GDSIDB: Global Digital Sea Ice Data Bank at NSIDC

Note: The GDSIDB project has not been active since 2005. This page is no longer being updated. It will remain online as a reference for later work with sea ice chart digital formats.

About GDSIDB

The World Meteorological Organization (WMO) Commission on Marine Meteorology (now the Joint WMO/ Intergovernmental Oceanographic Commission for Oceanography and Marine Meteorology, or JCOMM) established a Global Sea Ice Data Bank of digital sea ice chart information from the operational ice forecasting centers of participating nations in November 1986 (WMO, Summary Report of "Informal Workshop on feasibility of establishment of a Global Sea Ice Data Bank", Washington, D.C., Joint Ice Center, 3-5 November 1986). By bilateral agreement between NSIDC and the Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia, elaborated and signed by the directors of given institutions in September 1990 and approved by WMO Secretariat in 1991, two archiving centers (at NSIDC and AARI) were established.

The objective of the GDSIDB project was to preserve ice chart data for use by researchers, and to encourage its conversion from paper or graphical form to digital form. The GDSIDB began as a 1984 Commission on Marine Meteorology recommendation, because, at that time, most ice services produced paper charts by manually integrating various source data. The U.S. National Ice Center, for example, converted to a wholly digital method of producing and distributing charts in 1996. Prior to the use of digital technology by the ice services, charts could only be archived by storing them as paper products or by scanning them. The GDSIDB instituted a method for converting analog charts to raster digital products, established a format for them, and designated archive locations (at AARI and NSIDC). Most ice services now use GIS systems to produce charts, and this is spurring the development of a new GDSIDB archive format.

At NSIDC, GDSIDB data sets are handled under the NOAA data management project, and are part of the World Data Center for Glaciology, Boulder. NSIDC's efforts focused on acquiring funds for the digitization of historical paper charts, on reformatting digital chart data to make it easier for researchers to use, and on helping develop a new vector format. Florence Fetterer lead the GDSIDB project at NSIDC.

At AARI, Vasily Smolyanitsky lead the GDSIDB project. Work included the development of on-line browse tools for selected data sets, climatological products, and documentation including on-line terms of reference and glossaries in Russian and English. Potential users are encouraged to explore the GDSIDB at AARI, where you will find data products and information not available on the NSIDC GDSIDB site.

noaa at nsidc logowmo logo

GDSIDB Structure and Meetings

The GDSIDB was a project under JCOMM. A Steering Committee for the GDSIDB was co-chaired by Ivan Frolov,  the then Director of AARI in St. Petersburg, Russia; and Roger Barry, the then Director of NSIDC at the University of Colorado, USA. The Steering Committee met approximately every two years, and in 2001, was composed of representatives from Australia, Canada, China, Japan, Russia, and the U.S.

The JCOMM Expert Team on Sea Ice contributed to the GDSIDB project. The Team was chaired by Vasily Smolyanitsky, AARI, and, in 2001, included representatives from Argentina, Canada, China, Denmark, Germany, Iceland, Japan, Russia, and the U.S. The WMO provides this information about JCOMM:

"In line with its status as a technical commission of WMO, JCOMM is an intergovernmental body of technical experts in the field of oceanography and marine meteorology, with a mandate to prepare both regulatory (what Member States shall do) and guidance (what Member States should do) material relating to marine observing systems, data management and services. The role of the full commission in session is to act as a final review body for activities, proposals and recommendations prepared for it by its sub-structure of working groups, expert teams and rapporteurs. Based on these, it then prepares recommendations for actions by Member States, for consideration and adoption by the respective governing bodies of WMO and IOC."

GDSIDB meetings were documented in WMO reports. The following reports are provided courtesy of the AARI GDSIDB. The AARI GDSIDB Web site includes other related documentation as well.

GDSIDB Sessions Reports
(PDF files from AARI)

See Also

GDSIDB Data Formats

The data formats for the GDSIDB are Sea Ice Grid (SIGRID) sometimes called SIGRID-1, SIGRID-2, and SIGRID-3. These and related formats are described below.

SIGRID

On sea ice charts, ice parameters are represented by symbols and accompanying numbers giving the values of the ice parameters. The symbols varied depending on what nation was compiling the chart until the 1980s, when an international standard was developed by the WMO. The egg code, which gets its name from the shape of the symbol used to embody the WMO standard sea ice information, is now used for most sea ice charts. The U.S. National Ice Center Web site has an explanation of the egg code and examples of operational ice charts.

SIGRID is an alphanumeric coding of ice chart information obtained by overlaying a grid on the original paper chart and encoding the ice information in each grid cell. Thompson (1981) provides a description of the proposal for the SIGRID-1 format. The official 1989 version of SIGRID-1 is described in the Annex to Recommendation 11 on pages 81 to 111 of the Abridged Final Report of the Tenth Session of the WMO Commission for Marine Meteorology which contains a number of differences from the 1981 proposal. In 1994, a simplified version of the original format, SIGRID-2 (WMO, 1994), was adopted and is described in the report Format to Provide Sea Ice Data for the World Climate Program (SIGRID-2) (Also available as a PDF, 272 KB).

SIGRID encodes the information in each egg as illustrated by the following example:

NIC Sea Ice Chart Example

NIC sea ice chart showing the egg code. The numbers in the egg give total concentration (usually as a range); partial concentration of the first, second, and third thickest ice; stage of development of the first, second, and third thickest ice; and other information such as form, if available. See the NIC ice chart symbology page for more information.

The SIGRID string captures all the information in the egg above.

The nominal resolution of a SIGRID grid is 15 minutes latitude. The longitudinal resolution varies with latitude, as illustrated by the drawing at left and the plot at right:

Longitudinal Resolution DrawingLongitudinal Resolution Plot
 

SIGRID-3

While converting data from SIGRID to EASE-Grid makes it easier for most to use, SIGRID and EASE-Grid formats are limited in that they do not contain all the information in the original chart; therefore, they cannot be used to reconstruct the original chart. The illustration below shows why. In the SIGRID raster format, a single point within a cell represents the entire cell, and the shape of the boundary between regions is lost. To preserve this information and to avoid losing spatial resolution, a vector rather than raster format is needed.

In 1997, AARI proposed a vector format called CONTOUR 2; however, the sea ice community did not adopt this format. In 1999, work on a new vector format began based on ESRI shapefiles. The vector format preserves the chart information in a series of vertices that define the spatial extent of each ice region or polygon, and in a table with a record of attributes for each polygon encoded in SIGRID descriptors for that polygon's egg code. Background information on this new format, SIGRID-3, is found in the International Ice Charting Working Group's Ad Hoc Format discussion and on the SIGRID-3 development Web site. The SIGRID-3 format was adopted by JCOMM as an official WMO format in May, 2004. It may be referenced as "SIGRID-3: A Vector Archive Format for Sea Ice Charts. JCOMM Technical Report Series No. 23, 2004, WMO/TD-No. 1214." 

SIGRID Raster Format
Source: NSIDC Special Report - 9: Methods for Regridding AARI Data in SIGRID Format to the EASE-Grid Projection.

Most ice centers now use GIS tools for ice chart production. SIGRID-3 is relatively easy for those centers to output as part of their production routine. This should lead to increased ice center participation in the GDSIDB.

EASE-Grid

SIGRID to EASE
SIGRIDINF :RFAA:099:A7680002400:BO410213:C0015: D06CTCABCCNCD: SIGRID01:E98201049999:F001 =K002:L021163:M0213 :R19CT92CA808799CB208...02LL...

A chart in SIGRID format is an ASCII file that must be interpreted by a computer program before the information it contains can be viewed. Because there are ten layers of information per chart, the format makes the data difficult to compare and analyze. The ten layers reflect the egg code: total ice concentration, concentration of the first thickest ice, stage of development of the first thickest ice (these are WMO-designated stages such as nilas, second year ice, and so forth), form of first thickest ice (generally fast ice is the only form used, out of several allowed by SIGRID), concentration of the second thickest ice, stage of development of the second thickest ice, form of second thickest ice, concentration of the third thickest ice, stage of development of the third thickest ice, and form of the third thickest ice. To simplify viewing and data analysis, NSIDC and AARI reformatted the collection of GDSIDB data from AARI and created the data set, Sea Ice Charts of the Russian Arctic in Gridded Format, 1933-2006. Data were re-gridded from SIGRID to the Equal-Area Scalable Earth Grid (EASE-Grid). EASE-Grid is a grid and projection combination used at NSIDC and elsewhere. It is described in the All About EASE-Grid Web page. One advantage of EASE-Grid is that the grid cell size remains the same with latitude.

The above figure illustrates how information in the ASCII SIGRID file is regridded and displayed. In this case the concentration of first year ice is shown.

References

IICWG. 2004. SIGRID-3: A Vector Archive Format for Sea Ice Charts. JCOMM Technical Report Series No. 23, WMO/TD-No. 1214.

Thompson, T. 1981. Proposed Format for Gridded Sea Ice Information (SIGRID).Unpublished report prepared for the World Climate Programme.

World Meteorological Organization. 1994. Format to Provide Sea Ice Data for the World Climate Program (SIGRID-2). World Meteorological Organization.

World Meteorological Organization. 1989. Abridged Final Report of the Tenth Session of the WMO Commission for Marine Meteorology. Paris, France. February 1989. World Meteorological Organization.

GDSIDB Data Holdings

Arctic and Antarctic Research Institute (AARI)

AARI's collection is easily viewed using an on-line browse tool. There you will find statistical summaries and data series of total concentration provided as GIF images.

Arctic
Greenland Sea
Baltic Sea
Antarctic

National Snow and Ice Data Center (NSIDC)

The GDSIDB was initially established as a pilot program using data from test year 1982. At present, the GDSIDB at NSIDC consists of the data sets in the table below. Note that NSIDC has distributed only the U.S. National Ice Center (NIC) data and Russian Federation, AARI, data.

Users often find simple gridded ice concentration data easier to work with than SIGRID-1, SIGRID-2, or SIGRID-3 data. For this reason, NSIDC published an EASE-Grid version of the NIC and AARI data.

Most ice services have no easy way to produce charts in SIGRID-1, SIGRID-2, or SIGRID-3 format. As a result, the GDSIDB lacks complete records from all services with the exception of the Japan Meteorological Agency. This problem has been addressed through theInternational Ice Charting Working Group Ad Hoc Format team, and will be taken up by JCOMM.
 

History of GDSIDB Data Sets at NSIDC
Arctic (Alaskan and Canadian coasts)
Originator William H. Dehn and Sea Ice Consultants, Inc.
Record length/
Chart frequency
1953-1986; frequency varies from about 80 to about 350 charts per year
Format

PNG and TIFF

Data available
from NSIDC?
Yes. The Dehn Collection of Arctic Sea Ice Charts, 1953-1986 is publicly available.
NSIDC reference numbers G01111, FD0170
Arctic (complete coverage)
Originator U.S. National Ice Center
Record length/
Chart frequency
1972-2004; monthly climatology products are median, maximum, minimum, first quartile, and third quartile concentrations, as well as frequency of occurrence of ice at any concentration for 33 year, 10 year, and 5 year periods
Format EASE-Grid, GIF and GIS (geodatabase)
Data available
from NSIDC?
Yes. The data set title is National Ice Center Arctic Sea Ice Charts and Climatologies in Gridded Format
NSIDC reference number G02172
Arctic and Antarctic
Originator U.S. National Ice Center
Record length/
Chart frequency
1972-1994, every seven days
Format SIGRID-1

(EWG Atlas is in SIGRID, EASE-Grid, and GIS formats.)
Data available
from NSIDC?
No.
NSIDC reference numbers FD4, FD20, G00793
EWG Atlas: G01962
Notes SIGRID data were distributed on a CD-ROM titled "NIC Arctic and Antarctic Sea Ice Data", published by NIC and NOAA NCDC. Coding errors for ice type were discovered the CD-ROM was removed from circulation.

The Arctic portion was replaced in 2000 by the quality-controlled data on the Environmental Working Group Joint U.S.-Russian Arctic Sea Ice Atlas and later by the National Ice Center Arctic Sea Ice Charts and Climatologies in Gridded Format.
Canadian Arctic
Originator Canadian Ice Service
Record length/
Chart frequency
March 2006-present; weekly
Format SIGRID-3
Data available
from NSIDC?
Yes. We archive the data, but are not distributing the data set as of 12/10/2007.
NSIDC reference number G02171
Eurasian Arctic
Originator Russian Federation, AARI
Record length/
Chart frequency
1953-1990, every ten days
Format Original format: SIGRID-1,2
Distributed version: EASE-Grid
Data available
from NSIDC?
No. This data set has been replaced by the AARI 10-Day Arctic Ocean EASE-Grid Sea Ice Observations and then replaced in 2007 by Sea Ice Charts of the Russian Arctic in Gridded Format, 1933-2006.
NSIDC reference numbers FD157
EASE-Grid product: G02119
Russian Arctic
Originator AARI
Record length/
Chart frequency
1933-2006; chart frequency varies (charts were compiled every 10 days during the navigation season and monthly for the rest of the year over most of the time series)
Format SIGRID-1 and EASE-Grid
Data available
from NSIDC?
Yes. The Sea Ice Charts of the Russian Arctic in Gridded Format, 1933-2006 data set is publicly available.
NSIDC reference number G02176
Notes There is a data gap between 1993 and 1996.
Great Lakes
Originator U. S. National Ice Center, Canadian Ice Service
Record length/
Chart frequency
1973-74 ice season to present; frequency varies per year throughout the ice season
Format Most files are available in GIF format
Data available
from NSIDC?
Yes. The Great Lakes Ice Charts data set is available.
NSIDC reference numbers G00486, FD0055
Gulf of Newfoundland, Hudson Bay, Arctic
Originator Canadian Ice Service
Record length/
Chart frequency
1962-1982, 1962-1983, 1959-1980
Format SIGRID-1
Data available
from NSIDC?
No.
NSIDC reference numbers FD168, rcvd 1992, 1998
Notes No plans to distribute.
Sea of Okhotsk
Originator Japan Meteorological Agency
Record length/
Chart frequency
1971-last ice season, every five days
Format SIGRID-1,2
Data available
from NSIDC?
No.
NSIDC reference numbers FD042
Notes NSIDC plans to convert this data set to EASE-Grid before distribution.
Various
Originator Argentina, Canada, Japan, U.S., and USSR
Record length/
Chart frequency
1982
Format SIGRID-1
Data available
from NSIDC?
No.
NSIDC reference numbers FD111, rcvd 1989
Notes SIGRID Global Sea Ice Data bank Test Tape. No plans to distribute.

SIGRID-3 Development

June 1, 2004

The Ad Hoc Format Working Group's efforts have lead to a new WMO JCOMM-sanctioned format. The descriptive document may be referenced as:

IICWG. 2004. SIGRID-3: A Vector Archive Format for Sea Ice Charts. JCOMM Technical Report Series No. 23, WMO/TD-No. 1214.

ESRI Shapefile Technical Description (PDF file)

Sample SIGRID-3 Charts

Document History

September 2019 - A. Windnagel condensed the GDSIBD web pages into one web page and added the note that these pages are no longer updated and are kept for hisotrical purposes only.