bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial fields of Antarctic sea-ice concentration anomalies for summer–autumn and their relationship to Southern Hemisphere atmospheric circulation during the period 1979–2009
Authors: Barreira Sandra , Compagnucci Rosa Hilda 
Published: June 2011

AbstractSummer–autumn monthly sea-ice concentration anomaly (SICA) fields in Antarctica obtained from satellite data for the period 1979–2009 were analysed with Varimax-rotated T-mode principal component analysis (PCA). the first three PCA scores described the SICA spatial behaviour and explained 38.07% of the total variance. the related atmospheric circulation characteristics were analysed using 850 hPa height and surface air-temperature anomalies for the months clustered by the corresponding SICA composites, which were based on PCA loadings above a ±0.3 threshold. the principal characteristics of SICA can be seen between the Ross and Weddell Seas, areas that remained ice-covered during the analysis period. Elsewhere around Antarctica, small distinct characteristics occur mostly in embayments. the leading summer–autumn SICA pattern shows a structure with two centres of equal sign located one over the Weddell and the other over the Ross Sea–southwest Pacific Ocean sector and a centre of opposite sign over the Bellingshausen and Amundsen Seas. the second SICA pattern is represented by a dipole over the Weddell Sea as a result of an increase (decrease) in sea-ice concentration in the northern sector (positive phase) and a decrease (increase) in the southern region, together with a positive (negative) centre over the Ross and Amundsen Seas. the latter pattern is characterized by equal-sign anomalies on both sides of the Antarctic Peninsula and opposite-sign centres all around Antarctica with the highest intensity over the Ross Sea.
An intercomparison between AMSR-E snow-depth and satellite C- and Ku-band radar backscatter data for Antarctic sea ice
Authors: Kern Stefan , Ozsoy-Cicek Burcu , Willmes Sascha , Nicolaus Marcel , Haas Christian , Ackley Stephen 
Published: June 2011

AbstractAdvanced Microwave Scanning Radiometer (AMSR-E) snow-depth data for Antarctic sea ice are compared with ship-based visual observations of snow depth, ice type and ridged-ice fraction, and with satellite C-band and Ku-band radar backscatter observations for two ship cruises into the Weddell Sea (ISPOL 2004–05,WWOS 2006) and one cruise into the Bellingshausen Sea (SIMBA 2007) during late winter/spring. Most (>75%) AMSR-E and ship-based snow-depth observations agree within 0.2 m during WWOS and SIMBA. Remaining observations indicate substantial underestimations of snow depths by AMSR-E data. These underestimations tend to increase with the ridged-ice fraction for WWOS and SIMBA. In areas with large snow depths, a combination of relatively stable low C-band radar backscatter and variable Ku-band radar backscatter is associated with undeformed first-year ice and may indicate snow metamorphism at this time of year during SIMBA. In areas with small snow depths, a combination of relatively stable low Ku-band radar backscatter, high C-band radar backscatter and low C-band radar backscatter standard deviations is associated with rough first-year ice during SIMBA. This information can help to better understand causes of the observed AMSR-E snow-depth bias during late-winter/spring conditions with decreasing average snow depth and to delineate areas where this bias occurs.
Comparison of seasonal sea-ice thickness change in the Transpolar Drift observed by local ice mass-balance observations and floe-scale EM surveys
Authors: Haas Christian , Goff Herve Le , Audrain Samuel , Perovich Don , Haapala Jari 
Published: June 2011

AbstractLocal and transect ice-thickness measurements were performed between May and November 2007 on an ice floe in the Transpolar Drift of the Arctic Ocean using an ice mass-balance buoy and electromagnetic induction (EM) sounding. Repeated EM surveys along an originally 2160m long profile including level and deformed ice showed that between June and September modal and mean thicknesses decreased by 0.6 and 0.86m respectively. the modal thickness decrease is in good agreement with the thinning of 0.6m observed by the ice mass-balance buoy at one location on unponded ice during the same period, although the local observations do not capture the different melt rates on level and rough ice. the paper discusses methodological and operational challenges in sustaining both measurements over periods of several months, and concludes that more work needs to be done to better understand their representativeness.
Thermodynamic investigation of an evolving grease to pancake ice field
Authors: De La Rosa Sara , Maus Sönke , Kern Stefan 
Published: June 2011

AbstractWe present results from a laboratory tank study of ice growing from saline water in a wave field, focusing on the transition from a predominantly frazil/grease-ice cover to a pancake-ice cover. Combining surface temperature observations with direct and indirect determinations of ice salinity and solid fraction, we describe the evolution of frazil- and pancake-ice area fraction, salinity and solid-ice volume fraction over the course of 1 day. In the investigated stage of transition, frazil ice surrounding the pancakes was found to have rather constant properties: a surface temperature 0.4–0.6 K below the freezing point of the underlying sea water, a salinity of 24–26 g kg–1 and a solid volume fraction of 0.25–0.29. the average salinity of young pancake ice, estimated from heat and salt budgets, decreased from 18 to 15 g kg–1, while average solid volume fractions increased from 0.6 to 0.7. the transition from frazil to pancake is estimated to take place when solid fractions reach 0.37–0.40 and surface temperatures are 0.7–0.9 K below the freezing point. We find that, for proper modelling of the grease–pancake system, it is important to distinguish between a surface and volumetric fraction of pancakes and grease ice.
Meteoric ice contribution and influence of weather on landfast ice growth in the Gulf of Finland, Baltic Sea
Authors: Uusikivi Jari , Granskog Mats A. , Sonninen Eloni 
Published: June 2011

AbstractThe stable oxygen isotopic composition (δ18O), texture and stratigraphy of landfast ice in Santala Bay, Gulf of Finland, were studied annually from 1999 to 2009. Apart from one year when there was no ice, maximum ice thickness ranged from 0.22 to 0.60 m. Maximum ice thickness was determined primarily by average air temperature, and a simple accumulated freezing-degree-day–ice-thickness model explained 86% of ice-thickness variance. the total ice thickness each winter was dominated by columnar ice and intermediate granular/columnar ice formed at the base of the ice cover. Meteoric ice (snow ice and superimposed ice) accumulated at the top of the ice cover each winter and constituted 4–39% of the total ice thickness (ice mass). Snow ice formed in seven of the ten winters; superimposed ice formed in only three winters. the snow fraction in the meteoric ice contributed 1–30% annually of the total ice mass, with an average of 8.8%.
Ion fractionation in young sea ice from Kongsfjorden, Svalbard
Authors: Maus Sönke , Müller Susann , Büttner Juliane , Brütsch Sabina , Huthwelker Thomas , Schwikowski Margit , Enzmann Frieder , Vähätolo Anssi 
Published: June 2011

AbstractThe fractionation of major sea-water ions, or deviation in their relative concentrations from Standard Mean Ocean Water ratios, has been frequently observed in sea ice. It is generally thought to be associated with precipitation of solid salts at certain eutectic temperatures. the variability found in bulk sea-ice samples indicates that the fractionation of ions depends on the often unknown thermal history of sea ice, which affects the structure of pore networks and fate of solid salts within them. Here we investigate the distribution of ions in Arctic sea ice that is a few weeks old with a reconstructible thermal history. We separate the centrifugable (interconnected) and entrapped (likely disconnected) contributions to the ice salinity and determine their ion fractionation signatures. the results indicate that differential diffusion of ions, rather than eutectic precipitation of cryohydrates, has led to significant ion fractionation. the finding emphasizes the role of coupled diffusive–convective salt transport through complex pore networks in shaping the biogeochemistry of sea ice.
A comparison of satellite-derived sea-ice motion with drifting-buoy data in the Weddell Sea, Antarctica
Authors: Schwegmann Sandra , Haas Christian , Fowler Charles , Gerdes Rüdiger 
Published: June 2011

AbstractWe compare a satellite-derived sea-ice motion dataset obtained from the US National Snow and Ice Data Center with daily ice drift by drifting buoys between 1989 and 2005. the satellite data were derived from daily composites of passive-microwave satellite measurements by means of a cross-correlation method and were supplemented with data from visible and thermal channels of the Advanced Very High Resolution Radiometer. Seasonal and interannual variations of the agreement between the two datasets are discussed. In addition, regional differences in the agreement and correlation coefficients of buoy- and satellite-derived drift components are analyzed. Results show that the overall drift regime can be well described by satellite-derived drift data but 71% of the retrieved drift velocities are lower than those observed by buoys. Nevertheless, correlation coefficients, r, between the two datasets are 0.587 for the zonal and 0.613 for the meridional drift component. the correlation coefficients between monthly averages of buoy- and satellite-derived zonal and meridional drift components are on average 25.7% and 16.4% lower in summer (October–February) than in winter (March–September), with the exception of January. In January, correlation coefficients are about 62.6% (zonal) and 66.5% (meridional) lower than in winter. Furthermore, deviations between zonal buoy- and satellite-derived drift are 80% larger in the second half than in the first half of the year. the observed yearly and regional averaged agreement between the two datasets depends strongly on the season when buoy data were collected and on the number of coincident buoy and satellite data, which was often very low.
An emerging technique: multi-ice-core multi-parameter correlations with Antarctic sea-ice extent
Authors: Sneed Sharon B. , Mayewski Paul A. , Dixon Daniel A. 
Published: June 2011

AbstractUsing results stemming from the International Trans-Antarctic Scientific Expedition (ITASE) ice-core array plus data from ice cores from the South Pole and Siple Dome we investigate the use of sodium (Na+), non-sea-salt sulfate (nssSO42–) and methylsulfonate (MS–) as proxies for Antarctic sea-ice extent (SIE). Maximum and mean annual chemistry concentrations for these three species correlate significantly with maximum, mean and minimum annual SIE, offering more information and clarification than single ice-core and single species approaches. Significant correlations greater than 90% exist between Na+ and maximum SIE; nssSO42– with minimum and mean SIE; and MS– with mean SIE. Correlations with SIE within large geographic regions are in the same direction for all ice-core sites for Na+ and nssSO42– but not MS–. All ice cores display an SIE correlation with nssSO42– and MS–, but not all correlate with Na+. This multi-core multi-parameter study provides the initial step in determining which chemical species can be used reliably and in which regions as a building block for embedding other ice-core records. Once established, the resulting temporal and spatial matrix can be used to relate ice extents, atmospheric patterns, biological productivity and site conditions.
Modelling the reorientation of sea-ice faults as the wind changes direction
Authors: Wilchinsky Alexander V. , Feltham Daniel L. , Hopkins Mark A. 
Published: June 2011

AbstractA discrete-element model of sea ice is used to study how a 90˚ change in wind direction alters the pattern of faults generated through mechanical failure of the ice. the sea-ice domain is 400 km in size and consists of polygonal floes obtained through a Voronoi tessellation. Initially the floes are frozen together through viscous–elastic joints that can break under sufficient compressive, tensile and shear deformation. A constant wind-stress gradient is applied until the initially frozen ice pack is broken into roughly diamond-shaped aggregates, with crack angles determined by wing-crack formation. Then partial refreezing of the cracks delineating the aggregates is modelled through reduction of their length by a particular fraction, the ice pack deformation is neglected and the wind stress is rotated by 90˚. New cracks form, delineating aggregates with a different orientation. Our results show the new crack orientation depends on the refrozen fraction of the initial faults: as this fraction increases, the new cracks gradually rotate to the new wind direction, reaching 90˚ for fully refrozen faults. Such reorientation is determined by a competition between new cracks forming at a preferential angle determined by the wing-crack theory and at old cracks oriented at a less favourable angle but having higher stresses due to shorter contacts across the joints.
Grease-ice thickness parameterization
Authors: Smedsrud Lars H. 
Published: June 2011

AbstractGrease ice is a mixture of sea water and frazil ice crystals forming in Arctic and Antarctic waters. the initial grease-ice cover, or the grease ice forming during winter in leads and polynyas, may therefore have mixed properties of water and ice. Most sea-ice models use a lower thickness limit on the solid sea ice, representing a transition from grease ice to solid ice. Before grease ice solidifies it is often packed into a layer by the local wind. Existing field measurements of grease ice are compared and used to evaluate a new thickness parameterization including the drag from the wind as well as the ocean current. the measurements support a scaling of the wind drag and the back pressure from the grease-ice layer using a nonlinear relation. the relation is consistent with an increasing grease-ice thickness towards a solid boundary. Grease-ice data from Storfjorden, Svalbard, confirm that tidal currents are strong enough to add significant drag force on the grease ice. A typical wind speed of only 10ms −1 results in a 0.3m thick layer of grease ice. Tidal currents of 0.5ms −1 will pack the grease ice further towards a stagnant boundary to a mean thickness of 0.8 m.
Interaction between Antarctic sea ice and synoptic activity in the circumpolar trough: implications for ice-core interpretation
Authors: Schlosser Elisabeth , Powers Jordan G. , Duda Michael G. , Manning Kevin W. 
Published: June 2011

AbstractInteractions between Antarctic sea ice and synoptic activity in the circumpolar trough have been investigated using meteorological data from European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-analysis and sea-ice data from passive-microwave measurements. Total Antarctic sea-ice extent does not show large interannual variations. However, large differences are observed on a regional/monthly scale, depending on prevailing winds and currents, and thus on the prevailing synoptic situations. the sea-ice edge is also a preferred region for cyclogenesis due to the strong meridional temperature gradient (high baroclinicity) in that area. the motivation for this study was to gain a better understanding of the interaction between sea-ice extent and the general atmospheric flow, particularly the frequency of warm-air intrusions into the interior of the Antarctic continent, since this influences precipitation seasonality and must be taken into account for a correct climatic interpretation of ice cores. Two case studies of extraordinary sea-ice concentration anomalies in relation to the prevailing atmospheric conditions are presented. However, both strong positive and negative anomalies can be related to warm biases in ice cores (indicated by stable-isotope ratios), especially in connection with the negative phase of the Southern Annular Mode.
Selective retention in saline ice of extracellular polysaccharides produced by the cold-adapted marine bacterium Colwellia psychrerythraea strain 34H
Authors: Ewert Marcela , Deming Jody W. 
Published: June 2011

AbstractThe retention of salts in laboratory-grown ice was compared to the retention of extracellular polysaccharide substances (EPS) produced by the cold-adapted marine gammaproteobacterium, Colwellia psychrerythraea strain 34H. Saline ice was formed, by means of a cold-finger apparatus, from artificial sea-water solutions containing either native dissolved EPS from strain 34H, the same EPS but heat-treated, or dissolved EPS from the uninoculated growth medium. Results indicated that only the native (unheated) EPS of strain 34H was retained preferentially in the ice. Temperature and volumetric measurements of the ice further suggested a link between the heat-labile fraction of this EPS of marine bacterial origin and potential habitat alteration. Bacterial EPS may join algal EPS in our understanding of how extracellular polymers help to establish and sustain the microbial community that inhabits sea ice.
Antarctic sea-ice extents and concentrations: comparison of satellite and ship measurements from International Polar Year cruises
Authors: Ozsoy-Cicek Burcu , Ackley Stephen F. , Worby Anthony , Xie Hongjie , Lieser Jan 
Published: June 2011

AbstractAntarctic Sea Ice Processes and Climate (ASPeCt) ship-based ice observations, conducted during the Sea Ice Mass Balance in the Antarctic (SIMBA) and Sea Ice Physics and Ecosystem eXperiment (SIPEX) International Polar Year (IPY) cruises (September–October 2007), are used to validate remote-sensing measurements of ice extent and concentration. Observations include varied sea-ice types at and inside the ice edge of West (~90˚ W) and East (~120˚ E) Antarctica. Time series of Advanced Microwave Scanning Radiometer–Earth Observing System (AMSR-E) ice extents and US National Ice Center (NIC) ice edges were obtained for the 2007–08 periods bracketing the period these cruises were conducted. A comparison between passive microwave satellite imagery and ASPeCt observations of sea-ice concentration during two cruises was also performed. In 90˚W regions, the concentrated pack ice indicated good correlation between ship observations and passive microwave estimates of the ice concentration (R2 = 0.80). In the marginal zone of West Antarctica and over nearly the entire sea-ice zone of East Antarctica, correlation dropped to R2 < 0.60. These findings are consistent with other studies comparing passive microwave and ship observations and further verify that the East Antarctic sea-ice zone is more marginal in character. There are significant ice-edge differences between AMSR-E and NIC between late November 2007 and early March 2008 such that the AMSR-E sea-ice extent estimate is 1–2 × 106 km2 less than the NIC estimate.
Behaviour of dissolved organic matter during formation of natural and artificially grown Baltic Sea ice
Authors: Müller Susann , Vähätalo Anssi V. , Granskog Mats A. , Autio Riitta , Kaartokallio Hermanni 
Published: June 2011

AbstractDuring sea-ice formation, the dissolved constituents of water are rejected from ice crystals. the initial fractionation of dissolved organic matter (DOM) in the Baltic Sea ice was studied through two freezing experiments and by sampling natural sea ice. DOM was characterized by the spectral absorption of chromophoric DOM (CDOM) and the parallel factor analysis of DOM fluorescence. Molecular weight measurements of DOM were applied to assess changes in the molecular size distribution of DOM in new sea ice relative to parent sea water. Both in the newly formed artificial and the natural sea ice, CDOM was enriched by 34–39% relative to salinity. the same three identified DOM fluorophores were present both in sea water and ice but enriched by 15–54% relative to salinity in ice. After the incorporation of DOM into ice, the ageing of ice decreased the spectral slope coefficient and the molecular weight of DOM. This study shows that physical processes during freezing of brackish water enrich chromo- and fluorophoric DOM relative to salts in sea ice.
Characterization of dissolved organic matter (DOM) from glacial environments using total fluorescence spectroscopy and parallel factor analysis
Authors: Dubnick Ashley , Barker Joel , Sharp Martin , Wadham Jemma , Lis Grzegorz , Telling Jon , Fitzsimons Sean , Jackson Miriam 
Published: June 2011

AbstractAquatic dissolved organic matter (DOM) is a major reservoir of reduced organic carbon and has a significant influence on heterotrophic biological productivity and water quality in marine and freshwater environments. Although the forms and transformations of DOM in temperate aquatic and soil environments have been studied extensively, this is not the case for glacial environments. In this study, fluorescent excitation–emission matrices (EEMs), parallel factor analysis (PARAFAC) and cluster analysis were used to characterize the fluorescing components of DOM in ice and water samples from supraglacial, englacial, subglacial and proglacial environments of seven glaciers in the Canadian Arctic, Norway and Antarctica. At least five significant fluorescent DOM fractions were identified, which accounted for 98.2% of the variance in the dataset. These included four protein-like components and one humic-like component. The predominantly proteinaceous character of DOM from these glaciers is very different from the more humic character of DOM described previously from lacustrine, fluvial, estuarine and marine environments. DOM from the sampled glaciers is broadly similar in character despite their geographically distinct locations, different thermal regimes and inter- and intra-site differences in potential organic matter sources. Glacier ice samples had a relatively low ratio of humic-like :protein-like fluorescence while meltwater samples had a higher ratio.
Effects of loss of perennial lake ice on mixing and phytoplankton dynamics: insights from High Arctic Canada
Authors: Veillette Julie , Martineau Marie-Josée , Antoniades Dermot , Sarrazin Denis , Vincent Warwick F. 
Published: June 2011

AbstractPerennially ice-covered lakes are well known from Antarctica and also occur in the extreme High Arctic. Climate change has many implications for these lakes, including the thinning and disappearance of their perennial ice cover. The goal of this study was to consider the effects of transition to seasonal ice cover by way of limnological observations on a series of meromictic lakes along the northern coastline of Ellesmere Island, Nunavut, Canada. Conductivity-temperature profiles during a rare period of ice-free conditions (August 2008) in these lakes suggested effects of wind-induced mixing of their surface freshwater layers and the onset of entrainment of water at the halocline. Sampling of the mixed layer of one of these meromictic lakes in May and August 2008 revealed a pronounced vertical structure in phytoplankton pigments and species composition, with dominance by cyanobacteria, green algae, chrysophytes, cryptophytes and dinoflagellates, and a conspicuous absence of diatoms. The loss of ice cover resulted in an 80-fold increase in water column irradiance and apparent mixing of the upper water column during a period of higher wind speeds. Zeaxanthin, a pigment found in cyanobacteria, was entirely restricted to the <3μm cell fraction at all depths and increased by a factor of 2–17, with the greatest increases in the upper halocline region subject to mixing. Consistent with the pigment data, picocyanobacterial populations increased by a factor of 3, with the highest concentration (1.65 × 108 cells L−1) in the upper halocline. Chlorophyll a concentrations and the relative importance of phytoplankton groups differed among the four lakes during the open-water period, implying lake-specific differences in phytoplankton community structure under ice-free conditions.