Climate Change Indicators in the United States Lake Ice

Climate Change Indicators in the United States: Lake Ice
www.epa.gov/climate-indicators - Updated August 2016

Lake Ice

This indicator measures the amount of time that ice is present on lakes in the United States.
Background

The formation of ice cover on lakes in the winter and its disappearance the following spring depends on
climate factors such as air temperature, cloud cover, and wind. Conditions such as heavy rains or
snowmelt in locations upstream or elsewhere in the watershed also affect the length of time a lake is
frozen. Thus, ice formation and breakup dates are key indicators of climate change. If lakes remain
frozen for longer periods, it can signify that the climate is cooling. Conversely, shorter periods of ice
cover suggest a warming climate.

Changes in ice cover can affect the physical, chemical, and biological characteristics of a body of water.
For example, ice influences heat and moisture transfers between a lake and the atmosphere. Reduced
ice cover leads to increased evaporation and lower water levels, as well as an increase in water
temperature and sunlight penetration. These changes, in turn, can affect plant and animal life cycles and
the availability of suitable habitat. Additionally, ice cover affects the amount of heat that is reflected
from the Earth's surface. Exposed water will absorb and retain heat, making the Earth's surface warmer,
whereas an ice- and snow-covered lake will reflect more of the sun's energy and absorb less. (For more
information on ice and snow reflecting sunlight, see the Snow Cover indicator.)

The timing and duration of ice cover on lakes and other bodies of water can also affect society—
particularly in relation to shipping and transportation, hydroelectric power generation, and fishing. The
impacts can be positive or negative. For example, reduced ice cover on a large lake could extend the
open-water shipping season but require vessels to reduce their cargo capacity, as increased evaporation
leads to lower water levels.

About the Indicator

This indicator analyzes the dates at which lakes freeze and thaw. Freeze dates occur when a continuous
and immobile ice cover forms over a body of water. Thaw dates occur when the ice cover breaks up and
open water becomes extensive.

Freeze and thaw dates have been recorded through human visual observations for more than 150 years.
The National Snow and Ice Data Center maintains a database with freeze and thaw observations from
more than 700 lakes and rivers throughout the Northern Hemisphere. This indicator focuses on 14 lakes
within the United States that have the longest and most complete historical records. The lakes of
interest are located in Minnesota, Wisconsin, New York, and Maine.

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Climate Change Indicators in the United States: Lake Ice
www.epa.gov/climate-indicators - Updated August 2016

Key Points

• The lakes covered by this indicator are generally freezing later than they did in the past. Freeze
dates have shifted later at a rate of roughly half a day to one-and-a-half days per decade (see

•	Thaw dates for most of these lakes show a trend toward earlier ice breakup in the spring (see
Figure 2). Spring thaw dates have grown earlier by up to 24 days in the past 110 years (see
Figure 3). All of these lakes were found to be thawing earlier in the year.

•	The changes in lake freeze and thaw dates shown here are consistent with other studies. For
example, a broad study of lakes and rivers throughout the Northern Hemisphere found that
since the mid-1800s, freeze dates have occurred later and thaw dates have occurred earlier,
both shifting at an average rate of 0.8 days to one day per decade.1

Figure 1).

2

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Jffc, Climate Change Indicators in the United States: Lake Ice

www.epa.gov/climate-indicators - Updated August 2016

Figure 1. Date of First Freeze for Selected U.S. Lakes, 1850-2015

November 1

December 1

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Climate Change Indicators in the United States: Lake Ice

www.epa.gov/climate-indicators - Updated August 2016

Figure 2. Date of Ice Thaw for Selected U.S. Lakes, 1840-2015

March 1

4->

April 1

May 1

June 1

1840

1860

1880

1900

1920 1940

Year

I960

1980

2000

2020

Cobbosseecontee Lake

Lake Mendota

Mirror Lake

Damariscotta Lake

Lake Monona

— Moosehead Lake

Detroit Lake

Lake Osakis

— Otsego Lake

Geneva Lake

— Lake Superior

— Sebago Lake

Lake George

at Bayfield

Shell Lake

This figure shows the ice-off date, or date of ice thawing arid breakup, for 14 U.S. lakes. The data are
available from as early as 1850 to 2015, depending on the lake, and have been smoothed using a nine-
year moving average.

Data source: Various organizations3

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Climate Change Indicators in the United States: Lake Ice

www.epa.gov/climate-indicators - Updated August 2016

Figure 3. Change in Ice Thaw Dates for Selected U.S. Lakes, 1905-2015

Detroit Lake

-2 days

Lake Osakis
-1 day

Lake Superior at Bayfield

-24 days

Shell Lake

-6 days

Moosehead Lake

-6 days

Cobbosseecontee Lake Damariscotta Lake

-10 days V -9 days

Mirror Lake

-6 days

Lake Monona

_ _ -8 days
Lake Mendota

-5 days \

Geneva Lake
-4 days

Lake George'

-4 days

Otsego Lake

-4 days

Sebago Lake

-15 days

Change in ice thaw date:

0 Earlier

This figure shows the change in the "ice-off date, or date of ice thawing and breakup, for 14 U.S. lakes
during the period from 1905 to 2015. All of the lakes have red circles with negative numbers, which
represent earlier thaw dates. Larger circles indicate larger changes.

Data source: Various organizations4

Indicator Notes

Although there is a lengthy historical record of freeze and thaw dates for a much larger set of lakes and
rivers, some records are incomplete, with breaks ranging from brief lapses to large gaps in data. This
indicator is limited to 14 lakes with sufficiently complete historical records. The four Maine lakes and
Lake Osakis only have data for ice thaw, so they do not appear in Figure 1 (first freeze date).

Data used in this indicator are all based on visual observations. While the procedures for making
observations of lake ice are consistent over time, visual observations by individuals are open to some
interpretation and can differ from one individual to the next. In addition, historical observations for
lakes have typically been made from a particular spot on the shore, which might not be representative
of lakes as a whole or comparable to satellite-based observations. Considerations for defining the thaw
date are specific to each lake.

Data Sources

Data through 2004 for most lakes were obtained from the Global Lake and River Ice Phenology
Database, which is maintained by the National Snow and Ice Data Center. These data are available at:

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Climate Change Indicators in the United States: Lake Ice
www.epa.gov/climate-indicators - Updated August 2016

http://nsidc.org/data/lake river ice. More recent data were obtained from state, local, and other
organizations that collected or compiled the observations.

1 Benson, B.J., J.J. Magnuson, O.P. Jensen, V.M. Card, G. Hodgkins, J. Korhonen, D.M. Livingstone, K.M. Stewart,
G.A. Weyhenmeyer, and N.G. Granin. 2012. Extreme events, trends, and variability in Northern Hemisphere
lake-ice phenology (1855-2005). Climatic Change 112(2):299-323.

2 [see full list starting on next page]

3 [see full list starting on next page]

4 [see full list starting on next page]

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Climate Change Indicators in the United States: Lake Ice
www.epa.gov/climate-indicators - Updated August 2016

Lake Ice: Citations for Figures 1, 2, and 3
Figure 1

Detroit Lake, Minnesota, 2006-2015

Minnesota Department of Natural Resources. Accessed June 2016. www.dnr.state.mn.us/ice in.
Geneva Lake, Wisconsin, 2005-2015

Geneva Lake Environmental Agency Newsletters. Accessed June 2016.
www.genevaonline.com/~glea/newsletters.php.

Lake George, New York, 2005-2014

Lake George Association. Accessed June 2016. www.lakegeorgeassociation.org/who-we-
are/documents/lce-ln-lce-Out2Q15.pdf.

Lake Mendota and Lake Monona, Wisconsin, 2011-2015

North Temperate Lakes Long Term Ecological Research site. Accessed June 2016.
https://lter.limnology.wisc.edu/lakeinfo/ice-data?lakeid=ME and
https://lter.limnology.wisc.edu/lakeinfo/ice-data?lakeid=MO.

Otsego Lake, New York, 2005-2014

State University of New York (SUNY) Oneonta Biological Field Station. Annual Reports. Accessed May
2015. www.oneonta.edu/academics/biofld/PUBS/ANNUAL/2013/29-Otsego-lce-History-2014.pdf.

Shell Lake, Wisconsin, 2005-2015

Washburn County Clerk. 2016. Personal communication.

Mirror Lake, New York, 2016

Lake Placid News. Accessed June 2016. www.lakeplacidnews.com.

All other data

NSIDC (National Snow and Ice Data Center). 2014. Global lake and river ice phenology. Last updated
January 2014. http://nsidc.org/data/lake river ice.

oEPA

Figure 2

Cobbosseecontee Lake, Damariscotta Lake, Moosehead Lake, and Sebago Lake, Maine, 1800s-2008
Hodgkins, G.A. 2010. Historical ice-out dates for 29 lakes in New England, 1807-2008. U.S. Geological
Survey Open-File Report 2010-1214.

Cobbosseecontee Lake, Damariscotta Lake, Moosehead Lake, and Sebago Lake, Maine, 2009-2015
U.S. Geological Survey. 2016. Personal communication.

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Climate Change Indicators in the United States: Lake Ice
www.epa.gov/climate-indicators - Updated August 2016

Detroit Lake, Minnesota, 2006-2015
Lake Osakis, Minnesota, 1867-2015

Minnesota Department of Natural Resources. Accessed June 2016.
www.dnr.state.mn.us/ice out/index.html.

Geneva Lake, Wisconsin, 2005-2015

Geneva Lake Environmental Agency Newsletters. Accessed June 2016.
www.genevaonline.com/~glea/newsletters.php.

Lake George, New York, 2005-2014

Lake George Association. Accessed June 2016. www.lakegeorgeassociation.org/who-we-
are/documents/lce-ln-lce-Out2Q15.pdf.

Lake Mendota and Lake Monona, Wisconsin, 2011-2015

Mirror Lake, New York, 2007-2012

Adirondack Daily Enterprise. Accessed December 2013. www.adirondackdailyenterprise.com.

Mirror Lake, New York, 2013-2015

Lake Placid News. Accessed June 2016. www.lakeplacidnews.com.

Otsego Lake, New York, 2005-2014

State University of New York (SUNY) Oneonta Biological Field Station. Annual Reports. Accessed May
2015. www.oneonta.edu/academics/biofld/PUBS/ANNUAL/2013/29-Otsego-lce-Historv-2014.pdf.

Shell Lake, Wisconsin, 2005-2015

Washburn County Clerk. 2016. Personal communication.

All other data

NSIDC (National Snow and Ice Data Center). 2014. Global lake and river ice phenology. Last updated
January 2014. http://nsidc.org/data/lake river ice.

Figure 3

Cobbosseecontee Lake, Damariscotta Lake, Moosehead Lake, and Sebago Lake, Maine, 1905-2008
Hodgkins, G.A. 2010. Historical ice-out dates for 29 lakes in New England, 1807-2008. U.S. Geological
Survey Open-File Report 2010-1214.

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Climate Change Indicators in the United States: Lake Ice
www.epa.gov/climate-indicators - Updated August 2016

Cobbosseecontee Lake, Damariscotta Lake, Moosehead Lake, and Sebago Lake, Maine, 2009-2015
U.S. Geological Survey. 2016. Personal communication.

Detroit Lake, Minnesota, 2006-2015
Lake Osakis, Minnesota, 1905-2015

Minnesota Department of Natural Resources. Accessed June 2016.
www.dnr.state.mn.us/ice out/index.html.

Geneva Lake, Wisconsin, 2005-2015

Geneva Lake Environmental Agency Newsletters. Accessed June 2016.
www.genevaonline.com/~glea/newsletters.php.

Lake George, New York, 2004-2015

Lake George Association. Accessed June 2016. www.lakegeorgeassociation.org/who-we-
are/documents/lce-ln-lce-Out2Q15.pdf.

Lake Mendota and Lake Monona, Wisconsin, 2011-2015

Mirror Lake, New York, 2007-2012

Adirondack Daily Enterprise. Accessed December 2013. www.adirondackdailventerprise.com.

Mirror Lake, New York, 2013-2015

Lake Placid News. Accessed June 2016. www.lakeplacidnews.com.

Otsego Lake, New York, 2005-2014

State University of New York (SUNY) Oneonta Biological Field Station. Annual Reports. Accessed May
2015. www.oneonta.edu/academics/biofld/PUBS/ANNUAL/2013/29-Otsego-lce-History-2014.pdf.

Shell Lake, Wisconsin, 2005-2015

Washburn County Clerk. 2016. Personal communication.

All other data

NSIDC (National Snow and Ice Data Center). 2014. Global lake and river ice phenology. Last updated
January 2014. http://nsidc.org/data/lake river ice.

oEPA

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