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    This data set contains sea ice extent at the end of each month, January 1973 - December 1982. The charts are digitized on a 1 degree latitude by 2.5 degree longitude grid. The sea ice was computed for 10 degree longitude "slices" with aerial extent stored in the data set for each of 36 longitude sectors for each month. Ice area is expressed in units of 1000 square kilometers.

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    Publication title: Ice Atlas of the Northern Hemisphere.Includes bibliographical references, sea ice charts, and river ice charts. Charts and tabular data are divided into 7 major sections: 1) Northern Hemisphere, sea ice, 2) Northern Hemisphere, river ice, 3) Grand Banks Region, 4) Baltic Sea, 5) Black Sea. 6) White Sea, and 7) Okhotsk Sea Region.Contains annual mean river ice in relation to navigation; monthly mean and extremes of sea ice; monthly types of ice; monthly extremes and range of limits of ice. Includes approximately 40 years of record.Available from the NOAA Library System: URL http://www.lib.noaa.gov/.

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    Digitized sea ice concentration and stages of development grids for the North Polar Basin (Arctic Ocean) are made available via anonymous ftp for both PC/DOS and UNIX users, but can be distributed on floppy diskettes. The data, which are divided into two sections: Western sector (24W to 110E) and Eastern sector (105E to 130W), are part of a vast historic archive starting from the 1930s. At present (February 1995) data is available for 1967 through 1990 for the Eastern sector and 1972 through 1990 for the Western sector; files for 1972 contain data for both sectors. AARI is planning to complete the time series beginning with the 1953 charts by the end of 1995. Data are digitized from integrated sea ice charts generated by the operational division of AARI. The charts are produced through the assimilation and analysis of visual and instrumental aircraft observations and satellite data acquired by AARI over 10 day periods. The data are compiled on 1:1.5 million, 1:2 million and 1:5 million equiangular stereographic and mercator projections at resolutions of 0.1 km for aircraft survey and less than 4 km for satellite imagery. The boundaries are accurate from 2 to 4 km under normal conditions and up to 50 km under the worst conditions. The integrated charts are digitized and stored in SIGRID, the WMO tandard exchange format for digitized sea ice charts. References: Bushuev, A. V., R. G. Barry, V. M. Smolyanitsky, and V. J. Troisi (Steering Group for the Global Digital Sea Ice Data Bank). 1994. Format to Provide Sea Ice Data for the World Climate Program (SIGRID-2). Final version. WMO, Commission for Marine Meteorology. 14p. Environment Canada. 1989. Ice Charts: WMO Symbols for the Hatching of Total Concentration of Ice. Manual of Standard Procedures for Observing and Reporting Ice Conditions. Atmospheric Environment Service. Ottawa, Ontario. 3-21 - 3-31. Environment Canada. 1992. Ice Terminology: Ice Codes and Symbols, Egg Code. MANIS, Manual of Ice Services. Atmospheric Environment Service. Ottawa, Ontario. sect. A.3. Kurskikh, B. A. ed. 1984. International symbols for sea ice charts and sea ice nomenclature. Leningrad, Gidrometeoizdat. Oksenova, E.I. ed. 1981. Rukovodstvo po proizvodstvu ledovoi aviarazvedki [Manual for aerial reconnaissance of ice]. Leningrad, Gidrometeoizdat.WMO. 1989. Sea Ice Nomenclature. WMO-259. Geneva. WMO Commission for Marine Meteorology. 1989. Format for the archival and exchange of sea ice data in digital form (SIGRID). Manual on Marine Meteorological Services. Part II, Recommendation 11, CMM-X. WMO, Geneva, 32p.

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    The NOAA/NASA Pathfinder Program SSM/I Level 3 EASE-Grid Brightness Temperatures will consist of three series produced on CD-ROM, one series each for the EASE-Grid Northern Hemisphere, Southern Hemisphere and Cylindrical (global) projections. Grids represent spatially interpolated data. The interpolation technique maximizes the radiometric integrity of original brightness temperature values, maintain high spatial and temporal precision, and involve no averaging of original swath data. Coverage is global and spans the Pathfinder SSM/I Benchmark period, from 1 August 1987 through 30 November 1988. Resolution is 25 km for all channels and 12.5 km for the 85 GHz channels. There are 18 brightness temperature files per day for a given projection (nine each for ascending and descending passes), and two (ascending and descending) corresponding time files. Data are contained in flat binary files, either one image per file consisting of two-dimensional 2-byte integer arrays of brightness temperatures in tenths of Kelvins, or in the case of time files, two-dimensional 1-byte integer arrays consisting of GMT in tenths of hours. Data are available as processing is completed, with completion of the data set projected for the end of 1995. Data are available via ftp, on CD-ROM and through the Internet. Contact NSIDC User Services for information.

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    DMSP F11 monthly averaged sea ice concentration grids in the polar stereographic projection are produced based on daily sea ice concentration grids generated using the NASA Team algorithm. Processing is continuous beginning 3 December 1991, and continues the series begun with F8 monthly averaged data. Although a high degree of correlation exists between F8 and F11 data (Abdalati et al. 1995), regression coefficients (NSIDC 1995) have been applied in deriving F11 daily ice concentrations, which form the basis for this data set. Monthly averaged data files contain ice concentration in percent ranging from 0% to 100%. Then, ice concentrations are delineated using 0%, 5%, 10% and 15% as the minimum concentrations included in the averages (e.g.: a 5% cutoff sets all data values between 1% and 5% to 0%). These four thresholds accommodate as many potential applications as possible. Grids are 8-bit raster images stored in HDF. Data in compressed tar files are distributed via ftp, on sidads.colorado.edu (IP address 128.138.135.20).

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    The CSIRO coupled model has been used in a モtransientヤ greenhouse experiment. This model contains atmospheric, oceanic, comprehensive sea-ice (dynamic/thermodynamic plus leads), and biospheric submodels. The model control run (over 100 years long) employed flux corrections and displayed only a small amount of cooling, mainly at high latitudes. The transient experiment (1% increase in CO2 compounding per annum) gave a 2°C warming at time of CO2 doubling. The model displayed a モcold startヤ effect with a (maximum) value estimated at 0.3°C. The warming in the transient run had an asymmetrical response as seen in other coupled models, with the Northern Hemisphere (NH) warming more than the Southern Hemisphere (SH). However, the land surface response in this model is different from some other transient experiments in that there is not a pronounced drying of the midlatitudes in the NH in summer. In the control run the ice model gave realistic ice distributions at both poles, with the NH ice in particular displaying considerable interdecadal variability. In the transient run the ice amount decreased more in the NH than the SH (corresponding with a greater NH warming). The NH ice extent and volume in summer was considerably reduced in depth and extent compared to the control. However, the model ice dynamics and thermodynamics allowed for a successful regrowth of the ice during the winter season to give a coverage comparable to that of the control run, although thinner. During the transient run there is a freshening of the surface salinity in the oceans at high latitudes. In the SH this is caused mainly by increases in precipitation over evaporation. The same is true for the NH, but it is found that there is a similar magnitude contribution to the polar freshening from ice melt and land runoff changes. The freshening in the North Atlantic reduces the strength of the meridional overturning by 35% at time of doubling of CO2. Other changes in the global climate at the end of the transient run relative to the control run are also investigated.

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    Thirty-four drift tracks in the Arctic Ocean pack ice are collected in a unified tabular data format, one file per track. Data are from drifting ships, manned research stations on ice floes (ice islands) and data buoys. Track names are FRAM (ship, 1893 to 1896), NP-01 through NP-20 (Soviet North Pole Stations on ice floes, 1937, 1950, 1954 to 1970), IGY-A and IGY-B (International Geophysical Year buoys, 1957 to 59), T-3 (Fletcher's Ice Island, 1959 to 1970), ARLIS-II (ice island buoy, 1961 to 1965), BTAE (British Transarctic Expedition 1968 to 1969), seven AIDJEX buoys (1972), TEGG (Soviet ship Tegettnoff 1972 to 1973) and St. Anna (Russian ship, 1912 to 1914). Data have been smoothed, interpolated and projected to a two-dimensional coordinate system. Processing applied to original, sporadic data yielded x,y coordinates every two days, and associated velocities (first derivatives) u and v, in centimeters per second. Data are available via anonymous ftp or on various types of magnetic media. Please contact NSIDC User Services for access information.

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    Variable Name (Sampling): Sea Ice Extent (Maximum Extend Along 169W (Spring)) ID: 49 Region: Bering Sea Data Type: Sea Ice Units: normalized, degree N Lon.:169W Lat.: 60N Start Year: 1965 End Year: 1997

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    Time sequences of surface based measurements of passive microwave emission from growing saline ice reported by Wensnahan et al. (1993) are used to explore the possibility of developing a satellite based sea ice concentration algorithm which solves for the presence of thinner ice. It is shown that two classes of thinner ice can be distinguished from mixtures of open water (OW), first-year (FY) ice, and multiyear (MY) ice. The two classes do not necessarily correspond to specific World Meteorological Organization ice types; rather, newly formed ice represents a brief transition spectrum between OW and thin ice. Newly formed ice appears to be optically thick at 37 and 90 GHz and has a relatively dry surface. The thin ice spectrum occurs when the ice is greater than 4 cm thick and appears to result from the accumulation of brine at the surface of the ice. Thin ice has a relatively stable spectrum characterized by high brightness temperatures, a near-zero spectral gradient at vertical polarization, and a large difference between vertical and horizontal polarizations. Supervised principal component analysis (PCA) was done of laboratory data using 10 channels of passive data: vertical and horizontal polarization at 6.7, 10, 19, 37, and 90 GHz. Analyses were also done on subsets of the laboratory data at 6.7 to 37 GHz as well as 19 to 90 GHz, representing the scanning multichannel microwave radiometer (SMMR) and special sensor microwave imager (SSM/I) satellite frequencies, respectively. Using all of the channels or the SMMR subset makes it possible to solve for mixtures of OW and FY, MY, newly formed and thin ice but with large errors. However, any four of these scene types can be distinguished with reasonable accuracy. The SSM/I frequencies allow determination of at most four of these scene types but with moderate errors. PCA was used in a case study of SSM/I data from the Bering Sea for April 2, 1988. Winds from the north formed thin ice areas which the NASA Team algorithm interprets as large amounts of OW and MY ice. With PCA, these same areas are interpreted as 20-30% OW near the lee shores but otherwise as consisting almost entirely of thin ice. We conclude that thin ice can be detected using satellite data. However, questions remain as to how the thin ice spectrum varies with environmental conditions, how it evolves to that of FY, and how this evolution affects the predicted concentrations of thin ice.

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    A dynamic sea ice model based on granular material rheology is presented. The sea ice model is coupled to both a mixed layer ocean model and a one-layer thermodynamic atmospheric model, which allows for an ice albedo feedback. Land is represented by a 6-m thick layer with a constant base temperature. A 10-year integration including both thermodynamic and dynamic effects and incorporating prescribed climatological wind stress and ocean current data was performed in order for the model to reach a stable periodic seasonal cycle. The commonly observed lead complexes, along which sliding and opening of adjacent ice floes occur in the Arctic sea ice cover, are well reproduced in this simulation. In particular, shear lines extending from the western Canadian Archipelago toward the central Arctic, often observed in winter satellite images, are present. The ice edge is well positioned both in winter and summer using this thermodynamically coupled oceanヨiceヨatmosphere model. The results also yield a sea ice circulation and thickness distribution over the Arctic, which are in good agreement with observations. The model also produces an increase in ice formation associated with the dilatation of the ice medium along sliding lines. In this model, incident energy absorbed by the ocean melts ice laterally and warms the mixed layer, causing a smaller ice retreat in the summer. This cures a problem common to many existing thermodynamicヨdynamic sea ice models