Measurements of transmitted irradiance under sea ice and corresponding incident solar radiation at the surface have been performed on multi-year ice during the Oden_AO18 campaign (Arctic Ocean 2018: MOCCHA – ACAS - ICE) Central Arctic / North Pole drift station between 19 August and 13 September 2018. The radiation measurements have been performed with Ramses spectral radiometes (TriOS, Rastede, Germany). All data are given in full spectral resolution interpolated to 1.0 nm, and integrated over the entire wavelength range (broadband, total: 320 to 950 nm). The irradiance sensor (cos-collector) was installed on the ROV. The transmittance is the ratio between transmitted irradiance and incident irradiance. All times are given in UTC.