bluuebunny/crossref_metadata_2025_split huggingface dataset:
Standardization of electromagnetic–induction measurements of Sea-ice thickness in polar and Subpolar Seas
Authors: Tateyama K. , Shirasawa K. , Uto S. , Kawamura T. , Toyota T. , Enomoto H. 
Published: December 2007

AbstractElectromagnetic–induction (EM) instruments can be used to estimate Sea-ice thickness because of the large contrast in the conductivities of Sea ice and Sea water, and are currently used in investigations of Sea-ice thickness. In this Study we analyze Several Snow, ice and Sea-water Samples and attempt to derive an appropriate formula to transform the apparent conductivity obtained from EM measurements to the total thickness of Snow and ice for all regions and Seasons. This was done to Simplify the EM tuning procedure. Surface EM measurement transects with the instrument at varying heights above the ice were made in the Chukchi Sea, off East Antarctica, in the Sea of Okhotsk and in Saroma-ko (lagoon). A Standardized transformation formula based on a one-dimensional multi-layer model was developed that also considers the effects of water-filled gaps between deformed ice, a Saline Snow Slush layer, and the increase in the footprint Size caused by increasing the instrument height. The overall average error in ice thickness determined with the Standardized transform was <7%, and the regional average errors were 2.2% for the Arctic, 7.0% for the Antarctic, 6.5% for the Sea of Okhotsk and 4.4% for Saroma-ko.
Ship-borne electromagnetic induction Sounding of Sea-ice thickness in the Southern Sea of Okhotsk
Authors: Uto Shotaro , Toyota Takenobu , Shimoda Haruhito , Tateyama Kazutaka , Shirasawa Kunio 
Published: December 2007

AbstractRecent observations have revealed that dynamical thickening is dominant in the growth process of Sea ice in the Southern Sea of Okhotsk. That indicates the importance of understanding the nature of thick deformed ice in this area. The objective of the present paper is to establish a Ship-based method for observing the thickness of deformed ice with reasonable accuracy. Since February 2003, one of the authors has engaged in the core Sampling using a Small basket from the icebreaker Soya. Based on these results, we developed a new model which expressed the internal Structure of pack ice in the Southern Sea of Okhotsk, as a one-dimensional multilayered Structure. Since 2004, the electromagnetic (EM) inductive Sounding of Sea-ice thickness has been conducted on board Soya. By combining the model and theoretical calculations, a new algorithm was developed for transforming the output of the EM inductive instrument to ice + Snow thickness (total thickness). Comparison with total thickness by drillhole observations Showed fair agreement. The probability density functions of total thickness in 2004 and 2005 Showed Some difference, which reflected the difference of fractions of thick deformed ice.
Surface albedo measurements over sea ice in the Baltic Sea during the spring snowmelt period
Authors: Pirazzini Roberta , Vihma Timo , Granskog Mats A. , Cheng Bin 
Published: December 2007

AbstractThe snow/ice albedo was studied during a 4 week field experiment over first-year sea ice in the Gulf of Bothnia, Baltic Sea, in spring 2004. Observations were made on radiative fluxes, cloud cover, wind, air temperature and humidity, as well as snow/ice temperature, thickness, density and grain size. The albedo variation during the observation period was large: the daily mean albedo ranged from 0.79 over a new snow cover to 0.30 over bare, melting ice. The evolution of the albedo was related to the surface properties, but existing parameterizations based on Arctic data did not explain the observations well. The snow thickness was found to be the most critical factor affecting the albedo. A new parameterization was derived for the albedo dependence on snow thickness, to be applied over the Baltic Sea in spring, when periods of melting and freezing alternate but the ice is still relatively thick (about 0.6 m). The diurnal cycle of solar radiation was large, and the snow/ice metamorphism due to the melting during daylight and refreezing during the night caused a diurnal albedo cycle with a maximum in the early morning and a minimum in the afternoon, with an albedo difference up to 0.14 between the two.
Recent changes in the Arctic melt Season
Authors: Stroeve Julienne , Markus Thorsten , Meier Walter N. , Miller Jeff 
Published: December 2007

AbstractMelt-season duration, melt-onset and freeze-up dates are derived from Satellite passive microwave data and analyzed from 1979 to 2005 over Arctic Sea ice. Results indicate a Shift towards a longer melt Season, particularly north of Alaska and Siberia, corresponding to large retreats of Sea ice observed in these regions. Although there is large interannual and regional variability in the length of the melt Season, the Arctic is experiencing an overall lengthening of the melt Season at a rate of about 2 weeks decade–1. In fact, all regions in the Arctic (except for the central Arctic) have Statistically Significant (at the 99% level or higher) longer melt Seasons by >1 week decade–1. The central Arctic Shows a Statistically Significant trend (at the 98% level) of 5.4 days decade–1. In 2005 the Arctic experienced its longest melt Season, corresponding with the least amount of Sea ice Since 1979 and the warmest temperatures Since the 1880s. Overall, the length of the melt Season is inversely correlated with the lack of Sea ice Seen in September north of Alaska and Siberia, with a mean correlation of –0.8.
Growth, properties and relation to radar backscatter coefficient of sea ice in Lützow-Holm Bay, Antarctica
Authors: Kawamura Toshiyuki , Wakabayashi Hiroyuki , Ushio Shuki 
Published: December 2007

AbstractBased on studies in the Antarctic Oceans, the contribution of the snow cover to sea-ice growth has become of major interest. Snow can result in upward ice growth in contrast with ordinary downward congelation growth at the bottom. A sea-ice study was conducted to verify the upward ice growth found in a previous study and to investigate the relation between sea-ice growth and radar backscattering signature. Sea-ice samples collected at four points in Lützow-Holm Bay, Antarctica, from 1998 to 2003 are analyzed. Analyses of snow-/ice-gauge measurements, snow depth and ice structure reveal an extremely large amount of upward ice growth of up to 1.0 m during one full year compared with a slight amount of downward growth. The upward growth was caused mostly by snow ice and to a lesser extent by superimposed ice. The salinity profile remained unchanged, although the ice survived the summer melt season. Characteristics of superimposed ice such as salinity, δ18O values and structure were obliterated during the summer, implying complete melting or dissolution of the superimposed layer. The ERS-2 backscatter showed a remarkable annual variation: It had a minimum value in midsummer and increased abruptly to a maximum value in late summer, then decreasing gradually in wintertime. The relation of the backscatter coefficient to the growth and properties of the snow cover and sea ice are discussed.
A comparison of physical properties and strength of decaying first-year ice in the Arctic and sub-Arctic
Authors: Johnston M. 
Published: December 2007

AbstractMeasurements made on first-year ice in the Arctic and sub-Arctic are used to show that ice from both regions decays in a similar manner during the spring/summer melt season. One notable difference is that melt-induced changes in sub-Arctic Labrador occur about 2 months earlier than in the Arctic. In both regions, the temperature and strength of the ice change gradually over the season, whereas the bulk salinity and thickness of the ice do not change substantially until later in the season, when the ice becomes isothermal at a temperature of –1.8˚C. Results show that the seasonal decrease in the strength of first-year sea ice and the temperature-induced increase in brine volume are correlated. Once the ice is devoid of salt in late summer, the air volume continues to increase but has minimal effect on the ice strength.
Impacts of the variability of Second-year ice types on the decline of the Arctic perennial Sea-ice cover
Authors: Comiso Josefino C. 
Published: December 2007

AbstractThe observed rapid decline in the Arctic perennial ice cover is one of the most remarkable Signals of change in the Arctic region. Updated data now Show an even higher rate of decline of 9.8% decade–1(1978–2005) than the previous report of 8.9% decade–1(1978–2000). To gain insights into this decline, the variability of the Second-year ice, which is the relatively thin component of the perennial ice cover, is Studied. The perennial ice cover in the 1990s was observed to be highly variable, leading to relatively high production of Second-year ice that may in part explain the observed ice thinning during the period and have triggered further decline. The microwave Signature of Second-year ice is Shown to be different from that of the older multi-year ice types and, Surprisingly, more Similar to that of first-year ice. This in part explains why previous estimates of the area of multi-year ice during the winter period are considerably lower than the area of the perennial ice cover during the preceding Summer. Analysis of multichannel cluster maps in conjunction with Submarine ice-draft data indicates ability to detect regions covered primarily by Second-year ice and hence to infer ice-thickness information from the microwave data. The periodic increase of Second-year ice in the 1990s was apparently followed by continuous decline due in part to anomolously warm temperatures during the latter period that Shortened the ice Season and kept first-year ice from getting thick enough to Survive the Summer and become Second year ice.
Antarctic Sea-ice velocity as derived from SSM/I imagery
Authors: Heil P. , Fowler C.W. , Lake S.E. 
Published: December 2007

AbstractSea-ice velocities derived from remotely Sensed microwave imagery of the Special Sensor Microwave/Imager (SSM/I) have been analyzed for changes over time in Antarctic Sea-ice velocity, for the period 1988–2004. Year-to-year variability in mean Antarctic annual SSM/I-derived ice Speed is Small (17 year Standard deviation (SD) = 0.008 ms–1), with greater interannual variability in the zonal (eastward positive) velocity components (17 year SD = 0.016ms–1). Seasonally, minimum ice Speed is encountered during Summer, when nearly all Antarctic Sea ice is within the marginal ice zone. Ice motion peaks during winter and Spring, due to high velocities encountered in the outer pack of the Seasonal Sea-ice zone. The correlation (R2= 0.47) between winter Southern Annular Mode (SAM) and mean winter ice Speed highlights the importance of atmospheric forcing on Sea-ice dynamics. The Spatial pattern of the correlation of the Standardized SAM index with the June–November ice Speed exhibits a wave-3 pattern, which matches the Sea-level pressure distribution. Sea-ice Speed in the upstream regions of quasi-stationary centres of low Sea-level pressure is likely to increase (decrease) during high (low) SAMyears, and the opposite for Sea-ice Speed in the downstream regions of the centres.
Implications of shortwave cloud forcing and feedbacks in the Southern Ocean
Authors: Key Erica L. , Minnett Peter J. 
Published: December 2007

AbstractMeasurements of the incident solar radiation taken during the Antarctic Remote Ice Sensing Experiment (ARISE) aboard the R/VAurora Australisin the Southern Ocean and springtime Antarctic ice pack are analyzed together with all-sky cloud imagery to determine the incident shortwave cloud radiative forcing at the surface. For most solar zenith angles (Z<82˚) in this dataset, the primary shortwave cloud effect is to induce cooling of the surface; as the sun approaches the horizon, however, the shortwave effects become negligible or even positive. The clear-sky atmospheric transmissivity over the length of the cruise is 0.91, a value comparable to those derived from measurements taken at various locations in the Arctic during daylight periods. Although the presence of clouds has a great effect on the surface heat budget and provides a negative shortwave feedback that may stabilize the polar atmosphere, the effect on the photosynthetically active radiation available to ice algae is relatively small in comparison to the effects of even small amounts of snow on sea ice.
Controls of the landfast ice–ocean ecosystem offshore Barrow, Alaska
Authors: Jin Meibing , Deal Clara J. , Wang Jia , Shin Kyung-Hoon , Tanaka Nori , Whitledge Terry E. , Lee Sang Heon , Gradinger Rolf R. 
Published: December 2007

AbstractBased on biophysical ice-core data collected in the landfast ice off Barrow, Alaska, USA, in 2002 and 2003, a one-dimensional ice–ocean ecosystem model was developed to determine the factors controlling the bottom-ice algal community. The data and model results revealed a three-stage ice-algal bloom: (1) onset and early slow growth stage before mid-March, when growth is limited by light; (2) fast growth stage with increased light and sufficient nutrients; and (3) decline stage after late May as ice algae are flushed out of the ice bottom. Stages 2 and 3 are either separated by a transition period as in 2002 or directly connected by ice melting as in 2003, when in situ light and nutrient enrichment experiments showed only light limitations. The modeled net primary production of ice algae (NPPAi) from March to June is 1.2 and 1.7 g Cm–2for 2002 and 2003, respectively, within the range of previous observations. Model sensitivity studies found that overall NPPAiincreased almost proportionally to the initial nutrient concentrations in the water column. A phytoplankton bloom (if it occurs as in 2002) would compete with ice algae for nutrients and lead to reduced NPPAi. About 45% of the NPPAiwas exported to the shallow benthos.
Scattering of ice-coupled waves by variable sea-ice terrain
Authors: Vaughan Gareth L. , Squire Vernon A. 
Published: December 2007

AbstractThe reflection and transmission of ice-coupled waves under a sea-ice sheet is re-examined in this work. Recent theory can account for inhomogeneities in ice sheets such as the sails of pressure ridges and cracks or leads, but has only examined small numbers of features. Here the scattering coefficients can be obtained for an ice sheet containing a region of arbitrarily varying thickness that more closely approximates a real ice sheet and, consequently, models wave scattering more effectively. We explore the consequences of inverting ridge keels, placing the mass above the ice sheet as a technique by which the keel can be partially accounted for. It is found that the ridge sails themselves can reasonably be neglected. Upward-looking submarine sonar data are used to demonstrate the use of the model, noting that there are choices as to how to interpret such data. The model is tested to establish its sensitivity to these choices.
Ice mass-balance buoys: a tool for measuring and attributing changes in the thickness of the Arctic sea-ice cover
Authors: Richter-Menge Jacqueline A. , Perovich Donald K. , Elder Bruce C. , Claffey Keran , Rigor Ignatius , Ortmeyer Mark 
Published: December 2007

AbstractRecent observational and modeling studies indicate that the Arctic sea-ice cover is undergoing significant climate-induced changes, affecting both its extent and thickness. The thickness or, more precisely, the mass balance of the ice cover is a key climate-change indicator since it is an integrator of both the surface heat budget and the ocean heat flux. Accordingly, efforts are underway to develop and deploy in situ observing systems which, when combined with satellite remote-sensing information and numerical models, can effectively monitor and attribute changes in the mass balance of the Arctic sea-ice cover. As part of this effort, we have developed an autonomous ice mass-balance buoy (IMB), which is equipped with sensors to measure snow accumulation and ablation, ice growth and melt, and internal ice temperature, plus a satellite transmitter. The IMB is unique in its ability to determine whether changes in the thickness of the ice cover occur at the top or bottom of the ice cover, and hence provide insight into the driving forces behind the change. Since 2000, IMBs have been deployed each spring from the North Pole Environmental Observatory and in several other areas, including a few in the Beaufort Sea and Central Basin. At this point, the collective time series is too short to draw significant and specific conclusions regarding interannual and regional variability in ice mass balance. Comparisons of available data indicate that ice surface ablation is greater in the Beaufort region (67–80 cm), relative to the North Pole (0–30 cm), consistent with a longer period of melt in the more southerly location. Ablation at the bottom of the ice (22 cm), maximum ice thickness (235 cm) and maximum snow depth (28 cm) were comparable in the two regions.
The role of Langmuir circulation in suspension freezing
Authors: Kempema Edward W. , Dethleff Dirk 
Published: December 2007

AbstractIn November 2004 we used an acoustic Doppler velocimeter (ADV) to measure the three components of velocity in Langmuir circulation (LC) cells when frazil was forming in a lake. LC circulation was indicated by windrows of slush ice on the water surface. We also collected samples of lake water, ice interstitial water and ice to determine their sediment concentrations. The ADV record showed rotating currents in the cross-wind/vertical plane indicative of LC. Downward-directed velocities were large enough to entrain frazil into the water column for 27% of the 97 min observation time at the ADV location. Sediment concentrations in the ice and interstitial water samples were greater than concentrations in water-column samples collected in upwelling zones of LC cells. We conclude that suspension freezing was forming particle-laden ice as frazil trapped below LC convergence zones grew in downwelled, supercooled water. The rotating roll vortices of Langmuir circulation play an important role in forming sediment-laden ice.
Estimation of thin Sea-ice thickness from NOAA AVHRR data in a polynya off the Wilkes Land coast, East Antarctica
Authors: Tamura Takeshi , Ohshima Kay I. , Enomoto Hiroyuki , Tateyama Kazutaka , Muto Atsuhiro , Ushio Shuki , Massom Robert A. 
Published: December 2007

AbstractAntarctic coastal polynyas are major areas of intense ocean–atmosphere heat and moisture flux, and associated high Sea-ice production and dense-water formation. Their accurate detection, including an estimate of thin ice thickness, is therefore very important. In this paper, we apply a technique originally developed in the Arctic to an estimation of Sea-ice thickness using Us National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) data and meteorological data in the Vincennes Bay polynya off Wilkes Land, East Antarctica. The method is based upon the heat-flux calculation using Sea-ice Surface temperature estimates from the Satellite thermal-infrared data combined with global objective analysis (European Centre for Medium-Range Weather Forecasts (ECMWF)) data. The validity of this method is assessed by comparing results with independent ice-surface temperature and ice-thickness data obtained during an Australian-led research cruise to the region in 2003. In thin-ice (polynya) regions, ice thicknesses estimated by the heat-flux calculation using AVHRR and ECMWF data Show reasonable agreement with those estimated by (a) applying the heat-flux calculation to in Situ radiation thermometer and meteorological data and (b) in Situ observations. The Standard deviation of the difference between the AVHRR-derived and in Situ data is ∽0.02 m. Comparison of the AVHRR ice-thickness retrievals with coincident Satellite passive-microwave polarization ratio data confirms the potential of the latter as a means of deriving maps of thin Sea-ice thickness on the wider Scale, uninterrupted by darkness and cloud cover.
Observations of unusual fast-ice conditions in the southwest Ross Sea, Antarctica: preliminary analysis of iceberg and storminess effects
Authors: Brunt Kelly M. , Sergienko Olga , MacAyeal Douglas R. 
Published: December 2007

AbstractMassive tabular icebergs (∽1000km2surface area, ∽1011 kg mass) arrived in the southwest Ross Sea in early 2001 where they remained relatively immobile for the next 4 years. During the period of their presence, extensive landfast sea ice (fast ice) waxed and waned along the Victoria Land coast, with maximum coverage exceeding typical coverage prior to the arrival of the icebergs by a factor of 5. The purposes of this study are to determine (1) whether the extensive ‘iceberg blockade’ extending from Ross Island to Drygalski Ice Tongue was indeed, as intuition suggests, responsible for the unusual fast-ice conditions, and (2) how storm frequency, intensity and seasonal timing may have mitigated the effects of the icebergs. Our simple analysis of glaciological and atmospheric conditions observed during 2001–05 suggests that iceberg movement alone is not sufficient to explain fast-ice variability; and, in fact, it is the detailed interplay between storms and iceberg location that determine this variability.
In situ measurements of the direct-current conductivity of Antarctic Sea ice: implications for airborne electromagnetic Sounding of Sea-ice thickness
Authors: Reid J.E. , Pfaffling A. , Worby A.P. , Bishop J.R. 
Published: December 2007

AbstractAirborne, Ship-borne and Surface low-frequency electromagnetic (EM) methods have become widely applied to measure Sea-ice thickness. EM responses measured over Sea ice depend mainly on the Sea-water conductivity and on the height of the Sensor above the Sea-ice–sea-water interface, but may be Sensitive to the Sea-ice conductivity at high excitation frequencies. We have conducted in Situ measurements of direct-current conductivity of Sea ice using Standard geophysical geoelectrical methods. Sea-ice thickness estimated from the geoelectrical Sounding data was found to be consistently underestimated due to the pronounced vertical-to-horizontal conductivity anisotropy present in level Sea ice. At five Sites, it was possible to determine the approximate horizontal and vertical conductivities from the Sounding data. The average horizontal conductivity was found to be 0.017 Sm–1, and that in the vertical direction to be 9–12 times higher. EM measurements over level Sea ice are Sensitive only to the horizontal conductivity. Numerical modelling has Shown that the assumption of zero Sea-ice conductivity in interpretation of airborne EM data results in a negligible error in interpreted thickness for typical level Antarctic Sea ice.