Ice Salinity Research Articles

Seasonal development of the properties and composition of landfast sea ice in the Gulf of Finland, the Baltic Sea

The seasonal development of the structure, salinity, and stable oxygen isotopic composition (δ18O) of landfast sea ice was studied during the winter seasons 1999–2001 in the Gulf of Finland in the Baltic Sea. The main focuses were on the seasonal and the interannual variability in ice properties and composition and on the contribution of meteoric ice to sea ice mass balance. Results provide a first statistical description of the seasonal evolution of sea ice in mild ice climate conditions. The ice has a characteristic structure with an upper granular ice layer, composed almost exclusively of superimposed ice and snow‐ice, averaging at 20–35% of the total ice thickness. The remaining is composed of columnar or intermediate granular columnar ice, depending on growth conditions. While salinity shows a uniform profile through the ice, δ18O shows lower values in the surface because of meteoric ice formation. The thin ice cover is susceptible to changes in atmospheric conditions, and rapid changes in ice salinity are connected to changes in the ice thermal regime and flooding. The contribution of meteoric ice varied from 0 to 35% (by mass), depending on season and year. Superimposed ice formation is a recurring process and significantly contributed to ice growth (up to 20% by mass), especially late in the season during snowmelt‐freeze cycles. Liquid precipitation also cause formation of intermittent superimposed ice layers at these latitudes. The contribution of meteoric ice to sea ice mass balance is largely dependent on the amount and timing of snow accumulation and timing of snowmelt‐freeze processes, which all showed large year‐to‐year variation. The conditions presented here may start to occur at higher latitudes if global warming continues.

Ex Vivo Ureteroscopic Treatment of Calculi in Donor Kidneys at Renal Transplantation

We evaluated the safety and efficacy of ex vivo ureteroscopy (ExURS) as a means of rendering the donated kidney stone-free at live donor renal transplantation. A total of 10 suitable kidney donors with small, unilateral nonobstructive calculi underwent live donor nephrectomy (8 open flank, 2 hand assisted transperitoneal). Immediately after cold perfusion, ExURS was performed in an iced saline solution. Access to the collecting system was via the ureteral stump. Calculi were either removed with endoscopic baskets and/or completely fragmented with Holmium laser lithotripsy. Access to the renal collecting system was technically successful in all cases. A total of 10 stones, ranging in largest diameter from 1 to 8 mm (average 5.2) were visualized. Of the kidneys 6 had solitary stones, 2 had 2 stones and 1 had no stone. Of 10 stones 9 were successfully removed and/or fragmented with an average procedure time of 6.5 minutes (range 3 to 28). Indwelling ureteral stents were placed at transplantation in 5 of 10 kidneys. There were no intra-operative or postoperative ureteral complications. At 1 month after transplant serum creatinine ranged from 0.9 to 2.7 mg/dl (average 1.5). At a mean followup of 33.2 months new stones have not formed in any recipients and at mean 36.4-month followup no new calculi have formed in the remaining kidney of any donors. ExURS is a technically feasible means of rendering a stone bearing kidney stone-free without compromising ureteral integrity or renal allograft function.

Hypothermic retrograde jugular perfusion reduces brain damage in rats with heatstroke.

To determine whether direct retrograde ice saline infusion in the jugular vein without cardiopulmonary bypass protects rat brains after heatstroke. Randomized, controlled, prospective study. University physiology research laboratory. Sprague-Dawley rats (270-320 g, males). Rats were randomized into three groups and given a) no resuscitation after onset of heat stroke (HS, n = 8); b) ice saline infusion in the femoral vein after onset of heat stroke (HS + F, n = 8); or c) retrograde ice saline infusion in the external jugular vein after onset of heat stroke (HS + J, n = 8). Rats were exposed to an ambient temperature of 43 degrees C after vessel cannulation. Their mean arterial pressure, heart rate, colonic temperature, and brain temperature were continuously recorded. Survival time and brain pathology were checked. Although colonic temperature decreased 0.8-1.0 degrees C 15 mins after heatstroke in all groups, no treatment-related changes in colonic temperature were noted in any group. However, significant changes were observed in brain temperature. Fifteen minutes after heatstroke, brain temperature was 37.6 +/- 0.4 degrees C, 36.1 +/- 0.4 degrees C, and 33.6 +/- 0.8 degrees C in HS, HS + F, and HS + J, respectively. Survival time was 16.1 +/- 2.1, 33.0 +/- 3.8, and >120 mins in these groups, respectively. Neuron damage score was significantly lower in HS + J and without lateralization. We successfully demonstrated that direct retrograde hypothermic perfusion via the jugular vein without cardiopulmonary bypass protected the brain after heat stroke. This technique cooled the brain but did not significantly interfere with body temperature.

Controle da hemoptise maciça com broncoscopia rígida e soro fisiológico gelado

INTRODUÇÃO: A hemoptise volumosa é uma condição com alta morbidade e mortalidade, independentemente do tratamento instituído. Vários métodos são utilizados para o controle do sangramento agudo. A instilação de soro fisiológico gelado através de broncoscópio rígido foi descrita em 1980. OBJETIVO: Determinar a eficácia de instilações repetidas de soro fisiológico gelado a 4ºC através de broncoscópio rígido no controle agudo de hemoptise maciça. MÉTODO: Uma série de 94 pacientes, com hemoptise maciça, foi tratada durante sangramento ativo com broncoscopia rígida e lavagem do pulmão sangrante com soro fisiológico gelado. Foi considerado sucesso terapêutico a ausência de sangramento nos 15 dias subseqüentes. Causas de hemoptise, com o respectivo número de pacientes: tuberculose pulmonar, 78 (83%), sendo tuberculose ativa em 48 e seqüela de tuberculose em 30; bronquiectasias, seis; câncer de pulmão, cinco; aspergiloma intracavitário, três, e desconhecida, dois. O sítio de sangramento foi localizado em 93 pacientes (99%). O volume médio de soro infundido durante a broncoscopia foi de 528ml e variou de 160ml a 2.500ml. RESULTADOS: O sangramento cessou durante o procedimento em todos os pacientes. Em 15 pacientes foi feita alguma intervenção (cirurgia, embolização ou radioterapia) num prazo menor que 15 dias, e nestes a eficácia da lavagem não pôde ser avaliada. A hemoptise recorreu em 20 dos 79 pacientes acompanhados por mais de 15 dias. Houve necessidade de nova lavagem com soro fisiológico uma vez em 13 pacientes, duas vezes em seis e três vezes em um paciente. CONCLUSÃO: O controle imediato da hemorragia traqueobrônquica com a administração de soro fisiológico gelado através de broncoscopia rígida é efetivo e pode ser repetido em caso de recorrência do sangramento. O procedimento é seguro e permite que o tratamento definitivo possa ser realizado em melhores condições clínicas.

Profiles of dimethylsulphoniopropionate (DMSP), algal pigments, nutrients, and salinity in the fast ice of Prydz Bay, Antarctica

Total dimethylsulphoniopropionate (DMSPt), chlorophylla(Chla), and algal marker pigments were measured in 12 fast ice cores collected from Prydz Bay, eastern Antarctica (68°–69°S, 77°–79°E) in October 1997 and November 1998. Patterns of DMSPt distribution through the ice were similar on spatial scales of meters to tens of kilometers within ice sheets grouped according to growth history. This reflects the association of DMSP in fast ice with autotrophic biomass distribution, which is intrinsically linked with ice growth and differed between the ice sheets. The 12 fast ice cores were divided into three groups on the basis of ice thickness and year. Concentrations of DMSPt ranged widely from 9 to 1478 nM with marked peaks occurring within each core. Mean DMSPt concentrations were higher (200 nM) in the medium first‐year ice (0.7–1.2 m) than in the thick (>1.2 m) first‐year ice (90 nM), mainly because of a local surface algal assemblage that may be atypical. The fast ice algal assemblages in surface, interior, and bottom ice were dominated by diatoms (Fucoxanthin:Chlaconcentrations >80%). Dinoflagellates and haptophytes were generally small and variable components of the assemblages (Peridinin:Chla2–11% and 19′‐hexanoyloxyfucoxanthin:Chla2–4%, respectively). Our data support the important contribution of diatoms to DMSP production in sea ice. Nutrient (nitrate, silicate, phosphate) concentrations were measured for one group of cores. Silicate and Chlaconcentrations were significantly correlated (r = 0.30, P < 0.02, Pearson), implying that silicate availability may have regulated algal growth. The Si:P:N ratio in interior ice (27:1:10) was different to that in surface and bottom ice (46:1:23). We have summarized DMSP data reported from six Antarctic sea ice studies to investigate whether comparisons within the growing database need to consider differences in sea ice type, thickness, location, or season. Although concentrations from individual samples ranged over 4 orders of magnitude (<1 to >1000 nM,n= 410), the mean DMSP concentrations during spring/summer were within the range of 107–322 nM, with an overall mean of 178 nM. Mean DMSP concentrations in Antarctic sea ice appear to be comparable between studies and across the Antarctic sea ice zone. We estimate that the Antarctic sea ice zone may contain up to 9 Mmole sulphur as DMSP.

Sea ice formation on a very cold surface

[1] In this study laboratory experiments of sea ice formed on a vertical surface with initial temperature of −30 to −50°C are presented. The ice formation is rapid, and in 300 s >5 mm of sea ice is formed. Ice formation cooled and salinified the water, and induced a vertical down wards flow of ∼5 mm/s with a boundary layer about 5 mm thick. This ice has a structure with columnar crystals that have small circular cross sections (0.2–1.0 mm) and sea ice salinities are between 24 and 32. A simple model approach indicate that the thermal conductivity of such ice is lower than for other types of sea ice.

Sea ice biological communities and nutrient dynamics in the Canada Basin of the Arctic Ocean

Salinity, concentrations of silicate (Si), phosphate (P), and chlorophyll a (chl a), and the species composition of floral and faunal communities were assessed in multi-year (MY) and first-year (FY) ice, and at the water–ice interface, during the SHEBA ice camp drift in the Canadian Basin of the Arctic Ocean, October 1997–October 1998. Mean integrated salinity values varied from 0.1±0.8‰ within the snow–ice boundary to 3.2±1.46‰ at the water–ice interface in the MY ice. Salinity of FY ice increased with increasing ice thickness, from 0.41±0.19‰ in October to 3.39±1.75‰ in March. We found very low concentrations of both Si and P in MY and FY ice in late fall (<0.01 μM), after the summer season of 1997. Mean integrated concentration of nutrients increased with the freeze-up of ice, reaching maximum values in the summer of 1998. Ice algal biomass was dominated by diatoms in the MY and FY ice, with more pennate than centric species. Species of dinoflagellates and green algae were subdominant. Green algae, typically confined to the upper part of the ice, were distributed throughout the ice thickness. During summer, the brackish-water green alga Ulothrix implexa formed long rope-like tufts attached to the hull of the icebreaker; development of this species has not previously been observed in the central Arctic Ocean. Biomass, cell abundance and chl a concentrations were high in the bottom sections of both MY and FY ice during the pre-freezing period, then decreased in winter and reached maximum values in spring and summer. The total algal biomass showed a pattern similar to chl a dynamics, decreasing from 1.7 μg C l −1 in October to values <0.1 μg C l −1 in winter. Algal carbon biomass and chl a concentration co-varied significantly in the FY ice ( r 2=0.79), but less so in the MY ice ( r 2=0.49). An unexpected feature with respect to sea ice invertebrates was the absolute absence of living interstitial fauna within the interior of MY and FY sea ice. In addition, the under-ice fauna was species-poor. Comparisons of SHEBA results with historical data showed that the physical–chemical characteristics of sea ice and the biological structure of ice communities found in this study were very different from conditions during the 1970s. It is likely that the changes resulted from increased melting of the arctic ice pack over the last two decades.

On the Role of Sea Ice and Convection in a Global Ocean Model

Abstract An earlier estimate regarding the possible impact of sea ice on deep-ocean water mass properties and the global thermohaline circulation in a coupled sea ice–ocean general circulation model (OGCM) is updated. Compared to the earlier application, the main upgrade is a subgrid-scale plume-convection parameterization that replaces conventional grid-cell-wide convective adjustment. The different treatment of convection leads to some noticeable differences in some of the repeated sensitivity experiments. For example, in an experiment where sea ice salinity is assumed to be that of the upper ocean, thus neglecting the primary effect of sea ice formation and melting on the ocean's buoyancy forcing, Antarctic Bottom Water formation comes essentially to a halt, the global deep-ocean properties and thermohaline circulation thus being almost solely determined by North Atlantic Deep Water. The much weaker impact in the earlier estimate turns out to be mainly due to excessive open-ocean convection in the Sout...

ACTIVE ENDOCARDIAL COOLING OF EXPLANTED HEARTS BY ICED SALINE CIRCULATED VIA NOVEL INTRA VENTRICULAR BALLOON CATHETERS

Hypothermia is an important component of cardiac myocyte preservation during organ procurement and ischemic arrest. At the time of organ implantation passive rewarming occurs. This re-warming can be partially prevented by employing an external cooling jacket but these devices are cumbersome and often obstruct the surgical field. We have developed a novel approach that provides active endocardial cooling via intraventricular cooling balloons. An intracardiac cooling device was created using a modified surgical glove secured to the end of a hemodyalysis catheter. Use of a dual port catheter allowed for continuous circulation of saline to the balloon. Two such catheters were then connected in parallel and placed in the right and left ventricles via the pulmonic and aortic roots respectively. Saline was added through a side port to allow for precise control of intraventricular volume. A roller pump directed saline through cooling coils to the balloons. An explanted diseased human heart was obtained from the recipient at the time of transplantation and placed in a simulated thoracic cavity that consisted of a shallow pool of 32°C saline circulating in a metal basin. Needle temperature probes were placed in the right and left ventricular walls. Temperature curves were recorded during passive re-warming and compared to active cooling using either the intraventricular balloon device or direct ventricular filling with iced saline (4°C). Between experiments the heart was submerged in an iced saline bath for 10 minutes to obtain maximal global cooling. Right and left ventricular temperatures increased 18.0°C (from 9°C to 27°C) and 14.3°C (from 12°C to 26.5°C) respectively during the 75-minute period of passive cooling. This represents an average increase of 1.1°C/5 minute interval. With the addition of the device, ventricular temperatures rose 6.5°C (from 12.5°C to 19.0°C) and 5.3°C (from 13.2°C to 18.5°C). an average 0.4°C/5 minute interval. Lastly, the temperature in the right and left ventricles directly filled with iced saline increased only 1.8°C (from 10°C and 11.8°C) and 5.5°C (from 11°C to 16.5°C) respectively, an average rise of only 0.25°C/5 minute interval. Myocardial cooling during organ implantation can be accomplished by active circulation of iced saline to the ventricular endocardium. While not as efficient as direct iced saline ventricular filling, with design modifications such a device may provide a measurable benefit on organ preservation and subsequent ventricular function.

REIMPLANTATION OF AN AMPUTATED PENIS IN PREPUBERTAL BOYS

Case 1. A 7-year-old boy presented to the emergency room from elsewhere 1 hour after distal penile amputation, which had occurred accidentally during circumcision. The penis had been completely severed 5 mm. proximal to the corona, transecting the urethra and the corpora, and devascularizing the distal portion (fig. 1). The amputated part had been placed in sterile ice saline solution and it accompanied the patient. Using general anesthesia the proximal stump and amputated penis were irrigated with normal saline. Under operating microscopy the deep dorsal and cavernous arteries, veins and nerve fibers were not identifiable. A tourniquet was applied around the proximal stump to gain vascular control of the proximal cavernosum during the procedure. A 8Fr Foley catheter was inserted through the urethra of the amputated part and remaining proximal urethral stump, and passed on into the bladder (fig. 1). End-to-end urethral mucosa anastomosis was formed with 6-zero polyglactin interrupted sutures over the Foley catheter. The corpus spongiosum was then repaired using interrupted 6-zero polyglactin sutures. The tunica albuginea was closed with interrupted 5-zero polyglactin to restore corporeal continuity. The fascial layer and skin were then closed with a 6-zero polyglactin suture. A mild compressive gauze dressing was placed over the distal penis to control bleeding. Parenteral broad-spectrum antibiotics were administered for antimicrobial prophylaxis. Testosterone enanthate (25 mg.) was injected on day 1 after the operation. By the end of postoperative week 1 a thin eschar was forming around the meatus on the glans penis. The Foley catheter was removed at the end of postoperative week 3. The thin eschar around the meatus gradually peeled off, leaving appropriate glans tissue and a meatus with a good cosmetic appearance at week 4 (fig. 2). Two months postoperatively penile cosmesis was excellent, glans sensation was present, and early morning erection and erectile response to touch had been reestablished. Voiding was normal. Case 2. A 12-year-old boy presented 1 hour after accidental amputation of the distal glans penis during circumcision. The excised tissue included the whole glans penis and distal urethra. Amputation had occurred at the level of the coronal sulcus dorsolaterally and the urethra was transected just proximal to the meatus. A 8Fr Foley catheter was inserted into the bladder to stabilize the amputated penis. Under operating microscopy the urethra was anastomosed with interrupted 6-zero polyglactin sutures over the catheter. The edge of the amputated glans was closed over the reattached part of the proximal penile shaft skin and fascial layer with interrupted 6-zero polyglactin sutures. A mild compressive dressing was placed on the glans penis. Testosterone enanthate (50 mg.) was injected on day 1 after the operation. The Foley catheter was removed after 2 weeks. Eschar around the meatus remained until 7 weeks postoperatively. At 3 months there was mild meatal stenosis. Early morning erection was maintained and there was an erectile response during penile manipulation. Glans sensation was present but decreased.

Time-series observations of the structure and properties of brackish ice in the Gulf of Finland

AbstractThe Baltic Sea is a semi-enclosed brackish water basin where sea ice occurs annually. The sea-ice study discussed here was conducted as a Finnish-Japanese cooperative research programme entitled "Ice Climatology of the Okhotsk and Baltic Seas’’ to investigate the structure and properties of the brackish ice in the Baltic Sea. Ice, snow and water samples were collected at Santala Bay, near the mouth of the Gulf of Finland, once a week from 20 January to 12 April 1999. The salinity and oxygen isotopic composition (δ18O) of the samples were measured. The ice samples were analyzed stratigraphically. The ice was composed of a granular upper layer, occupying approximately one-third of the entire ice thickness, and underlying columnar ice toward the bottom. The crystallography structure and δ18O values reveal that the granular ice consisted of two layers with different origins, i.e. snow ice and superimposed ice. The fraction of snow relative to the total thickness was estimated. The limited data show a significant contribution of the snow cover to the sea-ice development. The salinity of the granular ice was higher than that of the columnar ice, implying that the mechanism of entrapment of brine may be different between the two ice types.

A one‐dimensional percolation model of flooding and snow ice formation on Antarctic sea ice

A one‐dimensional thermodynamic sea ice growth model is developed with emphasis on seawater flooding and snow ice formation on Antarctic sea ice. To examine the possibility that flooding is the result of brine percolation through a porous ice matrix, and the consequences of this percolation on the salinity structure and mass balance of the ice, flooding is modeled in a semiheuristic fashion by examining two possible regimes for seawater and brine infiltration through the porous ice into the snowpack. A standard model assumes that the upward flow of brine is horizontally homogeneous and brine flow is modeled using a Darcian scheme. A simple model assumes that the infiltrating brine does not interact with the internal ice brine network, but instead percolates upward through cracks, or is restricted in spatial extent. Results of simulations are shown for the climatology in the Ross Sea and compared to field data from one autumn and one winter cruise aboard the R/V Nathaniel B. Palmer in 1995. Sensitivity studies are performed to show the effects of variations in climate forcing. The dependence of brine percolation and snow ice formation on key thermophysical parameters is investigated. Results indicate that the mass balance depends very strongly on the brine flow regime. In the standard model, ice salinities and brine volumes are greatly affected by brine percolation, creating a strong feedback between flooding and future snow ice production. Snow ice formation for the simple model was much more predictable and depended primarily on snow load. Comparison of results with field data indicate that if brine percolation is the major mechanism for flooding and snow ice formation, then there must be either substantial convective redistribution of salt to maintain ice porosity, or the flow must be spatially inhomogeneous.

Crystalline structure and physical properties of ship superstructure spray ice

In February and March 1990 the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) made measurements of superstructure ice on a US Coast Guard cutter in the Bering Sea. Twenty–three ice samples were removed from bulkheads, decks and icicles during two icing events. Ice crystal measurements included crystal size, shape, orientation, brine–pocket location, size and shape, internal layering, and air–bubble sizes. Ice property measurements included salinity, density and temperature, with computed estimates of air and brine volume. This paper describes crystal and physical properties of the accreted ice and their relationship to ice sample position on the ship. Texturally, accreted ice resembled frazil ice that forms from the consolidation of freely nucleated ice crystals in sea water. This resemblance is also reflected in bulk salinities, ranging from 24‰ to 7‰, compared with frazil formed during the initial stages of freezing of sea water, where bulk salinities can exceed 10‰. Crystalline structures of accreted ice ranged from rounded to polygonal. Generally, rounded crystals would be expected for ice formed from sea–spray droplets, polygonal crystals may be attributed to thermally driven modification. No trend towards reorientation of crystallographic c–axes in either freshly accreted or thermally modified ice was observed. Mean crystal sizes ranged from 0.56 mm to 1.15 mm, with even larger crystals in icicles. Ice salinity averaged ca .12‰ on bulkheads and ca .21‰ on decks. Ice densities ranged from 0.69 to 0.92 Mg m −3 and were generally higher on decks. Bulkhead ice had larger computed total porosity and air volume and lower brine volume than deck ice. Samples taken from decks and bulkheads generally compared well with Russian and Japanese measurements.

Profiles of DMSP, algal pigments, nutrients and salinity in pack ice from eastern Antarctica

Concentrations of dimethylsulphoniopropionate (DMSP) were measured in seven pack ice cores from three sites in eastern Antarctica to determine their relation to algal pigments, nutrients (nitrate, silicate and phosphate) and bulk salinity. The algal groups haptophytes, dinoflagellates and diatoms were identified in surface, interior and bottom assemblages in the pack ice cores using the photosynthetic marker pigments 19′-hexanoyloxyfucoxanthin (HEX), peridinin (PER) and fucoxanthin (FUC), respectively. DMSP concentrations were significantly correlated (P<0.01, Pearson) with chlorophyll-a (r=0.58), HEX (r=0.75), PER (r=0.79) and FUC (r=0.63) concentrations. The pool of DMSP within the pack ice (mean 107nM) was contributed mainly by interior and bottom algal assemblages (mean 94 and 268nM, respectively), whilst the surface algal assemblages were minor contributors (mean 18nM). DMSP production and/or accumulation appears to differ between surface, interior and bottom pack ice algal assemblages due to differences in biomass, class composition, and possibly the unique environmental conditions experienced by each assemblage. In pack ice, diatoms appear to be important producers of DMSP, due to their dominance of algal assemblages.

Physical properties, spectral reflectance and thickness development of first year fast ice in Kongsfjorden, Svalbard

A ground truth study was performed on first year fast ice in Kongsfjorden, Svalbard, during spring 1997 and 1998. The survey included sea ice thickness monitoring as well as observation of surface albedo, attenuation of optical radiation in the ice, physical properties and texture of snow and sea ice. The average total sea ice thickness in May was about 0.9 m, including a 0.2 m thick snow layer on top. Within a few weeks in both years, the snow melted almost completely, whereas the ice thickness decreased by not more than 0.05 m. During spring, the lower part of the snow refroze into a solid layer. The sea ice became more porous. Temperatures in the sea ice increased and the measurable salinity of the sea ice decreased with time. Due to snow cover thinning and snow grain growth, maximum surface albedo decreased from 0.96 to 0.74. Texture analysis on cores showed columnar ice with large crystals (max. crystal lenght > 0.1 m) below a 0.11 m thick mixed surface layer of granular ice with smaller crystals. In both years, we observed sea ice algae at the bottom part of the ice. This layer has a significant effect on the radiation transmissivity.

The role of snow on the thermal dependence of microwave backscatter over sea ice

Our understanding of snow distribution in the polar regions is severely restricted owing to the heterogeneity, both in space and time, of this solid precipitate. Processes such as vapor and mass fluxes across the interface are, to a large extent, controlled by the presence and geophysical state of the snow cover on sea ice. Numerous studies have shown the importance of snow cover in ecosystem processes and particularly in photosynthetically active radiation extinction. Researchers are currently exploiting developments in electromagnetic interaction theory in an attempt to measure snow thickness distributions remotely. In this paper, we investigate the dependence of radar backscatter on snow thickness over smooth first‐year ice. We use data from the Seasonal Sea Ice Monitoring and Modeling Site located in the Canadian Archipelago. Results show that the thermodynamics of the snow cover affect wave propagation, attenuation, and scattering through the control that brine volume exerts on interfacial characteristics of the snow and ice layers. The effect is subtle and specific to certain ranges of salinity, surface roughness and thickness of sea ice. We describe the phenomenon responsible for this effect using a microwave model consistently for both complex effective permittivities and backscatter coefficients coupled to a one‐dimensional model. We validate the physical principles using in situ field data. We then discuss the potential of synthetic aperture radar in estimating snow thickness distributions under these specific conditions using both observed and modeled microwave scattering.

Linkages between salinity and brine channel distribution in young sea ice

A high‐resolution study of bulk salinity was undertaken on laboratory‐grown sea ice to determine the extent of spatial variability of salinity and whether this was associated with brine channel structures. Ice samples at two different stages of development were compared with respect to physical state, brine distribution, and brine channel structures. Cold, growing sea ice is shown to have steep bulk salinity gradients and a highly variable brine distribution that is closely linked to the location and morphology of brine channels. Areas of high bulk salinity are found to correspond directly to the positions of the brine channels, and these areas are surrounded by ice that shows significant brine depletion. It is observed that redistribution of the brine occurs as the ice cover goes through warming and melting phases. The redistribution is attributed to an increase in porosity and pore connectivity permitting migration of brine through the ice. The distribution of brine in “warm” ice is shown to be more homogeneous and independent of brine channel structures. A number of mechanisms exploiting the enhanced mobility of brine in warm sea ice are used to explain the changes in the salinity profiles and brine distribution.

Physical properties, spectral reflectance and thickness development of first year fast ice in Kongsfjorden, Svalbard

A ground truth study was performed on first year fast ice in Kongsfjorden, Svalbard, during spring 1997 and 1998. The survey included sea ice thickness monitoring as well as observation of surface albedo, attenuation of optical radiation in the ice, physical properties and texture of snow and sea ice. The average total sea ice thickness in May was about 0.9 m, including a 0.2 m thick snow layer on top. Within a few weeks in both years, the snow melted almost completely, whereas the ice thickness decreased by not more than 0.05 m. During spring, the lower part of the snow refroze into a solid layer. The sea ice became more porous. Temperatures in the sea ice increased and the measurable salinity of the sea ice decreased with time. Due to snow cover thinning and snow grain growth, maximum surface albedo decreased from 0.96 to 0.74. Texture analysis on cores showed columnar ice with large crystals (max. crystal lenght > 0.1 m) below a 0.11 m thick mixed surface layer of granular ice with smaller crystals. In both years, we observed sea ice algae at the bottom part of the ice. This layer has a significant effect on the radiation transmissivity.

Classification of sea ice types in the Ross Sea, Antarctica from SAR and AVHRR imagery

ERS-2 synthetic aperture radar (SAR) and Advanced Very High Resolution Radiometer (AVHRR) imagery are used to examine spectral characteristics of late winter/early spring ice in the Ross Sea, Antarctica. The combined spectral signatures are used to distinguish six ice types: fast ice, new ice, smooth first year ice, rough first year ice, thin new ice/wind roughened open water and glacial ice. The procedure firstly involves 'picking' class boundaries from SAR imagery based on the morphology of a speckle reduced backscatter spectrum. These class boundaries are then used as input to an iterative segmentation procedure that involves the repeated application of a speckle reduction filter to the image. For an image from late September 1996 the segmentation procedure enabled separation of five general ice categories each with a characteristic backscatter range. However because of the combined contributions of ice thickness, surface roughness, salinity and water content to the SAR backscatter, further decision criteria are required to separate some physical ice types unable to be resolved individually using this method. Coincident and co-registered infrared data from the AVHRR sensor are used to extract spectral characteristics for the final ice classes. Using this procedure we were able to distinguish floating glacier ice from thin new ice/wind roughened open water and new ice from nearshore fast ice. These ice types were unable to be separated using SAR backscatter intensity alone. In addition image subtraction was also able to clearly delineate areas of shore fast ice.

A Gibbs thermodynamic potential of sea ice

A thermodynamic potential function for air-free sea ice, specific Gibbs free energy (free enthalpy) G( s, t, p), has been computed in terms of sea ice salinity s, temperature t and pressure p. Its numerical application is restricted to brine salinities up to 40 g/kg and to applied pressures not exceeding 10 MPa. Using the assumption of brine–ice equilibrium the Gibbs potential is derived from Gibbs free energies of seawater and of pure water ice. Explicit mathematical expressions are deduced theoretically for various thermodynamic properties of sea ice including, e.g., specific heat at constant pressure, isothermal compressibility, isobaric thermal volume expansion coefficient, isochoric pressure coefficient, and temperature of maximum volume. Care is taken for pressure dependencies of all properties and for appropriate salinity root expansions due to Debye–Hückel theory of electrolytic solutions. Simplified computation formulas are proposed for some important quantities.