A warming climate can bring about physical, chemical, and biological changes in Lake Champlain. While some of the physical and chemical changes are fairly straight-forward, others are speculative. Potential biological changes are even more difficult to predict.
Physical changes mostly involve the temperature of the lake. Higher winter temperatures lead to a reduction in winter ice cover. You may have noticed that such reductions have already begun. Prior to the 1950s it was highly unusual for Lake Champlain not to freeze in a given year, but recently an absence of ice cover has become a fairly regular event. Higher temperatures mean the lake will stratify earlier in the spring — setting up a warm layer of water over a colder deeper layer — and will stay stratified longer. A 1979 study stated stratification in the Main Lake typically began in early June; more recently, however, stratification has begun in early- to mid-May.
Most computer models predict an increase in precipitation in the Northeast as global temperatures rise. Furthermore, the intensity of precipitation events is likely to increase, meaning more rains of 1 inch or more. More intense storms will likely mean increases in flooding and erosion-related run-off. More erosion will lead to more nutrient pollution in the lake.
Chemically, decreases in the oxygen content of lake water will likely occur. Warm water holds less oxygen than cold water. Additionally, the longer duration of summer stratification will increase the likelihood of oxygen depletion in lower layers of the lake water. Such oxygen depletion occurs fairly regularly in the Northeast Arm of the lake.
Predicting biological changes in Lake Champlain as a result of global warming means attempting to integrate the impacts of all the physical and chemical change on each species and speculating about how they will affect that species’ interactions with other species. Fish will need to adapt because spawning in many species is triggered by optimum temperatures. Earlier warming will mean earlier spawning. Perhaps more importantly, available habitat for cold-water species like trout and salmon could decrease, while habitat for warm-water species like bass could increase.