LAKE GEORGE, N.Y. (NEWS10) — When the weather starts to get warm, eyes around Lake George turn to the water. In the winter, ice hardens across the lake, typically thick enough to walk across, and often enough for snowmobiles and even cars. Ice fishers, snowmobilers, and tourists rely on that ice—as does the ecosystem on the lake itself.
The notches on the thermometer outside your deck can be one indication of when things will solidify, and then start to melt, but there’s a lot more to it than that. So how can you predict when the ice will start to melt?
That’s a question posed by IBM researcher Campbell D. Watson, who has spent time working with data modeling for the Jefferson Project, a collaboration between IBM, Rensselaer Polytechnic Institute and the Lake George Association that creates predictive models for environmental monitoring and prediction on Lake George. Watson’s team gathered data on when the lake was frozen from end to end. The collection of that data is a great reminder that science isn’t always about crunching numbers. It can be as easy as taking a walk.
“One day, I discovered there was this beautifully long data set about ice cover on Lake George. I think 1912 is when it started,” said Watson, who specializes in climate and sustainability research. “Every single year, an ice-in and ice-out. One of the things I learned about this data set is that the declaration of ice-in is when someone can walk from the northern tip of the lake to the southern tip, end to end.”
That ice-in date is the point where the lake is considered fully frozen. Every year in the record that Watson acquired lists an ice-in date, up until 1980. Since then, Lake George averages out to having fully frozen around 70% of the subsequent 42 years.
The IBM team gathered ice-in and ice-out records and built a model, which Watson said was able to predict ice-in and ice-out dates within a range of about five days. Historical temperature data is crucial in determining when the ice will come and go, but there are other factors to consider as well. Wind can bring warmer water to the surface, or rapidly cool surface ice.
One more element that can delay ice melt is actually further snowfall. Falling snow can add to the thickness of ice, and also turns the surface of a frozen water body white. That change in color increases the lake’s albedo – the amount of sunlight it reflects.
“A white surface reflects a lot of light and heat,” Watson explained. “It’s like wearing a black T-shirt versus a white T-shirt.”
Night life and ice life
Over the last two weeks, the Capital Region has seen temperatures reliably stay above freezing during the day. The midday high on Tuesday hung around 50, and sunny to boot. Those temperatures have dipped back down by night. Contrasting with the day, Tuesday night was forecast to shoot right back down below freezing.
Even on nights when temperatures don’t pass below the dreaded 32-degree line, that waxing and waning of cooling affect the layer of ice that winter has left behind on Lake George. When ice melts during the day and refreezes at night, things typically stay the same in terms of ice thickness; or, if they do change, the shift is slow.
The bigger change, of course, comes once the days get consistently warm, and the nights don’t back down as far in temperature. When ice does melt, it’s not like one big ice cube. Melting causes structural integrity to fracture, which in turn causes the sheet of ice across the lake to start to break up. When ice is still thick but more permeable—”rotten ice” is the term—that thickness doesn’t mean it’s stable. That can create some scary situations.
“I can speak from personal experience,” said Vincent Moriarty, another IBM researcher with experience at The Jefferson Project’s Bolton Landing research center. “I’ve had this happen on more than one occasion, where you’ll have a solid thickness of ice; you’ll have a melt-off and re-freezing of a very thin layer on top. You can put your foot through that and feel like you’re about to drown in an abyss, and then you’ll hit the real ice layer.”
The recommended ice thickness for walking is 4 inches. That won’t stop some ice fishers, who choose to test their luck as things start to thin out. Ice fishing requires holes to be drilled down through the ice. While that may sound like another blow to structural integrity, Moriarty says there’s unlikely to be almost any effect on the ice.
Moriarty’s focus of study is ecology within the lakes. Life under the surface of Lake George changes depending on how early or late the ice melts—more than researchers knew for a long time.
“I think for many, many years, people just assumed the ice came over and then everything goes to sleep, and things wake up in the spring, so there’s no point in measuring that,” Moriarty said. “I think what we’re finding is that that isn’t at all the case.”
The snowy albedo effect comes back around when looking underneath the water’s surface. A lake with clear ice and no snow on top will allow a lot of sunlight to penetrate the ice layer. Moriarty cited Lake Baikal, in Siberia, as famous for the clarity of the ice. There’s a lot more activity among fish and plant life under a lake like Baikal than there is under one covered by a sheet of snow.
As light reaches below the surface, plant growth begins to pick up the pace. Temperature stratification—the concept of layers of different water temperatures—can grow stronger, as well. While the lake is frozen over, there’s a limit to how much oxygen is under the water, but fish and other life are still using what’s there. Less oxygen after melting means that the layers of temperature in the water are not able to exchange as freely.
One freeze closer to the last
The IBM data set Watson’s team used trained machine learning models to predict ice-in and ice-out by looking at years from 1912 all the way up to 2000. Then, the model was used to make predictions for the remaining 20 or so years. After that, global climate models were used to project into the future of ice cover on Lake George, all the way to 2100.
“What we found is an undeniable loss of ice in the second half of the century,” Watson said. “By the end of the century, close to 2100, there are expected to be no winters with ice.”
Almost every single climate model being used by scientists like Watson predicts an increase in average temperatures over the next century. That means that events like the Lake George Winter Carnival won’t be able to use the lake the way it does now, with hundreds of visitors, snowmobiles, cars, and even dogsleds visiting the ice once it has enough inches to be deemed safe.
No model is perfect, though. One area where the IBM model falters is in the prediction of sudden outbreaks of extreme cold. Watson recalled the polar vortex, a term for a region of polar air circulating the Earth’s poles that can hugely influence weather patterns.
“With the right jetstream, suddenly we have a cold air intrusion from the north, and temperatures just drop dramatically. These are likely to occur more frequently in the future, even though temperatures will be increasing,” Watson said. “So what we might see are winters where the temperatures do plummet and ice does form. It’s just not particularly captured in the climate models.”