This dataset consists of vertical profiles of underwater downwelling irradiances at several UVR (305, 313, 320, 340 and 380nm) and PAR wavelengths, from June to August 2004. Vertical light profiles were performed using a PUV-511 underwater radiometer (Biospherical Instruments) that provides a measure of cosine-corrected downwelling irradiance in the UVR and PAR. Irradiances were corrected by the dark values and normalized to the ambient conditions at the beginning of the profile, using ambient values given by a GUV-510 surface radiometer (Biospherical Instruments) mounted on the top of the wheelhouse of the CCGS Amundsen.

Samples were collected at 5 sites ranging in water depth from 100 to 595 m at least once in each season (ice-covered and open-water condition) between March and August 2008 onboard the icebreaker CCGS Amundsen. At each sampling station, an USNEL box corer was deployed for collecting seafloor sediments. From each box core, 5 sub-cores of 11 cm diameter and 20 cm sediment depth were taken for assessing benthic carbon remineralisation in microcosm incubations and 3 additional subcores of 5 cm diameter and 10 cm length were taken for determining sediment properties. Incubations of sediment microcosms were run in a dark, temperature-controlled room (2-4 °C) for 24-48 h. Each sediment microcosm was sieved through a 0.5 mm mesh under running sea water at the end of incubations to determine biomass of macrofaunal communities. The sieve residue was preserved in a buffered 4% seawater-formaldehyde solution and analysed for species composition and abundance under a stereomicroscope in the lab.

This dataset consists of continuous records of downwelling irradiances at several UVR (305, 313, 320, 340 and 380nm) and PAR wavelengths, from September to November 2003 and from June to August 2004. The GUV-510 surface radiometer (Biospherical Instruments), mounted on the top of the wheelhouse of the CCGS Amundsen, provided a measure of cosine-corrected downwelling irradiance in the UVR and PAR.