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Canadian Ice Service Arctic Regional Sea Ice Charts in SIGRID-3 Format

Summary

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). Each regional shapefile (.shp) (encoded in SIGRID-3 format) and associated metadata file (.xml) are combined into a tar archive file (.tar) for distribution. All data are available via FTP.

Citing These Data

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

Overview Table
 

Category Description
Data format Shapefiles (.shp) encoded in SIGRID-3 format and XML files (.xml) archived together in tar files (.tar)
Spatial coverage Canadian Arctic regions:
  • Northern Canadian waters: Western Arctic, Eastern Arctic, and Hudson Bay
  • Southern Canadian waters: Great Lakes and East Coast

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)

Temporal resolution:
  • Northern Canadian waters: weekly (summer) and bi-weekly (winter)
  • Southern Canadian waters: weekly (winter); files are not produced in the summer
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
Partial Concentration
Stage of development
Ice Form
Metadata access View metadata
Data access Data are available via FTP

Table of Contents

1. Contacts
2. Background Information
3. Detailed Data Description
4. Data Acquisition and Processing
5. Data Access and Related Collections
6. References and Related Publications
7. Acknowledgements
8. Document Information

1. Contacts

Investigator

Dan Fequet
Canadian Ice Service
Environment Canada
373 Sussex Drive, Block E
Ottawa, Ontario K1A0H3

Technical Contact

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
e-mail: nsidc@nsidc.org

2. Background Information

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).

3. Detailed Data Description

SIGRID-3 Format Description

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.
 

Egg code description
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).
 

SIGRID-3 metadata table example
Figure 2. Metadata Table from cis_SGRDRHB_20061211_pl_a.tar.
This example shows how the egg code parameters (CT, CA, CB) in Figure 1 are mapped to individual SIGRID-3 codes.

 

Parameters

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).

Spatial Coverage and Resolution

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.
 

Spatial Coverage Map
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.

Projection

For GIS users opening the shapefiles, here is a preview of the geographic coordinate system (WGS 1984) projection (.prj) file:

NSIDC adds a projection (.prj) file to each tar file received from the CIS. Each projection file contains the exact same content. 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.

Temporal Coverage and Resolution

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.

Table 1. Start Dates of Data by Region
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.

Format

Data are available as shapefiles (.shp) encoded in SIGRID-3 format. The shapefiles are accompanied by metadata in XML (.xml) format and are archived together in tar files (.tar). The sea ice data in the shapefiles are encoded in SIGRID-3 format. Review CIS 2006 for a complete description of the differences between the CIS SIGRID-3 format and the official SIGRID-3 format (IOC 2004).

The CIS followed the SIGRID-3 (IOC 2004) instructions for decoding sea ice, but they made a few modifications to the SIGRID-3 metadata fields in the metadata (.xml) file. 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)

File and Directory Structure

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.

Top Level Directory Structure
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.

Region Subdirectories
Figure 5. Directory Structure within a Region

File Naming Convention

Tar file

The tar files are named according to the following convention and as described in Table 1:

cis_SGRDRXX_YYYYMMDD_pl_v.tar

Within each tar (.tar) file, there are four files that constitute a shapefile (.shp, .shx, .dbf, and .prj) and an associated metadata file (.xml).

Shapefile and Metadata File

The shapefiles and their associated metadata files are named according to the following convention and as described in Table 2:

cis_SGRDRXX_YYYYMMDD_pl_v.xxx

Where:

Table 2. Naming Convention Description
Variable Description
cis Denotes that this file is from the Canadian Ice Service
SGRD SIGRID-3 format
RXX Region name abbreviation
GL: Great Lakes
EC: East Coast
WA: Western Arctic
EA: Eastern Arctic
HB: Hudson Bay)
YYYY 4-digit year
MM 2-digit month
DD 2-digit day
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.

Sample Data Record

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).
 

Example of a shapefile in ArcMap
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.

 
Example of a shapefile in ArcMap
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.

Sample metadata record
Figure 8. Sample Metadata Record for cis_SGRDRHB_20080324_pl_a.xml

File Size

Tar files range in size from 340 KB to 4.2 MB.

Error Sources

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.

Quality Assessment

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".

4. Data Processing

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.

5. Data Access and Related Collections

Data Access

Data are available via FTP.

Software and Tools

The shapefiles can be read using GIS software and the tar files can be opened using tar extraction software.

Related NSIDC Data Collections

Other Related Data Collections

The ice services of the International Ice Chart Working Group may also have collections.

6. References and Related Publications

References

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

Kokaly, R. F. 1996. Methods for Regridding AARI Data in SIGRID Format to the EASE-Grid Projection. NSIDC Special Report 9. Boulder, Colorado USA: National Snow and Ice Data Center.

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.

Thompson, T. 1981. Proposed Format for Gridded Sea Ice Information (SIGRID). World Meteorological Organization, Geneva, Report, World Climate Program, 28 pp.

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.

Related Publications

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.

7. Acknowledgements

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).

8. Document Information

Acronyms

Table 3 lists the acronyms used in this document.

Table 3. Acronyms
Acronym Description
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
tar Tape Archive
URL Uniform Resource Locator
XML Extensible Markup Language
WMO World Meteorological Organization

Document Authors

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.

Document Creation Date

October 2009

Document Revision Date

January 2011: A. Windnagel implented changes requested by Dan Fequet.
July 2010: A. Windnagel added a paper to the related publications section.

Document URL

http://nsidc.org/data/docs/noaa/g02171_CIS_seaice_regional/index.html