Winter is an exciting time of year for those of us close to freshwater, as ice advances across the surfaces of lakes and ponds. Ice skaters and skiers eagerly await the season of thick ice, and ice fishers get ready to set up their shacks. With the temperature dips and peaks of this December in particular, it is possible to see a large expanse of ice one day, only to have fully open water the next. On the pond at Fields Pond Audubon Center, the past weeks have brought many such fluctuations, with the ice advancing, receding, and advancing again each day.
The date of first complete ice cover, or “ice-in,” is an important marker in the seasonal cycle, or phenology, of a lake or pond. Tracking the ice-in dates of water bodies over many years is an excellent way to track climate change, too. Since colonization, settler communities have been recording ice-in and ice-out dates for purposes of fishing, log driving, and boat travel, and those historic records are invaluable for tracking long-term change. According to the U.S. Geological Survey, over the past 150 years, average ice-in date in Maine lakes has become an average of 9 days earlier in northern and western Maine and 16 days earlier in southern Maine.
Under the ice, you might expect life to be fairly still, because isn’t it too cold? But a layer of ice keeps the water beneath just above the freezing point, and life is surprisingly active. Aquatic insects continue crawling and swimming around, living their lives as if nothing has happened. They do this by changing their physiology, trading in their summer body chemistry for one specially adapted to the cold temperatures of winter. Imagine if we did that too, restructuring the most basic parts of our bodies instead of bundling up!
Do you want to interact more with this wintery aquatic world? Our friends at Lake Stewards of Maine coordinate a network of volunteer ice monitors around the state. To explore data in real time or to submit records yourself, check out the ice tracking page on the website.
If you want to learn more about life under and above the ice, drop in to our Fish Lead Free Celebration at Fields Pond Audubon Center on February 15 from 9 am–12 pm. Grab a cup of hot chocolate and join our naturalists out on the ice to learn how we can help care for the critters under the ice!
