NOAA Atlas An Electronic Atlas of Great Lakes Ice Cover Winters: 1973 - 2002 Raymond A. Assel National Oceanic and Atmospheric Administration Great Lakes Environmental Research Laboratory Ann Arbor, Michigan 48105

Introduction
Synoptic ice chart observations for the Great Lakes began in 1960. A synoptic ice chart usually covers only a portion of one or more of the Great Lakes. Synoptic ice charts for a 20-winter base period (1960 to 1979) were digitized (Assel, 1983), and a multi-winter statistical analysis of ice concentration patterns over nine half-month periods (Dec. 16-31 to April 16-30) was published as a National Oceanic and Atmospheric Administration (NOAA) Great Lakes Ice Atlas (Assel et al., 1983) 20-years ago. Composite ice charts, a blend of observations from different data sources (ships, shore, air craft, and satellite) that cover the entire area of the Great Lakes for a given date, and which may contain some estimated ice cover data, were produced starting in the 1970s. A 30-winter (1973-2002) set of composite ice charts was digitized, and a multi-winter statistical analysis of the climatology of the ice cover concentration was completed.

The results of this analysis are published here as an electronic NOAA Great Lakes Ice Atlas. Detailed documentation and description of analysis methods, and a discussion of the resulting products, will supplement this atlas as a series of reports. The first report in that series (Assel, Norton, and Cronk, 2002) describes the original data set and is included here. Other reports, journal articles, and ancillary data will be added as they become available. See Reference section below for updates. Please cite this atlas (Assel, 2003) and those reports when using these data.

This Atlas contains approximately 1.4-gigabytes of data, much of which is in compressed files (about 4-gigabytes when uncompressed). Because of its large size it is not practical to download the entire atlas from the Internet. Therefore, it is also being made available on CD-ROM and DVD formats. To request a copy of the atlas on CD-ROM or DVD send an email to iceatlas.glerl@noaa.gov.

Data and Analysis Products
Original Ice Charts. The original ice chart data set consists of over 1200 digitized ice charts. These ice charts display observed ice cover over each Great Lake throughout every winter season from 1973 to 2002. Ice chart data is available as Arc/Info Export, ASCII grids, and graphic files.

Analysis Products. There are three analysis products. The first product includes ice charts of the following: dates of the first reported ice, dates of the last reported ice, and ice duration for each winter, as well as, the maximum, minimum and average ice cover concentrations.

The second product is the 30-year annual daily ice cover time series. The daily time series was used to create: 1) computer animations of spatial patterns of ice cover for each winter, 2) line plots of lake averaged ice cover for each lake over the 30 winters.

The third product is weekly statistics. There are weekly ice charts and grids of: maximum, 3rd quartile, median, 1st quartile, and minimum ice cover concentrations for the 30-winter base period. The weekly statistics are based on the original ice chart data set and not on the daily time series.

Links for each product noted above contain an introductory section with pertinent information on file names, structure, and data. Secondary documentation links provide additional details in some cases. General background on the overall NOAA Great Lakes Ice Atlas is provided in the Read Me file. It is highly recommended that users read this background information prior to accessing the data.

Concluding Remarks
The NOAA Great Lakes Ice Atlas is a national resource for those seeking information on Great Lakes ice cover climatology. It provides a benchmark of ice cover and ice cover variation of the Great Lakes during the last quarter of the 20th century and early years of the 21st Century. The NOAA National Ice Center and the Canadian Ice Service use information from this atlas in making operational analysis products of Great Lakes ice cover. Portions of these data have also been used by other federal and state government agencies, academia, and the private sector for research, educational, operational, and engineering applications. This atlas and dataset will be archived at the National Snow and Ice Data Center (http://nsidc.org). The Great Lakes Environmental Research Laboratory (GLERL) will maintain the Internet version of the atlas, http://www.glerl.noaa.gov/data/ice/atlas/, for several years to come and will still continue to supply CD-ROM and DVD versions of the atlas after that.

Acknowledgments
This work was funded in part by NOAA’s Earth System and Data Information Management program. The NIC and the CIS provided the historic ice charts. Mr. David Norton's (GLERL) contributions during the data reduction and quality control phases of this project were critical for its successful completion. University of Michigan’s Cooperative Institute for Limnology and Ecosystems Research (CILER) staff; D. Meyers, B.A. Hibner, N. Morse, P.J. Trimble, K. Cronk, and M. Rubens and GLERL staff; Ms. Deborah Lee, provided invaluable contributions to this project. Ms. Janet Szczesny (CILER), Ms. Cathy Darnell (GLERL), and Mr. Gregory Lang (GLERL) were instrumental in the development of the GUI. This is GLERL Contribution Number 1266.

Reference
Assel, R.A. 2005. Great Lakes weekly ice cover statistics. NOAA Technical Memorandum GLERL-133. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 27 pp. ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-133/

Assel, R.A. 2004. Lake Erie ice cover climatology - basin averaged ice cover: winters 1898-2002. NOAA Technical Memorandum GLERL-128. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 15 pp. ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-128/

Assel, R.A. 2003. Great Lakes monthly and seasonal accumulations of freezing degree days - winters 1898-2002. NOAA Technical Memorandum GLERL-127. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 36 pp. ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-127/

Assel, R.A. 2003. Great Lakes Ice Cover, First Ice, Last Ice, and Ice Duration: Winters 1973-2002. NOAA TM GLERL-125. Great Lakes Environmental Research Laboratory, Ann Arbor, MI.ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-125/tm-125.pdf

Assel, R.A., K. Cronk, and D.C. Norton. 2003. Recent trends in Laurentian Great Lakes ice cover. Climatic Change 57:185-204. http://www.glerl.noaa.gov/pubs/fulltext/2003/20030001.pdf.

Assel, R.A. 2003. Great Lakes ice cover-winter 2003 compared with GLERL's 30-winter ice cover climatology. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 2 pp. http://www.glerl.noaa.gov/pubs/brochures/

Assel, R.A. 2003. An Electronic Atlas of Great Lakes Ice Cover. NOAA Great Lakes Ice Atlas, Great Lakes Environmental Research Laboratory, Ann Arbor, Michigan 48105.

Assel, R.A., D. C. Norton, and K. C. Cronk. 2002. A Great Lakes Digital Ice Cover Data Base for Winters 1973_2000. NOAA Technical Memorandum GLERL_121, Great Lakes Environmental Research Laboratory, Ann Arbor, MI.

Assel, R.A. and D.C. Norton. 2001. Visualizing Laurentian Great Lakes ice cycles. EOS Transactions 82(7):83. http://www.agu.org/eos_elec/00259e.html.

Assel, R.A., F.H. Quinn, G.A. Leshkevich, and S.J. Bolsenga, 1983. Great Lakes Ice Atlas. NOAA Atlas No. 4. Great Lakes Environmental Research Laboratory, Ann Arbor, MI.

Assel, R.A., 1983. A Computerized Ice Concentration Data Base for the Great Lakes. NOAA DR ERL GLERL-24. Great Lakes Environmental Research Laboratory, Ann Arbor, MI. ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-024/dr-024.pdf

Technical Notes

• To view PDF files: download a free copy of Adobe Acrobat Reader from the Adobe website.
  
• To open .zip files: Many compression utilities, such as WINZIP (http://www.winzip.com/), PKZIP (http://www.pkware.com/), or Stuffit Expander (http://www.stuffit.com/), can be used. Note: these files were originally created and compressed on a Windows platform. Please be aware that formatting errors may occur if uncompressed using a non-Windows platform.
  
• To view .AVI animation files: any software capable of playing ".avi", such as Microsoft Windows Media Player may be used. Windows Media Player may be downloaded from the Microsoft website.
  
• To view .FLC animation files: any software capable of playing ".flc", such as QuickTime, may be used. QuickTime may be downloaded from the Apple website.

Disclaimers
The NOAA Great Lakes Ice Atlas is maintained by the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory (GLERL). NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA and GLERL cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.

Specific products and manufacturers are mentioned throughout the NOAA Ice Atlas. Mention of these products or manufacturers does not constitute an endorsement by GLERL, NOAA, or the Department of Commerce.

Introduction | Original Ice Charts | First Ice, Last Ice & Ice Duration | Daily Ice Cover Time Series
Weekly Ice Cover Statistics | Contact

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