Ice-on
What is it? Ice is considered 'on' if ice completely covers the body of water from your point of view. Similarly, ice is considered ‘off’ when you no longer see any ice from the same vantage point.
Why is it important? Over time, ice coverage can show trends that could indicate warming. While one individual year may be colder or warmer, scientists are more interested in the trends.
What does it mean? Every winter is different, so it can take a few years to find out if there have been any real changes. Make sure you keep track of the vantage point you will be observing each year.