GROUP
Plymouth Field Course 2019
4
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ESTUARY
CTD Depth Profiles
Density Depth Profile:
Temperature Depth Profile:
The density of most stations was relatively constant; density does not vary much with depth. Station 1 (B) had a depth less than 5 metres, and it showed the most variation between the surface and seafloor. The lowest density shown at Station 1(B) was at approximately 1021 kg/m3, and the highest was at 1023 kg/m3. Station 5 (F) had an increase in density with depth, where there was a 1 kg/m3 difference between the surface and the bottom. The overall density increased as the boat travelled further into the estuary. The density of Station 1(B) was the lowest, whilst the maximum density was approximately 1026 kg/m3, at Station 8 (I) and Station 9 (J).
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Compared to the density and salinity profiles, the temperature depth profile showed the opposite pattern; some temperatures were higher at the surface and lower at the seafloor while others remained relatively constant. There were visible thermoclines at Station 1 (B), Station 4 (E), and Station 9 (J). Station 8 (I) showed a slight decrease from 16 °C at the surface to 15.5 °C at depth. In addition, the overall temperature of the water column was highest at Station 1 (B), and lowest at Stations 8 (I) and 9 (J), with the temperature decreasing as the boat traveled further into the estuary.
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Salinity Depth Profile:
The salinity pattern was similar to density; more than half of the transects were relatively constant along depth, as the estuary was well-mixed. Station 5 (F), Station 6 (G) and Station 8 (I) showed an increase salinity with depth; the salinity increased from approximately 33 to 34, 33.5 to 34, and 34.5 to 35 respectively. Station 1 (B) varied the most between the surface and the depth, which the transect ranges from 30.5 to 32.5.
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