impact of horizontal spreading on light propagation in melt pond covered seasonal sea ice in the canadian arctic 1 melt pond covered sea ice is a ubiquitous feature of the summertime arctic ocean when meltwater collects in lower lying areas of ice surfaces horizontal transects were conducted during june 2008 above and below landfast sea ice with melt ponds to characterize surface and bottom topography together with variations in transmitted spectral irradiance we captured a rapid progression from a highly flooded sea ice surface with lateral drainage toward flaws and seal breathing holes to the formation of distinct melt ponds with steep edges as the mass of the ice cover decreased due to meltwater drainage and rose upward with respect to the seawater level the high scattering properties of ice above the water level i e white ice were continuously regenerated while pond waters remained transparent compared to underlying ice the relatively stable albedos observed throughout the study even as ice thickness decreased were directly related to these surface processes transmission through the ice cover of incident irradiance in the 400 700 nm wave band ranged from 38 to 67 and from 5 to 16 beneath ponded and white ice respectively our results show that this transmission varied not only as a function of surface type melt ponds or white ice areal coverage but also in relation to ice thickness and proximity to other surface types through the influence of horizontal spreading of light thus in contrast to albedo this implies that regional transmittance estimates need to consider melt pond size and shape distributions and variations in optical properties and thickness of the ice cover

the mechanisms of sea ice melt pond formation and evolution 1 a series of observations were made on melting first year landfast arctic sea ice near barrow alaska to explore the seasonal evolution of melt pond coverage observations of pond coverage albedo and ice properties are combined with terrestrial lidar measurements of surface topography and meltwater balance to quantitatively identify the timing and role of mechanisms driving pond coverage the formation of interposed fresh ice is found to eliminate meltwater percolation through early pond formation and allow widespread ponding well above sea level pond drainage to sea level occurs principally by horizontal meltwater transport over the ice surface to macroscopic flaws freeboard loss caused by buoyancy decline as the ice thins controls pond growth late in the melt season after percolation begins the majority of the macroscopic flaws that drain melt ponds to sea level are observed to develop from brine drainage channels within the ice a simple thermodynamic model of meltwater percolation illustrates that fresh meltwater inflow causes pores in the ice to either shrink and freeze shut or enlarge based on initial size and ice temperature this threshold behavior of pore diameter controls both the blockage of smaller pores with interposed ice and the enlargement of larger brine drainage channels to allow meltwater drainage the results identify links between the temporal evolution of pond coverage and ice temperature salinity and thickness providing new opportunities to realistically parameterize ponds and summer ice albedo within sea ice models

snow dunes a controlling factor of melt pond distribution on arctic sea ice 1 the location of snow dunes over the course of the ice growth season 2007 08 was mapped on level landfast first year sea ice near barrow alaska landfast ice formed in mid december and exhibited essentially homogeneous snow depths of 4 6 cm in mid january by early february distinct snow dunes were observed despite additional snowfall and wind redistribution throughout the season the location of the dunes was fixed by march and these locations were highly correlated with the distribution of meltwater ponds at the beginning of june our observations including ground based light detection and ranging system lidar measurements show that melt ponds initially form in the interstices between snow dunes and that the outline of the melt ponds is controlled by snow depth contours the resulting preferential surface ablation of ponded ice creates the surface topography that later determines the melt pond evolution

the percolation phase transition in sea ice sea ice exhibits a marked transition in its fluid transport properties at a critical brine volume fraction p c of about 5 percent or temperature t c of about 5 c for salinity of 5 parts per thousand for temperatures warmer than t c brine carrying heat and nutrients can move through the ice whereas for colder temperatures the ice is impermeable this transition plays a key role in the geophysics biology and remote sensing of sea ice percolation theory can be used to understand this critical behavior of transport in sea ice the similarity of sea ice microstructure to compressed powders is used to theoretically predict p c of about 5 percent

equations for determining the gas and brine volumes in sea ice samples on a etabli des equations utilisables pour determiner le taux de gaz inclus dans la glace de mer a partir de mesures de densite de salinite et de temperature dans des gammes de temperatures entre 2 c et 30 c inversement ces relations peuvent etre utilisees pour calculer la densite de la glace de mer en fonction de la temperature et de la salinite en prenant en compte a la fois la presence de gaz et de cristaux de sel dans la glace on donne aussi des equations qui permettent le calcul du volume de gaz et d eau salee dans la glace a des temperatures autres que celle pour laquelle la densite a ete determinee

energy budget of first year arctic sea ice in advanced stages of melt 1 during an 8 day drift in july august 2012 in the nansen basin all components of the energy budget of melting first year sea ice were observed absorption of solar radiation by the ice and ponds was the largest source of energy to the ice at almost all times during the drift however oceanic heat flux also provided significant heating and dominated during one wind event longwave fluxes provided a relatively small cooling effect and atmospheric heat fluxes were negligible the aggregate scale albedo of this younger thinner ice was significantly lower than at surface heat budget of the arctic ocean sheba and the transmittance was significantly higher here despite similar pond and open water fractions the oceanic heat flux was only half of the solar flux through the ice to the water producing warm water near the surface that might delay ice growth in autumn an important effect of the transition to thinner first year ice in the high arctic

a model of the three dimensional evolution of arctic melt ponds on first year and multiyear sea ice during winter the ocean surface in polar regions freezes over to form sea ice in the summer the upper layers of sea ice and snow melts producing meltwater that accumulates in arctic melt ponds on the surface of sea ice an accurate estimate of the fraction of the sea ice surface covered in melt ponds is essential for a realistic estimate of the albedo for global climate models we present a melt pond sea ice model that simulates the three dimensional evolution of melt ponds on an arctic sea ice surface the advancements of this model compared to previous models are the inclusion of snow topography meltwater transport rates are calculated from hydraulic gradients and ice permeability and the incorporation of a detailed one dimensional thermodynamic radiative balance results of model runs simulating first year and multiyear sea ice are presented model results show good agreement with observations with duration of pond coverage pond area and ice ablation comparing well for both the first year ice and multiyear ice cases we investigate the sensitivity of the melt pond cover to changes in ice topography snow topography and vertical ice permeability snow was found to have an important impact mainly at the start of the melt season whereas initial ice topography strongly controlled pond size and pond fraction throughout the melt season a reduction in ice permeability allowed surface flooding of relatively flat first year ice but had little impact on the pond coverage of rougher multiyear ice we discuss our results including model shortcomings and areas of experimental uncertainty

incorporation of a physically based melt pond scheme into the sea ice component of a climate model the extent and thickness of the arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in september 2005 and 2007 these minima have not been predicted in the ipcc ar4 report suggesting that the sea ice component of climate models should more realistically represent the processes controlling the sea ice mass balance one of the processes poorly represented in sea ice models is the formation and evolution of melt ponds melt ponds accumulate on the surface of sea ice from snow and sea ice melt and their presence reduces the albedo of the ice cover leading to further melt toward the end of the melt season melt ponds cover up to 50 of the sea ice surface we have developed a melt pond evolution theory here we have incorporated this melt pond theory into the los alamos cice sea ice model which has required us to include the refreezing of melt ponds we present results showing that the presence or otherwise of a representation of melt ponds has a significant effect on the predicted sea ice thickness and extent we also present a sensitivity study to uncertainty in the sea ice permeability number of thickness categories in the model representation meltwater redistribution scheme and pond albedo we conclude with a recommendation that our melt pond scheme is included in sea ice models and the number of thickness categories should be increased and concentrated at lower thicknesses

icesat over arctic sea ice interpretation of altimetric and reflectivity profiles 1 we provide an assessment of the icesat altimeter for studying the arctic ocean and examine the magnitude of the large and small scale expressions of geophysical processes embedded in the elevation profiles this analysis includes data from six surveys at the large scale the response of the ice covered ocean to atmospheric loading is near ideal i e approximately 1 cm hpa after removal of the inverted barometer effects and best available geoid the elevation signal is still dominated by unresolved geoid residuals 0 4 m that can be seen in the similarity of the remaining spatial patterns seasonal differences in elevations over multiyear ice are consistent with snow depth climatology the broad differential spatial patterns are indicative of interannual differences in multiyear ice coverage associated with advection patterns in the derived surface roughness fields correspond to the seasonal and perennial ice zones seen in quikscat data at the small scale near coincident radarsat imagery provides a spatial context for understanding the signature of the observed elevations waveforms and reflectivity in particular those associated with thin ice open water multiyear ice and ridges the precision of the elevation estimates measured over relatively flat sea ice identified in synthetic aperture radar sar imagery is 2 cm the unambiguous identification of ridged areas in coupled icesat radarsat analysis could be used to enhance the utility of sar imagery for examining ridge distributions over a 20 day period we monitored the evolution of the reflectivity of a newly opened lead the steep increase in reflectivity due to snow coverage suggests that dips in icesat reflectivity are likely areas of thin ice and could serve as a basis for selection of tie points for use as sea level reference identification of these tie points is crucial for accurate estimation of sea ice freeboard

sea ice albedo climate feedback mechanism abstract the sea ice albedo feedback mechanism over the arctic ocean multiyear sea ice is investigated by conducting a series of experiments using several one dimensional models of the coupled sea ice atmosphere system in its simplest form ice albedo feedback is thought to be associated with a decrease in the areal cover of snow and ice and a corresponding increase in the surface temperature further decreasing the areal cover of snow and ice it is shown that the sea ice albedo feedback can operate even in multiyear pack ice without the disappearance of this ice associated with internal processes occurring within the multiyear ice pack e g duration of the snow cover ice thickness ice distribution lead fraction and melt pond characteristics the strength of the ice albedo feedback mechanism is compared for several different thermodynamic sea ice models a new model that includes ice thickness distribution the ebert and curry model the maykut and untersteiner model and the semtner level 3 an

integrated chitinozoan conodont and graptolite biostratigraphy from the upper part of the cape cormorant formation middle ordovician western newfoundland the cape cormorant formation of the table head group exposed on the port au port peninsula western newfoundland is composed of dark brown to black shales with interbeds of thin calcareous silty and sandy distal turbidites distinctive carbonate conglomerates and breccias derived from the foundering shelf are occasionally found in the formation the sediments accumulated in the foreland basin formed during the early stage of the taconic orogeny the faunas from the upper part of the cape cormorant formation include graptolites conodonts and chitinozoans the graptolites are well preserved but are of low diversity and are referred to the darriwil pterograptus elegans zone conodonts recorded from the distal turbidites are rare and fragmented the faunas include taxa that are known from the st george and table head groups the conodont fauna is tentatively assigned to the histiodella kristinae phylozone and to the younger unzoned interval the chitinozoans are well preserved and the yield is high the

recent changes in arctic sea ice melt onset freezeup and melt season length 1 in order to explore changes and trends in the timing of arctic sea ice melt onset and freezeup and therefore melt season length we developed a method that obtains this information directly from satellite passive microwave data creating a consistent data set from 1979 through present we furthermore distinguish between early melt the first day of the year when melt is detected and the first day of continuous melt a similar distinction is made for the freezeup using this method we analyze trends in melt onset and freezeup for 10 different arctic regions in all regions except for the sea of okhotsk which shows a very slight and statistically insignificant positive trend 0 4 d decade 1 trends in melt onset are negative i e toward earlier melt the trends range from 1 0 d decade 1 for the bering sea to 7 3 d decade 1 for the east greenland sea except for the sea of okhotsk all areas also show a trend toward later autumn freeze onset the chukchi beaufort seas and laptev east siberian seas observe the strongest trends with 7 d decade 1 for the entire arctic the melt season length has increased by about 20 days over the last 30 years largest trends of over 10 d decade 1 are seen for hudson bay the east greenland sea the laptev east siberian seas and the chukchi beaufort seas those trends are statistically significant at the 99 level

in situ measurements of radionuclide concentrations in south of mugla city turkey the paper presents distribution of radionuclide elements for different samples of igneous metamorphic and sedimentary rocks in the south of mugla city turkey the composite image maps for each of radioelement ratios eu eth and k radiogenic heat producing map rhp and absorbed dose rate of these radionuclides in air were calculated and generated anomaly maps the obtained results were compared with geological units of the study area it has been observed that western side of the study area the bodrum peninsula is mainly characterized volcanic rocks that display high radioactivity concentrations for u th and k 120 2 bq kg 101 60 bq kg and 690 1 bq kg respectively the latite andesite association causes higher th concentrations varying between 1 5 and 101 6 bq kg higher u and th anomalies are close relation with the mineral compositions of the volcanic rocks and their silica contents due to k bearing minerals such as k feldspar orthoclase sanidine biotite higher k concentrations are determined on the other hand metamorphic and sedimentary rocks is dominant in the eastern side of the study area the sedimentary units have the lowest radioactive concentrations for u th and k 8 0 20 and 24 bq kg respectively whereas marble and cherty marbles has higher u and k concentrations it has been also seen that schist and calc schists exhibit important thorium enrichment 80 100 bq kg

thin and thinner sea ice mass balance measurements during sheba 1 as part of a large interdisciplinary study of the surface heat budget of the arctic ocean sheba we installed more than 135 ice thickness gauges to determine the sea ice mass balance while installing these gauges during the fall of 1997 we found that much of the multiyear ice cover was only 1 m thick considerably thinner than expected over the course of the yearlong field experiment we monitored the mass balance for a wide variety of ice types including first year ice ponded ice unponded ice multiyear ice hummocks new ridges and old ridges initial ice thicknesses for these sites ranged from 0 3 to 8 m and snow depths varied from a few centimeters to more than a meter however for all of their differences and variety these thickness gauges sites shared a common trait at every site there was a net thinning of the ice during the sheba year the thin ice found in october 1997 was even thinner in october 1998 the annual cycle of ice thickness was also similar at all sites there was a steady increase in thickness through the winter that gradually tapered off in the spring this was followed by a steep drop off in thickness during summer melt and another tapering in late summer and early fall as freeze up began maximum surface melting was in july while bottom ablation peaked in august combining results from the sites we found an average winter growth of 0 51 m and a summer melt of 1 26 m which consisted of 0 64 m of surface melt and 0 62 m of bottom melt there was a weak trend for thicker ice to have less winter growth and greater net loss for the year however ice growth was also impacted by the snow depth considerable variability was observed between sites in both accretion and ablation the total accretion during the 9 month growth season ranged from zero for thick ridged ice to more than a meter for young ice ponds tended to have a large amount of surface melting while ridges had considerable bottom ablation

winter snow cover on the sea ice of the arctic ocean at the surface heat budget of the arctic ocean sheba temporal evolution and spatial variability 1 the evolution and spatial distribution of the snow cover on the sea ice of the arctic ocean was observed during the surface heat budget of the arctic ocean sheba project the snow cover built up in october and november reached near maximum depth by mid december then remained relatively unchanged until snowmelt ten layers were deposited the result of a similar number of weather events two basic types of snow were present depth hoar and wind slab the depth hoar 37 of the pack was produced by the extreme temperature gradients imposed on the snow the wind slabs 42 of the snowpack were the result of two storms in which there was simultaneous snow and high winds 10 m s 1 the slabs impacted virtually all bulk snow properties emphasizing the importance of episodic events in snowpack development the mean snow depth n 21 169 was 33 7 cm with a bulk density of 0 34 g cm 3 n 357 r2 of 0 987 giving an average snow water equivalent of 11 6 cm 25 higher than the amount record by precipitation gauge both depth and stratigraphy varied significantly with ice type the greatest depth and the greatest variability in depth occurring on deformed ice ridges and rubble fields across all ice types a persistent structural length in depth variations of 20 m was found this appears to be the result of drift features at the snow surface interacting with small scale ice surface structures a number of simple ways of representing the complex temporal and spatial variations of the snow cover in ice ocean atmosphere models are suggested

the layered character of snow covers snow studies have generally ignored the layered nature of snow covers having achieved a good understanding of the properties and processes in homogeneous snow snow scientists should develop more insight into the evolution of the layers and their effects on overall snow response many of the outstanding problems in snow studies can only be solved by dealing with snow as a layered medium the various mechanisms by which layers are generated their effects and some of the outstanding research problems are described here

impact of melt ponds on arctic sea ice simulations from 1990 to 2007 1 the extent and thickness of the arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in september 2007 and 2011 and climate models did not predict this decline one of the processes poorly represented in sea ice models is the formation and evolution of melt ponds melt ponds form on arctic sea ice during the melting season and their presence affects the heat and mass balances of the ice cover mainly by decreasing the value of the surface albedo by up to 20 we have developed a melt pond model suitable for forecasting the presence of melt ponds based on sea ice conditions this model has been incorporated into the los alamos cice sea ice model the sea ice component of several ipcc climate models simulations for the period 1990 to 2007 are in good agreement with observed ice concentration in comparison to simulations without ponds the september ice volume is nearly 40 lower sensitivity studies within the range of uncertainty reveal that of the parameters pertinent to the present melt pond parameterization and for our prescribed atmospheric and oceanic forcing variations of optical properties and the amount of snowfall have the strongest impact on sea ice extent and volume we conclude that melt ponds will play an increasingly important role in the melting of the arctic ice cover and their incorporation in the sea ice component of global circulation models is essential for accurate future sea ice forecasts

modeling the summertime evolution of sea ice melt ponds 1 we present a mathematical model describing the summer melting of sea ice we simulate the evolution of melt ponds and determine area coverage and total surface ablation the model predictions are tested for sensitivity to the melt rate of unponded ice enhanced melt rate beneath the melt ponds vertical seepage and horizontal permeability the model is initialized with surface topographies derived from laser altimetry corresponding to first year sea ice and multiyear sea ice we predict that there are large differences in the depth of melt ponds and the area of coverage between the two types of ice we also find that the vertical seepage rate and the melt rate of unponded ice are important in determining the total surface ablation and area covered by melt ponds

surface and melt pond evolution on landfast first year sea ice in the canadian arctic archipelago the evolution of landfast sea ice melt pond coverage surface topography and mass balance was studied in the canadian arctic during may june 2011 and 2012 using a terrestrial laser scanner snow and sea ice sampling and surface meteorological characterization initial melt pond formation was not limited to low lying areas rather ponds formed at almost all premelt elevations the subsequent evolution of melt pond coverage varied considerably between the 2 years owing to four principle temporally variable factors first the range in premelt topographic relief was 0 5 m greater in 2011 rougher surface than in 2012 smoother surface such that a seasonal maximum pond coverage of 60 and maximum hydraulic head of 204 mm were reached in 2011 versus 78 and 138 mm in 2012 a change in the meltwater balance production minus drainage caused the ponds to spread or recede over an area that was almost 90 larger in 2012 than in 2011 second modification of the premelt topography was observed during mid june due to preferential melting under certain drainage channels some of the lowest lying premelt areas were subsequently elevated above these deepening channels and unexpectedly became drained later in the season third ice interior temperatures remained 1 2 c colder later into june in 2012 than in 2011 even though the ice was 0 35 m thinner at melt onset thereby delaying permeability increases in the ice that would allow vertical meltwater drainage to the ocean finally surface melt was estimated to account for approximately 62 of the net radiative flux to the sea ice cover during the melt season

tracer studies of pathways and rates of meltwater transport through arctic summer sea ice 1 at the surface heat budget of the arctic ocean sheba program s field site in the northern chukchi sea snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998 pathways and rates of meltwater transport were derived from tracer studies h218o 7be and release of fluorescent dyes complemented by in situ sea ice permeability measurements it was shown that the balance between meltwater supply at the surface averaging between 3 5 and 10 5 mm d 1 and ice permeability between 10 9 m2 determines the retention and pooling of meltwater which in turn controls ice albedo we found that the seasonal evolution of first year and multiyear ice permeability and surface morphology determine four distinct stages of melt at the start of the ablation season stage 1 ponding is widespread and lateral melt flow dominates several tens of cubic meters of meltwater per day were found to drain hundreds to thousands of square meters of ice through flaws and permeable zones significant formation of underwater ice composed between 50 of meteoric water formed at these drainage sites complete removal of snow cover increase in ice permeability and reductions in hydraulic gradients driving fluid flow mark stage 2 concurrent with a reduction in pond coverage and albedo during stage 3 maximum permeabilities were measured with surface meltwater penetrating to 1 m depth in the ice and convective overturning and desalination found to dominate the lower layers of first year and thin multiyear ice enhanced fluid flow into flaws and permeable zones was observed to promote ice floe breakup and disintegration concurrent with increases in pond salinities and 7be advective heat flows of several tens of watts per square meter were derived promoting widening of ponds and increases in pond coverage stage 4 corresponds to freeze up roughly 40 of the total surface melt was retained by the ice cover within the ice matrix as well as in surface and under ice ponds with a total net retention of 15 based on this work areas of improvement for fully prognostic simulations of ice albedo are identified calling for parameterizations of sea ice permeability and the integration of ice topography and refined ablation schemes into atmosphere ice ocean models

changes in arctic sea ice result in increasing light transmittance and absorption 1 arctic sea ice has declined and become thinner and younger more seasonal during the last decade one consequence of this is that the surface energy budget of the arctic ocean is changing while the role of surface albedo has been studied intensively it is still widely unknown how much light penetrates through sea ice into the upper ocean affecting sea ice mass balance ecosystems and geochemical processes here we present the first large scale under ice light measurements operating spectral radiometers on a remotely operated vehicle rov under arctic sea ice in summer this data set is used to produce an arctic wide map of light distribution under summer sea ice our results show that transmittance through first year ice fyi 0 11 was almost three times larger than through multi year ice myi 0 04 and that this is mostly caused by the larger melt pond coverage of fyi 42 vs 23 also energy absorption was 50 larger in fyi than in myi thus a continuation of the observed sea ice changes will increase the amount of light penetrating into the arctic ocean enhancing sea ice melt and affecting sea ice and upper ocean ecosystems

processes and imagery of first year fast sea ice during the melt season an analysis of first year fast sea ice during the melt season has been made by using surface measurements and aircraft radar and photographic imagery obtained during a field study near prince patrick island in the canadian archipelago from june 13 to july 13 1982 and satellite imagery from landsat and seasat distinct changes observed in the properties of the snow layer and the sea ice were a temporary increase in small scale surface roughness caused by formation of nodules of ice at the snow ice interface extensive snow melt and surface flooding development of surface water drainage networks and low topography around fractures and seal breathing holes and a rapid draining of much of the surface water from the extensive salinity profiles obtained two zones of rapid desalination in the first year ice were observed one zone extending from the air ice interface downward toward the center of the ice sheet that resulted from surface warming and drainage of the surface melt water through the ice and the other zone extending from the sea ice interface upward toward the center of the ice sheet that resulted from heating and separation of seawater and ice caused by a layer of low salinity meltwater beneath the ice formed from surface meltwater runoff aircraft radar imagery detected changes in the amount of surface water and in the development of topography surrounding drainage features similar changes were detected in coincident landsat multispectral scanner mss imagery of the study area and in seasat radar imagery and landsat mss imagery of the prince of wales strait from july 1978

transpolar observations of the morphological properties of arctic sea ice save for an area between 8830 0 n and 8930 0 n where polynyas and thin ice were observed surveys of snow depth ice thickness and ice properties were conducted at ice stations thickness observations suggest a general latitudinal trend of increasing ice thickness moving northward with considerable variability from floe to floe and within a single floe average floe thicknesses varied from 1 0 to 2 8 m and the standard deviation of thickness on an individual floe was as large as 1 m ice crystallography showed a large amount of granular ice the average optical equivalent soot content was 4n g cg 1 for new snow 8 ng c g 1 for the surface granular layer of multiyear ice and 18 ng c g 1 for the interior of multiyear ice indicating a tendency of the particulates to concentrate at the surface with melting

superimposed ice formation and surface energy fluxes on sea ice during the spring melt freeze period in the baltic sea the development of land fast sea ice and overlying snow was monitored during a 4 week period until the snow cover had completely disappeared at a site in the gulf of bothnia baltic sea 63 57 n 19 85 e the meteorological and radiative boundary conditions were continuously recorded during the observation period a 15 cm thick snow layer on the ice was transformed into a 7 cm thick granular ice layer superimposed ice on the ice surface contributing significantly about 11 to the total ice thickness approximately 1 cm w e of the snow was sublimated neither snow ice formation nor basal ice growth was significant during the same period the salinity and isotopic 18 o composition of the ice indicated that prior to the experiment a 7 cm layer of superimposed ice had already formed hence superimposed ice layers contributed 22 of the total ice thickness by the time all snow had disappeared the advancing spring decrease in surface albedo diurnal cycle in the incoming solar radiation and synoptic scale changes in the cloud cover and the air ice turbulent heat fluxes caused variations in the heat budget of the snowpack superimposed ice formation due to refreezing of meltwater occurred during most nights of the study period and the most important refreezing periods were under such synoptic conditions that the air and snow surface temperatures also remained below zero during daytime in contrast to typical summer conditions in polar oceans low snow surface temperatures acted as the primary heat sink for the refreezing of meltwater