Schweitzer, Peter N. 1995 2.0 remote-sensing image U.S. Geological Survey Digital Data Series DDS-27 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/dds/dds27/ http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice.exe (Microsoft Windows) http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice.bin (Linux x86) http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice.kit (Tcl/Tk starkit) http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice-viewer.dmg.gz (Mac OSX) http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/dds27.zip (Source code) This data set represents the results of calculations carried out on sea-ice-concentration data from the SMMR and SSM/I instruments. The original data were obtained from the National Snow and Ice Data Center (NSIDC). The data set also contains the source code of the programs that made the calculations. The objective was to derive monthly averages for the whole 13.25-year series (1978-1991) and to derive a composite series of monthly averages representing the variation of an average year. The resulting file set contains monthly images for each of the polar regions for each year, yielding 160 files for each pole, and composite monthly averages in which the years are combined, yielding 12 more files. Averaging the images in this way tends to reduce the number of grid cells that lack valid data; the composite averages are designed to suppress interannual variability. Also included in the data set are programs that can retrieve seasonal ice-concentration profiles at user-specified locations. These nongraphical data retrieval programs are provided in versions for UNIX, extended DOS, and Macintosh computers. Graphical browse utilities are included for the same computing platforms but require more sophisticated display systems. The purpose of this data set is to provide paleoclimate researchers with a tool for estimating the average seasonal variation in sea-ice concentration in the modern polar oceans and for estimating the modern monthly sea-ice concentration at any given polar oceanic location. It is expected that these data will be compared with paleoclimate data derived from geological proxy measures such as faunal census analyses and stable-isotope analyses. The results can then be used to constrain general circulation models of climate change. The data contained in this data set are derived from the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/ Imager (SSM/I) data produced by the National Snow and Ice Data Center (NSIDC) at the University of Colorado in cooperation with the U.S. National Aeronautics and Space Administration (NASA) and the U.S. National Oceanic and Atmospheric Administration (NOAA). The basic data come from satellites of the U.S. Air Force Defense Meteorological Satellite Program. NSIDC distributes three collections of sea- ice-concentration grids on CD-ROM: data from the Nimbus-7 SMMR (October 25, 1978 through August 20, 1987) are provided on volume 7 of the SMMR Polar Data series (NASA, 1992); data from the SSM/I are provided on two separate volumes, covering the periods from July 9 of 1987 to December 31 of 1989, and from January 1 of 1990 through December 31 of 1991, respectively. The NASATEAM data from revision 2 of the SSM/I CD-ROM's were used to create the present data set. SMMR images were collected every 2 to 3 days, whereas SSM/I data are provided in daily ice-concentration grids. Apart from a number of small gaps (5 or fewer days) in the record, the only long period for which no data are available is December 3 of 1987 through January 12 of 1988, inclusive. As ancillary data, the ETOPO5 global gridded elevation and bathymetry data (Edwards, 1989) were interpolated to the resolution of the NSIDC data; the interpolated topographic data are included. 19781025 19911231 SMMR aboard Nimbus-7 satellite became fully operational on 781025; that instrument was replaced but the observations were continued by the SSM/I aboard DMSP F8 satellite. Complete Irregular -180.0 180.0 90.0 -90.0 168.35,30.98 135.00,39.43 102.34,31.37 45.00,56.35 -9.97,34.35 -45.00,43.28 -80.74,33.92 -135.00,55.50 -39.23,-42.24 -51.32,0.00 -39.23,42.24 -54.66,90.00 -41.45,135.00 -54.66,180.00 -41.45,-135.00 -54.66,-90.00 none Oceanography Sea-Ice Concentration ISO 19115 Topic Categories oceans None Arctic Ocean Southern Ocean Augmented FIPS 10-4 and FIPS 6-4, version 1.0 OC10 = Arctic OC50 = Southern None Present none none Peter N. Schweitzer U.S. Geological Survey mailing address

Mail Stop 954 National Center U.S. Geological Survey 12201 Sunrise Valley Drive

Reston VA 20192 USA (703) 648-6533 (703) 648-6252 pschweitzer@usgs.gov http://geochange.er.usgs.gov/pub/data/sea_ice/Derived/images/gif/north/02n.gif Average February Northern Hemisphere sea-ice concentration plotted on a polar stereographic projection of the North Pole GIF http://geochange.er.usgs.gov/pub/data/sea_ice/Derived/images/gif/south/02s.gif Average February Southern Hemisphere sea-ice concentration plotted on a polar stereographic projection of the South Pole GIF Originally compiled using UNIX, data remain the same. The graphical software has been rewritten in Tcl/Tk to promote portability across operating systems. Peter N. Schweitzer 1993 remote-sensing image 2.0 U.S. Geological Survey Digital Data Series DDS-10 Library of Congress Cataloging-in-Publication Number 93-9075 http://pubs.usgs.gov/dds/dds10/ Calculation of sea-ice-concentration values from brightness temperatures is described extensively in the user's guides of the source data products and in the NASA publication dealing with the SMMR data. Included in the data set are the UNIX shell scripts and makefiles that were used to derive the averages and create the tables and images. Source code is provided for all programs written by the author. Included in the data set is a table enumerating the days for which sea-ice-concentration data were available in the source material. In general, images were available every 2 days during the time period from 781025 through 870709, when the SMMR was used, and images were available every day during the period 870709 through 911231, when the SSM/I was used. A large gap (871202 through 880113) occurred when the SSM/I became temporarily inoperative. Other gaps in the SSM/I record were not longer than five consecutive days. The grids provided in the source data (supplied by NSIDC) are described in the user's guides of the relevant products, and the positional accuracy of the pixels is dealt with both in the user's guides and in the NASA report on the SMMR data. NASA 1992 remote-sensing image Goddard Space Flight Center SMMR Polar Data volume 7 The volume also contains brightness temperature data from 870401 through 870820. The CD-ROM is labelled USA_NASA_971_SMR_0007. The data are distributed by NSIDC Distributed Active Archive Center, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309-0049. SMMR CD-ROM from NSIDC CD-ROM 19781025 19870820 National Snow and Ice Data Center, 1994, Nimbus-7 SMMR polar radiances and Arctic and Antarctic sea ice concentrations on CD-ROM user's guide, version 3: Boulder, Colorado, National Snow and Ice Data Center, 23 p. Monthly average sea-ice-concentration files in the present data set for the period 781025 through 870820 were derived from these Nimbus-7 SMMR ice-concentration data. NSIDC 1992 remote-sensing image DMSP SSM/I brightness temperature and sea-ice concentration grids for the polar regions on CD-ROM volume 1, revision 2 The data are distributed by NSIDC Distributed Active Archive Center, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309-0049. DMSP/SSMI ICE Grids volume 1 CD-ROM 19870709 19891231 National Snow and Ice Data Center, 1992, DMSP SSM/I brightness temperature and sea ice concentration grids for the polar regions on CD-ROM, User's guide: National Snow and Ice Data Center Special Report 1, [300 p]. Monthly average sea-ice-concentration files in the present data set for the period 19870709 through 19891231 were derived from these DMSP F8 SSM/I ice-concentration data. NSIDC 1993 remote-sensing image DMSP SSM/I brightness temperature and sea-ice concentration grids for the polar regions on CD-ROM volume 2, revision 2. The data are distributed by NSIDC Distributed Active Archive Center, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309-0049. DMSP/SSMI ICE Grids volume 2 CD-ROM 19900101 19911231 National Snow and Ice Data Center, 1992, DMSP SSM/I brightness temperature and sea ice concentration grids for the polar regions on CD-ROM, User's guide: National Snow and Ice Data Center Special Report 1, [300 p]. Monthly average sea-ice-concentration files in the present data set for the period 19900101 through 19911231 were derived from these DMSP F8 SSM/I ice-concentration data. Edwards, Margaret H. 1989 remote-sensing image Boulder, Colorado U.S. National Oceanic and Atmospheric Administration, National Geophysical Data Center ETOPO5 CD-ROM 1950 1989 The data set was published in 1989. Documentation provided by NGDC indicates the data were derived from sources produced during the period 1950 through 1980. Elevation and bathymetry used in the graphical data retrieval programs of DDS-27 were derived from ETOPO5. Calculate monthly averages and composite monthly averages. The Bourne shell script do_avgs describes the manner in which the program average was used to calculate the monthly and composite monthly average sea-ice concentration files. The program average is given a list of sea-ice-concentration data files in HDF format. For each grid cell in the images, it calculates the arithmetic average of the corresponding cell in the input files and writes the average image into a new file. This program is run once for each month of each year represented in the original data to yield monthly averages. Then the composite monthly averages are calculated using the monthly averages for each year. DMSP/SSMI Ice Grids volume 1 DMSP/SSMI Ice Grids volume 2 1994 Create GIF and PICT images of monthly and composite monthly averages. The Bourne shell script do_imgs converts the monthly average and composite monthly average files into GIF and PICT images. This script uses two programs from the freely available PbmPlus toolkit developed by Jeff Poskanzer. 1994 Regrid ETOPO5 elevation and bathymetry data to fit sea-ice concentration grid. The ETOPO5 global gridded elevation and bathymetry data set describes world topography on a grid whose cells measure 5 minutes of latitude by 5 minutes of longitude. Since the ice-concentration data are given in a polar stereographic projection, the elevation of cells in the ice-concentration grid must be determined by appropriately sampling or interpolating the ETOPO5 data. Because the ETOPO5 grid is finer than the ice-concentration grid, a sampling algorithm was combined with a spatial averaging scheme to derive the desired elevation data. The program that implements this algorithm is called topo.c; its strategy is to find the ice grid cell coordinates of the center of each ETOPO5 cell and to calculate the average depth of all of the ETOPO5 cells that fall within an ice grid cell. The results are two 16-bit images with big- endian byte ordering in which each signed 16-bit word describes the average depth or elevation in meters (sea level is zero) of a cell in the ice-concentration grid. Along with the 16-bit depth data files, displayable images are created using depthppm.c in portable pixmap format, and from that intermediate stage, GIF and PICT images are created using the PbmPlus toolkit. Depthppm reduces the complexity of the depth data by assigning one color to a range of depths. The relationship between depth ranges and colors is given in the source-code file depthppm.c. The Bourne shell script do_topo carries out these operations. ETOPO5 1994 Create 2-degree by 2-degree gridded ASCII data files. One of the principal derivative products of this data set is a set of ice-concentration grids in which the grid cell size and position match those produced by the USGS PRISM project for its reconstruction of the climate of the Pliocene, a warm interval about 3 million years before present. These grids are tab-delimited ASCII files suitable for use in spreadsheet programs; each cell of the spreadsheet represents the ice-concentration value of one grid cell measuring 2 degrees latitude by 2 degrees longitude. This calculation is carried out by the Bourne shell script do_tabs. The procedure is to use a list of the geographic coordinates of the grid cell centers as the request file for the program u_rtrv. The result is a table where each row is a grid cell, and columns 3 through 14 represent the ice-concentration profile for each grid cell (columns 1 and 2 reiterate the grid cell coordinates). The grid cell centers are given in the files grid_n.2x2 and grid_s.2x2 for the Northern and Southern Hemispheres, respectively. The output of u_rtrv is stored in the files arctic.2x2 and antarctic.2x2. By using the UNIX cut command, the columns themselves were isolated in separate files, and the program table.c was used to rearrange each column into a tab-delimited ASCII table suitable for entry into a spreadsheet. 1994 Graphical viewer software rewritten using Tcl/Tk to enable the viewer to run on current operating systems: Microsoft Windows and Linux. 20040510 Fixed a serious bug in u_rtrv.c in which the program required the HDF data file name to contain ".s" in order to consider the data to be southern-hemisphere data. This caused pixel coordinates calculated from geographic locations in the south polar region to be incorrect. The gridded data files were affected by this bug, so the files in Derived/grid/south have been rebuilt with corrected information. Thanks to Dr. Simon H.H. Nielsen (post-doc at Univ Florida) for pointing out the problem. 20040728 Raster Pixel 304 448 Pixel 316 332 Polar Stereographic 135.0 70.0 0.0 0.0 row and column 25000 25000 meters Polar Stereographic 0.0 -70.0 0.0 0.0 row and column 25000 25000 meters Hughes 6378.273 298.27941 Ice-concentration grid cell Any of the one-byte data elements in the sea-ice- concentration files self-evident Ice-concentration grid cell value The proportion of the ocean area represented by the grid cell that is covered with sea ice. Calibrations of the SMMR and SSM/I instruments are described in the following three publications: Gloersen, P., Campbell, W.J., Cavalieri, D.J., Comiso, J.C., Parkinson, C.L., and Zwally, H.J., 1993, Arctic and Antarctic sea-ice, 1978-1987: Satellite passive-microwave observations and analysis: NASA Special Publication no. 511, 290 p. National Snow and Ice Data Center, 1994, Nimbus-7 SMMR polar radiances and Arctic and Antarctic sea ice concentrations on CD-ROM user's guide, version 3: Boulder, Colorado, National Snow and Ice Data Center, 23 p. National Snow and Ice Data Center, 1992, DMSP SSM/I brightness temperature and sea ice concentration grids for the polar regions on CD-ROM, User's guide: National Snow and Ice Data Center Special Report 1, [300 p]. 0 100 percent sea-ice cover 1 -99 Missing data NSIDC -88 Land area NSIDC ETOPO5 grid cell Any of the two-byte data elements in the files etopo5.n and etopo5.s self-evident ETOPO5 grid cell value Height of the land surface or depth of the sea floor, relative to mean sea level. NOAA/NGDC. 1992. Integrated Global Elevation and Bathymetry. Digital Data. NOAA/NGDC/WDC-A, Boulder, Colorado. Digital raster data on a 5-minute geographic (lat/long) 2160x4320 grid. In: Global Ecosystems Database Version 1.0: Disc A. Boulder, CO: NOAA National Geophysical Data Center. 1 independent single-attribute spatial layer on CD-ROM. 18.6 MB. [First published in 1989.] -10783 8000 meters 1 Peter N. Schweitzer U.S. Geological Survey mailing address

Mail Stop 954 National Center U.S. Geological Survey 12201 Sunrise Valley Drive

Reston VA 20192 USA (703) 648-6533 (703) 648-6252 pschweitzer@usgs.gov U.S. Geological Survey Digital Data Series DDS-27 Although all data and software published on this CD-ROM have been used by the USGS, no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials. GIF 89a Sea-ice concentration unzip 1.5 megabytes http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/dds27.zip starkit Stand-alone runtime (Tcl/Tk starkit, usable with Linux x86, Microsoft Windows, and MacOSX, requires tclkit to run) Sea-ice concentration display application tclkit ice.kit 1.5 megabytes http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice.kit EXE Stand-alone runtime (Tcl/Tk starpack executable, UPX compressed) for Microsoft Windows Sea-ice concentration display application execute 1.5 megabytes http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice.bin ELF Stand-alone runtime (Tcl/Tk starpack executable, UPX compressed) for Linux x86 Sea-ice concentration display application execute from a Linux command shell 1.5 megabytes http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice.bin Compressed disk image Compressed disk image containing the application Sea-ice concentration display application gzip -d 1.5 megabytes http://geo-nsdi.er.usgs.gov/metadata/digital-data/27/ice-viewer.dmg.gz none 20040728 Peter N. Schweitzer mailing address

Mail Stop 954 National Center U.S. Geological Survey 12201 Sunrise Valley Drive

Reston VA 20192 USA (703) 648-6533 (703) 648-6252 pschweitzer@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998