Home OFFSHORE ESTUARINE GEOPHYSICS PONTOON 

CTD Temperature, Salinity, Density and Fluorometry Depth Profiles

A) Station 61

B) Station 62

C) Station 64

D) Station 66

E) Station 67

Figure 1 A-E illustrates temperature, salinity, density and fluorometry depth profiles for all 5 stations along the transect offshore of the Fal Estuary. Data was collected on 2/7/14 between 07:15 and 18:00 UTC.

(Click individual graphs to enlarge).

For figure 1A at station 61, there was an initial decrease in temperature with depth from roughly 17.08°C at 1m depth to roughly 17.01°C at 10m depth. There was then an increase in temperature with depth between 10m and roughly 23m, with the highest temperature at 17.07°C. There was an increase in fluorometry between 1m and 12m depth followed by a rapid decrease and then a steady decrease. The fluorometry data was lowest around 0.85 V at 1m and 23m and it was highest at 17.09 V. The salinity data decreased from 35.08 at 1m and fluctuates between 35.05 and 35.06 between 2-12m. The salinity then increased to roughly 35.11 at 23m depth. The density steadily decreased between 2m to  23m from 1025.56 kgm to 35.11 kgm.

For figure 1B at station 62 there was a decrease in temperature between almost 18°C at the surface to 13°C just over 60m depth, with an exponential decrease within the first 20m of the water column. There was a steady decrease in fluorometry between the surface (0.05 V) and roughly 30m at 0.10 V followed by a rapid increase to roughly 0.23 V and then a rapid decrease back down to 0.10 V at 40m. There was then a steady decrease back down to 0.05 V at just over 60m. The salinity fluctuated between the surface and around 60m, resulting in a slight overall decrease between the surface (roughly 35.15) to around 60m (roughly 35.25). The density decreased between the surface (1025.4 kgm) and 60m (1026.8 kgm).

For figure 1C at station 64 the temperature slowly decreased from 18°C at the surface to just below 18°C at 20m and then rapidly decreased at the thermocline to 12°C over a few metres. The temperature then remained constant at just over 12°C until the bottom of the water sampled. There was a slow increase in fluorometry from the surface (0.05 V) to roughly 20m, where there was a sudden increase to around 0.35 V at roughly 25m. This was followed by a decrease back to just over 0.05 V at roughly 30m. The fluorometry was then constant from 30m to the bottom of the water column sampled. The salinity fluctuated between the surface and just above 20m, where it then rapidly decreased to around 34.92 at 20m and then increased back to roughly 35.18, where it remained constant to the deepest water sampled. The density increased slightly to 20m and then rapidly increased to around 25m, followed by a steep increase to the deepest water sampled.

For figure 1D at station 66 the temperature slowly decreased between the surface and 20m, followed by a rapid decrease at the thermocline to roughly 13°C at 25m. It then steadily decreased to 30m and then remained constant until the bottom of the water column sampled. The fluorometry increased slightly between the surface and 20m, followed by a rapid increase from 35.05 V to 35.23 V and then decreased back to 35.05 V. It then remained constant at 35.05 V from 30m to the deepest water sampled. The salinity steadily decreased to 20m, followed by a rapid decrease to 35.02 salinity. The salinity then remained constant with depth to the where the bottom sample was taken from. The density showed a similar pattern to salinity. The density first increased slightly with depth then increased rapidly, followed by a steady increase to the bottom of the water column.

For figure 1E at station 67 the temperature decreased gradually between the surface at just below 18°C to just over 50m and around 14°C. The fluorometry gradually increased from 0.07 V at the surface to 0.17 V at roughly 20m, followed by a gradual decrease to 0.07 V at just over 50m. The salinity initially decreased from 35.13 to 35.05, followed by a decrease to 35.16 at just over 50m. The density gradually increased from 35.06 at the surface to 35.16 at the bottom of the water column sampled.

ADCP

Richardson’s Number

A) Station 61 Ship Track

B) Station 62 Ship Track

C) Station 64 Ship Track

D) Station 66 Ship Track

E) Station 67 Ship Track

Figures 2 A-E illustrate the ship track at each of the stations. Data was collected on 02/07/2014 between 07:15 and 18:00 UTC.

(Click individual graphs to enlarge).

A) Transect 1 Ship Track

B) Transect 2 Ship Track

C) Transect 3 Ship Track

D) Transect 4 Ship Track

E) Transect 5 Ship Track

Figures 3 A-E illustrate the ship track for each of the transects. Data was collected on 02/07/2014 between 07:15 and 18:00 UTC.

Figures 4 A-E illustrates the velocity contours for each of the stations. Data was collected on 02/07/2014 between 07:15 and 18:00 UTC.

(Click individual graphs to enlarge).

A) Station 61 Velocity Contour

B) Station 62 Velocity Contour

C) Station 64 Velocity Contour

D) Station 66 Velocity Contour

E) Station 67 Velocity Contour

A) Transect 1 Velocity Contour

B) Transect 2 Velocity Contour

C) Transect 3 Velocity Contour

D) Transect 4 Velocity Contour

E) Transect 5 Velocity Contour

Figures 5 A-E illustrate the velocity contours for each of the transects. Data was collected on 02/07/2014 between 07:15 and 18:00 UTC.

(Click individual graphs to enlarge).


A) Station 61

B) Station 62

C) Station 64

Figures 6 A-E illustrate the calculated Richardson’s number against depth for each station offshore of the Fal Estuary. Data was collected on 02/07/2014 between 07:15 and 18:00 UTC.

(Click individual graphs to enlarge).

Physical Offshore Results

Stations ship tracks

The current velocity represented in figure 2A is shown to be ~0.1m/s, which is slower than the expected ~0.6m/s according to Tidal Diamond F. Direction of flow is inconsistent at this station.

The current velocity at station 62 (figure 3B) is shown to be 0.05-0.4m/s in general, which is faster than the expected slack of 0.22m/s according to Tidal Diamond F over the sampling period. The Figure does indicate an increase in current velocity over the sampling period, which is expected due to the tidal cycle. The direction of flow appears to be 200-230° which is in keeping with Tidal Diamond F information.

In figure 2C, current velocity is shown to be 0.2-0.5m/s over the sampling period, which is almost fitting with the expected 0.6m/s according to Tidal Diamond F. The general velocity does not change significantly over the sampling period which is also fitting with Tidal Diamond F. The direction of current flow is ~250° which is ~45° different to the 215° expected.

Current velocities are 0.2-0.3m/s, in figure 2D, which is fitting with Tidal Diamond F expected 0.25m/s over the sampling period. The general velocity does not change over the sampling period and the direction of flow is ~260°, which is ~40° different from the expected 220° but in keeping with the difference at the previous station.

The current velocities 67 (figure 2E) at station are 0.1-0.2m/s within the sampling period, which is slightly faster than expected from Tidal Diamond F. The general velocity does not change over the sampling period. The direction of flow is ~270°, whilst Tidal Diamond F gives it as 293°.


Stations velocity profiles

Current velocity in figure 4A is shown to be 0.05-0.2m/s, which is slower than the expected ~0.6m/s according to Tidal Diamond F. Current velocity does not appear to differ significantly down the water column. Maximum depth is shown as ~33m and maximum sampled depth at ~30m.

Figure 4B shows that current velocity is shown to be 0.05-0.5m/s over the sampling period which is faster than the expected slack of 0.25m/s according to Tidal Diamond F. The figure does indicate an increase in the velocity of the water column throughout the sampling period, which is shown by an increase in blue, and decrease in purple. The early block of readings on the right show a slowly moving water column that is ~0.1m/s, and fitting with Tidal Diamond. The central block shows general velocities of ~0.2, and the left block ~0.3, which does fit better with Tidal Diamond information. The velocity increase is most prominent in depths past 20m. Maximum depth is ~65m, maximum sampled depth ~55m.

Figure 4C shows the velocity Contour for data collected with ADCP whilst on Station 64, the third of our stations, on 02/07/2014 from 13:20:39 to 15:04:28. Current velocity is shown to be generally 0.25-0.6m/s which is in keeping with Tidal Diamond F. Velocity does not change significantly with depth or over the sampling period. Maximum depth is ~75m and maximum sampled depth ~60m

Current velocities at station 66 (figure 4D) are 0.1-0.4m/s within the sampling period, with averages over the water column of ~0.25m/s, which is fitting with the Tidal Diamond F. The general velocity does decrease over the sampling period, more noticeable at depths past 20m and also in keeping with Tidal Diamond information. Maximum depth is ~75m, maximum sampling depth is ~60m.

The current velocity differs over the water column at station 67 (figure 4E), with 0-20m being 0.2-0.4m/s, and 20-40m being 0.05-0.2m/s. This is slightly faster than expected from Tidal Diamond F. Current velocity does not vary over the sampling period, but does noticeably with depths, as stated. Maximum depth ~60m, maximum sampling depth ~45m


Transects velocity profiles

Figure 5A shows the Velocity Profile taken for transect 1. Data display and interpretation is limited, due to 91% Bad Bins. For the values recovered, flow is seen to be 0.1-0.4m/s, this is about what is expected according to the nearest Tidal Diamond which suggests a flow of 0.36m/s reducing to slack over the survey period. Due to the large number of bad readings, no interpretation is possible at depths past 15m.

Figure 5B shows the Velocity Profile taken for transect 2. Data display and interpretation is limited due to 86% Bad Bins. For values recovered, flow is seen to be 0.1-0.6m/s, this is similar to the value predicted at the nearest Tidal Diamond of 0.26-0.46m/s over the period. Due to the large number of bad readings, little interpretation is possible after 20m depth for the majority of the transect, although maximum depth is ~80m.

Figure 5C shows the velocity profile for transect 3. Data display and interpretation is limited to 82% bad bins. For values recovered, flow was seen to be 0.2-0.6m/s. This is expected according to tidal diamond F which estimates 0.62m/s. Due to the large number of bad readings, little interpretation past 20m is possible, although the maximum depth is ~75m.

Figure 5E shows velocity profile for transect 4. Current velocities are ~0.3m/s which was in keeping with tidal diamond F which suggests velocities of 0.25m/s for the sample period. Due to the large amount of bad bins on this transect, data interpretation was not possible at depths past ~20m, although the maximum depth is ~70m.

Figure 5E shows velocity profile for transect 5. Current velocities appear to be 0.05-0.25m/s which is broadly within the expected 0.05 by tidal diamond F. The faster observed velocity could be due to the large number of bad bins which means that only the surface ~25m has given velocity results. There was also a large disparity in maximum depths, from ~10-60m which, makes comparisons difficult.


Transects Stick ship Track

Figure 3A shows the Stick Ship Track taken for transect 1. Data display and interpretation is limited due to 91% Bad Bins. For the data displayed, the flow appears to be ~0.3m/s, which is about what is expected according to the nearest Tidal Diamond which suggests a flow of 0.36m/s reducing to slack over the survey period. The Tidal Diamond also suggests an expected net flow at 40°. This is observed when averaging data.

Figure 3B shows the Stick Ship Track taken for transect 2. Data display and interpretation is limited due to 86% Bad Bins. For the data displayed, the flow appears to be ~0.3m/s. This is fitting with the Tidal Diamond (50°02’.5N 004°58’.8W) of 0.26-0.46m/s over the period. Tidal charts also indicate a likely flow to the south-west at 214° which is also visible here. The data collected is not able to be confirmed as a good representation of the water column however, as interpretation was not possible for the majority of the transect at over 20m depth.

Figure 3C shows Stick Ship Track for Transect 3. Current velocity appears to be ~0.4m/s, which was in keeping with Tidal Diamond F. The direction of flow is also in keeping with Tidal Diamond F. Data interpretation was limited due to 82% bad bins. Maximum sampling depth was ~20m, so Stick Ship Track data is not representative of the whole water column.

Figure 3D shows stick ship track for transect 4. Current velocities appear to be ~0.3m/s, which was in keeping with the suggested 0.25m/s from tidal diamond F for the sample period. The tidal diamond also suggests a direction of flow of 220° that can be seen in the figure. Due to the large number of bad bins, the stick ship track was only representative of the upper 20m of the ~70m water column.

Figure 3E shows stick ship track for transect 5. Current velocities appear to be ~0.3m/s which was more than expected according to tidal diamond F. This could be due to the lack of data at depths past ~25 as a result of bad bins. The direction of flow was ~260° which was ~30° different to the expected 293° according to the tidal diamond, however this could also be due to the lack of samples over the full depth.


D) Station 66

E) Station 67

Figure 6A shows that the Richardson’s Number (Ri) was constant at roughly 0.0 from the surface to 20m depth, indicating a laminar flow. The flow appeared to be turbid at roughly 12m depth at Ri 0.36.

Figure 6B also shows a constant laminar flow of 0 Ri between the surface and roughly 56m depth. The flow was turbulent at roughly 48m depth, with an Ri of 12.

Figure 6C showed that the flow was laminar for the entirety of the water column sampled. The Ri was greatest between the surface and 5m (0.05 Ri) and was followed by 0.03 Ri between 18m and 21m depth. The remainder of the water column had a constant Ri of 0.00.

Figure 6D shows that the flow was laminar between the surface and roughly 56m depth. The Ri was highest at around 20m depth (0.13 Ri), with the remainder of the water column having a constant Ri of 0.00.

Figure 6E  shows that the Ri was laminar (0.00 Ri) for the entirety of the water column except between roughly 16 and 19m where the flow was turbulent as it had a Ri of 0.35. at roughly 33m depth the Ri increased to 0.1, however the flow was still laminar



Disclaimer - These views are of the students of group 11 only and do not reflect the views and opinions of the National Oceanography Centre or the University of Southampton..