The Canadian Ice Service (CIS) produces digital Arctic regional sea ice charts for marine navigation, climate research, and input to the Global Digital Sea Ice Data Bank (GDSIDB). The ice charts are created through the manual analysis of in situ, satellite, and aerial reconnaissance data. The ice charts have information on ice concentration, stage of development, and ice form, following World Meteorological Organization terminology. These sea ice charts begin in 2006 and goes to near present depending on the region and is updated approximately once a week, however, not all regions are updated with the same frequency and to the same end date. The data set covers the following regions of the Canadian Arctic: Northern Canadian waters (Western Arctic, Eastern Arctic, and Hudson Bay) and Southern Canadian waters (Great Lakes and East Coast). These data are in SIGRID-3 format with associated ancillary files archived together in tar files (.tar) for distribution. All data are available via FTP.
To broaden awareness of our services, NSIDC requests that you acknowledge the use of data sets distributed by NSIDC. Please refer to the citation below for the suggested form, or contact NSIDC User Services for further information. We also request that you send us one reprint of any publication that cites the use of data received from our Center. This helps us to determine the level of use of the data we distribute. Thank you.
The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title and version number, dates of the data you used (for example, December 2003 to March 2004), publisher: NSIDC, and digital media.
Canadian Ice Service. 2009. Canadian Ice Service Arctic regional sea ice charts in SIGRID-3 format. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N51V5BW9
|Data format||SIGRID-3 format with associated ancillary files archived together in tar files (.tar)|
|Spatial coverage||Canadian Arctic regions:
Northernmost Latitude: 83.193722° N
Southernmost Latitude: 39.527768° N
Easternmost Longitude: 21.969245° E
Westernmost Longitude: 164.050015° W
|Temporal coverage and resolution||Temporal coverage: 2006 - present (See the Temporal Coverage section for specific start dates by region)
|Tools for accessing data||Geographic Information System (GIS) software
Tar extraction software
|File naming convention||See the File Naming Convention section for more information.|
|File size||Tar files range from 340 KB - 4.2 MB|
|Parameters||Sea Ice Concentration
Stage of development
|Metadata access||View metadata|
|Data access||Data are available via FTP|
2. Background Information
3. Detailed Data Description
4. Data Acquisition and Processing
5. Data Access and Related Collections
6. References and Related Publications
8. Document Information
Canadian Ice Service
373 Sussex Drive, Block E
Ottawa, Ontario K1A0H3
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
The Canadian Ice Service (CIS) is an operational data provider with a primary objective of serving the operational user community. This support results in part in the production of regional ice charts over the Canadian Arctic. The Manual of Standard Procedures for Observing and Reporting Ice Conditions (MANICE) is the authoritative guide produced by the CIS that explains how sea ice charts are produced (Environment Canada 2005).
Originally, operational data centers denoted ice characteristics by grouping the ice with similar characteristics into polygons. Within each area or polygon, ice was identified by an egg code. The egg code, termed this way because of its shape, was a way to map the ice characteristics such as total ice concentration, partial concentrations, stage of development, and form of ice on a paper map. Figure 1 shows the ice categories included in the egg code. This method worked well, but then the digital era emerged and operational centers shifted their focus from paper charts to digital ice charts and used GIS techniques to process data and produce ice charts. With this digital transformation came a shift from the paper egg codes to a digital representation of sea ice conditions.
The operational data centers needed a way to incorporate the information
from the paper charts to a digital format. In the 1980s, a Sea Ice Grid (SIGRID)
format was developed (Thomson 1981) and adopted
as a World Meteorological Organization (WMO) standard shortly thereafter. This
format has evolved over time with the latest version, which is now a vector
format, called SIGRID-3 (IOC 2004). For a more complete
history of the egg code and ice chart digitization, including a summary of the
SIGRID-3 format, see the History
of Ice Chart Digitization section of the National Ice Center Arctic Sea
Ice Charts and Climatologies in Gridded Format documentation and the material
at the Global Digital Sea Ice Data Bank site.
|Figure 1. Ice Categories in Egg Code
Egg code that depicts ice in an area by total concentration, partial concentration, stage of development, and form of ice. Image courtesy of Environment Canada. Used with permission.
The SIGRID-3 look-up table converts the ice codes into meaningful sea ice characteristics.
For example, in Figure 2, the Total Ice Concentration (CT) value
of 80 translates to a CT of 8/10 (IOC 2004).
|Figure 2. Metadata Table from
This example shows how the egg code parameters (CT, CA, CB) in Figure 1 are mapped to individual SIGRID-3 codes.
The parameters include total ice concentration, partial concentration, stage of development, and ice form. Sea ice thickness can be assessed using stage of development as a proxy for thickness (NIC 2006).
This data set covers the Canadian Arctic regions including Northern Canadian waters (Western Arctic, Eastern Arctic, and Hudson Bay) and Southern Canadian waters (Great Lakes and East Coast). Figure 3 displays these regions.
Note: The specific geographic coordinates for each region are listed in the metadata associated with that region.
|Figure 3. Spatial Coverage Map
This map shows the spatial coverage of the Canadian Arctic regions for both the Northern Canadian waters and the Southern Canadian waters. Image courtesy of the Canadian Ice Service.
Because this data set is provided as vector shapefiles, there is no inherent resolution.
NSIDC adds a projection (.prj) file to each tar file received from CIS. NSIDC renames the projection file to correspond to the shapefile file name in each tar file. For example: cis_SGRDRHB_20061211_pl_a.shp and cis_SGRDRHB_20061211_pl_a.prj.
Shapefiles from 01 March 2006 through 24 July 2011 use the following projection in the projection file (.prj):
Shapefiles after 24 July 2011, use the following projection in the projection file (.prj):
PROJCS["WGS_1984_Lambert_Conformal_Conic",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]], PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",0.0], PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-100.0],PARAMETER["Standard_Parallel_1",49.0], PARAMETER["Standard_Parallel_2",77.0],PARAMETER["Latitude_Of_Origin",40.0],UNIT["Meter",1.0]]
Temporal coverage spans from 2006 to the present. The start date of the data for each region differs. See Table 1 for a list of start dates by region. Data begin in 2006 when production of the ice charts in SIGRID-3 format began. Users should note that the CIS has produced regional ice charts since 1968 in .e00 format, but these files are not included in this SIGRID-3 data set.
|Region||Start Date of Data|
|Western Arctic||May 2006|
|Eastern Arctic||June 2006|
|Hudson Bay||May 2006|
|Great Lakes||Dec 2006|
|East Coast||May 2006|
The temporal resolution is as follows:
Each ice chart contains up to 72 hours of input data. For example, a chart dated 16 October 2006 may contain data from the previous three days, as noted in each metadata file.
These data are available in SIGRID-3 format. The SIGRID-3 format includes several files: a shape file (.shp), with associated files (.dbf, .prj, .shx), and a metadata file (.xml). Each set of files is combined into a tar file (.tar) for distribution.
The CIS followed the SIGRID-3 (IOC 2004) instructions for decoding sea ice, but made a few modifications to the SIGRID-3 metadata files (.xml). Review CIS 2006 for a complete description of the differences between the CIS SIGRID-3 format and the official SIGRID-3 format (IOC 2004). These deviations from the CIS SIGRID-3 metadata format (noted almost verbatim from CIS 2006) are listed below:
There were also modifications made at the CIS to the coastlines as noted in CIS 2006:
SIGRID-3 files issued from CIS contain coastline vector features which are derived from the Digital Chart of the World (DCW) data set of 1993. The DCW was originally created by the Environmental Systems Research Institute (ESRI) at the request of the US Defense Mapping Agency (DMA) using aeronautical charts at a 1:1,000,000 scale as the primary data source.
CIS introduced a new coastline for the winter of 2008. This was a modified version of the 1:1,000,000 scale data set from World Vector Shoreline Plus (WVS+), 3rd Edition, 2004. WVS+ is a digital database product consisting of country, coastline, and ocean coverage for the entire world. WVS+ was produced by the National Geospatial-Intelligence Agency (NGA), formerly the National Imagery and Mapping Agency (NIMA). The coastline data used in WVS+ was developed using coastal nautical charts produced by the DMA.
The DCW and the WVS+ data set contains vector data which has been customized at CIS to correct gross errors, particularly in the Canadian Arctic and Greenland.
These modified coastlines for North America are incorporated into data products generated by CIS. The underlying reference frame for the data is the World Geodetic System of 1984 (WGS84) using the updated WGS Earth ellipsoid (2004). (CIS 2006)
The data files in this data set are available via FTP. This section describes the directory structure of the FTP site. The top level of the directory structure, G02171, is divided into five main directories (one for each region of this data set): East_Coast, Eastern_Arctic, Great_Lakes, Hudson_Bay, and Western_Arctic. Refer to Figure 4.
|Figure 4. Top Level Directory Structure|
Each region directory is further broken down by the four-digit year. Refer to Figure 5. Within each year is the tar file that contains the shapefile and the associated metadata file.
|Figure 5. Directory Structure within a Region|
The tar files are named according to the following convention and as described in Table 1:
Within each tar (.tar) file, there are four files that constitute a shapefile (.shp, .shx, .dbf, and .prj) and an associated metadata file (.xml).
The shapefiles and their associated metadata files are named according to the following convention and as described in Table 2:
|cis||Denotes that this file is from the Canadian Ice Service|
|RXX||Region name abbreviation
GL: Great Lakes
EC: East Coast
WA: Western Arctic
EA: Eastern Arctic
HB: Hudson Bay)
|pl||Feature type (pl: polygon)|
|v||Version number. Permits multiple charts per day
a: 1st version
b: 2nd version
and so forth
|.xxx||File extension (.shp, .shx, .dbf, .prj, and .xml)|
Note: In some cases, the original files needed to be replaced with newer files. These newer files have the following file naming convention: cis_SGRDREA_YYYYMMDD_pl_v_YYYYMMDDTTTTTT.tar The later variables (YYYYMMDDTTTTTT) contain a timestamp. The time stamp is GMT and corresponds to the time that the file was created.
This section contains some sample data records including a sample
of two SIGRID-3 shapefiles: One for the Great Lakes Region (Figure 6) and one for the Hudson Bay Region (Figure 7). Further, the beginning portion of a
metadata file is also displayed (Figure 8).
|Figure 6. cis_SGRDRGL_20080324_pl_a.shp
shapefile opened in ArcMap
The symbology was modified to correspond to some images in the National Ice Center Climatology data set. The results show the varying ice concentration around the Great Lakes.
|Figure 7. cis_SGRDRHB_20080324_pl_a.shp
shapefile opened in ArcMap
The symbology was modified to correspond to some images in the National Ice Center Climatology data set. The results show the varying ice concentration in the Hudson Bay.
Each shapefile contains an associated metadata file. The metadata files for the various regions are very similar. They differ only on these specific metadata fields: <bounding> (coordinates), <pubdate>, <title>, and <caldate>. Here is the beginning portion of metadata from cis_SGRDRHB_20080324_pl_a.xml that corresponds to Figure 2.
|Figure 8. Sample Metadata Record for cis_SGRDRHB_20080324_pl_a.xml|
Tar files range in size from 340 KB to 4.2 MB.
Not all potential sources of error have been identified. Users can look at MANICE (Environment Canada 2005) for more information. There are potential errors introduced with the manual assimilation process. See the section on Other Related Data Collections and References and Related Publications for more information.
A full quality assessment of this data set was not completed. However, the metadata files state the following:
"The reliability and accuracy of the data set is directly related to the availability, resolution and the effects of atmospheric (cloud, daylight, etc.) and ground (snow, rain, sea state, etc.) conditions on the source information. The source information is incorporated in the Regional Ice Analysis if the source information publication or acquisition date is plus or minus three days of the Regional Ice Analysis publication date. The only exception is the Regional Ice Analysis source information where we use the previous publication date".
The CIS uses the operational Ice Service Integrated System (ISIS) to create the regional ice charts based on MANICE procedures (Environment Canada 2005). The CIS takes input from various sources such as satellites, aerial reconnaissance, and ship reports based on data availability. They create coverages and then convert the coverages to shapefiles with corresponding metadata. Each metadata (.xml) file lists the sources used. Users should note that this list of sources is comprehensive and lists all possible data sources, not just the data sources that directly relate to that shapefile.
Data are available via FTP.
The shapefiles can be read using GIS software and the tar files can be opened using tar extraction software.
The ice services of the International Ice Chart Working Group may also have collections.
Canadian Ice Service. 2006. Canadian Ice Service SIGRID-3 Implementation 2006. Environment Canada, 14 pp.
Environment Canada. 2005. Manual of Standard Procedures for Observing and Reporting Ice Conditions (MANICE). Issuing authority: Assistant Deputy Minister, Meteorological Service of Canada: http://www.ec.gc.ca/glaces-ice/default.asp?lang=En&n=08D7D137-1.
Intergovernmental Oceanographic Commission of UNESCO. 2004. SIGRID-3 : A Vector Archive Format for Sea Ice Charts. JCOMM Technical Report No. 23, WMO/TD-No. 1214: ftp://ftp.wmo.int/Documents/PublicWeb/amp/mmop/documents/JCOMM-TR/J-TR-23-SIGRID3/JCOMM-TR23-SIGRID3.pdf
National Ice Center. 2006. National Ice Center Arctic Sea Ice Charts and Climatologies in Gridded Format. Edited and compiled by F. Fetterer and C. Fowler. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.
Tivy, A., S. E. L. Howell, B. Alt, S. McCourt, R. Chagnon, G. Crocker, T. Carrieres, and J. J. Yackel. 2011. Trends and variability in summer sea ice cover in the Canadian Arctic based on the Canadian Ice Service Digital Archive, 1960–2008 and 1968–2008. J. Geophys. Res. 116: C03007, doi:10.1029/2009JC005855.
Smith, O. P. 2000. Observers Guide to Sea Ice. National Oceanic and Atmospheric Administration, Hazardous Materials Response Division, Office of Response and Restoration: http://response.restoration.noaa.gov/book_shelf/695_seaice.pdf.
We thank Richard Chagnon and Dan Fequet from the Canadian Ice Service for providing this data set to NSIDC.
Distribution of the data set from NSIDC is supported by funding from NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) and the National Geophysical Data Center (NGDC).
Table 3 lists the acronyms used in this document.
|CIS||Canadian Ice Service|
|DCW||Digital Chart of the World|
|FTP||File Transfer Protocol|
|GDSIDB||Global Digital Sea Ice Data Bank|
|ISIS||Ice Service Integrated System (the CIS operational system)|
|MANICE||Manual of Standard Procedures for Observing and Reporting Ice Conditions|
|NSIDC||National Snow and Ice Data Center|
|SIGRID||Sea Ice Grid|
|URL||Uniform Resource Locater|
|XML||Extensible Markup Language|
|WMO||World Meteorological Organization|
L. Ballagh prepared this document based on SIGRID-3 guidelines (IOC 2004), CIS SIGRID-3 implementation (CIS 2006), the metadata files, and on correspondence with R. Chagnon and F. Fetterer. Document edited by A. Windnagel.
January 2011: A. Windnagel implented changes requested by Dan Fequet.
July 2010: A. Windnagel added a paper to the related publications section.