WATER TEMPERATURE VARIATION IN THE WESTERN MOUNTAINS OF MAINE

Documenting local temperature variability has become increasingly important for identifying long-term patterns of climatic change. Seasonal and annual temperature changes in lakes and ponds in the western mountains of Maine are of interest to evaluate local climate trends and to identify major influences on water temperature in high elevation ponds with small watersheds. Baseline temperature data for air and surface water temperatures were collected at three locations from July through September: Webb Lake (207 m) and Tumbledown pond (875 m) in Weld, ME, and Cranberry pond (866 m) in the Bigelow range north of Kingfield, ME. This pilot study seeks to address the following questions: What is the relationship between air and water temperatures? What is responsible for the onset of a significant rise or fall in water and air temperatures? What is the influence of elevation on water temperature variability?

Water and air temperatures follow similar trends, however the average monthly air temperatures at both Tumbledown and Bigelow are cooler than the average monthly water temperatures. For example, the September average air temperature was ~12 degrees C and the average surface water temperature was ~15 degrees C. Surface water temperatures followed similar trends at all three locations, but temperatures were warmest at the lowest elevation (Webb Lake) and coolest at the highest elevation (Tumbledown).

Water temperature at each location is a function of multiple factors, including insolation, precipitation, air temperature, surface area, and water volume. We initially predicted that summer rain events might be responsible for drops in water temperature, but the comparison of water temperatures to precipitation records indicates water temperatures were falling up to a day in advance of the rain event at both locations. While there is a close correlation between insolation and air temperature, we will demonstrate that cloud cover plays a prominent role in moderating surface water temperature.