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Ref. No. [UMCES] CBL 2015-014
ACT VS15-07
50
Great Lakes Field Test Site
A month-long moored field test was conducted in Lake Michigan from June 21 to July
19, 2014. The Great Lakes deployment site was located at 43.23°N, 86.34°W on a fixed pier at
the Lake Michigan Field Station of the NOAA Great Lakes Environmental Research Laboratory,
in Muskegon, Michigan. The site is located at the outfall of Lake Muskegon into Lake Michigan
with a depth of approximately 3 meters. The temperature range during deployment was 11.6°C
through 24.9°C and salinity averaged 0.031.
Photo 8.
Aerial view of Lake Michigan and Muskegon Lake (left) and rack deployment at GL Site.
Time series results of ambient conditions for water depth, temperature, and salinity are
given in figure 26. Temperature ranged from 11.6 to 24.9 and salinity from 0.024 to .035 over
the duration of the field test. While there are no tidal cycles at this site there was significant
exchange between the open lake and the protected basin within the break wall as evidenced by
significant changes in salinity and water depth. The bottom panel displays the maximum
difference recorded between all reference thermistors (RBR Solo and SBE26) mounted at the
same depth and different locations across the mooring rack. The average temperature difference
observed across the space of the mooring rack was 0.08 ±0.18
o
C, with a maximum of 2.53
o
C.
As noted above, it is not possible to quantify the exact difference between the averaged reference
temperature and that measured by the test instrument, but differences resulting from this
variation and variation in the chemistry of the water across will be minimized because the
sampling bottle integrates across the mooring space.
The EXO sonde deployed for the Great Lakes field deployment also contained two
separate pH probes and each probe is reported on separately and designated as EXO-pH1 and
EXO-pH2 as defined by the probes location ID. Both pH probes operated continuously over the
29 days of the deployment and each generated 2661 pH measurements at 15 minute intervals.
Time series results of the EXO-pH1 and corresponding reference pH results are given in figure
27. Ambient pH measured by the EXO-pH1 ranged from 7.84 to 8.60, compared to the range
captured from reference samples of 8.013 to 8.526. The bottom panel presents the time series of
the difference between instrument and reference pH measurements for each matched pair (n=98
observations). The average and standard deviation of the difference between EXO-pH1 and