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Trends and Variabilityfor Ice Cover
on Inland LakesJohn J. MagnusonBarbara J. Benson
Center for LimnologyUniversity of Wisconsin-Madison
Magnuson Photo
Lake Ice Data and Coherent Dynamics
Spatial Pattern across the Great Lakes Region
Updated Lake Ice Global Database and Analyses
The Longest Lake Ice Record
Ice Duration on Lake Mendota
0
30
60
90
120
150
180
1850 1875 1900 1925 1950 1975 2000
19 days less per 100 years
10 shortest ice covers
10 longest ice covers
Ice Duration on Lake Mendota
Magnuson 2007
Climate Dynamic Lake DynamicLake
Filter
Amplify
Attenuate
Delay
ExtendReverberate
1 2 3 4 5
Year6 7 8 9
1 2 3 4 5
Year6 7 8 9
External Dynamics Impart Lake Dynamics
Magnuson et al. 2004
Definition of Coherence or Synchrony
Is the degree to which different locations(lakes) behave similarly or dissimilarlythrough time.
Is measured by the correlation betweentime series of the same parameter onpairs of lakes. (usually r or r2)
Long-TermEcological Research (LTER) Lakes in North CentralWisconsin
Kratz et al. 2006
Trout LakeTrout BogCrystal BogMendota
SparklingCrystal Lake
Monona
Big MuskellungeAllequash
Wingra
February
Northern Wisconsinr2 = 0.92
N vs. Sr2 = 0.25
Southern Wisconsinr2 = 0.82
1980 1985 1990 1995 2000
March
April
May
Coherent Dynamics in Ice-Off DatesIc
e-O
ff Da
teMay
Feb.
Apr.
Mar.
1980 1990 2000
North WI r2 = 0.92
South WI r2 = 0.82
Magnuson et al. 2004
LTER Lakes N. WI
r2 = 0.92
PhysicalVariables
Magnuson et al. 2004
Ice-Off Dater2 = 0.92
96 93 90 87 84 81 78 75 72
5452504846444240
Latit
ude
°N
Minn.
Wisc.
Mich. N.Y.
Ont.
Longitude °WMagnuson, Benson, Jensen, et al. 2004
Lake Ice-off Sites in Great Lakes Regionsince the mid 1970s
Coherent Dynamics and Spatial Pattern
Area Differences in Coherence
0.190.23
0.43
0.48 0.29
5452504846444240
Latit
ude
°N
96 93 90 87 84 81 78 75 72
r2 in respect to Minnesota
Longitude °WMagnuson, Benson, Jensen, et al. 2004
Jenson, Benson, Magnuson et al. 2007
Spatial PatternTrends in Ice Out Dates
Moving States - Going to Arkansas?
UCS/ESA 2003
Observed Northward Movementof the April 15 Lake Breakup Date
by 5-year Intervals from 1975 to 2004
Jenson, Benson, Magnuson et al. 2007
Breakup Date
Update on Long-Term Dynamics of Lake Ice Phenology across the
Northern Hemisphere
Barbara Benson, Olaf Jensen, and John Magnuson
Photo: J. J. Magnuson
winter 1855-1856 through winter 2004-2005
Ice Data• 150 years
• No more than 15 years missing/lake
• Lake Ice Analysis Group database + more recentdata and updates
• 9 freeze and 17 breakup time series
• 18 lakes
Benson et al. In progress
Benson et al. In progress
-4
-3
-2
-1
0
1
2
3
1850 1870 1890 1910 1930 1950 1970 1990 2010
breakup spring temperature8 per. Mov. Avg. (breakup) 8 per. Mov. Avg. (spring temperature)
Mean Ice Breakup Anomalies (17 lakes) vsSpring N. Hemisphere Temperature Anomalies
Benson et al. In progress
R2 = 0.3
What are the long-term (150 year) trendsin ice freeze and breakup dates acrossthe Northern Hemisphere?
Benson et al. In progress
-20
-10
0
10
20
30
BREAKUP
FREEZE
NE
US
N c
entra
l US
EUR
OPE
AS
IA
NE
US
N c
entra
l US
EUR
OPE
AS
IA
150 YEAR TRENDS (days/century)
later
earlier
Benson et al. In progress
How do the long-term trends comparewith the recent period (30 years)?
Benson et al. In progress
-10
-8
-6
-4
-2
0
2
TRENDS (days/decade): ICE BREAKUP
NE
US
N c
entra
l US
EUR
OPE
AS
IA
N c
entra
l US
NE
US
EUR
OPE
AS
IA
150 year data 30 year data
12 out of 17 more rapid trend in last 30 years
later
earlier
Benson et al. In progress
Northern Hemisphere Winters1855-1856 through 2004-2005
• Substantial shared variance of ice breakup anomalies withair temperature anomalies.
• Trends of freeze date are consistently toward later freeze(8.4 days/century) and earlier breakup (8.5 days/century).
• Rates of change in freeze and breakup dates have beenmore rapid in the last 30 years.
• More rapid global warming in past thirty years has beenexpressed differently in the ice phenology in differentregions of the Great Lakes.
• Shared variance in ice off dates is large across the GreatLakes region.
The Longest Lake Ice Observations
1443-Present
-60
-30
0
30
1400 1500 1600 1700 1800 1900 2000
1443-1825 -- ice on earlier by 1 day per century
1800-1993 --Ice off earlierby 19 days per century
Lake Suwa, Japan, Ice-on Time Series from 1443 - 1993(30 days subtracted from years before 1880)
Ice-
On
Date
(0 =
Dec
. 31)
Later
Magnuson et al.preliminary
later
later
IPCC 2001
Suwa KoLake Ice Wisconsin
Lake Ice
Lake Ice Data versus Thermometer & Paleo Measurements
ThermometerReadings
Ice Cores and Tree Rings
