Great Lakes Environmental Research Laboratory 
National Oceanic and Atmospheric Administration 
US Department of Commerce 
2300 Washtenaw Avenue 
Ann Arbor, MI 48104 
(313) 668-2235, FTS 378-2235 
Publications 
Great Lakes Ice Atlas 
Assel; Ra Ass et alls 
Publication Date: July 1983 
Location: Great Lakes including surrounding bays and 
harbors 
Contents: Over 2,800 historic Great Lakes ice charts spanning 20 winters 
(1960-79) were digitized and converted to discrete 5- by 5-km grid cells. 
This data set was analyzed to produce a series of 46 plates, including 9 for 
each of the five Great Lakes with 1 extra plate for Lake Michigan. The plates 
portray charts of maximum, minimum, and normal ice concentration patterns and 
observation density for nine semimonthly periods beginning the last half of 
December and ending the last half of April. The percent of the surface area 
covered by ice was calculated for each ice chart and summarized in tabular 
format. In addition, a 10-year data set of ice thickness in the nearshore 
zone of the Great Lakes, i.e., primarily in bays and harbors, is presented to 
identify ice thickness ranges and ice stratigraphic patterns for the Great 
Lakes Region. To complete this atlas, air temperatures at 25 stations on the 
perimeter of the Great Lakes for an 80-winter period (1898-1977) were used to 
classify winter severity into five severity classes, based on freezing degree- 
days. Winter severity trends for the preice and postice concentration clima- 
tology periods are identified on an annual and semimonthly time scale for 
individual stations and for lake-wide averages. 
This atlas is an updated version of NOAA's 1971 publication, Technical 
Memorandum NOS LSCR1 by Donald R. Rondy. Additional data or information about 
Great Lakes ice conditions can be obtained from the bibliography and reference 
list of both publications. 
Available From: Information Service 
Great Lakes Environmental Research Laboratory 
National Oceanic and Atmospheric Administration 
US Department of Commerce 
2300 Washtenaw Avenue 
Ann Arbor, MI 48104 
(313) 668-2235, FTS 378-2235 
Additional Information: Contact appropriate Coast Guard Offices listed 
in Appendix E for additional ice information. 
