Oceanographic conductivity, temperature and depth (CTD) data from expedition ARTofMELT, Arctic Ocean, 2023

Julia Muchowski, Noemie Planat, Lina Aleke Holthusen, Magnus Asmussen

Processed conductivity, temperature and depth (CTD) data collected from the Swedish icebreaker Oden during the expedition ARTofMELT (Atmospheric Rivers and the Onset of Arctic Melt) in the Fram Strait pack ice during the spring transition between May and June 2023.

These CTD data include high resolution (0.2 m) vertical profiles of the water column properties in terms of salinity, temperature, dissolved oxygen, turbidity, fluorescence and CDOM (colored dissolved organic matter) over a total of 23 casts. Station names are related to ice floes, that the icebreaker Oden was moored to.

In this dataset, processing of the raw data output was done by converting the raw output in voltage to SI units, a lowpass filter was applied to remove spikes, corrections were applied that take care of the fact that the sensors are mounted with a spatial distance from each other, and the data are binned vertically.

MarineHydrographyCTDConductivityTemperatureDissolved OxygenTurbidityFluorescenceArcticArctic OceanARTofMELTARTofMELT 2023 expeditionIcebreaker Oden

Name

Version

Citation

References

Muchowski J, Planat P, Holthusen LA, Asmussen M (2025) Oceanographic conductivity, temperature and depth (CTD) data from expedition ARTofMELT, Arctic Ocean, 2023 — raw data. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-artofmelt-2023-ctd-raw-1

Holthusen LA, Planat P, Asmussen M, Muchowski J (2025) Oceanographic vertical microstructure profiler (VMP) data from expedition ARTofMELT, Arctic Ocean, 2023 — subset with CTD data. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-artofmelt-2023-vmp-ctd-1

Data description

This dataset is provided in two folders accompanied by a configuration file. Total size ~35 MB.

Data folders

profiles

Processed and quality-controlled CTD data from the downcast in csv files with data from each CTD cast. All files follow the naming convention

• AOM23-station-[station number]-cast[cast number].*

Each file contains the following parameters.

• time NMEA time in UTC in the format yyyy-mm-dd HH:MM:SS.SSS
• lat Latitude (°N)
• lon Longitude (°E)
• pressure pressure (dbar)
• pump Pump status (on/off)
• T1, T2 In situ Temperature (°C) for first/second sensor pack
• S1, S2 Practical Salinity (PSU) from first/second sensor pack
• OXY1_SAT Oxygen Saturation (%) from second sensor pack
• OXY1_ML Oxygen Concentration (ml/l) from second sensor pack
• FLUOR Fluorescence, WET Labs ECO-AFL/FL (mg/m³)
• TURB Turbidity, WET Labs ECO (NTU)
• CDOM Colored dissolved organic matter (ppb)
• DESC Descent rate (m/s)
• ALTIM Altimeter reading of distance above the seafloor (m)
• CNT Scan count
• T1_quality_flag Quality flag for temperature sensor in first sensor pack
• T2_quality_flag Quality flag for temperature sensor in second sensor pack
• S1_quality_flag Quality flag for salinity sensor in first sensor pack
• S2_quality_flag Quality flag for salinity sensor in second sensor pack
• OXY1_quality_flag Quality flag for oxygen sensor in second sensor pack

Note that there was a dual temperature/conductivity sensor pack with only a single oxygen sensor in the second pack installed on the CTD.

Definition of quality flags:

• 0 = good data
• 1 = sketchy data
• 2 = bad data

All collected temperature, salinity and oxygen sensor data were quality controlled.

Data were flagged bad when: out of range, difference between the dual sensors, significant outliers - especially at the top and bottom of profiles. In addition, salinity data were flagged bad if the pump status was off.

Data were flagged as sketchy when abrupt changes occured (spikes, outliers) or unexplainable differences between the dual sensors occured.

All other data are flagged as good.

In some casts NMEA positioning was not available, therefore the fields lat and lon are empty in the data files. CDOM data from station 01 are lacking and filled with zeros in the corresponding first two csv files.

In the associated raw CTD dataset is a list (logbook csv file) included with station numbers, times, latitude and longitude for all 23 CTD casts.

btl_files

Processed data for each water sample that was taken in a text file with the ending _u.btl, created by the SBEDataProcessing software, with _u indicating that the data were collected during the upcast.

Each file contains a header that provides metadata to the cast, the used sensors, and their calibration data. For each bottle thas was sampled, the following parameters are included as average only:

• Bottle Position
• Date Time Date and time in the format mmm-dd-yyyy HH:MM:SS
• Potemp090C and Potemp190C Potential temperature (°C) derived from in situ temperatures in first and second sensor pack using the TEOS10 toolbox
• Sbeox0ML/L Oxygen (ml/l)
• Sbeox0PS Oxygen saturation (%)
• SvCM Soundvelocity (m/s)
• DepSM Depth (salt water, m) (if calculated)
• DepFM Depth (fresh water, m) (if calculated)
• Sal00 and Sal11 Practical salinity (psu) from the first and second sensor pack
• Density00 and Density11 Density (kg/m^3) from the two temperature and salinity sensor packs
• Sigma00 and Sigma11 Density with reference pressure of 0 dbar (kg/m^3) from the two temperature and salinity sensor packs

The following parameters are included as average and in addition, the standard deviation (sdev), their minimum value (min) and maximum value (max) while the bottle was fired are provided:

• Dz/dtM Descent rate (m/s)
• Latitude Latitude (°N)
• Longitude Longitude (°E)
• TimeS elapsed seconds since the beginning of the CTD cast (s)
• T090C and T190C In situ temperature (°C) from the two sensor packs
• Sbeox0V Oxygen sensor raw data (V)
• PrDM Pressure, Digiquartz, Strain Gauge (db)
• AltM Altimeter reading of distance to seafloor (m) this value starts to be reliable when approaching the last 100m above the seafloor
• C0S/m and C1S/m Conductivity (S/m)

Processing of the data was done using Tunatools, a Python wrapper around the SBEDataProcessing software. As part of the SBEDataProcessing software, raw data output in voltage is converted to SI units, a lowpass filter is applied to remove spikes, corrections are applied that take care of the fact that the sensors are mounted with a spatial distance from each other, and the data are binned vertically.

Configuration file

Calibration coefficients and dates of the applied calibrations are provided for all sensors in the configuration file AOM23_config_cal2023.xmlcon. The file can be opened in a text editor or with the SBE software DisplayConFile, which is part of the above mentioned SBEDataProcessing software.

Comments

Instrumentation

Data were collected with a Seabird 911 CTD. The CTD was equipped with a 24 Niskin bottle (12 liters) rosette and the following sensors: Dual SeaBird temperature (SBE 3), conductivity (SBE 04C), dissolved oxygen (SBE 43), turbidity and fluorescence (WET Labs ECO-AFL/FL), a Turner Cyklos Fluorometer collecting CDOM (colored dissolved organic matter) data and a Benthos Altimeter PSA-916D. Practical salinity and in situ temperature can be converted to conservative temperature and absolute salinity using the TEOS-10 equation of state.

Associated raw data

The raw data, from which this dataset is derived, was created by Muchowski et al. (2025) and is available separately.

Related CTD data

CTD data collected from a vertical microstructure profiler (VMP) are also available (Holthusen et al. (2025).

The expedition

Data were collected during the ARTofMELT 2023 expedition on board the Swedish icebreaker Oden, which was organized by the Swedish Polar Research Secretariat from 8 May through 14 June, 2023.

Project

ARTofMELT 2023 expedition

Publisher

Bolin Centre Database

License

Creative Commons Attribution 4.0 International License (CC BY 4.0)

First name

Julia

Last name or organisation

Muchowski

Email address

julia.muchowski@polar.se

Address

Swedish Polar Research Secretariat; c/o Luleå tekniska universitet

Postal code

SE-971 87

City

Luleå

Country

Sweden

GCMD science keyword

Earth science > Oceans

GCMD location

Ocean > Arctic Ocean

Dataset language

English

Begin date

2023-05-07

End date

2023-06-15

DOI

Time