When I was in seventh grade, my entire class embarked on a journey. Over the course of several months, we followed the adventures of Sylvia Englund Michel, a researcher at University of Colorado Boulder, as she travelled to Antarctica to collect ice cores that might help unlock the history of climate. It was one of the first experiences that got me interested in environmental science, and sparked questions including: how exactly do we know what our weather was like in the past, before we had radar or satellites or weather balloons to take the data?
It turns out that ice might hold the answer. In Antarctica, researchers collect cores of ice going hundreds of meters deep into the ground. Due to the concept of superposition – that, absent outside interference, things on top must have come more recently than things on the bottom – scientists can use cores not only to look deeper into the ice, but farther into history. They then perform tests on samples from these cores – looking at, e.g., the chemical makeup of the atmosphere as trapped in snow – to develop a picture of earth’s weather thousands of years in the past.
Luckily there are ways ice can be used to measure changes in weather quite a bit closer to home: through ice-in and ice-out records on Maine’s lakes and bays.
Tracking the day that a lake freezes over, and the day that the ice melts in the spring, provides an easy record of the weather that year. A cold fall might lead to an early ice-in, while an unusually warm spring could set an earlier ice-out. In the case of larger lakes like Sebago, some winters might not even see the entire lake covered in ice. By looking at the way these dates change over time, researchers can build a picture of weather changes from year-to-year, and thus, climate.
Maine happens to have one of the country’s best records of ice dates, including data from Sebago lake going back to 1807. While much of this data was originally recorded informally, in shopkeepers’ notebooks or even on barn walls, today these records are kept by the USGS, Maine DACF, and non-profit groups like Lake Stewards of Maine.
This data is useful not just to identify long-term trends, but because the ice itself affects the health of the lake. For example, an earlier ice-out date gives photosynthetic organisms like phytoplankton and algae a head-start on spring growth, potentially causing overabundance and other ecological issues later in the year.
So next time you’re in Robinson Woods, or along Great Pond, keep an eye out – the ice might be holding more secrets than you realized. (And if you happen to know of any ice records for bodies of water in Cape Elizabeth, I would love to hear about it.)
– Philip Mathieu, CELT Education Coordinator