bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combined satellite- and ULS-derived sea-ice flux in the Weddell Sea, Antarctica
Authors: Drinkwater Mark R. , Liu Xiang , Harms Sabine 
Published: November 2007

AbstractSeveral years of daily microwave satellite ice drift are combined with moored upward-looking sonar (ULS) ice drafts into an ice-volume flux record at points along a flux gate across the Weddell Sea, Antarctica. Monthly ice transport varies at the mooring locations from a maximum export of 0.4 m3 s−1 near joinville Island to −0.4 m3 s−1 imported along the Fimbul and Riiser-Larsen ice-shelf margins. Winter peaks are observed at each end of the flux gate, where high concentrations of deformed ice are advected in and out of the basin along the coastline. The central gyre, in contrast, exhibits negligible seasonality and much smaller volume transports. During the period of overlapping ULS operation, the mean monthly integrated ice export west of the gyre center is 59 × 103 m3 s−1, and the import in the East Wind Drift is −17 x103 m3s-1. ULS data are compared with ERS satellite observation of radar backscatter to obtain an empirical relationship between ice thickness and the rate of change of backscatter with incidence angle. Resulting proxy ice-thickness data are combined with Special Sensor Microwave/Imager-derived ice velocities to obtain seasonally varying estimates of net ice-volume flux for the period 1992−98. Significant interannual variability is observed in ice-volume flux expressed as fresh-water transport. A maximum annual mean of 0.054 Sv is observed in 1992; with a minimum of 0.015 Sv in 1996. A 6 year mean transport of 0.032 Sv is observed. Maximum seasonal ice export occurs in July 1992, with a minimum in November 1996. The 10 year mean area flux is 30 × 103 m2s–1 Interannual variations in net volume flux closely follow variations in area flux, with summer minima in 1990/91 and 1996/97. Maximum area transport occurs in 1991, and although this predates the ERS-1 scatterometer data, ice-thickness estimates by Harms and others confirm 1991 as a decadal peak in net integrated fresh-water transport.
Decadal variability in high northern latitudes as simulated by an intermediate-complexity climate model
Authors: Goosse H. , Selten F. M. , Haarsma R. J. , Opsteegh J. D. 
Published: November 2007

AbstractA 2500 year integration has been performed with a global coupled atmospheric-sea-ice-ocean model of intermediate complexity with the main objective of studying the climate variability in polar regions on decadal time-scales and longer. The atmospheric component is the ECBILT model, a spectral T21 three-level quasi-geostrophic model that includes a representation of horizontal and vertical heat transfers as well as of the hydrological cycle. ECBILT is coupled to the CLIO model, which consists of a primitive-equation free-surface ocean general circulation model and a dynamic-thermodynamic sea-ice model. Comparison of model results with observations shows that the ECBILT-CLIO model is able to reproduce reasonably well the climate of the high northern latitudes. The dominant mode of coupled variability between the atmospheric circulation and sea-ice cover in the simulation consists of an annular mode for geopotential height at 800 hPa and of a dipole between the Barents and Labrador Seas for the sea-ice concentration which are similar to observed patterns of variability. In addition, the simulation displays strong decadal variability in the sea-ice volume, with a significant peak at about 18 years. Positive volume anomalies are caused by (1) a decrease in ice export through Fram Strait associated with more anticyclonic winds at high latitudes, (2) modifications in the freezing/melting rates in the Arctic due to lower air temperature and higher surface albedo, and (3) a weaker heat flux at the ice base in the Barents and Kara seas caused by a lower inflow of warm Atlantic water. Opposite anomalies occur during the volume-decrease phase of the oscillation.
Sea ice and the stability of north and northeast Greenland floating glaciers
Authors: Reeh Niels , Thomsen Henrik Højmark , Higgins Anthony K. , Weidick Anker 
Published: November 2007

AbstractThe interaction between sea ice and glaciers has been studied for the floating tongue of Nioghalvfjerdsfjorden glacier, northeast Greenland (79°30’N, 22° W). Information from glacial geological studies, expedition reports, aerial photographs and satellite imagery is used to document the glacier front position and fast-ice conditions on millennial to decadal time-scales. The studies indicate that the stability of the floating glacier margin is dependent on the presence of a protecting fast-ice cover in front of the glacier. In periods with a permanent fast-ice cover, no calving occurs, but after fast-ice break-up the glacier responds with a large calving activity, whereby several years of accumulated glacier-ice flux suddenly breaks away. Climate-induced changes of sea-ice conditions in the Arctic Ocean with seasonal break-up of the near-shore fast ice could lead to disintegration of the floating glaciers. The present dominant mass loss by bottom melting would then to a large extent be taken over by grounding-line calving of icebergs. The local influx of fresh water from the north Greenland glaciers to the sea would be reduced and the local iceberg production would increase.
Seasonal contrasts in snow-cover characteristics on Ross Sea ice floes
Authors: Morris Kim , Jeffries Martin O. 
Published: November 2007

AbstractSnow-cover characteristics on ice floes in the Ross Sea, Antarctica, were examined during cruises in autumn 1998 and summer 1999. The autumn snow cover was shallower, colder and had higher and more variable salinity, and smaller single and composite grain-sizes than the summer snow cover. The autumn snow cover was dominated by rounded particles in chains of grains and clusters, while the summer snow cover was composed primarily of melt clusters. There was extensive flooding of the summer snow cover at the snow/ice interface. The summer snow cover was nearly isothermal and close to the melting point. It exhibited obvious signs of melting and refreezing in the form of ice lenses, pipes and superimposed ice, although no melt ponds were evident. Many of the ice lenses were located directly above the saline standing water found on most of the summer ice floes.
Arctic sea-ice oscillation: regional and seasonal perspectives
Authors: Wang Jia , Ikeda Moto 
Published: November 2007

AbstractVariability of the sea-ice cover (extent) in the Northern Hemisphere (Arctic and subpolar regions) associated with the Arctic Oscillation (AO) is investigated using historical data from 1901 to 1997. A principal-component analysis (empirical orthogonal functions (EOFs)) was applied to sea-ice area (SIA) anomalies for the period 1953−95. The leading EOF mode for the SI A anomaly shows an in-phase fluctuation in response to the AO and is called the Arctic sea-ice oscillation (ASIO). Arctic sea ice experiences seasonal variations that differ in timing and magnitude. Four types of seasonal variation are identified in the Arctic sea ice, and are superimposed on long-term interannual to decadal variability. Consistent with the total Arctic SIA anomaly eight regional SIA anomalies have shown significant in-phase decrease (downward trend) since 1970, possibly part of a very long-term (century) cycle. Thus, it is recommended that SIA anomalies in the sensitive seasons be used to better capture interannual, interdecadal and longer (century) variability. Major decadal and interdecadal time-scales of SIA anomalies are found at 12−14 and 17−20 years. In the Sea of Okhotsk, a century time-scale is evident. The reduction rate (negative trend) of the total Arctic sea-ice cover in the last three decades is −4.5% per decade, with the summer rate being the highest (-10.2% per decade). The contribution to this total reduction varies from region to region, with sea-ice cover in the Greenland and Norwegian Seas experiencing the highest reduction rate of −20.2 % per decade.
Seasonal transformation of water masses, circulation and brine formation observed in Storfjorden, Svalbard
Authors: Haarpaintner Jörg , O’Dwyer Jane , Gascard Jean-Claude , Haugan Peter M. , Schauer Ursula , Østerhus Svein 
Published: November 2007

AbstractThe transformation of ocean water masses at high latitudes is closely related to the freezing and melting processes during the year. Downward salt fluxes from brine rejection during freezing increase the salinity and density of the water column underneath. Fresh-water input from river run-off and melting of sea ice reduces the density, mainly of the surface layer. Hydrographic profiles collected in Storfjorden, Svalbard, in spring and summer, show the strong seasonal and interannual variability of the water masses. Using, in addition, data from moorings, a ship-borne acoustic Doppler current profiler and drifting buoys, and results from models of ice drift, polynya evolution, ice formation and convection processes during freezing, we document the seasonal water-mass transformation and try to explain its interannual variability. The advection of ice and water through the two northern sounds and over the sill in the south of the fjord is examined. The release of brine-enriched bottom water over the sill must be balanced by advection from the Barents Sea in the upper layers. The interannual variability of the brine-enriched bottom layer is very high, and higher salinities are observed in a milder winter. The density anomaly resulting from freezing might depend more on the ice cover and geographical position of the polynya than on the total atmospheric forcing during winter.
The Antarctic Circumpolar Wave in a global, high-resolution, coupled ice-ocean model
Authors: Zhang Yuxia , Semtner Albert J. 
Published: November 2007

AbstractThe Antarctic Circumpolar Wave (ACW) is identified by White and Peterson (1996) as anomalies in sea-level pressure, meridional wind stress (MWS), sea-surface temperature (SST) and sea-ice extent (SIE) propagating eastward over the Southern Ocean. In this study, the ACW is examined using a global coupled ice-ocean model with an average horizontal grid size of 1/4°. The model is forced with 1979−93 daily average atmospheric data from the European Centre for Medium-range Weather Forecasts (ECMWF) re-analysis (ERA). The sea-ice model includes both dynamics and thermodynamics, and the ocean model is a primitive-equation, free-surface, z-coordinate model. Both standing and propagating oscillations are present in ERA surface net heat-flux (NHF) and MWS anomalies. The ocean and ice respond to such atmospheric forcing with similar standing and propagating oscillations. For the propagating mode, SIE, SST and sea-surface salinity anomalies propagate eastward with a period of about 4−5 years and take about 8−9 years to encircle the Antarctic continent. Thus, the simulated ACW is a wavenumber-2 phenomenon which agrees with the ACW identified by White and Peterson (1996). The correctly simulated strength of the Antarctic Circumpolar Current, which governs the phase speed of oceanic anomalies, in our high-resolution model is essential for obtaining the observed wavenumber-2 ACW mode in the ocean. The ACW signature is also present in ocean temperature and salinity anomalies down to about 1000 m depth with similar eastward-propagating speed. The anomalies in the interior ocean are more coherent and intense over the Pacific and Atlantic sectors than over the Indian sector. Northward (southward) MWS anomalies, northward (southward) SIE anomalies, cold (warm) SST anomalies and saltier (fresher) than normal salinity anomalies are in phase, while less (more) than normal NHF is 90° out of phase with them, indicating the ACW in sea ice and ocean is a response to that in the atmosphere.
Modeling the formation and evolution of oriented fractures in sea ice
Authors: Hibler W.D. 
Published: November 2007

AbstractWhile sea-ice drift tends to be a relatively coherent field moving largely in response to spatially averaged wind, strain-rate observations show relative ice motion to be much more of a chaotic field with deformation occurring along narrow intersection strikes between effectively rigid plates. This relative motion also has considerable energy at high frequencies which are not coherent with the wind forcing. Plastic rheologies for a strongly interactive medium are inherently able to predict such fractures. To investigate this phenomenon, this paper presents a basic anisotropic theory for multiple-oriented weaknesses. When coupled with short-term evolution equations for ice strength, this model is found to yield strong zones of failure over the Arctic basin, with relatively rigid motion in between. These failure lines typically occur along geostrophic wind contours. These zones are also found to be created with appropriate "Coulombic" isotropic rheologies. When combined with a previously developed inertial embedding procedure for the oceanic boundary layer, the resulting deformation field tends to fluctuate with considerable power near the inertial period even though the wind field is constant. The mechanisms necessary for obtaining such oriented features are discussed.
Seasonal changes in Arctic sea-ice morphology
Authors: Perovich Donald K. , Richter-Menge Jacqueline A. , Tucker Walter B. 
Published: November 2007

AbstractThe morphology of the Arctic sea-ice cover undergoes large changes over an annual cycle. These changes have a significant impact on the heat budget of the ice cover, primarily by affecting the distribution of the solar radiation absorbed in the ice-ocean system. In spring, the ice is snow-covered and ridges are the prominent features. The pack consists of large angular floes, with a small amount of open water contained primarily in linear leads. By the end of summer the ice cover has undergone a major transformation. The snow cover is gone, many of the ridges have been reduced to hummocks and the ice surface is mottled with melt ponds. One surface characteristic that changes little during the summer is the appearance of the bare ice, which remains white despite significant melting. The large floes have broken into a mosaic of smaller, rounded floes surrounded by a lace of open water. Interestingly, this break-up occurs during summer when the dynamic forcing and the internal ice stress are small During the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment we had an opportunity to observe the break-up process both on a small scale from the ice surface, and on a larger scale via aerial photographs. Floe break-up resulted in large part from thermal deterioration of the ice. The large floes of spring are riddled with cracks and leads that formed and froze during fall, winter and spring. These features melt open during summer, weakening the ice so that modest dynamic forcing can break apart the large floes into many fragments. Associated with this break-up is an increase in the number of floes, a decrease in the size of floes, an increase in floe perimeter and an increase in the area of open water.
Investigating the anomalous sea-ice conditions in the Canadian High Arctic (Queen Elizabeth Islands) during summer 1998
Authors: Jeffers Sharon , Agnew Tom A. , Alt Bea Taylor , de Abreu Roger , McCourt Steve 
Published: November 2007

AbstractThe Queen Elizabeth Islands of the Canadian Arctic Archipelago exhibit one of the most complex sea-ice regimes in the Northern Hemisphere. Time series of minimum monthly passive-microwave sea-ice area (1979−98), minimum sea-ice extent, melting degree-days (1961−98) and minimum sea ice from the new Canadian Ice Service digital database (1968−98) are examined. The extreme nature of the amount of sea-ice melt in the summers of 1998 and 1962 is evident in these time series. The 38 year record of minimum ice, to date, shows no significant trend. Details of the sea-ice behavior during summer 1998 were then examined within 13 individual sea-ice regimes. The multi-year fast-ice plugs in both Sverdrup Channel and Nansen Sound broke up and became truly mobile in 1998. Discussion focuses on the areas surrounding the multi-year plugs, relating sea-ice conditions to weather. Results emphasize the importance of the timing of synoptic events in combination with strong thermal preconditioning in determining the sea-ice conditions in this area during summer 1998.
How a region of cracked sea ice affects ice-coupled wave propagation
Authors: Squire Vernon A. , Dixon Tony W. 
Published: November 2007

AbstractBy deriving the appropriate Green’s function, a model is developed that allows the interaction of normally-incident, ice-coupled waves with any number of cracks to be studied analytically. For a single crack a simple formula for the reflection and transmission coefficients, R and T, emerges that yields identical results to the computationally intensive work of Barrett and Squire (1996) but is much easier to apply. A crack is found to behave as a steep low-pass filter, allowing long waves through while inhibiting shorter waves, although there is also some fine structure to the response curve. The introduction of more cracks is straightforward. While in that case a formula for R and T is also possible in principle, it is easier to express the result as the solution of a simple matrix equation of order 2N, where N is the number of cracks. It is found that perfect transmission (|R| = 0) occurs at a set of discrete periods, hereinafter called a comb, for N > 1 and that the comb becomes finer as period decreases. For both periodically distributed cracks and ones that are randomly spaced, the gross shape of the response curve remains similar. The results suggest that it is improbable that waves travelling through the Arctic basin can be used as a remote-sensing agent to determine mean ice thickness. The Green’s function technique employed in this paper furnishes solutions to other problems of interest.
Arctic sea-ice morphological characteristics in summer 1996
Authors: Wadhams P. , Davis N.R. 
Published: November 2007

AbstractA sea-ice thickness profile obtained in September 1996 from the Greenland Sea and the Eurasian Basin, extending as far as the North Pole, has shown an unusually open ice cover with low mean drafts, large amounts of open water and little deep pressure ridging. Comparisons with data obtained from the same region in October 1976 show that mean ice draft has declined by 43% and that the decline can largely be ascribed to a loss of the thickest ice.
Recent fluctuation of snow cover on mountainous areas in Japan
Authors: Shimizu Masujiro , Abe Osamu 
Published: November 2007

AbstractTo monitor the snow-cover distribution in relation to meteorological conditions on high mountainous areas in Japan, NIED constructed a snow-observation network which it has operated for approximately 10 years. The network consists of seven pairs of stations, each comprising a mountainous site and a low-lying flatland site, from Hokkaido district in the north to San-in in the southwest. Data obtained include snow depth, snow weight, air temperature and global solar radiation. This study presents recent fluctuation of snow cover on mountainous areas for several recent winters in Japan. Most winters were warmer than average, but winter 1995/96 was normal, and maximum snow depths were recorded in high-elevation areas. Seventy-seven avalanche accidents occurred in winter 1995/96. The relationship between meteorological and snow conditions in mountainous areas and flatland areas was analyzed.
Aeolian susceptibility maps: methodology and applications
Authors: Font D. , Furdada G. , Vilaplana J. M. 
Published: November 2007

AbstractIn this paper we present a new methodology for the study of drifting-snow phenomena at an Alpine site This method emphasizes the accurate determination of local wind directions and the distribution of snow denudation and accumulation zones through the observation, measurement and mapping of aeolian “snowforms” and drifts. The aim is to find out whether the local wind directions on extensive surfaces in mountain areas (of about a few km2) are independent of the main wind intensity and direction, and whether valid erosion and accumulation zones are spatially stable and can be established for dominant winds. The methodology proposed to study the spatial distribution of snow by the wind has been used in the redesign of an old ski slope at La Molina, a resort in the eastern Spanish Pyrenees. Results have been very useful for deciding the design of the slopes. Therefore, we believe that the prediction of spatial snow distribution by wind in mountain areas, without the need for expensive instruments, has a valuable part to play in the management of mountain and ski resorts and roads, and in avalanche forecasting.
A nearest-neighbor model for regional avalanche forecasting
Authors: Brabec Bernhard , Meister Roland 
Published: November 2007

AbstractThe application of nearest-neighbor algorithms to the task of regional avalanche forecasting in Switzerland is presented in this paper. The database used for the development of the model consists of snow and weather data from 60 manual weather stations and conventionally estimated avalanche-hazard levels. All these data are collected by the Swiss Federal Institute for Snow and Avalanche Research on a daily basis during winter. Data between 1987 and 1996 (10 winters) are used for our study. For the manual weather stations a nearest-neighbor model has been developed: NXD-VG calculates the 10 nearest-neighbor days by using a Euclidean weighted distance metric. A regional avalanche-hazard map is calculated by interpolating the results of NXD-VG between the stations. The avalanche forecasters can access the results of the model calculation directly because they are integrated into a program for bulletin construction. The model was validated using three complementary approaches. First, the database is cross-validated for all the winters available to estimate an unbiased prediction error of the models for two selected stations. Second, selected situations of the database are recalculated. Third, the model output is compared daily to the official forecasts published during winter 1999/2000.
The influence of the forest on night-time snow surface temperature
Authors: Höller Peter 
Published: November 2007

AbstractSnow surface temperature (Ts) plays an important role in the formation of surface hoar or near-surface faceted crystals The goal of this study was to obtain detailed information on Ts in different forest stands nelr the timberline. The investigations were conducted during clear nights and showed that the snow surface temperature is influenced very strongly by the forest canopy. While the air temperature was very similar on the different experimental sites, Ts was higher in the forest than in the open field; on the south-facing slope the difference between the forest and the open field was 3–4.5°C, and on the north-facing slope approximately 3–7°C. Taking into account that εair is 0.7 and εtree is 0.94, the incoming radiation (I ↓) for the different experimental sites was calculated by the equation of Brunt (the canopy density was estimated using photographs taken with an 8 mm fish-eye). To calculate Ts, air temperature and averaged values of the net radiation (because the net radiation (I) has only a small range of variation during clear nights) were used. The results show that the calculated values were higher than the measured values (by approximately 2°C). However, a better correlation was found by using lower values of the emissivity (εair0.67 and εtree0.91).