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Ref. No. [UMCES] CBL 2015-011
ACT VS15-04
41
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 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 17. 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
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 by the sampler
integrating across the mooring space.
The Troll 9500 operated continuously over the 29 days of the deployment and generated
2673 observations at 15 minute intervals. The range in ambient pH measured by the Troll 9500
was 8.24 to 9.57 compared to 8.013 to 8.526 for the reference pH measurements (Fig. 18). The
bottom panel presents the time series of the difference between the instrument and reference pH
for each matched pair (n=98 observations). The average and standard deviation of the difference
for the entire deployment was 0.60 ± 0.15 with a total range of 0.27 to 0.90.