Float WMO_ID: 5901615

Float WMO_ID: 5901615




Table of Contents

  1. Float Information
  2. Float Location
  3. Surface Pressure
  4. Potential Temperature-Salinity Plot
  5. Temperature-Salinity Comparison with Nearby Floats
  6. Inversions
  7. Salt Hooks
  8. Parameter Sections and Initial QC Notes
  9. WJO/OW Results
  10. Anomaly Plot
  11. Comparison with Nearby Argo
  12. Salinity Drift Assessment
  13. Float Summary



Section 1: Float Information

The table below provides basic information about the float, including primary sensors, mission parameters and current status of profiles.

This float has been declared dead after a total of 130 profiles.

Institute CSIRO
Principal InvestigatorSusan Wijffels
Pressure SensorDruck (serial number=10273)
CTD SensorAPEX-SBE-41 (serial number=2902)
CTD Sampling ModeBurst Sampler
Controller BoardAPF 8
Additional Sensors/SoftwareNone
Park Depth1000 m
Profile Depth2000 m
Launch Date26-04-2007
Number of D-moded Profiles130
Calibration Date06-05-2012
Pressure DriftSurface Pressure Offset corrected
Salinity DriftNo salinity drift detected





















Section 2: Float Location

Float trajectory and location plot

This float was deployed by the MV Wellington Express in the southwest Pacific at 29.02 °S, 160.2°E on the 26th April 2007. Since its deployment the float has followed a large anti-clockwise path over the topographically shallow, undersea ridge known as the Lord Howe Seamount Chain. The float’s drift depth was 2000 m and it grounded on numerous profiles over the shallower parts of the ridge. The New Caledonia Basin (greater than 3500m) flanks the ridge on the east while in the west water depths are greater than 4500m in the northern part of the Tasman Abyssal Plain. The float has grounded on the Australian continental shelf and is moving south with the EAC.


Section 3: Reported Surface Pressure

The surface pressure for this float is shown in the plot below.


Surface Pressure plot

Section 4: Potential Temperature-Salinity Plot

Potential Temperature-Salinity (a), Location (b, Max Temperature (c) and Sea Surface Salinity (d) plots located below.

Potential Temperature-Salinity, Location and Max Temperature and Sea Surface Salinity plots

Surface temperatures generally varied between 19 and 25 ºC and surface salinities from 35.3 to 35.9.


The three plots below highlight an unusual profile in the series (pf 45). The top left plot is salinity versus depth with pf 45 highlighted in red, the top right plot is the TS plot from gilson for profiles 1 to 45 (with pf 45 in red). The bottom plot is the TS plot for profiles 1 to 63 with early profiles (1 to 45 in blue to green to yellow), profile 45 in black and profiles 46 to 63 in orange red.


Salinity-Depth plot from Gilson1 TS from Gilson plot Potential Temperature-Salinity deepest theta levels alternate plot Potential Temperature-Salinity deepest theta levels alternate plot

The last profile in our series available for delayed mode processing, (profile 45) exhibited a sudden and large, step-wise jump in salinity, just above the salinity minimum in Antarctic Intermediate Water (AAIW) present at around 800 to 1000m. The AAIW suddenly became significantly colder (0.017) and fresher (0.06) between 800 and 750 m depth. At first glance, a sudden jump like this would tend to indicate sensor drift caused by instrument damage or bio-fouling. However, the shape of the profile was also significantly different at the surface, with much fresher and warmer waters than previous profiles. Inspection of subsequent, real-time profiles, (profiles 46 to 63) revealed two distinct clusters of profiles distinguished by different AAIW salinity signatures. This clearly showed that the observed drift is real and caused by the float traversing a water mass boundary during its upward ascent into a water mass with markedly different AAIW properties.


Section 5: Temperature-Salinity Comparison with Nearby Floats

The two plots below show a). the location of this float (black circles) in relation to the position of other nearby argo floats (coloured circles) and b). The potential-temperature/salinity curve for this float (in black) compared to nearby argo floats (coloured).

Potential Temperature-Salinity nearby comparison plot

The plot below shows the potential-temperature/salinity relationship for the deepest theta levels where the relationship between the two parameters should show the least variation (left). The potential-temperature/salinity relation for the deepest theta levels for this float (in black) and nearby argo floats (coloured) is displayed below (right).


Potential Temperature-Salinity deepest theta levels plot Potential Temperature-Salinity nearby deep comparison plot

The deep profiles at depth for this float are obviously divided into two separate clusters sampling different water masses. Nearby Argo floats show that there is a large spread in the data at depth (0.02) and that this separation is due to the float sampling different water masses in different basins separated by a ridge.


Section 6: Inversions

There were inversions in profiles; 26,34,79. These were not significant and were not flagged.


Section 7: Salt Hooks

Salt hooks were located in profiles; 9,10,11,12,13,15,16,31,32,33,34,35,36,37,38,39,61,62,64,65,66,67,68,71,77,78,79,80,81,82,83,84,85,,86,87,89,92,93,96,100,101,102. These were flagged as QC 4 for both T & S.


Section 8: Parameter Sections and Initial QC Notes

The float grounded on multiple profiles; 1, 2, 3, 4, 5, 6, 7, 8, 14, 17, 18 to 33, 43 to 45. Some of the grounded profiles exhibited strange values at the bottom of the profiles, these were QC'd as 4 for both T & S.


Float trajectory overlayed on bathymetry, (left) and over climatological salinity (right)
Float trajectory and bathymetry plot Float trajectory and salinity plot

Potential temperature section with time, (left) surface to 2000m and (right) surface to 500m

Potential Temperature Plot - Full Depth Range Potential Temperature Plot - Surface to 500m

Salinity section with time, (left) surface to 2000m and (right) surface to 500m

Salinity Plot - Full Depth Range Salinity Plot - Surface to 500m

Potential density section with time, (left) surface to 2000m and (right) surface to 500m

Potential Density Plot - Full Depth Range Potential Density Plot - Surface to 500m

A section plot of salinity over time clearly illustrates the abrupt change in water mass properties that occurred at profile 45. AAIW is typically centred at around 1000 m with a distinct salinity minimum. This water mass was markedly fresher over the western and north-western parts of the ridge (profiles 46 to 63) and to a lesser extent in profiles 1 to 3, compared to the AAIW encountered over profiles 4 to 44 over the south-eastern parts of the float trajectory. The isopycnals are displaced upwards over the ridge by the shallowing topography, moving colder, fresher AAIW about 200m up into the water column. The convoluted topography in the region may restrict mixing between basins and create complex pathways of flow resulting in the large observed variability in AAIW water mass properties.


Section 9: WJO/OW Results

The plot below shows the analysis of salinity drift using the WJO/OW software.


WJO/OW plot

Section 10: Anomaly Plots

The four plots below show the salinity anomalies on theta surfaces compared to (a) the Gouretski and Kolterman climatology, (b) the CARS (CSIRO Atlas of Regional Seas)/WOA (World Ocean Atlas) climatology, (c) the anomalies within the float series itself, (i.e. the salinity anomaly of each profile from the mean profile average for the float and (d) the raw float salinity compared to the CARS and G&K climatological salinity on a deep theta surface.


Anomaly Plot

The float is very close to the climatologies.


Section 11: Comparison with Nearby Argo

The plots below show the raw float salinity data (solid blue line) compared to neighbouring argo floats (coloured symbols) on a deep potential temperature surface. The locality map shows the location of the profiles for this float and for neighbouring floats.


Nearby Argo Comparison Plot Nearby Argo Location Plot

The float has distinctly crossed a water mass boundary at profile 45. There is a 0.02 to 0.03 spread in the data on a deep theta level. The float is in the middle of the argo envelope.


Section 12: Salinity Drift Assessment

This float required no salinity drift correction.



Section 13: Float Summary

Final Check Plot

The plot below summarises the QC flags and salinity differences for the raw and adjusted salinity fields in the final delayed mode files submitted to the GDAC.



Created 06-05-2012