice extent alone is an inadequate descriptor of the regional sea ice state/conditions, from both a climatic and ecological perspective; further information is required on thickness and dynamics/deformation.

Long-term changes in lake ice cover in Finland*

The freeze-up and break-up records of almost ninety lakes, and ice thickness of about thirty lakes, were analysed in order to identify long-term changes in the ice regime in Finland. The longest time series of break-up and freeze-up of ice in lakes are available from the early 19th century, while the earliest ice thickness measurements started in the 1910s. The analysis showed that there is a significant change towards earlier ice break-up in Finland except in the very north from the late 19th century to the present time. There is also a significant trend towards later freeze-up and thus also towards a shorter ice cover duration for the longest time series. However, for most lakes, for which data are not available prior to 1900, there are no significant trends. The ice thickness seems to have increased over the last 40 years, although there are significant trends only in half of the investigated lakes and significant decrease in the maximum ice thickness was found in four lakes in southern Finland. The increased ice thickness is most likely due to heavy snow on the ice and production of snow ice.

Does Model Sensitivity to Changes in CO2 Provide a Measure of Sensitivity to Other Forcings?

Abstract Simulation of both the climate of the twentieth century and a future climate change requires taking into account numerous forcings, while climate sensitivities of general circulation models are defined as the equilibrium surface warming due to a doubling of atmospheric CO2 concentration. A number of simulations with the Massachusetts Institute of Technology (MIT) climate model of intermediate complexity with different forcings have been carried out to study to what extent sensitivity to changes in CO2 concentration (SCO2) represent sensitivities to other forcings. The MIT model, similar to other models, shows a strong dependency of the simulated surface warming on the vertical structure of the imposed forcing. This dependency is a result of “semidirect” effects in the simulations with localized tropospheric heating. A method for estimating semidirect effects associated with different feedback mechanisms is presented. It is shown that forcing that includes these effects is a better measure of expected surface warming than a forcing that accounts for stratospheric adjustment only. Simulations with the versions of the MIT model with different strengths of cloud feedback show that, for the range of sensitivities produced by existing GCMs, SCO2 provides a good measure of the model sensitivity to other forcings. In the case of strong cloud feedback, sensitivity to the increase in CO2 concentration overestimates model sensitivity to both negative forcings, leading to the cooling of the surface and “black carbon”–like forcings with elevated heating. This is explained by the cloud feedback being less efficient in the case of increasing sea ice extent and snow cover or by the above-mentioned semidirect effects, which are absent in the CO2 simulations, respectively.

Are dust storm activities in North China related to Arctic ice–snow cover?

The generation and development of dust storms are controlled by land surface conditions and atmospheric circulations. The latter, in turn, is influenced by the global ice–snow cover. In this study, we examine the relationship between the characteristics of dust storm activities in north China and the changes of global climate patterns. In particular, we are interested in whether Arctic ice–snow cover is related to the dust storm frequencies and intensities in north China. Our analysis, based on the monthly data for the period from 1954 to 1994, shows that this is indeed the case. This result suggests that the Arctic ice–snow cover can be used for the long-term prediction of dust storm activities in north China, and dust storm activities also serve as an indicator of global climate change.

Water flow through Mittivakkat Glacier, Ammassalik Island, SE Greenland

Geografisk Tidsskrift, Danish Journal of Geography 106(1):25–43, 2006 The seasonal variability of hourly discharge of the Mittivakkat Glacier, SE Greenland was analyzed at the beginning and the end of the ablation period (May 2005 and August 2004). Spatial and temporal variations in the drainage system, water flow velocity, and travel time through the different media: snow, firn, and glacier ice were estimated. The glacier runoff hydrograph was calculated using the time-area method (a conceptual model) and the snow distribution was modeled using a physically based snow evolution model (SnowModel). Ink and dye tracer experiments, together with water flow measurements and observations, were conducted during August 2004 and May 2005 to estimate flow velocities through snow, firn, and glacier ice. The Mittivakkat Glacier contained five different water flow paths through the different media of the partially snow-covered glacier in August 2004, and three paths when the glacier was fully snow-covered in May 2005. In both August 2004 and May 2005, flow experiments revealed velocities ranging from 1.5× 10−4 to 4.3× 10−4 m s−1 through the snow cover, 3.5× 10−4 to 9.2× 10−4 m s−1 at the interface between the snow and the impermeable glacier ice, an average of 5.0× 10−2 m s−1 for inter-rill flow, a range from 0.46 to 1.84 m s−1 in supraglacial channels, and a maximum travel time of approximately 21 hours (time of concentration) through the different Mittivakkat Glacier flow paths. A 3 to 4 how and 5 to 7 hour lag time occurred in August and May, respectively. On a daily basis, the hourly surface melt exceeded the hourly time- area glacier runoff from 4 a.m. to 3 p.m. in August and May, indicating a temporary englacial melt-water storage. The time-area glacier runoff was compared with stage observed runoff during August indicating a R2-value of 0.85. Daily peak runoff values of the time-area runoff and stage runoff correspond well in duration and variability, with a maximum range of 1.57 m3 s−1 for August.

Growth, properties and relation to radar backscatter coefficient of sea ice in Lützow-Holm Bay, Antarctica

AbstractBased on studies in the Antarctic Oceans, the contribution of the snow cover to sea-ice growth has become of major interest. Snow can result in upward ice growth in contrast with ordinary downward congelation growth at the bottom. A sea-ice study was conducted to verify the upward ice growth found in a previous study and to investigate the relation between sea-ice growth and radar backscattering signature. Sea-ice samples collected at four points in Lützow-Holm Bay, Antarctica, from 1998 to 2003 are analyzed. Analyses of snow-/ice-gauge measurements, snow depth and ice structure reveal an extremely large amount of upward ice growth of up to 1.0 m during one full year compared with a slight amount of downward growth. The upward growth was caused mostly by snow ice and to a lesser extent by superimposed ice. The salinity profile remained unchanged, although the ice survived the summer melt season. Characteristics of superimposed ice such as salinity, δ18O values and structure were obliterated during the summer, implying complete melting or dissolution of the superimposed layer. The ERS-2 backscatter showed a remarkable annual variation: It had a minimum value in midsummer and increased abruptly to a maximum value in late summer, then decreasing gradually in wintertime. The relation of the backscatter coefficient to the growth and properties of the snow cover and sea ice are discussed.

Amundsen Sea ice production and transport

Drift and variability of sea ice in the Amundsen Sea are investigated with ice buoys deployed in March 2000 and a coupled ice‐ocean model. The Bremerhaven Regional Ice Ocean Simulations (BRIOS) model results are compared with in situ ocean, atmosphere, and sea ice measurements; satellite observations; and 8–19 months of buoy drift data. We identify a zone of coastal westward drift and a band of faster eastward drift, separated by a broad transition region characterized by variable ice motions. The model represents drift events at scales approaching its resolution but is limited at smaller scales and by deficiencies in the National Centers for Environmental Prediction forcing. Two thirds of the modeled ice production in the southern Amundsen moves westward near the coast, its transport modulated by meridional wind strength, damping sea ice formation in the eastern Ross Sea. Half of the ice exported from the Ross moves eastward into the northern Amundsen Sea, a net sea ice sink that also receives more than one third of the ice generated to its south. A low rate of exchange occurs with the Bellingshausen Sea, which must have a more independent ice regime. Snow ice formation resulting from high precipitation accounts for one quarter of the ice volume in the Amundsen Sea, aiding the formation of thick ice in a region with generally divergent ice drift. Freshwater extraction by sea ice formation is roughly balanced by precipitation and ice shelf melting, but a positive trend in the surface flux is consistent with an Amundsen source for reported freshening in the Ross Sea.

Variability of snow and ice thermal, physical and optical properties pertinent to sea ice algae biomass during spring

Changes in the thermal, physical and optical properties of the snow–sea ice system and feedbacks between various temporal and spatial scales affect accumulation of microalgae at the sea ice bottom and are the focus of this research. During the spring transition period, May 4 to June 9, 2002, we closely monitored atmospheric conditions and properties of the snow–sea ice system, including thermal, physical and optical properties of the snow cover (e.g., temperature, grain size, light attenuation), ice thickness and salinity, and biomass of bottom ice algae. Results show that snowdrift size averaged 31.2 by 10.6 m with a depth range of 2 to 45 cm. Snowpacks also varied in age, distinguished by coincident peaks of snow salinity and grain size and a lower PAR extinction coefficient. Spatial variability of the snowpack was superimposed by temporal variability associated with seasonal snow–ice melt and wind redistribution of snow. Maximum biomass of ice algae was observed under intermediate snow covers. Under thin snow covers, algae biomass declined steadily coincident with seasonal warming and desalination of the ice cover. Under thick snow covers, algae biomass was negatively correlated with snow depth. These results suggest that thin snow covers were associated with a thermal effect causing sloughing of algae, whereas under deep snow, algae were still light limited and thermally insulated from the warming atmosphere. Our results highlight the importance of snow cover history on the sea ice system operating below. Furthermore, in the context of current climate change scenarios, shifts in snow depth would result in decreases of ice algae biomass.

Description and first results of an explicit electrical scheme in a 3D cloud resolving model

The three-dimensional non-hydrostatic mesoscale model MésoNH of the French community offers the numerical environment to develop a cloud electrification scheme in a consistent way with the original mixed phase microphysical scheme. The charge separation mechanisms are entirely due to non-inductive processes and result from elastic ice–snow, ice–graupel and snow–graupel collisions. The electric charges carried by each of the five hydrometeor categories are transported along the airflow and are exchanged according to the various microphysical mass transfer rates but assuming a power law distribution of the individual charges as a function of the particle size. The electric field is diagnosed at each time step after integrating the electric potential induced by a net charge density in the Poisson equation. Finally, a lightning ash is triggered when the electric field locally steps over a given threshold. It propagates in two opposite directions until the magnitude of the electric field falls below a prescribed value. A fractal branching algorithm is then activated to extend lightning streamers away from the main channel and toward cloudy regions where substantial charge densities are present. Charges are neutralized along the tortuous lightning path with a simple procedure that preserves total charge conservation. The complete electrification scheme tested for an ideal case of vigorous supercellular storm shows an intense electrical activity all along its lifecycle. We show that the model is able to produce a direct tripolar structure of the charges as the result of a temperature charge reversal of − 10 °C and of the different sedimentation rates of the hydrometeors.

Lake ice growth and decay in central Alaska, USA: observations and computer simulations compared

AbstractThe Canadian Lake Ice Model (CLIMo), a one-dimensional, thermodynamic model with unsteady heat conduction and penetrating solar radiation, is used to simulate ice growth and decay on shallow ponds in and near Fairbanks, central Alaska, USA. Simulations are compared with observations of ice thickness and composition (snow ice, congelation ice), freeze-up, break-up and duration. Simulations run using US National Weather Service meteorological data as input variables do not agree well with ice-thickness measurements. The simulations improve significantly when the model is run with more representative, locally measured data for air temperature and depth of snow on the ice. The causes of some discrepancies between simulations and observations are discussed and some suggestions for model improvements are made.