Attributes {
    PRES {
        Float64 _FillValue NaN;
        String units "dbar";
        String sensor_serial_number "0972";
        String sensor_calibration_date "20-Feb-14 ";
        String coverage_content_type "coordinate";
        String standard_name "sea_water_pressure";
        String long_name "Pressure due to seawater";
        String positive "down";
        Float64 valid_min -1.000000000000000;
        Float64 valid_max 12000.00000000000;
        String axis "Z";
        String sensor_mount "mounted_on_shipborne_profiler";
    }
    TIME {
        Float64 _FillValue NaN;
        String units "Days since 1970-01-01 00:00:00";
        String standard_name "time";
        String long_name "Average time of measurements";
        String SBE_source_variable "timeS";
        String axis "T";
        String coverage_content_type "coordinate";
    }
    TEMP {
        Float64 _FillValue NaN;
        String units "degree_Celsius";
        String standard_name "sea_water_temperature";
        String long_name "Sea water temperature";
        String processing_level "Data manually reviewed";
        String QC_indicator "good data";
        String sensor_serial_number "5299";
        String sensor_calibration_date "08-Sep-20";
        Float64 valid_min -3.000000000000000;
        Float64 valid_max 40.00000000000000;
        String sensor_mount "mounted_on_shipborne_profiler";
        String reference_scale "ITS-90";
        String coverage_content_type "physicalMeasurement";
    }
    CNDC {
        Float64 _FillValue NaN;
        String units "S m-1";
        String standard_name "sea_water_electrical_conductivity";
        String long_name "Seawater electrical conductivity";
        String processing_level "Instrument data that have been converted to geophysical values";
        String QC_indicator "unknown";
        String sensor_serial_number "3742";
        String sensor_calibration_date "10-Sep-20";
        Float64 valid_min 0.000000000000000;
        Float64 valid_max 50.00000000000000;
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
    }
    OXYV {
        Float64 _FillValue NaN;
        String units "volt";
        String long_name "Raw signal (voltage) of instrument output by oxygen sensor";
        String processing_level "Instrument data that have been converted to geophysical values";
        String QC_indicator "unknown";
        String sensor_serial_number "1740";
        String sensor_calibration_date "17-Oct-20";
        Float64 valid_min 0.000000000000000;
        Float64 valid_max 1000.000000000000;
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
    }
    PSAL {
        Float64 _FillValue NaN;
        String units "1";
        String standard_name "sea_water_practical_salinity";
        String long_name "Practical salinity";
        String comment "Salinity values have been compared with salinometer measurements from bottle samples from >1000 dbar (n=16). The average offset (CTD minus salinometer) was -0.0038. This was considered within the total margin of error, except for one notable outlier at station sta010_01, where a salinity difference of -0.0164 was found. Removing this offset from the profile brings the bottom temperature-salinity properties closer to the deep water masses further offshore along the same transect. Sta010_01 was also the first profile taken after the unloading operations, during which the CTD package was unsupervised inside a shipping container for several days, where e.g. accretion of salt crystals in the conductivity cell may have led to a time-depended bias when measurements were resumed. However, at this point, we cannot conclude whether the difference at this station is related to a sensor offset or an inaccurate salinometer sample, and no correction was applied to any of the profiles in this file, and with a greater uncertainty to be accounted for at sta010_01.";
        String processing_level "Data manually reviewed";
        String QC_indicator "good data";
        String sensor_serial_number "5299, 3742";
        String sensor_calibration_date "08-Sep-20, 10-Sep-20";
        Float64 valid_min 2.000000000000000;
        Float64 valid_max 41.00000000000000;
        String sensor_mount "mounted_on_shipborne_profiler";
        String reference_scale "PSS-78";
        String coverage_content_type "physicalMeasurement";
        String manual_editing "14 data points have been removed from this variable based on visual inspection.";
    }
    DOXY_instr {
        Float64 _FillValue NaN;
        String units "mL l-1";
        String standard_name "volume_fraction_of_oxygen_in_sea_water";
        String long_name "Dissolved oxygen from sensor. Not calibrated against water samples.";
        String comment "Not compared with water sample oxygen measurements. Quality unknown!";
        String processing_level "Instrument data that has been converted to physical values";
        String QC_indicator "unknown";
        String sensor_serial_number "1740";
        String sensor_calibration_date "17-Oct-20";
        Float64 valid_min 0.000000000000000;
        Float64 valid_max 1000.000000000000;
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
    }
    STATION {
        String long_name "CTD station ID";
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
        String cf_role "profile_id";
    }
    LATITUDE {
        Float64 _FillValue NaN;
        String units "degree_north";
        String standard_name "latitude";
        String long_name "latitude";
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
        String axis "Y";
    }
    LONGITUDE {
        Float64 _FillValue NaN;
        String units "degree_east";
        String standard_name "longitude";
        String long_name "longitude";
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
        String axis "X";
    }
    CRUISE {
        String long_name "Cruise ID";
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
    }
    CHLA {
        Float64 _FillValue NaN;
        String units "mg m-3";
        String standard_name "chlorophyll_concentration_in_sea_water";
        String long_name "Chlorophyll-A concentration calibrated against water sample measurements";
        String comment "No correction for near-surface fluorescence quenching (see e.g. https://doi.org/10.4319/lom.2012.10.483) has been applied.";
        String processing_level "Post-recovery calibrations have been applied";
        String QC_indicator "good data";
        String calibration_formula "chla_calibrated = A * chla_from_ctd + B";
        Float64 coefficient_A 0.08950000000000000;
        Float64 coefficient_B -0.09393025000000001;
        String sensor_serial_number "FLRTD-1547";
        String sensor_calibration_date "4-Jan-16";
        Float64 valid_min -1.900000000000000;
        Float64 valid_max 100.0000000000000;
        String sensor_mount "mounted_on_shipborne_profiler";
        String coverage_content_type "physicalMeasurement";
        String manual_editing "Profile *sta013_01* removed from the dataset due to issues with the sensors causing unrealistic values";
    }
    NC_GLOBAL {
        String title "CTD data (temperature, conductivity, salinity, chlorophyll, uncalibrated oxygen) from Troll Transect cruise 2020/21 to Dronning Maud Land, Antarctica";
        String summary "CTD data collected off the coast of Dronning Maud Land, Antarctica during the Troll Transect Cruise 2020/21. This dataset contains pressure-gridded (1 dbar) CTD data (temperature, conductivity, salinity, chlorophyll, uncalibrated oxygen) from 14 profiles collected between 28.12.2020 and 07.01.2021. Data were collected using an SBE911+ unit (other CTD data were collected during the cruise - they are not included here).

Stations from 010_01 constitute a meridional (offshore) transect along approximately 6.1\302\260E.

Data from an SBE 43 oxygen sensor are included (both as dissolved oxygen and raw sensor voltage) - please note that these data have not been calibrated or quality-controlled, and are provided as-is.

CTD Chlorophyll data were calibrated based on a linear fit of CTD fluorometer against bottle fluorescence measurements:
1. First, the median value of dark counts at depth was determined based on measurements from 100 to 500 m depth.
2. A visual inspection confirmed that there were no offsets between profiles.
3. To calibrate the bottle Chl-a data to the bottle fluorescence measurements, we first only considered the bottle Chl-a value when the standard deviation of the bottle value divided by the fluorescence measurement was < 0.15, to avoid highly noisy parts of the fluorescence profile. Then we subtracted the offset value (1.0495) from the bottle fluorescence measurement, then we fit a linear regression with the bottle Chl-a measurement.

Salinity values have been compared with salinometer measurements from bottle samples from >1000 dbar (n=16). The average offset (CTD minus salinometer) was -0.0038. This was considered within the total margin of error, except for one notable outlier at station sta010_01, where a salinity difference of -0.0164 was found. Removing this offset from the profile brings the bottom temperature-salinity properties closer to the deep water masses further offshore along the same transect. Sta010_01 was also the first profile taken after the unloading operations, during which the CTD package was unsupervised inside a shipping container for several days, where e.g. accretion of salt crystals in the conductivity cell may have led to a time-depended bias when measurements were resumed. However, at this point, we cannot conclude whether the difference at this station is related to a sensor offset or an inaccurate salinometer sample, and no correction was applied to any of the profiles in this file, and with a greater uncertainty to be accounted for at sta010_01.";
        String history "2020-12-28 to 2021-01-07: Data collection.
2021-01-13 to 2021-01-21: Processed to .cnv using SBE software (details in \"SBE_processing\").
2023-12-29: Post-processing.
2024-01-22: Creation of this netcdf file.";
        String id "TrollTransectCTD_2020_2021_v1";
        String version "1.0";
        String doi "10.21334/npolar.2023.b1504a66";
        String date_created "2024-01-22T14:16:27Z";
        String comment "Chlorophyll-a profiles calculated based on best fit against in-situ water sample measurements (see CHLA attributes for details). Oxygen NOT calibrated against water sample measurements.";
        String source "CTD profiles from SBE911+";
        String instrument "In Situ/Laboratory Instruments>Profilers/Sounders>CTD";
        String platform "Water-based Platforms>Vessels";
        String institution "Norwegian Polar Institute (NPI)";
        String cruise_name "TrollTransect Cruise 2020/2021";
        String project "Norwegian Polar Institute 2020/21 TrollTransect pilot project cruise; Ocean-ice shelf interaction and channelized Melting in Dronning Maud Land project, Research Council of Norway grant no. 295075";
        String area "Southern Ocean";
        String location "Kong H\303\245kon VII Hav / Dronning Maud Land (DML)";
        String license "CC-BY 4.0";
        String time_coverage_start "2020-12-28T09:19:47Z";
        String time_coverage_end "2021-01-07T10:59:14Z";
        String time_coverage_resolution "variable";
        String time_coverage_duration "P0000-00-10T01:39:27";
        Float64 geospatial_lat_max -67.01620000000000;
        Float64 geospatial_lon_max 10.62470000000000;
        Float64 geospatial_lat_min -70.01220000000001;
        Float64 geospatial_lon_min 5.514700000000000;
        String geospatial_bounds "POLYGON ((5.51 -70.02, 5.51 -67.01, 10.63 -67.01, 10.63 -70.02, 5.51 -70.02))";
        String geospatial_bounds_crs "EPSG:4326";
        Float64 geospatial_vertical_min 2.000000000000000;
        Float64 geospatial_vertical_max 3403.000000000000;
        String geospatial_vertical_positive "down";
        String geospatial_vertical_units "dbar";
        String geospatial_bounds_vertical_crs "EPSG:5831";
        String data_set_language "eng";
        String data_assembly_center "NO/NPI";
        String creator_name "Norwegian Polar Institute (NPI)";
        String creator_email "post@npolar.no";
        String creator_type "institution";
        String creator_institution "Norwegian Polar Institute (NPI)";
        String creator_url "www.npolar.no";
        String publisher_name "Norwegian Polar Institute (NPI)";
        String publisher_url "www.npolar.no";
        String publisher_email "post@npolar.no";
        String publisher_institution "Norwegian Polar Institute (NPI)";
        String keywords "OCEANS>OCEAN TEMPERATURE>OCEAN TEMPERATURE PROFILES,OCEANS>OCEAN CHEMISTRY>OXYGEN,OCEANS>SALINITY/DENSITY>OCEAN SALINITY>OCEAN SALINITY PROFILES,OCEANS>SALINITY/DENSITY>CONDUCTIVITY>CONDUCTIVITY PROFILES,OCEANS>OCEAN OPTICS>CHLOROPHYLL>CHLOROPHYLL CONCENTRATION";
        String binned "1 decibars (SBE software)";
        String SBE_processing "SBE SOFTWARE PROCESSING STEPS (extracted from .cnv file header):
1. Raw data read from e.g. STA018_01.HEX, STA018_01.XMLCON.
2. Oxygen hysteresis correction applied.
3. Wild editing applied.
   > Parameters: n_std (first pass): 2.0, n_std (second pass): 20.0, min_delta: 0.0,
   > # points per test: 100.0.
   > Applied to variables: prDM t090C c0S/m.
4. Cell thermal mass correction applied to conductivity from sensors: [primary, ]. 
   > Parameters ALPHA: [0.0300, 0.0000], TAU: [7.0000, 0.0000].
5. Low-pass filter with time constant 0.03 seconds applied to: t090C c0S/m sbeox0V flECO-AFL altM.
6. Low-pass filter with time constant 0.15 seconds applied to: prDM.
7. Loop editing applied.
   > Parameters: Minimum velocity (ms-1): 0.250, Soak depth range (m): 5.0 to 20, 
   > Bad scans excluded. Deck pressure offset: Yes.
8. Derived EOS-8 salinity and other variables.
9. Bin averaged (1 decibars).
   > Bad scans not excluded, skipped over 0 initial scans.
   > (No surface bin).";
        String source_files "E.g. STA018_01.HEX, STA018_01.XMLCON -> STA018_01.CNV";
        String featureType "profile";
        String standard_name_vocabulary "CF Standard Name Table v83";
        String instrument_vocabulary "NASA/GCMD Instrument Keywords Version 17.2";
        String keywords_vocabulary "NASA/GCMD Science Keywords 9.1.5";
        String iso_topic_category "oceans";
        String Conventions "ACDD-1.3, CF-1.8";
        String naming_authority "npolar.no";
        String ship "Malik Arctica";
        String program "Norwegian Polar Institute Antarctic Porgram, Research Council of Norway POLARPROG";
        String acknowledgement "Data collection and processing was a part of the Norwegian Polar Institute 2020/21 TrollTransect pilot project cruise and supported by the Ocean-ice shelf interaction and channelized Melting in Dronning Maud Land project, Research Council of Norway grant no. 295075";
        String data_set_progress "complete";
    }
}