The Effect of Air Temperature and Climate Warming on Water Temperature in
Severn Sound, Lake Huron
Abstract
In this study, 2004 and 2005 lake temperature data from Lake Huron near Severn Sound,
Ontario are analyzed and a relationship is found between air and water temperatures.
Regression analyses are used to characterize this relationship, with R-squared values
ranging from 26.6%-60.3%, indicating that a significant amount of the variance in water
temperatures is accounted for by the relationship with air temperature. The regression
equations from 2004 are used in conjunction with 2005 air temperature records to predict
2005 water temperatures at each logger. These predictions are accurate to within 2C.
This discrepancy is accounted for by climate warming, as an average air temperature
increase of 2.63C is observed in temperature records from Beausoleil Island weather
station, which is the station closest to the site of study.
1
Introduction
Water temperature in lakes is affected by heat exchanges with the atmosphere and
physical mixing of the water column (Finlay et al. 2001). Thus, any changes in the
temperature of the atmosphere would be expected to have an effect on water
temperatures. Water temperatures change continuously throughout the year, with
changes being most pronounced in the littoral, or near-shore zone, since the smaller
volume of water equilibrates more quickly with the air than does a larger body of larger
volume (Finlay et al. 2001). Since the littoral zone is the most productive (Finlay et al.
2001), its ecosystem is most greatly affected by temperature fluctuations. Several studies
have shown that water temperatures in lakes are well-correlated with air temperatures
(Crisp and Howson 1982; King et al. 1997; Hondzo and Stefan 1993; Livingstone and
Lotter 1998; Schindler et al. 1996).
There have been recent significant changes in global climate due to humaninduced changes in the chemistry of the atmosphere, which have created a warming trend
in past years (Mortsch and Quinn 1996). The effects of this warming directly impact the
thermal structure of lakes, and in doing so, indirectly affect energy budgets, nutrient
recycling, and primary productivity in the lake (King et al. 1997). As it has been
demonstrated in the literature that water temperature is affected by air temperature, yearly
variation in air temperature caused by global warming has important biological
implications. The timing of warming and cooling events affect the onset and duration of
thermal stratification (Hondzo and Stefan 1993), which in turn affects hypolimnetic
oxygen and winter ice cover, both of which influence the habitat of organisms in the lake
2
(King et al. 1997). Climate warming imposes higher positive net heat fluxes at the lake
surface earlier in the year, resulting in an earlier onset of stratification (Hondzo and
Stefan 1993).
The health, survival, and productivity of phytoplankton, zooplankton, and cold-,
cool-, and warm-water fish are affected by changes in their habitat (Mortsch and Quinn
1996). In 1999, King et al. concluded that warmer years resulted in greater growth of
yellow perch (Perca flavescens) and smallmouth bass (Micropterus dolomieui) in South
Bay, Lake Huron and Lake Opeongo, respectively, and rainbow smelt (Osmerus mordax)
showed a decline in the growth of young smelt but an increase in the growth of the older
smelt. These findings illustrate the effects that climate change can have on organisms in
the lake. The changes in their habitat as caused by climate change may provide optimal
conditions for the invasion of new exotics, as has been seen in recent years (Mortsch and
Quinn 1996). It can be expected that as lake thermal structures continue to change as
climate changes, new exotics will begin to dominate native organisms.
Water temperatures can be qualitatively measured using temperature loggers,
which are submersed into the lake and then continuously record the temperature at
constant intervals. These temperature records provide the data required to detect and
characterize relationships between water temperature and a number of other variables,
including air temperature, wind, and precipitation. The records are analyzed using
spreadsheet programs such as Microsoft Excel, and a statistical suite such as Minitab.
These relationships can be used to provide estimates of water temperature in past years or
3
to fill gaps in records (Crisp and Howson 1982). In 1982, Crisp and Howson concluded
that the best available single estimator of water temperature is air temperature. In the
present study, temperature logger data from 2004 and 2005 for 3 locations in an area of
Lake Huron near Severn Sound, Ontario are analyzed and correlated, and the efficiency
of using 2004 data to predict 2005 temperatures is evaluated. A similar study conducted
by King et al. in 1997 analyzed data for South Bay in Lake Huron from 1955-1992, and
observed shallower thermoclines and increased epilimnetic temperatures in years with
warmer climatic conditions.
4
Materials and Methods
Temperature loggers were placed into Severn Sound in both 2004 and 2005.
They were placed into the water in early June of 2004 and early May of 2005. In 2004,
loggers were placed at 5 locations, and in 2005, loggers were placed at 3 locations, all
very near to those in 2004. All loggers were placed within 7km of the mouth of the
Severn river at Port Severn. Loggers were tied to concrete blocks which held them
approximately 10cm above the bottom. The blocks were then placed in water of a depth
of 0.8-1.0m. The loggers were generally within 25 m of the shoreline or an island, or in a
reef that just reached the water’s surface. Figure 1 depicts the area in which the loggers
were placed and their placement relative to each other.
Figure 1: Temperature Logger Locations in 2004 and 2005. Loggers were placed
into the water in early June 2004 and May 2005, within 7km of the mouth of the
Severn River. Latitude and longitude coordinates for the loggers as well as shoreline
classification data were used with GIS to create the map.
5
Temperature logger data were received in Microsoft Excel format. Data for 2004
included temperatures recorded at 5 loggers, while data for 2005 included temperatures
recorded at 3 loggers, each of which was placed in a similar location to 3 of those used in
2004. The data for the 2 loggers whose locations were not replicated in 2005 was
deleted. As the analysis was focused on June temperatures in both years, temperatures
from other months were deleted from the spreadsheet. Additionally, temperatures
recorded before June 5 of each year were deleted, as these temperatures were likely
recorded before the loggers entered the water. Mean daily temperatures were calculated
as the average of each of the recordings for each day from June 5 to June 30 of each year.
Air temperature data were compiled from the weather records of the Beausoleil island
weather station. This is the weather station closest to the site being studied. The weather
data included several parameters, so air temperatures were isolated from this data and
placed into a Microsoft Excel spreadsheet. To make the data continuous with the
temperature logger data, the mean daily temperature was calculated as the average of
each of the recordings made throughout each day (the weather station usually provided
bi-hourly recordings). The relationship between air and water temperature for each year
was then analyzed using regression analysis with Minitab software. The regression
equation for 2004 provided by the regression analysis was then used to predict
temperatures for 2005, using the air temperatures for 2005. These predicted temperatures
were compared to the actual 2005 temperatures recorded in an Excel spreadsheet by
determining the absolute difference between observed and predicted temperatures. These
differences were then analyzed to determine how precise the measurements were, by
counting the number of differences less than 0.5C, between 0.5C and 1C, between 1C
6
and 1.5C, between 1.5C and 2C, and finally those greater than 2C. These counts
were then used to determine the frequency with which the regression equation gave
predictions within certain error intervals. The average air temperature increase between
2004 and 2005 was calculated by determining the differences in daily temperature
between years, deleting any extreme differences (>7C) and taking the mean of these
differences. The outlier level of >7C was chosen as this was a rare class among the
other differences, and these are not considered to be consistent with a steady yearly
increase in air temperature.
7
Results
Graphical analysis
In 2004, temperatures recorded by the loggers ranged from 17C to 26C
throughout the month of June. Temperatures reached a monthly high at approximately
June 17, and logger 8, located nearest to shore, recorded the highest temperatures of the
three loggers. Figure 2 illustrates the bi-hourly fluctuations in temperature recorded by
each of the loggers every in 2004, and Figure 3 illustrates daily fluctuations in
temperature. Figure 3 illustrates that there is more fluctuation in water temperature
within days than between days. Additionally, it is seen that air temperatures show
greater fluctuation than do water temperature.
June 5-30, 2004 Recorded Temperatures
29
Temperature (C)
27
25
23
Logger 6
Logger 7
Logger 8
21
19
17
15
6/2/04 0:00
6/7/04 0:00
6/12/04
0:00
6/17/04
0:00
6/22/04
0:00
6/27/04
0:00
7/2/04 0:00
7/7/04 0:00
Date:Time (mm/dd/yy:hh/mm)
Figure 2: Fluctuations in water temperature recorded by each logger in Severn
Sound in 2004. Loggers recorded temperatures approximately every 16 minutes.
Logger 8 is nearest to shore, followed by logger 7 and lastly logger 6, which is
furthest from shore.
8
June 5-30,2004 Mean Daily Temperatures
26
24
Temperature (C)
22
20
Logger6
Logger7
Logger8
Air Temperature
18
16
14
12
10
2-Jun
7-Jun
12-Jun
17-Jun
22-Jun
27-Jun
2-Jul
Date (mmdd)
Figure 3: Daily fluctuations in water temperature in June 2004 recorded by 3
temperature loggers in Lake Huron near Severn Sound. Daily temperatures are the
mean temperature recorded by each logger for each day. Daily air temperatures
are also plotted. Air temperature records are from Beausoleil Island weather
station, the station which is located closest to the site. The air temperature plotted is
the mean of all bi-hourly recordings for the day. Logger 8 is located nearest to
shore, followed by logger 7, and logger 6 is furthest from shore.
In 2005, water temperatures recorded by each of the loggers range from 21C to
approximately 27C, reaching the highest temperatures at the end of the month, around
June 29. Figure 4 illustrates the bi-hourly fluctuations in water temperature observed
throughout the month at each logger, and Figure 5 illustrates daily fluctuations, based on
the mean water temperature recorded by each logger for each day. Mid-month, a
decrease in water temperature is seen, beginning at approximately June 12 and not
increasing again until June 22. There is a similar period of lower temperatures observed
in air temperatures. In 2005, no single logger is observed to be continually higher than
the other loggers, as logger 8 records higher water temperatures early in the month, and
logger 6 records higher water temperatures later in the month.
9
June5-30, 2005 Recorded Temperatures
31
29
Temperature (C)
27
25
Logger 6
Logger 7
Logger 8
23
21
19
17
15
5/31/05
0:00
6/5/05 0:00
6/10/05
0:00
6/15/05
0:00
6/20/05
0:00
6/25/05
0:00
6/30/05
0:00
7/5/05 0:00
Date:Time (mm/dd/yy:hh/mm)
Figure 4: Fluctuations in water temperature recorded by 3 temperature loggers in
Lake Huron near Severn Sound. Loggers recorded the water temperature
approximately every 16 minutes. Logger 8 is located nearest to shore, followed by
logger 7, and logger 6 is located furthest from shore.
2005 Daily Mean Water and Air Temperatures
29
27
Temperature (C)
25
Logger 6
Logger 7
Logger 8
Air Temperature
23
21
19
17
15
2-Jun
7-Jun
12-Jun
17-Jun
22-Jun
27-Jun
2-Jul
Date (mm-dd)
Figure 5: Daily fluctuations in water temperature in June 2005 recorded by 3
temperature loggers in Lake Huron near Severn Sound. Daily temperatures are the
mean temperature recorded by each logger for each day. Daily air temperatures
are also plotted. Air temperature records are from Beausoleil Island weather
station, the station which is located closest to the site. The air temperature plotted is
the mean of all bi-hourly recordings for the day. Logger 8 is located nearest to
shore, followed by logger 7, and logger 6 is furthest from shore.
10
Statistical Analysis
All statistical analysis was carried out using Minitab. The results of regression
analyses of the water temperatures recorded at each logger in each year to air temperature
are presented in Table 1.
R2
6
Regression
Equation
y=17.0 + 0.203x
2005
6
y=14.4 + 0.431x
55.7%
2004
7
y=16.4 + 0.221x
34.7%
2005
7
y=14.0+ 0.431x
60.3%
2004
8
y=16 + 0.273x
26.6%
2005
8
y=15.1 + 0.393x
60.5%
Year
Logger
2004
46.2%
Table 1: Regression analysis of temperature logger data to air temperature data.
Linear relationships between air and water temperature are described by the
regression equation, in which the y-variable is water temperature and the x-variable
is air temperature. Water temperatures were recorded by 3 loggers in Lake Huron
near Severn Sound, and regression analyses were performed using data from June
5-30 of each year, 2004 and 2005. Air temperature data is from Beausoleil Island
weather station, which is the closest station to the site.
Table 1 shows that there is a stronger relationship between air and water temperatures in
2005, as the R-squared values are much higher in 2005. The R-squared value explains
how much of the variation in temperature is explained by the relationship, such that
higher values indicate stronger relationships. Graphical representations of the
relationship between air and water temperature in each year at each of the loggers are
found in Figure 6 for 2004 and Figure 7 for 2005.
11
Figure 6: Relationship between air and water temperatures as recorded at three
loggers in Lake Huron near Severn Sound in June 2004. Data were tested for
normality prior to performing the regression analyses, and all but logger 6 were
found to be normal. Three outliers were recognized by Minitab and were removed
to render the data for logger 6 normal. Air temperatures are those recorded by the
Beausoleil Island weather station which is closest to the site at which the water
temperatures were recorded.
12
Figure 7: Relationship between air and water temperatures as recorded at three
loggers in Lake Huron near Severn Sound in June 2005. Data were tested for
normality prior to performing the regression analyses, and all data were found to be
normal. Air temperatures are those recorded at the Beausoleil Island weather
station which is closest to the site where the water temperatures were recorded.
The 2004 regression equations in Table 1 were used to predict 2005 water
temperatures using the air temperature data for 2005. The results of this analysis are
tabulated in Table 2.
13
Error in
prediction
Frequency
Logger 6
Percentage
Frequency
Logger 7
Percentage
Frequency
Logger 8
Percentage
0-0.5C
4 15.38
5
19.23
7
26.92
0.5-1C
10 38.46
8
30.77
10
38.46
1-1.5C
12 46.15
10
38.46
13
50
1.5-2C
13 50
14
53.85
15
57.69
>2C
26 100
26
100
26
100
Table 2: Error observed in prediction model using regression equations from 2004
and air temperatures from 2005 to predict 2005 air temperatures. Frequencies are
the number of observations in each error range. Error is the difference between
2005 actual water temperatures and 2005 predicted water temperatures.
The individual regression analyses for each temperature logger in each year can be found
in the Appendix.
14
Discussion
The results of the study are consistent with previous findings in the literature
(Crisp and Howson 1982; King et al. 1997; Hondzo and Stefan 1993; Livingstone and
Lotter 1998; Schindler et al. 1996) as Figure 3 and Figure 5 show that there is a positive
correlation between air and water temperature. This relationship was validated
statistically using regression analysis (Figure 6 and Figure 7). The R-squared values
range from 26.6% to 60.3%, as in Table 1. Interestingly, the R-squared values at each of
the loggers in 2005 are higher than those in 2004, suggesting that there is a stronger
relationship between air and water temperature at higher temperatures, as 2005 was found
to be approximately 2.63C warmer than 2004. The finding that 2005 was in fact warmer
than 2004 also supports predictions on climate warming due to human-induced changes
in the atmosphere (Mortsch and Quinn 1996). Since the relationship is stronger between
air and water temperature at higher temperatures, it is possible that as the climate warms
more and more each year, predictions of water temperature based on this relationship will
become increasingly valid. Additionally, it appears that the predictions are more valid at
logger 8, which is nearest to shore, suggesting that there is a stronger relationship
between air and water temperature in the near-shore littoral zone. The R-squared values
indicate that approximately half of the variation in water temperatures is accounted for by
air temperature. The temperature of a lake is the result of complex interactions between
climate, hydrology, catchments, and in-lake processes of the lake (Schindler et al. 1996).
If these factors could be integrated into the prediction model, much higher R-squared
values, closer to 1, would be expected. However, Table 2 shows that predicting water
temperatures based on air temperatures and the previous year’s relationship is valid, as
15
more than half of the predictions for each logger were within 2C of the actual
temperature observed. Considering an average increase in air temperature of 2.63C, this
error can be accounted for completely by climate change. Therefore, the relationship
between air and water temperature provides a valid method of predicting approximate
lake temperatures based on water temperatures, within 2C.
The three loggers used were placed in similar locations each year, as seen in
Figure 1. Logger 8 was placed nearest to the shore, and Logger 6 was placed furthest
from the shore, with logger 7 at an intermediate distance from shore. In 2004, logger 8
recorded the highest temperatures and heated faster than the other loggers. This is likely
due to the smaller volume of water closer to shore, which allows the water to heat more
quickly than water of greater depth of volume. This finding is consistent with the
findings of Finlay et al. in 2001 that there are larger changes at shallower sites in a lake.
However, findings in 2005 were not consistent with those in 2004, as logger 6 most often
recorded the highest temperatures in 2005. This may be due to the fact that in 2005, the
lake temperatures are both higher and more unified among the loggers than in 2004.
The warming of both water and air temperatures documented both in the present
study and in the literature has important implications for the thermal structure of the lake
as well as the ecosystem of the lake. In 1999, King et al. documented changes in the
growth of certain fish as a result of climatic change. Changes in the growth of these fish
will then affect the growth and survival of the prey and predators of these fish. The
specific affects will depend on whether growth of the organism is increased or decreased
16
as a result of climate warming (King et al. 1999). In addition to changes to the food
chain in the lake, the thermal structure is affected, as warmer temperatures lead to an
earlier onset of stratification (Hondzo and Stefan 1993) and to reduced ice cover in winter
(Mortsch and Quinn 1996). Thermal stratification influences energy budgets, nutrient
recycling, and primary productivity (King et al. 1997), so the effects of climate warming
are felt throughout the lake. Climate warming also has an indirect effect on oxygen in the
lake, because lake oxygen increases with reduced winter ice cover, but it decreases as the
length of summer stratification increases (Livingstone and Lotter 1998), since oxygen is
not mixed to lower depths while the lake is stratified. This can have a profound effect on
organisms in the hypolimnetic zone, as they may become oxygen-deprived. Changes in
the lake conditions will probably allow the invasion of new exotic organisms in coming
years (Mortsch and Quinn 1996).
In conclusion, water temperatures in lakes are correlated with air temperature, and
statistical analysis indicates that 30-60% of the variation in temperatures is accounted for
by this relationship. Air temperatures increased by approximately 2.63C from 2004 to
2005, leading to an increase in lake temperatures. The relationship between air and water
temperature is quantified using regression analysis, and the resulting regression equations
can be used in conjunction with air temperatures to predict water temperatures within
2C. The climate warming observed has many direct and indirect effects on the lake, and
it is expected that with increased warming, conditions will change such that new exotics
will be able to inhabit the lake and dominate current organisms.
17
References
Crisp, D., and Howson, G. 1982. The effect of air temperature upon mean water
temperature in streams in the North Pennines and English lake district. Freshwater
Biology. 12:359-367.
Finlay, K., Cyr, H., and Shuter, B. 2001. Spatial and temporal variability in water
temperatures in the littoral zone of a multi-basin lake. Canadian Journal of
Fisheries and Aquatic Sciences. 58:609-619.
Hondzo, M. and Stefan, H. 1993. Regional water temperature characteristics of lakes
subjected to climate change. Climatic Change. 24:187-211.
King, J., Shuter, B., and Zimmerman, A. 1997. The response of the thermal stratification
of South Bay (Lake Huron) to climatic variability. Canadian Journal of Fisheries
and Aquatic Sciences. 54:1873-1882.
King, J., Shuter, B., and Zimmerman, A. 1999. Empirical links between thermal habitat,
fish growth, and climate change. Transactions of the American Fisheries Society.
128:656-665.
Livingstone, D. and Lotter, A. 1998. The relationship between air and water temperatures
in lakes of the Swiss plateau: A case study with paleolimnetic implications.
Journal of Paleolimnology. 19:181-198.
Mortsch, L. and Quinn, F. 1996. Climate change scenarios for Great Lakes Basin
ecosystem studies. Limnology and Oceanography. 41:903-911.
Schindler, D., Bayley, S., Parker, B., Beaty, K., Cruikshank, D., Fee, E., Schindler, E.,
and Stainton, M. 1996. The effects of climatic warming on the properties of
Boreal lakes and streams at the experimental lakes area, Northwestern Ontario.
Limnology and Oceanography. 41:1004-1017.
18
Appendix
Regression analysis of air and water temperature, Logger 6 2004
Daily mean water temperature (C)
22.0
21.5
21.0
20.5
20.0
19.5
12
13
14
15
16
17
18
19
Daily mean air temperature (C)
20
21
Figure 8: Regression analysis showing the relationship between air temperature and
water temperature at logger 6 in 2004. Temperatures recorded in Lake Huron
near Severn Sound. Air temperature data from Beausoleil Island weather station.
19
Regression analysis of air temperature to water temperature, Logger 7 2004
Daily mean water temperature (C)
23
22
21
20
19
12
14
16
18
20
22
Daily mean air temperature (C)
24
26
Figure 9: Regression analysis showing the relationship between air temperature and
water temperature at logger 7 in 2004. Temperatures recorded in Lake Huron
near Severn Sound. Air temperature data from Beausoleil Island weather station.
20
Regression analysis of water temperature to air temperature, Logger 8 2004
Daily mean water temperature (C)
25
24
23
22
21
20
19
18
17
16
12
14
16
18
20
22
Daily mean air temperature (C)
24
26
Figure 10: Regression analysis showing the relationship between air temperature
and water temperature at logger 8 in 2004. Temperatures recorded in Lake Huron
near Severn Sound. Air temperature data from Beausoleil Island weather station.
21
Regression Analysis of Air Temperature to Water Temperature, Logger 6 2005
Daily mean water temperature (C)
27
26
25
24
23
22
21
20
19
15.0
17.5
20.0
22.5
25.0
Daily mean air temperature (C)
27.5
Figure 11: Regression analysis showing the relationship between air temperature
and water temperature at logger 6 in 2005. Temperatures recorded in Lake Huron
near Severn Sound. Air temperature data from Beausoleil Island weather station.
22
Regression Analysis of Air Temperature to Water Temperature, Logger 7 2005
Daily mean water temperature (C)
27
26
25
24
23
22
21
20
15.0
17.5
20.0
22.5
25.0
Daily mean air temperature (C)
27.5
Figure 12: Regression analysis showing the relationship between air temperature
and water temperature at logger 7 in 2005. Temperatures recorded in Lake Huron
near Severn Sound. Air temperature data from Beausoleil Island weather station.
23
Regression Analysis of Air Temperature to Water Temperature, Logger 8 2005
Mean daily water temperature (C)
27
26
25
24
23
22
21
20
15.0
17.5
20.0
22.5
25.0
Mean daily air temperature (C)
27.5
Figure 13: Regression analysis showing the relationship between air temperature
and water temperature at logger 8 in 2005. Temperatures recorded in Lake Huron
near Severn Sound. Air temperature data from Beausoleil Island weather station.
24