Freeze up and thaw dates for Lake Opinicon, 1985-2010

Posted by: Mark Andrew Conboy and Philina English

In recent years a great deal of attention has been paid to monitoring phenological changes in organisms and annual events such as ice cycles on lakes. Longterm datasets are an invaluable resource for studying changes over time, especially in the face of rapidly rising global temperatures and associated climate change. Frank Phelan and Floyd Connor [Manager and Assistant Manager (until Feb. 2010) respectively] have kept track of the date of freeze-up and thaw of ice on Lake Opinicon since 1985. Here we summarize this data (Table 1).
Lake Opinicon is located on the Rideau Canal system in the Cataraqui-Gananoque Watershed. QUBS sits on the northwest shore of this lake. The lake has an area of 788 ha with approximately 61 km of shoreline (including islands). The mean depth is 2.8 m and the maximum measured depth is 11.3 m. Researchers use Opinicon extensively for studies of a variety of taxa including water mites, odonates, fish, turtles and plants, therefore making an understanding of lake ice phenology very important. Furthermore, changes in date of freeze-up and thaw can act as a proxy for monitoring climate change (Magnuson et al 2000; Futter 2003).

Figure 1. Dates of complete freeze-up of Lake Opinicon (1985-2009). There are missing records for the years 1987, 1991 and 2002. At the time of this blog post Lake Opinicon had not frozen for 2010. * The 2006 freeze-up took place in January of 2007. Click on picture to see a larger version of this image.

For our purposes the date of freeze-up means the day on which no more open water is found on Lake Opinicon. This is the formation of permanent ice with no patches of open water subsequently forming until the thaw. It is important to note that there is almost always some open water on Lake Opinicon where strong currents from in- and outflows preclude ice formation (i.e. Chaffey’s Lock, Davis Lock and Deadlock Bay) so complete freeze-up refers to all but these small areas. The earliest complete freeze-up on record (22 years) was on 24 November 1995. The latest was 1 January 2007 (for the winter of 2006-07) (Figure 1). The median day of freeze up is 9 December. We are missing records for the years 1987, 1991 and 2002 and at the time of this blog post Lake Opinicon had not frozen for 2010 (there was skim ice between Rabbit Island and Cow Island on November 6 and skim ice from shore to shore on November 23 that was later broken up by wind and waves. Some of the back bays have been frozen for a few days at a time but that ice is still ephemeral).

Date of thaw is the day on which generally no more ice is present on Lake Opinicon. At this date there is certainly no more fast ice (ice attached to shore) but a few small floating pieces may still be present, however in general there is no more ice left on the lake. The earliest complete thaw (26 years) was 26 March 2000. The latest was 23 April 1992 (Figure 2). The median day of thaw is 12 April.

Figure 2. Dates of complete thaw of Lake Opinicon (1985-2010). Click on picture to see a larger version of this image.

The longest duration of winter ice cover (22 years) was 143 days in the winter of 1995-96. The shortest was 97 days in the winter of 1999-2000 (Figure 3). The mean duration of ice cover on Lake Opinicon is 119 days. We could not calculate the duration of ice cover for the winters of 1987-88, 1991-92 and 2002-03 because of unknown dates of freeze-up.

Though some other Ontario lakes have shown a trend toward a longer ice-free season since the 1970’s (Futter 2003) there is no such trend apparent in the QUBS data. Clearly there is dramatic year to year variability in the timing of freeze-up and thaw events at Lake Opinicon. It

Figure 3. Days of ice cover on Lake Opinicon for the winters 1985-86 through 2009-10. Ice cover could not be calculated for the winters 1987-88, 1991-92 and 2002-03 because of unknown dates of freeze-up.

will likely take several more years before any trend that could be indicative of longterm climate change becomes evident.

Works Cited

1. Futter, M.N. 2003. Patterns and trends in Southern Ontario lake ice phenology. Environmental Monitoring and Assessment 88: 431-444.
2. Magnuson, J.J., Robertson, D.M., Benson, B.J.,Wynne, R.H., Livingstone, D.M., Arai, T., Assel, R.A., Barry, R.G., Card, V., Kuusisto, E., Granin, N.G., Prowse, T.D., Stewart, K.M. and Vuglinski, V.S. 2000. Historical trends in lake and river ice cover in the northern hemisphere. Science 289: 1743–1746.