N-ICE2015 ship-based conductivity-temperature-depth (CTD) data
CTD (salinity, temperature and depth) profiles from ship-based casts with SBE911 CTD and rosette and associated water sampling.
Simple
- Date (Revision)
- 2021-05-31
- Credit
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Paul Dodd
- Credit
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Amelie Meyer
- Credit
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Zoe Koenig
- Credit
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Adam Cooper
- Credit
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Lars H. Smedsrud
- Credit
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Morven Muilwijk
- Credit
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Victoire Rerolle
- Credit
-
Nikita Kusse-Tiuz
- Credit
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Jonas Miguet
- Credit
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Ingrid Onarheim
- Credit
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Peter Davis
- Credit
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Achim Randelhoff
- Status
- Completed
- Theme
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Lance
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ICE
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N-ICE2015
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Cast
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Floe-1
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Floe-2
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Floe-3
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Floe-4
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Leg-1
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Leg-2
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Leg-3
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Leg-4
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Leg-5
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Leg-6
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marine
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oceanography
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- Nasjonal tematisk inndeling (DOK-kategori)
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Kyst og fiskeri
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- Global Change Master Directory (GCMD) Keywords
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OCEANS | SALINITY/DENSITY | SALINITY
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OCEANS | OCEAN TEMPERATURE | THERMOCLINE
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OCEANS | SALINITY/DENSITY
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- Topic category
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- Oceans
))
- Begin date
- 2015-01-11
- End date
- 2015-06-24
- Distribution format
-
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N-ICE2015 datasets (text/html)
()
Distributor
- OnLine resource
- https://data.npolar.no/dataset/7f7e56d0-9e70-4363-b37d-17915e09a935 ( WWW:DOWNLOAD-1.0-http--download )
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JSON (edit URI) (application/json)
()
Distributor
- OnLine resource
- https://api.npolar.no/dataset/92262a9c-e6a4-59b5-9929-81c0429d7de6 ( WWW:DOWNLOAD-1.0-http--download )
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npolar.2017.92262a9c.zip (application/zip)
()
Distributor
- OnLine resource
- https://api.npolar.no/dataset/92262a9c-e6a4-59b5-9929-81c0429d7de6/_file/_all?filename=npolar.2017.92262a9c&format=zip ( WWW:DOWNLOAD-1.0-http--download )
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Data (application/zip)
()
Distributor
- OnLine resource
- https://api.npolar.no/dataset/92262a9c-e6a4-59b5-9929-81c0429d7de6/_file/_all/?filename=npolar.2017.92262a9c-data&format=zip ( WWW:DOWNLOAD-1.0-http--download )
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N-ICE2015 (text/html)
()
Distributor
- OnLine resource
- https://data.npolar.no/project/b98886ce-590a-48a8-b113-4b96e98c65c8 ( WWW:LINK-1.0-http--link )
-
N-ICE2015 datasets (text/html)
()
- OnLine resource
- https://data.npolar.no/dataset/7f7e56d0-9e70-4363-b37d-17915e09a935 ( WWW:DOWNLOAD-1.0-http--download )
- Statement
-
Shipboard CTD profiles in MatLab format, with complete and corrected 'metadata' (time position etc…). Standard quality control applied and post cruise calibration applied (see below).
Variables:
```
Name Size
C1_ship 4091x51 Conductivity sensor 1
C2_ship 4091x51 Conductivity sensor 2
P_ship 4091x1 Pressure (dbar)
S1_ship 4091x51 Practical salinity sensor 1
S2_ship 4091x51 Practical salinity sensor 2
T1_ship 4091x51 In situ temperature (oC) sensor 1
T2_ship 4091x51 In situ temperature (oC) sensor 2
lat_ship 1x51 CTD station latitude
lon_ship 1x51 CTD station longitude
sound_vel 4091x51 Water sounds velocity (m/s)
station_ship 1x51 CTD station number
time_ship 1x51 CTD station time
version 1x56 Data file version
```
Notes about quality control applied:
First attempted to use information from the pre/post temperature and conductivity data sheets from SBE following the procedure in their application note 31. But the results were rather poor when compared to bottle salinity data. There were 2 main problems: 1) A long time had elapsed between the cruise and pre/post calibrations. 2) There was a big jump in both the conductivity sensors between stations 16 and 17 (end of leg 1 and start of leg 2). This jump means that an assumption of even drift in conductivity slope with time is not valid. The conductivity slope corrections estimated using SBE’s application note 31 pre/post method did improve the accuracy of salinity measurements relative to bottle salinities, but had a negative effect on the precision (as estimated from the difference between the salinities measured by sensor pairs 1 and 2.
We accepted the temperature drift offset corrections (effectively zero) suggested by the pre/post calibration, but rejected the conductivity slope values derived from pre/post calibration and calculated conductivity slope corrections using bottle salinity values instead. We used the alternative procedure described in SBE application note 31 for calibration using on board bottle salinity measurements. A good number of bottle salinity results were available from deep water masses throughout the cruise. We estimated two slope corrections for each sensor. One for stations 1 to 16 during leg1 before the jump (applied in postcruise1-16.con) and one for stations after the jump (applied in postcruise17-51.con). Below are the conductivity slopes relative to bottle data estimated before any conductivity slope correction was applied (remember that pre/post calibration suggested that no temperature correction is required):
Stations 1-16 Primary conductivity: 0.99999052
Stations 1-16 Secondary conductivity: 1.00012038
Stations 17-51 Primary conductivity: 1.00021485
Stations 17-51 Secondary conductivity: 1.00022678
After applying these slope calibrations we get the following residual values:
Stations 1-16 Primary conductivity: 1.00000004
Stations 1-16 Secondary conductivity: 1.00000001
Stations 17-51 Primary conductivity: 0.99999999
Stations 17-51 Secondary conductivity: 1.00000003
Typical differences between the salinity measured by the sensor pairs are now less than 0.001.
If both sensor pairs were calibrated using the pre/post method there would be some merit in averaging the values from both sensor pairs to achieve the best possible absolute accuracy (they could be considered independent measurements). Here, however both sensors have been adjusted to agree with the bottle data, so we do not think there is much to gain by averaging them, rather use one and revert to the other if some spike or other bad data is encountered.
We have done some elementary data clean up - mostly just deleting the tops of profiles where the CTD wasn’t soaked for long enough to get accurate values. Bad data points were replaced with NaNs and not interpolated.
- File identifier
- 92262a9c-e6a4-59b5-9929-81c0429d7de6 XML
- Metadata language
- English
- Hierarchy level
- Dataset
- Date stamp
- 2022-05-27
- Metadata standard name
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CEOS IDN DIF
- Metadata standard version
-
9.8.4
Overviews
Spatial extent
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