Underwater spectral irradiance data (light attenuation) on the Tropic Seamount, eastern Atlantic

Attenuation of light along the water column (spectral irradiance, wavelength-resolved) was measured during the TRIDENT-2025 cruise onboard the R/V Sarmiento de Gamboa, in the frame of the Workpackage 2 – Environmental baseline assessment of project TRIDENT, funded by EU. The variation of light in the water column was directly measured using a spectroradiometer, model Ramses-ACC-VIS hyperspectral radiometer of TriOS (https://trios.de/en/ramses). It measures the radiance/irradiance for the UV/VIS spectral range within the wavelength range of 320 - 950 nm resolved into 190 channels, with spectral accuracy of 0.3 nm.  Data was collected by manually immersing the sensor over the side of the vessel, for 14 successful casts. Outputs from the instrument required processing and scripts were developed to read the data and reorganize them in a storable format, as well as to produce interpretable plots. During data reading, only positive depth measurements (below water) were kept, and abnormally high intensities were discarded.  The dataset comprises data (raw and processed) and respective interpretative plots, namely: * Table with location and date of each cast * Raw data:  original files from the instrument, only calibrated data * Reorganised data files: File with spectra (wavelength, intensity) for all depths, concatenated (one file for each cast; files named CAST_full.txt) Folders with one file for each spectra at each measurement depth (one folder for each cast; folders named CAST_spectra_per_depth) * Plots - for each cast: 1- Simple plot of intensity variation with spectra for all depths together (top plot); and plot of depth variation during the experiment (bottom plot). Spectrum lines with higher transparency in the top plot correspond to shallower depths.  2- Colourmap of light intensity variation with depth and with wavelength, in linear and logarithmic scales. 3- Line plots of intensity variation along depth for each wavelength band (bands of 25 nm width), in linear and logarithmic scales. Colours of line plots correspond to the respective wavelength colour.