Short-term temperature variation in Severn Sound
Bridget Dilauro
BIO332
Abstract
I examined an event of significant short-term temperature variation in Severn Sound in
the summer of 2004. Five temperature loggers in this area of Georgian Bay recorded water
temperature every 16 minutes. The temperature record was examined for ‘temperature jumps’
where the temperature changed by more than 0.6oC in 16 minutes. Such an event occurred on
September 4th where three of the loggers recorded temperature jumps greater than 0.6oC. The
wind record leading up to the event included a moderate Southeastward wind for five hours,
followed by a moderate Eastward wind for one hour, followed by a moderate Northwestward
wind for three hours. I hypothesized the wind directed the event by either forcing water from
Georgian Bay into the area or by initiating local upwellings and downwellings. I hoped to
predict additional temperature jumps using similar wind records. However when I tested my
predictions, only 8 out of 15 similar wind records lead to temperature jumps of at least 0.5oC. I
then examined the short-term temperature variation over the summer to compare the event on
September 4th to other events. I found 32 events with temperature jumps of more than 0.6oC. In
13 of these events, more than one logger ‘share’ the temperature jump. Because the temperature
changed so much, so rapidly, I believe these events are significant and merit further
investigation.
Introduction
The water temperature in lakes correlates with internal mixing, weather and strongly
correlates with air temperature. In 1959 McCombie studied water temperature and air
temperature in South Bay, Ontario. He found a strong correlation between air temperature and
surface water temperature using: 1) monthly means of the daily maximum-minimum air
2
temperature, and 2) water temperature recorded approximately every week. Though he
discovered a correlation, the use of monthly means creates a view of temperature variation that
is perhaps too perfect and does not allow a thorough examination of short-term variation.
Events such as seiches or downwellings and upwellings cause short-term variation in
water temperature. Temperature variation plays an important role in lakes by affecting the
vertical distribution of: 13 species of fish larvae (Hamann et al, 1981), juvenile sockeye salmon
(Levy et al, 1991), plankton, and by causing the movement of lake currents (Naumenko et al,
1996).
In a seiche, continuous wind, air pressure changes, heavy precipitation or flooding
forces surface water to one end of a lake. When the primary force ceases, the increased volume
of water on that end of the lake sinks, forcing the thermocline down. The thermocline oscillates
back and forth, alternatively bringing warm water deeper and cooler water higher (Wiegand
and Chamberlain, 1987). Upwellings and downwellings are caused by similar events. In an
upwelling, cold deep water is forced to the surface, and in a downwelling warm surface water is
forced to the bottom.
The temperature change may be rapid in response to seiches, upwellings or
downwellings and the change may be classified as large-scale or small-scale. In large-scale
events the temperature may shift by as much as 6oC or higher and occur over a period of days
(Niebauer et al, 1977). In small-scale events the temperature may shift by approximately 1- 3oC
and occur over hours (Csanady, 1974).
The new technology available to study the temperatures of water bodies, such as infared
(Naumenko et al, 1996), radiation thermometers or thermoscanners (Scarpace and Green, 1979)
3
and towed temperature sensors such as CTDs, (Filinov, 1996) should allow us to discover the
importance, frequency and source of short-term temperature variation
I studied short-term temperature variation using data from loggers in Severn Sound. A
group placed five temperature loggers in Severn Sound in the summer of 2004 (fig 1). The
loggers, at a depth of approximately 0.8m, recorded temperature every 16 minutes from June to
October. Weather data from this area is available for Beausoleil Island, approximately 20km
Northwest of Severn Sound and Midland, approximately 20km West of Severn Sound.
An examination of temperature variation reveals some ‘temperature jumps’ where the
temperature at one logger increases or decreases by a significant amount (>0.6oC) in 16
minutes. On several occasions, these jumps occur at many loggers within minutes. I examined
one such event on September 4th. I suspected high wind or a shifting wind pattern may have
forced local currents or Georgian Bay currents to shift and cause a rapid water temperature
change. I hoped to find trends in the wind record on September 4th that I could use to predict
similar temperature jumps. I then aimed to examine the amplitude and frequency of short-term
variation over the summer.
The temperature data provide a record of short-term and long-term changes over the
summer and offer many areas of study. Future projects could examine other aspects of
temperature variation or logger variation.
Figure 1: Location of loggers in relation to Georgian Bay and Severn Sound, summer
2004 (Image courtesy of http://www.lynximages.com/georgbay.htm)
4
The Event: Results and Discussion
I searched the temperature record to find significant temperature variation over 16
minute intervals. I chose an event on September 4th (fig 2) to study for three reasons:
1) The event showed significant temperature variation of greater than 0.6oC. 2) The
temperature variation occurs at three loggers, so it is unlikely to be a fluke event and also, may
be large in size – which increases my chance of predicting other events. And 3) the loggers
both increase and decrease in temperature significantly.
Figure 2: Temperature variation on September 4th 2004 recorded by five loggers in Severn
Sound every 16 minutes over a 12 hour period. Arrows point to approximately 16:00
Logger 3
Logger 7
Logger 4
Logger 6
Logger 8
26
Temp (oC)
Temp (oC)
26
24
22
9/4/04 12:00 9/4/04 18:00
24
22
9/5/04 0:00
Table 1:
Logger 3
Logger 4
Logger 7
Logger 6
Logger 8
9/4/04 12:00
9/4/04 18:00
9/5/04 0:00
Times and Temperature changes of
temperature jumps on September 4th
as seen in Fig 1.
16:04-16:20 Increase of 0.69oC
17:56-18:12 Decrease of 1.21oC
18:12-18:28 Decrease of 0.69oC
16:07-16:23 Increase of 0.61oC
17:27-17:43 Decrease of 0.69oC
16:44-17:00 Increase of 1.03oC
(No significant decrease <0.6oC)
(No significant change:
temperature change was < 0.6oC)
(No significant change:
temperature change was <0.6oC)
5
The events on September 4th are also significant because the temperature jumps are
much higher than the average amounts the temperature changed every 16 minutes during the
day (For Logger 3: the average change was 0.132oC/16min, Logger 4: 0.084oC/16min, Logger
6: 0.064oC/16min, Logger 7: 0.077oC/16min and Logger 8: 0.058oC/16min).
It is interesting to note the time of day when these temperature jumps occur. At 16:00 in
September the sun is likely falling in the sky and Severn Sound is likely cooling. The timing
may explain the sharp decreases in temperature: as the epilimnion cools rapidly, currents from
this upper layer may be forced down to the loggers. But even if this does explain the
temperature decreases, what explains the sudden temperature increase before cooling? In an
attempt to explain the variation, I studied the weather, particularly the wind record (Fig 3). I
suspected the temperature increase, and possibly the temperature decrease, may have resulted
from an event that had begun earlier in the day. I also examined the precipitation record and
found no precipitation was recorded on September 4th and no precipitation for five days prior.
Figure 3: Wind speed and direction on September 3rd and 4th 2004. Measurements were taken
at hourly intervals on Beausoleil Island approximately 20km NW of Severn Sound. Red circles
represent no wind (‘0’) was recorded at that hour. The green arrow points to 16:00.
6
There were some initial concerns about the wind record. The wind record data were
taken from Beausoleil Island, which is almost 20 km away from Severn Sound. Although this
may seem quite far, it was the closest data available and in fact, seiches have been measured
using wind data from long distances - for instance, in Wood Lake, using wind data from 15 km
south (Wiegand and Chamberlain, 1987). A continuous wind record was not available - because
wind was measured once an hour - this is not ideal, however other studies have used less
frequent measurements and did locate events and patterns. For example, Scarpace and Green in
1979 studied an upwelling on the southern shore of Lake Superior using wind measurements
taken every six hours and Csanady used hourly wind averages to study upwellings and
downwellings in Lake Ontario in 1974.
I chose to focus on wind and not on atmospheric pressure to make predictions, and
future projects may wish to examine if this was the right choice. However, previous studies
have noted the effects of atmospheric pressure and winds are hard to distinguish: one is usually
accompanied by the other (Hutchinson, 1957). Also, there exists a strong ‘cause and effect’
relationship between atmospheric pressure and wind. Wind usually results from the meeting of
high- pressure and low-pressure fronts: the high-pressure area pushes into the low-pressure area
as wind, to equilibrate the pressure difference (Aguado and Burt, 2001). I focused on wind
because the wind record displayed more variation and wind seems to be used more commonly.
I noted some trends in the wind record before the event (Fig 3). First I noted the
presence of ‘0’ winds (when there was no wind blowing) on 9/3/2004 22:00, 23:00, and
9/4/2004 6:00. However, because the ‘0’ winds occurred so long before the event and were so
short in duration, I chose not to focus on ‘0’ winds as a prediction tool. Table A1 in the
Appendix lists some initial findings using 15 instances of ‘0’ winds to predict temperature
7
shifts > 0.5oC. Events were correctly ‘predicted’ in eight of the 15 cases, however these events
should be studied further before any conclusions are drawn. The ‘0’ winds occur so long before
the event that it is difficult to say what their role may be. Also, of the eight predicted events,
two occur at only one logger. Finally, I did not examine the direction of wind recorded in the
hours between the ‘0’ wind, because finding wind directions that matched the September 4th
wind was difficult. It is possible the wind directions between the ‘0’ winds, and not the ‘0’
winds themselves, may cause the 15 events.
To make predictions, I focused on the wind nine hours before the event, particularly the
change in wind direction from Northwesterly to Southeasterly. These winds are of opposing
directions, a phenomenon which has been found to affect the start and end of seiches in Wood
Lake (Wiegand and Chamberlain, 1987).
The speeds of these winds are moderate – between 4km/h and 6km/h – much less than
the maximum speeds recorded over the summer (which reached 22km/h). I imagined high
speeds would cause bigger events because storms have been seen to cause events (Horn et al,
1986 and Vilibic and Orlic, 1999). But, high wind speeds may not be as important as direction
and duration. In a study of coastal upwellings and downwellings, winds as low as 1.6m/sec
(almost 5.76km/h) caused an up-downwelling cycle in Lake Superior (Niebauer et al 1977).
I hypothesized the Northwesterly wind may force water out of Severn Sound and the
Southeasterly wind may force water back in, taking with it warm Georgian Bay water which
might cause the temperature increase. Although the data are dated, Bennett in 1988 (using 1974
data) studied water temperatures in Georgian Bay. He found the warmest water in the
Southeastern corner of the bay, the area closest to Severn Sound. This patch of warm water
may be the source of the temperature increase. Of the three loggers affected by this temperature
8
jump on September 4th, Logger 3 may be increasing due to the influx of warmer Georgian Bay
water, while the increases at 4 and 7 may be explained by their location at the coast – perhaps a
local downwelling – or their temperature jumps may be a delayed reaction to the initial winds
forcing the water out of Severn Sound. Logger 8 may not be affected because it is higher and
therefore less likely to be affected by Georgian Bay water, or because it is more isolated from
local water movements, which could cause downwellings. Logger 6 may not have been affected
if the Georgian Bay currents entered Severn Sound from above the island near Logger 3 (see
fig 1) and continued moving to the Southeast -without reaching Logger 6.
Whether the wind caused a local event or forced water in from Georgian Bay, I
hypothesized similar wind records should indicate where other temperature jumps occurred. I
found similar wind patterns as those on September 4th and then studied logger temperatures to
locate any temperature jumps.
Predictions Results and Discussion
Results of the predictions are shown in Table 2. One of the main problems encountered
was that no wind record perfectly matched the original wind record. I decreased the variation
needed to qualify a temperature jump to 0.5oC in case these slight wind changes caused a
decrease in the amount of variation. Decreasing the variation needed to qualify to 0.4oC would
only add one more event – at #3. The wind speeds are not noted in the table because the
averages for each event were between 2.9 km/h and 8 km/h, which were not significantly
different from my main event – the average wind speed over nine hours on September 4th was
4.2km/h.
The other problem was that my predictions did not predict as accurately as I had hoped,
and not every similar wind event lead to a temperature jump.
9
Table 2: The results of using opposing wind to predict logger temperature jumps in Severn
Sound. The wind record of the original event is listed at the top. Each wind direction (ie: ‘SE’)
represents one hour. 15 wind events were studied to see if temperature jumps of > 0.5oC
occurred. If a jump occurred, the time/wind direction is shaded in gray and the logger(s) where
the jump occurred are noted. The wind events are divided into three columns to allow
comparison to the original event (which had three wind directions: SE wind, E wind in the
middle and then NW winds). Some events (ie: July 21) had no opposing wind in the middle.
Event
9/4/04
1. 9/23
2. 9/21
3. 6/25
4. 7/21
5. 9/20
6. 8/4
7. 8/13
8. 8/16
9. 6/17
10. 7/25
Wind Direction
SE, SE, SE, SE, SE
SE, SE, SE, SE, SE
SE, SE, SE
SE, SE
SE, SE, SE, SE, SE, SE, SE, SE
SE, SE, SE, SE
SE, SE
SE, SE
SE, SE
SE, SE, SE, SE, SE, SE, SE, SE, SE, SE, SE, SE, SE, SE
SE, SE, SE, SE
11. 7/18
12. 7/30
13. 7/3
14. 7/6
SE, SE, SE, SE
SE, SE, SE, SE, SE, SE
SE, SE, SE, SE
SE, SE, SE, SE
15. 7/24
SE, SE, S, SE, S, S, S, SE
E
E
E, E
E
S
S
S
S, S
W
NE
E, SE, E
S, S,
SE, W
NW, NW, NW, NW, NW
NW, NW, NE, NW
NW, NW
NW, NW, NW, NW, NW
NW, NW, N,
NW, NW, NW, NW
NW, NW, NW, NW, NW
NW, NW, NW, NW
NW, NW, NW, NW
NW, NW, NW, NW, NW, NW
NW, NW, NW, NW, NW, NW,
NW, NW, NW, NW
NW, NW, NW, NW, NW, NW
NW, NW, NW
NW, NW, E, SE, SE
NW, NW
Loggers
3,4, 7
3
6
3, 6,7
3,4
6
3
3 6,7,8
NW, NW, NW, NW, NW
Of the 15 events, 8 showed temperature jumps (Table 2) but four of these events only
occurred with one logger. These results in fact seem worse than the predictions using ‘0’ wind!
Why did the predictions fail?
Events # 7, 8 and 10 may not have caused a temperature jump because the
Southeastward winds did not last long enough to push water out of Severn Sound to meet with
Georgian Bay water. This may explain why event #9 does cause a temperature jump, because
the Southeastward winds persist for a long time. And for the same reason, Events #5 and 6 do
not cause variation, while #4 does, due to longer wind duration. However Event #3 displays a
jump and this event had Southeastward winds for only two hours. Perhaps the Eastward wind in
Event #3 helped to push local water off the coast of Severn Sound, causing a change. But if the
Eastward wind plays a role, why does Event #2 display no variation while Event #1 does?
10
Perhaps the longer duration of the Eastward wind in Event #2 causes local water to move too
far out of Severn Sound.
Event #11 displays a temperature jump and this event displays a Westward wind, in
place of the original Eastward wind. Perhaps this wind helps force Georgian Bay water into
Severn Sound. Event #12 has a Northeastward wind in place of the original Eastward wind,
which could have the same effect. For these two events the loggers most exposed to Georgian
Bay – Loggers 3 and 6 – are the ones affected, which would be expected if Georgian Bay’s
waters caused the events. Bryson and Stearns in 1959 noted that a 200-400m long ‘tongue’ of
water entered South Bay from Lake Huron. A similar event could occur from Georgian Bay
into Severn Sound, causing a temperature change at the loggers closest to the Georgian Bay
entrance (Loggers 3, 6 or 7).
Events #14 and 15 may lack jumps because there are too many changes of wind
direction, which could send the current in different directions and perhaps mix the water
evenly, limiting sharp increases or drops in temperature. However Event #13 displays many
changes in wind direction and shows jumps at four loggers.
Many of the events seem quite similar to the original, but not all lead to a temperature
jump. In 1977 Niebauer et al studied coastal upwellings and downwellings on Lake Superior
and found Northeasterly winds cause upwellings, but not every Northeasterly wind lead to an
upwelling. Obviously no predictions will be perfect, however their success rate (about 5/6 in
the month of July) was better than mine (8/15). Are there other reasons why these predictions
did not work?
Wiegand and Chamberlain in 1987 noted the response of lakes to wind depends not
only on the wind pattern, but also on the density structure of the lake at the time. The structure
11
of Severn Sound and Georgian Bay would not be identical throughout the summer so if density
structure variation affects temperature, not every prediction could work. However it was
difficult to locate data on the structure of these water bodies in 2004.
Distant events have caused upwellings, such as far-away-waves or seismic events
(Richards, 1981). It is possible that is the case for some of the larger variation I found.
However, it is unlikely distant events played a role in every event and again, I could not test
this theory without more data. Cushman-Roisin and O’Brien in 1983 noted downwellings and
upwellings occur as part of a continuous cycle, not simply as a response to a single wind event.
If this is the case, once again, more data would be needed to make predictions, not simply wind
from a few hours previous.
Many of these problems could not be addressed without more data. But there was one
problem I could address, if my original event was not significant – if 0.6oC was not a good
measure of significant variation – my predictions would not be valid. And if variation of 0.6oC
is common over the summer, my predictions would be useless. Therefore, I examined variation
over the summer to compare the September 4th event to other events.
Variation over the Summer: Results and Discussion
For each logger I calculated the change in temperature every 16 minutes (Sample
Calculations are shown in Appendix) and graphed these variation values. Among all loggers I
found 32 events with temperature jumps of > 0.6oC. Both distinct and shared events were seen.
I classified an event as ‘shared’ between loggers if the loggers each show the variation in a twohour span – this was the case in my original event with variation seen from about 16:00 to
18:00. Table 3 summarizes the data from each logger and a detailed table (Table 4) describes
12
the wind record of the 32 events. Although the September 4th event was identified as one of
significance, it has not been included in the totals, as it has already been examined (and was the
basis for the criteria).
Table 3: Summary of 32 events with temperature variation > 0.6oC in 16 minutes from Severn
Sound June 8th –Oct 1st 2004.
Total # Total #
# Events
# Events
# Events
# Events
# Events
Events Events
Shared
Shared
Shared
Shared
Shared
Alone
with
with
with
with
with
Logger 3
Logger 4
Logger 6
Logger 7
Logger 8
Logger 3
23
12
4
6
6
2
Logger 4
5
1
0
2
0
Logger 6
8
2
2
1
Logger 7
10
3
2
Logger 8
4
2
All
32
Loggers
The discovery of 32 events where the temperature jumped by 0.6oC justifies the use of
0.5oC and 0.6oC to find significant temperature variation. Though short-term variation is not
frequent, it does occur throughout the entire summer and at a significant rate. The variation
seems common enough to recommend further study. The September 4th event, being one of
those few events was likely a good candidate for study.
The variation among loggers – the fact that some loggers shared a particular event while
others did not (Table 3) – is expected. Not all water movements will be large enough to affect
all loggers and spatial variability has been documented by Csanady in 1974. He studied
upwellings and downwellings at various stations in Lake Ontario and found downwellings
recorded at one station were not recorded at others, even those in relatively close proximity.
An examination of the variation at each logger (see Table 3) reveals Logger 3 had more
than two times the variation found at all the other loggers. This could indicate the logger was
malfunctioning. However many of the events Logger 3 recorded were shared by other loggers.
13
Perhaps the variation occurs because Logger 3 was closest to Georgian Bay, making it most
susceptible to influxes of water from the larger water body. It is possible some of these influxes
only reached Logger 3, or were recorded as much smaller variation at the other loggers if the
influxes reached them. Logger 7 had the second highest number of events, likely due to its
proximity to the coast. And, unlike Logger 4, which is also on the coast, Logger 7 is less
isolated and, may be exposed to a Georgian Bay current moving along the top of the island (as
discussed previously). Logger 6 had the third highest number of events likely because, like
Logger 3, it is in the open water, exposed to Georgian Bay water movements and exposed to
movements of water from the coast. Logger 8 experienced the least number of events, likely
due to its isolation.
The patterns of logger sharing (Table 3) seem somewhat logical. Logger 3 shares many
events with Logger 6 and Logger 7 because these three loggers are in the open. However it is
strange that Logger 3 and Logger 4 share some events that other loggers do not (Table 4).
These two loggers are far apart and it would seem that any water movement that affects those
two loggers should affect one of the loggers between them. Perhaps, by chance, these events
are isolated and distinct at each logger.
Logger divergence may be related to the loggers’ proximity to the shore. Csanady in
1974, noted water closer to the shore was generally warmer. Future studies could relate logger
temperature to the proximity to shore.
Examining the wind records that occurred before the 32 events revealed no clear
correlation between wind and temperature variation (Table 4). And once again, no remarkably
high or low wind speeds were observed.
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Table 4: Details of 32 events of temperature variation > 0.6oC in 16 minutes from Severn Sound, 2004.
The wind directions recorded every hour leading up to the event are noted in the middle column written
from left to right– the events occurred in the last wind direction/ hour on the right and/or the hour
previous. The loggers where the temperature variation occurred are noted.
Event
*. 9/4/04
1. 6/16
2. 6/9
3. 6/11
4. 6/17
5. 6/16
6. 6/10
7. 6/30
8. 7/6
9. 7/3
10. 7/12
11. 7/21
12. 9/3
13. 6/8
14. 6/26
15. 7/1
16. 7/11
17. 7/7
18. 9/11
19. 6/9
20. 6/14
21. 6/8
22. 7/12
23. 7/11
24. 7/13
25. 9/23
26. 6/23
27. 6/23
28. 7/3
29. 7/22
30. 7/30
31. 8/2
32. 9/23
Wind Direction before event (event occurred at rightmost end)
Logger
SE, SE, SE, SE, SE, E, NW, NW, NW, NW
SW, SE, SE, SE, SE, SE, SE, E, SE
SW, SW, NW, NW, NW, NW, NW, N, NW
E, E, E, E, NE, NE, NE, NW, NW
SE, SE, SE, SE, SE, SE, SE, SE, SE
SE, SE, E, SE, SE, SE, SE, E, SE
NE, NE, NE, NE, NE, NE, NE, NW, NW
SE, SE, SE, SE, SE, SE, SE, E, SE
NW, NW, NW, 0, NE, SE, S
SE, SE, SE, E, SE, E, NW, NW, E
S, S, S, S, SE, S, S, NW, NW
SE, SE, SE, SE, SE, NW, NW, N, SE
NW, NW, NW, NW, NW, 0, SW, NW, W
SW, SW, SW, SW, SW, SW, SW, W, SW
W, NW, NW, NW, NW, NW, NW, NW, NW
SW, SW, S, SW, SW, SW, SW, SW, SW
SE, SE, SE, NW, N, NE, NW, NW, NW
SE, SE, S, S, SE, W, NW, NW, NW
S, S, S, SE, SE, SE, SE, SE, E
W, SW, SW, SW, NW, N, N, 0, N
SW, W, NW, SW, NW, NW, NW, SW, SW
SW, SW, SW, SW, SW, SW, SW, SW, SW
E, E, SE, S, S, S, S, SE, S
SW, SW, NW, NE, S, SE, SE, SE, NW
S, SE, S, SE, S, S, SE, SE, SE
SE, E, NW, NW, NE, NW, NW, NW, N
SW, SW, NW, NW, NW, SW, W, SW, SW
SW, SW, SW, SW, SW, SW, SW, SW, ?
W, W, 0, SE, SE, SE, SE, E, SE
SW, SW, NW, NW, NW, NW, NW, NW, NW
E, SE, SE, SE, SE, SE, SE, NE, NW
S, S, SE, SE, SW, SE, SE, SW, SW
SE, SE, SE, SE, SE, E, NW, NW, NE
34 7
4
34
34 7
34
3
7
7
3 678
7
3
78
3
7
3 67
7
3 6
6
6
3 6
3 6
3 6
8
8
3
3
3
3
3
3
3
3
3
3
3
3
Three events contain ‘0’ wind (#8, 12 and 19). Four events contain the same continuous
wind direction for 8-9 hours (#4, 14, 21 and 27) and of these events, the wind directions vary
between Southwestward, Southeastward and Northwestward. An examination of the amount of
changes in wind direction reveals two events (#6 and 29) where the wind direction changed
15
only once in the 8-9 hours. There are six events where the wind direction changed twice (# 3, 7,
13, 15, 18 and 28). There are five events where the wind direction changed three times (#1, 2,
10, 30 and 32). There are fifteen events where the wind direction changed four, or more times
(#5, 8, 9, 11, 12, 16, 17, 19, 20, 22, 23, 24, 25, 26 and 31). It may initially seem the changing
wind direction plays a role in logger variation. However using the change in wind direction
may be misleading because it does not take duration of the wind into account. The wind may
have been recorded after blowing for a few minutes – this small wind may not have any effect.
These latter 15 events should be studied further before conclusions are drawn.
An examination of winds that occurred at the beginning and end of each wind record
reveals various winds. Southeastward, Eastward, Southwestward, Northwestward and
Westward winds were seen to initiate events at the beginning of the records and Southeastward,
Northwestward and Northward winds were seen to occur just before an event began. Table A2
in the Appendix summarizes the wind data for the whole summer. Northwestward winds were
seen to dominate, which may account for their presence in the winds occurring at the beginning
and end of each event.
It was difficult to determine a pattern from this data. It should be noted that the
prevalence of variation at Logger 3 may bias the data examination, but it is difficult to say if
some of the variation recorded from Logger 3 should be removed. It is not clear at this time if
variation was due to the logger location or logger malfunction.
It is possible that wind did not cause some, or all, of these events. In Lake Chapala,
Mexico, Filonov in 2002 found patches of water 50-100m wide differing in temperature from
their surroundings by as much as 3oC. He hypothesized these fluctuations were due to warm or
cold water fronts. If local events caused such water patches in Severn Sound at certain times
16
during the year, wind data alone would not be sufficient to predict temperature jumps and may
explain why the predictions did not work. This phenomenon could also explain the variation
between loggers.
It is likely that the causes of temperature variation are more complex than wind
direction and wind speed. Lemmin in 1987 noted internal waves in Lake Baldeggersee
depended on constant wind along the lake’s axis, of at least 3m/sec, that persist for 3-4 hours.
Future studies may wish to examine wind duration or the relationship of wind direction to an
axis on Severn Sound.
The depth of the loggers also presents a problem. Seiches, downwellings and
upwellings are usually recorded as differences in water level (Bryson and Stearns, 1959),
current speeds or isotherm temperature variation (Blanton, 1975). None of these measurements
are available here, which makes it difficult to determine the cause of these events.
Finally, there is the question of whether short-term temperature variation should be
considered. Although it is clear variation occurred and it is unlikely all these events are flukes,
most reports on water movements remove short-term variation in order to clearly observe water
movements as they occur over hours or days, not minutes (Naumenko et al, 1996).
However, the fact remains that something happened at these loggers; sharp temperature
changes of over 1oC in 16 minutes were observed. In many cases, more than one logger showed
this change. Though attempting to make predictions using the available data was trickier than it
seemed, predicting these events may hold some value. Although 1oC may seem like a small
amount of variation to us, to the lives submerged in an aquatic world, a change of 1oC in 16
minutes could be a drastic change.
17
References
Aguado, E. and J. Burt. 2001. Understanding Weather and Climate. 2nd Ed. Prentice Hall, New
Jersey. P. 182.
Bennett, E. 1988. On the physical limnology of Georgian Bay. Hydrobiologia 163: 21-34.
Blanton, J. 1975 Nearshore lake currents measured during upwelling and downwelling of the
thermocline in Lake Ontario. J. Phys. Oceanogr 5: 111-124.
Bryson, R. and C. Stearns. 1959. A mechanism for the mixing of the waters of Lake Huron and
South Bay, Manitoulin Island. Limnol. Oceanogr 4(3): 246-51.
Csanady, G. 1974. Spring thermocline behaviour in Lake Ontario during IFYGL. J. Phys.
Oceanogr 4: 425-445.
Cushman-Roisin, B. and J. O’Brien. 1983. On wind and ocean-velocity correlations in a
coastal-upwelling system. J. Phys. Oceanogr 13: 547-550.
Filonov, A. 2002. On the dynamical response of Lake Chapala, Mexico to lake breeze forcing.
Hydrobiologia 467: 141-157.
Hamann, I., John, H., and E. Mittelstaed. 1981. Hydrography and its effects on fish larvae in
the Mauritanian upwelling area. Deep Sea Res. 28A(6): 561-575.
Horn, W., Mortimer, C. and D. Schwab. Wind-induced internal seiches in Lake Zurich
observed and modeled. Limnol. Oceanogr. 31(6): 1232-54.
Hutchinson, G.E. 1957. Treatise on Limnology. John Wiley & Sons, New York. p. 325.
Lemmin, U. 1987. The structure and dynamics of internal waves in Baldeggersee. Limnol.
Oceanogr. 32(1): 43-61.
Lerman, A. 1995. Physics and Chemistry of Lakes. Springer-Verlang. P. 111
Levy, D., Johnson, R. and J. Hume. 1991. Shifts in fish distribution in response to an internal
seiche in a stratified lake. Limnol. Oceanogr. 36(1) : 187-92.
McCombie, A. 1959. Some relations between air temperatures and the surface water
temperatures of lakes. Limnol. Oceanogr. 4 (3): 252-258.
Niebauer, H., Green, T. and R. Ragotzkie. 1977. Coastal upwelling/downwelling cycles in
southern Lake Superior. J. Phys. Oceanogr. 7(6): 918-927
18
Naumenko, M., Karetnikov, S., and A. Tikhomirov. 1996. Main features of the thermal regime
of Lake Ladoga during the ice-free period. Hydrobiologia. 322: 69-73
Richards, F.A. 1981. Coastal Upwellings. American Geophysical Union, Washington.
Scarpace, F., and T. Green III. 1979. The spatial variability of coastal surface water
temperature during upwelling. J. Phys. Oceanogr. 9: 638-643.
Vilivic, I. And M. Orlic. 1999. Surface seiches and internal Kelvin waves observed off Zadar
(East Adriatic). Estuarine, Coastal Shelf Sci. 48: 125-136
Wiegand, R. and V. Chamberlain. 1987. Internal waves of the second vertical mode in a
stratified lake. Limnol. Oceanogr. 32(1): 29-42
19
Appendix
Table A1: Using ‘0’ winds as a prediction tool. The original event on September 4th is
listed at the top of the table where 0 indicates a ‘0’ wind was recorded at that hour. X
represents one hour of wind. The X’s shaded indicate when temperature jumps > 0.5oC
occurred. The column on the right indicates which logger(s) recorded this temperature
jump. Data were obtained from hourly wind data at Beausoleil Island, summer 2004.
Date
Time of ‘0’ wind (0) and
Loggers
time of temperature jump > 0.5oC (shaded)
affected
9/4/ 2004
0,0,X,X,X,X,X,X,0,X, X,X,X,X,X,X,X,X,X,X
3,4, 7
1. 8/29
0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
2. 6/9
0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
3,4, 7,8
3. 7/9
0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
6,7,8
4. 7/17
0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
3
5. 8/16
0,,X,X,X,X,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X
6. 6/28
0,X,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
7. 7/11
0,X,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,
3, 6
8. 7/19
0,X,X,X,X,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X
9. 8/15
0,X,X,X,X,0,0,X,X,X,X,X,X,X,X,X,X,X,X,X
10. 9/10
0,0,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
3, 6
11. 6/17
0,0,X,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
4
12. 7/11
0,0,X,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X 3, 6,7
13. 9/23
0,X,X,X,0,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X
3, 6
14. 9/21
0,0,0,0,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X,X
15. 8/27
0,X,X,0,X,0,X,0,0,X,X,X,X,X,X,X,X,X,X,X,X
Table A2: Summary of the hourly wind record of Beausoleil
Island in the summer of 2004. Winds were recorded to the
nearest 10 degrees, ‘0’ represented no wind being recorded
and 360 represented a Northward wind.
Wind
Degree Equivalent
Percent
Direction
340,350,360,10,20
10.25%
N
30,40,50,60
2.78%
NE
70,80,90,100,110
6.13%
E
120,130,140,150
10.99%
SE
160,170,180,190,200 13.92%
S
210,220,230,240
14.52%
SW
250,260,270,280,290 9.80%
W
300,310,320,330
28.98%
NW
20
0 (NO
WIND)
0
2.64%
Sample calculations:
Calculating change in temperature every 16 minutes:
Time
(hrs:min)
A 00:04
B 00:20
C 00:36
D 00:52
Temperature
(oC)
18.39
18.39
18.23
18.43
Temperature
change (oC)
Absolute value of
temperature change (oC)
(AB) = 0
(BC) = -0.16
(CD) = +0.20
0
0.16
0.20
====================================================================
Improvements to existing data file:
Worksheet 1: Severn Sound Data
I eliminated events at the beginning and end of the record, where loggers were added and
removed.
I added a column beside the data for each logger and in the column I calculated the difference
in temperature every 16 minutes.
I highlighted, in red, events obtained from my logger variation graphs where temperature varied
by over 0.6oC. There are 32+ events. These events may form the basis for future studies.
Worksheet 2: Logger Variation Data:
I added five graphs which outline the variation every 16 minutes at each logger over the entire
summer.
Worksheet 3: Beausoleil Data:
I compiled the monthly data.
I highlighted in red, events obtained from my logger variation graphs where temperature varied
by over 0.6oC. 32+ events are highlighted; they may be useful in future studies of the weather
leading up to these events.
I created a Table to the right of the data, outlining a summary breakdown of wind direction
over the summer, which may be helpful in future projects studying wind variation.
Worksheet 4: Midland Data:
I added this data to provide further daily weather information of the area.
21