Great Lakes Ice Cover Data Set and Climatology

First Ice, Last Ice, and Ice Duration

Documentation: First Ice, Last Ice, and Ice Duration [pdf]

The GRID (ASCII files) and PLOT (PNG image files) files contain the results of an analysis of ice cover grids for dates of first ice, last ice and ice duration (total number of days with ice cover) for each winter season from 1973 to 2002, and for statistics (average, minimum and maximum) across all 30 winter seasons. These data have been compiled for dates when ice concentration was first and last reported to be equal or greater than nine threshold values: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% and 90%.

These data are based on observed ice concentrations from the grid ice concentration data set described in Assel et al (2002). Details of the analysis procedures and observations on trends in these data are given in Assel (2003), which can be downloaded in PDF format: Assel, R.A. 2003 NOAA TM GLERL-125. File name definitions for the uncompressed files, data codes for first ice, last ice and ice duration and file formats for the GRID files are given in the documentation.

Browse Plot Files: 30 winter plots for the first ice, last ice, and ice duration

First Ice Cover Plots
(ice concentration greater than or equal to: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%)
Last Ice Cover Plots
(ice concentration greater than or equal to: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%)
Ice Duration Plots
(ice concentration greater than or equal to: 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%)

Download complete sets of Grids and Plots:

First Ice, Last Ice, and Ice Duration

First Ice Grids / Plots

Last Ice Grids / Plots

Ice Duration Grids / Plots