Arctic Borderlands Ecological Knowledge Co-op: Projects -- Freeze-up and Break-up on Lakes

Guidelines for Observing Freeze-up and Break-up on Lakes

The timing of freeze-up and break-up on lakes should be a useful measure of how temperature varies between years. One of the suggestions at the 3^rd Annual Gathering was that observers in the communities could help collect this information on local lakes. Here are the suggested guidelines or protocol that community observers could use to collect standardized information on ice conditions at the start and end of winter. This information has been adapted from the International Tundra Experiment manual (ITEX 1993).

There are three steps involved in this study: (i) choosing a lake, (ii) collecting observations using the ITEX protocol, and (iii) reporting the observations so they can be used in future years.

The ITEX manual provides advice on several aspects of choosing a lake to take measurements on. From a community perspective it would be best to choose a lake that was easy to get to - easier access will allow more frequent and convenient observations. It may be important to establish one spot to stand at to collect the observations particularly if the lake is so big that you are unable to see the entire lake surface. This could be simply a matter of the observer deciding to walk to the same point on a beach or a ridge to make the observations. (When pans of ice start moving around the lake an observer might get different impressions by standing at different points.) Choose a convenient spot and stick with it. Try and choose a spot that a different observer in future years could easily find.

The size of the lake is also important. If the lake is too small it might not show much variation between years in the dates of freezing and melting. The ITEX manual suggests choosing a lake that is at least 50 hectares in size (e.g. 1 km long by 0.5 km wide) and at least 5 m deep.

The most valuable single piece of information in this study will be the actual date of freeze-up or break-up. When there is some ice on the lake (between open water and complete ice cover) the observer should give an estimate of the fraction of the lake that is covered by ice (to the nearest 5 or 10%). The ITEX protocol uses the following categories to describe the various stages of lake ice melting and thawing:

Break-up		Freeze-up
B0	No signs of break-up	F0	No ice formation
B1	Open water on shore	F1	Ice formation on shore
B2	Open water offshore	F2	Ice cover on bays
B3	Ice in movement	F3	Ice within visible range
B4	Final break-up	F4	Final freeze-up

The ITEX protocol also involves measuring the temperature of the surface water (top 5 cm) of the lake. This temperature data may be considered optional.

The importance of this last step should not be underestimated! There must be a way to ensure that observers in different years will be able to find the results from earlier work and that the important details such as which lake was monitored and the sighting position that was used. After freeze-up or break-up the person who has collected the observations should make sure that there is a permanent record that includes all the information collected in the study. A sample data sheet is provided as a model although observers may wish to modify this form.