All lakes
store and release heat energy. As lakes exchange
latent heat with the
atmosphere they affect the surrounding air temperature. In this lesson
you use WOW data to calculate
the heat budget of a lake. You also explore factors that play a role in the
lake/weather relationship.
Knowledge
Base
Consider your
experiences with air and water temperatures around lakes. During which
months does the water feel warmer than the air? At what times of day
does
water feel coldest? Warmest?
You may
need to review how to calculate water volumes for each one meter layer
of a lake. You also need to recall that it takes
1 calorie
to raise 1 cubic centimeter of water one degree (at 20°C) and 1
million calories to raise 1 cubic meter of water 1 degree if no changes
of state are involved.
Experimental
Design
Data Collection
-
Use water
temperature data collected at 1 meter intervals at 6 a.m., 2 p.m., 6
p.m., and 2 a.m. Record the temperatures in Table 1.
- List the surface area for each 1-meter deep layer in the lake (See
Ice Lake Total Heat Budget). Fill in that information in
column 2 of Table 2.
- Calculate the water volume in each 1-meter layer of the entire lake.
Fill that information in column 3 of Table 2.
Figure
1. Lake Surface Areas at 1 Meter Intervals
Ice
Lake |
|
Lake
Independence |
Depth
Intervals (m) |
Area
at surface of this depth (m2) |
|
Depth
Intervals (m) |
Area
at surface of this depth (m2) |
1
m |
1.600E+05 |
|
1
m |
3.290E+06 |
2
m |
1.481E+05 |
|
2
m |
2.875E+06 |
3
m |
1.362E+05 |
|
3
m |
2.625E+06 |
4
m |
1.244E+05 |
|
4
m |
2.275E+06 |
5
m |
1.126E+05 |
|
5
m |
1.925E+06 |
6
m |
1.008E+05 |
|
6
m |
1.675E+06 |
7
m |
8.890E+04 |
|
7
m |
1.350E+06 |
8
m |
7.710E+04 |
|
8
m |
9.750E+05 |
9
m |
6.520E+04 |
|
9
m |
7.000E+05 |
10
m |
5.640E+04 |
|
10
m |
4.200E+05 |
11
m |
4.160E+04 |
|
11
m |
2.050E+05 |
12
m |
2.970E+04 |
|
12
m |
1.560E+05 |
13
m |
1.790E+04 |
|
13
m |
1.310E+05 |
14
m |
6.300E+03 |
|
14
m |
1.100E+05 |
15
m |
4.000E+03 |
|
15
m |
9.000E+04 |
16
m |
1.000E+02 |
|
16
m |
7.000E+04 |
|
17
m |
4.000E+04 |
18
m |
1.000E+04 |
Data
Management and Analysis
- To raise
the temperature of water, energy is required. In lakes, what is the
source of energy?
- For each
layer of the lake, calculate the change in temperature between 6 a.m.
and 2 p.m. by subtracting the 6 o'clock in the morning temperature
from the temperature at 2 o'clock in the afternoon. Fill this information
in Table 2, Column 4 (Temperature change).
- Calculate
how many calories were involved in changing the water temperature
between 6 a.m. and 2 p.m. Fill that information in Table 2, column
5 (Calories used).
- Calculate
the temperature change between 6 p.m. in the evening and 2 a.m. at
night for each layer of the lake. Fill in that information in Table
2, column 6 (Temperature change).
- Calculate
how many calories were involved in changing the water temperature
between 6 .pm. and midnight. Fill those numbers in Table 2, column
7 (Calories used).
Table
1. Temperature Measurements for Ice Lake.
Date
data was collected by RUSS: ____________ |
Water
layer
|
6:00
a.m.
|
2:00
p.m.
|
6:00
p.m.
|
2:00
a.m.
|
0-1
m depth |
|
|
|
|
1-2
m depth |
|
|
|
|
2-3
m depth |
|
|
|
|
3-4
m depth |
|
|
|
|
4-5
m depth |
|
|
|
|
5-6
m depth |
|
|
|
|
Table
2. Water Volume and Energy Changes for Ice Lake
Date
data was collected by RUSS: ____________ |
Water
layer
|
Surface
area of this layer (m2)
|
Water
Volume (m3)
|
Temp.
change, (°C)
6am-2pm
|
Calories
used
|
Temp.
change, (°C)
6pm-2am
|
Calories
released
|
0-1
m depth |
|
|
|
|
|
|
1-2
m depth |
|
|
|
|
|
|
2-3
m depth |
|
|
|
|
|
|
3-4
m depth |
|
|
|
|
|
|
4-5
m depth |
|
|
|
|
|
|
5-6
m depth |
|
|
|
|
|
|
Interpretation
of Results
- What happened
to the energy that was given off when the lake's surface cooled?
- What happened to the energy given off by layers below the surface?
- How much total energy was released from the lake between 6 p.m.
and 2 a.m?
- How do
the temperature changes in layers below the surface of the lake compare
to temperature changes in the surface layer?
- How can
the energy released from lakes affect local weather patterns and the
surrounding environment?
- How might
the size of the lake affect its impact on the weather and surrounding
environment?
- Identify a large lake in Minnesota that probably affects the local
weather. Describe how and why you think this lake would affect the
local weather.
- Identify
an example of a large lake outside the U.S. that might affect local
weather. Describe how you could find out more about the affects of this
lake on the surrounding environment.
- A cubic centimeter of water requires 540 calories to boil (change from a liquid to a gas at 100°C).
This is an example of the different amounts of energy required when matter
changes state. How much energy would be required to boil off the top meter of
the lake beginning at 2pm? Where would you get that much energy?
- When a cubic centimeter of water freezes (changes from a liquid to a solid at 0°C),
80 calories of energy are released. (When water changes state
liquid to solid the amount of energy involved in the change
is different than the amount involved in incremental changes in temperature
while water is in the same state.) How much energy would be given
off for the top meter of the lake to freeze if the freezing began
at 2 am? [Hint, you have to calculate the energy released for
each degree of temperature drop, PLUS the 80 calories, for each cubic
centimeter.]
- How might
the energy released from a lake when it freezes affect the surrounding
environment?
Reporting
Results
Turn your
answers to 1-19 and the completed tables in to your teacher.
|