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Ice Data in Maine Lakes
An overview of data collected by volunteers at Lake Stewards of Maine on ice-in and ice-out dates that reveal changes in ice cover.
Introduction to Ice Data in Maine Lakes
Many of the large lakes in Maine have experienced an average decrease of about 13 days of ice cover between 1905 - 2019, with later freeze dates and earlier thaw dates (EPA).
- What is ice data?
- The data presented in this Story Map was collected by volunteers at Lake Stewards of Maine (LSM). Volunteers were responsible for recording the ice-in and ice-out dates of respective lakes while also monitoring the extent of ice cover throughout the winter season. The collected data was compiled, quality-assured, and analyzed by LSM staff prior to being made available to this audience.
- Why is this data important?
- The freezing and thawing of lakes are influenced by many factors including air temperature, cloud cover, and wind speed as well as weather events like snow and rain storms. As a result, monitoring the first freezes and thaws and relative ice cover through the winter season is an important indicator of climate change. The changes in these trends can affect the physical, biological, and chemical processes in the lakes, changing the turnover rate and productivity of the lake itself as well as its ability to support wildlife and other human-centric recreational activities.
Locations
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- LSM has collected corresponding data on 129 individual lakes, with data from as early as 1928.
- Below are the breakdowns of the number of lakes monitored per county:
- Oxford County: 28
- Kennebec County: 16
- Androscoggin County: 15
- Cumberland County: 11
- York County: 10
- Franklin County: 8
- Hancock County: 8
- Penobscot County: 8
- Lincoln County: 6
- Washington County: 5
- Aroostook County: 5
- Knox County: 5
- Waldo County: 3
- Piscataquis County: 3
- Somerset County: 2
- Sagadahoc County: 0
Regional Topography
Topographical map of elevations across the state of Maine
- Increases in elevation correspond to decreases in average temperature as well as lower air pressure. This change has an obvious impact on lakes as the colder temperatures enable ice to form earlier and persist for longer (in comparison to other regions with the same general location but different elevations).
- The western side of Maine is home to many high-elevation lakes which are subject to more extreme changes in temperature, and subsequently productivity, wildlife, and recreational activities as a result of a changing climate.
Regional Temperatures
A region's air temperature is vital to understanding patterns of freezing and thawing in lakes as water temperatures can change through the interaction of the lake surface and warm air as well as the tendency for water bodies to retain heat.
Higher temperatures in the summer mean that lakes will be warmer, causing ice to set in later, while warmer temperatures in the winter mean that lakes will likely thaw out earlier as well. These factors combine to decrease the annual ice coverage which can have significant consequences.
These graphs show the average temperatures in Maine from 1900-2014. The orange bars show averages over 5 year period, while the black dots show each year's average. The horizontal black lines show the long-term (entire period) averages for Maine, with summers at 16.1°F and winters at 62.9°F (NOAA National Centers for Environmental Information). .
Lake size (acreage) and depth also have an impact on ice-in and ice-out dates. Big lakes have more surface area that is exposed to the air and thus are more easily impacted by changes in weather and climate. Shallow lakes mix more easily, meaning warmed surface water will mix with the rest of the water body, causing quicker warming. Deep lakes have the opposite effect as water mixes less frequently and they are more likely to retain the thermal stratification, with surfaces temperatures being higher and water at the bottom of the pond being much colder.
Complied Ice-in and Ice-out Data
This figure shows the months that ice-ins were observed across Maine between 1988-2023, measured by the days from September 1st. For reference, day 50 is 10/21 and day 100 is 12/9.
The figure shows the months that ice-outs were observed across Maine between 1928-2023, measured by the days from December 1st. For reference, day 50 is 1/20, day 100 is 3/11, and day 150 is 4/30.
The first graph shows that the majority of ice-in observations across Maine occurred in November and December, though since 2005, there have been ice-ins occurring as late as January and even in February in 2022 and 2023 (over 120 days after September 1st) .
The second graph shows that the majority of ice-out observations across Maine were made in April and May. Since 2010, however, there have been some observations of ice-outs between December and March (under 100 days after December 1st).
Though the trends are likely not significant, it is important to note the changes in these patterns and continue to monitor them going forward.
All ice-in, ice-out, and open pocket data from 1928-2023
Ice Data Dashboard (ice-in on top and ice-out on the bottom)
These graphs show the number of observations across time. The graph on top shows ice-in data and the graph on the bottom shows ice-out data, both tallied by county. Use the scroll bar to adjust the time frame or zoom in on a specific period.
These graphs taken together highlight the "hot spots" for ice-in and ice-out dates across Maine, which, based on the most recent data appear to be around late December and early April. Below is the same data divided by county to provide a more in-depth looks at individual regions and lakes.
If you wish to explore what the weather was like on a particular day to help explain the observed ice-in or ice-out trends, click here !
Ice-in and Ice-out dates by county
Androscoggin County
Based on the data from 2023, it appears that lakes in the northern region of Androscoggin County experienced ice-in around mid-December while the lakes in the southern parts of the county experienced ice-in in early January. Ice-out dates were pretty consistent across the county, taking place between early and mid-April.
Monitoring these dates moving forward will be important to better understanding patterns and trends with regard to changes in ice cover in these lakes.
Aroostook County
Records in Aroostook County were updated more recently with historic data. From this historical record, we can see that ice out dates are getting earlier each year and ice in dates are getting later. It is important to recognize that the earliest ice-in date only goes back to 2003, so it is much less reliable data, and all of these are based on simple linear trends.
Reported ice-out dates almost entirely took place between mid-April and mid-May in Aroostook County. This is later than other parts of the state and consistent with the county's more northernly location. Although there is significant geographic distance (latitude) between the most northern Aroostook county lake and the most southern Aroostook county lake, minimal variation exists in the dataset. This implies that annual weather and stochastic variations between the lakes play a more significant role than their northernly distribution.
Cumberland County
Across Cumberland County, the data indicates that most lakes froze over between the last few days of December and the beginning of January. There appears to be less variation from North to South. Ice-out dates fell between the end of March and the beginning of April.
Franklin County
In Franklin County ice-in dates were pretty consistent in 2022, falling in the middle of December. Ice-out dates also generally fell in mid-April.
Franklin County's relatively northern location may be the reason that many lakes in the county had an earlier ice-in date, as colder temperatures likely set in earlier.
Hancock County
Hancock County's location on the coast and relatively south caused ice-in dates to fall between the last days of December and the first half of January. The ice-out dates generally fell in the second week of April, demonstrating a pretty consistent pattern within the county.
Kennebec County
Lakes in Kennebec County generally experienced freezing in the last few days of December which is roughly average given its north-to-south location. The ice-out dates averaged around mid-April.
Knox County
There is relatively little data on Knox County, and therefore there is no trend or average regarding ice-in dates. Data from Alford Lake shows ice-in happening in late January, though this is likely not a good average, given the size of the lake. Ice-out dates averaged in the first week of April, which is slightly earlier compared to many other counties.
Lincoln County
Across Lincoln County, ice-in dates fell within the last week of December while ice-out dates generally fell in the last week of March, with a couple experiencing ice-out in the first days of April.
More data comparing lakes in the northern region of the county compared to the south could indicate important trends regarding ice coverage variability from north-to-south.
Oxford County
Oxford County lakes had higher variability in ice-in dates, with ice coverage setting in across the month of December. Ice-out dates generally occurred in mid-April.
Oxford County is unique because historical data dating back to 1979 at Ellis Pond provide some context to inform trends that have been observed.
Ellis Pond Ice-In and Ice-Out Dates
Between 1988-2022, there has been a pretty significant variation in ice-in dates year-over-year, which appear to have a slight trend toward freezing later in the season, but this change is likely not significant.
Similarly, between 1979 and 2022, there was a pretty significant fluctuation in ice-out dates each year. This data shows a slight trend towards earlier ice-out, meaning that this data taken together, suggest that in the last 30 to 40 years there has been a decrease is overall ice coverage at Ellis Pond.
Though this is only one case study of a very specific location in Maine, the evidence points to the possibility that climate change is already having an effect on ice coverage, pointing to the inevitable social, ecological an economic consequences that would follow if these trends were to continue and become more prevalent.
Penobscot County
The lakes in the northern region of Penobscot County experienced ice-in as early as late November while larger lakes in the southern parts of the county did not experience complete freezing until early January. Ice-out dates averaged to be around mid-April across the county.
Piscataquis County
With very little data in Piscataquis County, it is hard to draw any specific patterns or trends, but it appears ice-in occurred around December and ice-out occurred in April.
Somerset County
The only piece of data in Somerset County regarding ice-in dates points to late December and early January, however, ice-out seems to occur around mid- to late April.
Given Somerset County's wide span from North to South, having more data here would provide insight on whether north-to-south differences in ice coverage are significant.
Waldo County
Based on the scarce data, it appears that ice-in in Waldo County happens around late January and ice-out occurs around mid-May.
Washington County
Observations of larger lakes in Washington County indicate that ice-in occurred in late January, while ice-out was around mid-April.
York County
In York County, ice-in dates varied from late December to late January, while ice-out dates remained fairly consistent in mid-April.
Conclusion
- Here are some of the main takeaways from this data:
- For counties with more comprehensive data, there appear to be emergent trends that indicate possible effects of climate change on the lakes.
- As shown by longitudinal data on Ellis Pond, there is some evidence of later ice-in and earlier ice-out dates on the pond, which will inevitably have social, economic, and ecological consequences for residents and lake users.
- For counties with less comprehensive data, these data points can serve as a baseline or a frame of reference for future observation.
- As climate change continues to exert its influence on the environment in multiple ways, it is important to consider what its impact on the natural cycles of lakes can have far-reaching effects both on wildlife and on human recreational activities.