Hanna Kauko

Sebastien Moreau

Tore Hattermann

In situ Chl a fluorescence was measured with a WETLabs ECO fluorometer, bin-averaged to 1 m bins, corrected for baseline shifts (certain stations; the difference between the mode value of the station in question and the global dataset mode was added) and calibrated (fitted linearly) with the help of the determined dark value (the mode of values below 500 m) and concurrent Chl a values from water samples. The upcast values (median of a 2 m window around the water sampling depth) were used for the calibration as water sampling happened during the upcast, whereas downcast values are included in this dataset (both as mat and netCDF file) as the water column is less disturbed during the downcast. R2 of the fit was 0.74 and 0.67 before and after a sensitivity setting change (data treated separately), respectively. Please note that the data are not corrected for non-photochemical fluorescence quenching (NPQ). [Xin et al. (2012)]( https://doi.org/10.4319/lom.2012.10.483) suggest a method to correct for NPQ in the absence of backscattering or irradiance profiles, based on extrapolating the mixed layer maximum value to the surface. Daytime profiles (based on local sunrise and sunset) are listed in the attached csv file. Please note also that the upper water column (15 m) may be disturbed by the ship.

See [Kauko et al. (2021)]( https://doi.org/10.3389/fmars.2021.623856) for more details. [See related dataset]( https://data.npolar.no/dataset/28fbddd2-0fb2-41c9-9f42-60146e28617f) for Chl a water sampling method and related pigment and biogeochemistry data. See also [nutrients]( https://doi.org/10.21335/NMDC-1503664923), [phytoplankton taxonomy and abundance]( https://data.npolar.no/dataset/283e500c-732b-4f9b-a48a-3bc4990e3f55) and [CO2]( https://doi.org/10.21334/npolar.2020.cc4bfb5f) data.

Mat file variable explanations:<br>

chla: Chlorophyll a concentration in mg/m3<br>

depth: sampling (measurement) depth in meter<br>

lat: latitude in degrees south<br>

lon: longitude in degrees east<br>

sampling_time: the different columns contain the year, month, day, hour and minute of the sampling time<br>

station_number: CTD station running number starting with number 52<br>

===<br>

In this dataset there are also included mixed layer depths (MLD; z_mld) for the stations (mat and csv files). Fluorescence measurements were done in connection with CTD (conductivity-temperature-depth) casts (SBE911+ system). MLD was defined as the depth where salinity increases by 0.01 between two pressure binned values (1 m bin size). The upper 15 m of the profiles was discarded due to spikes and possible disturbances by the ship and the profiles were filtered with a 7 pt running median filter to remove spikes.

CEOS IDN DIF

9.8.4