Irradiance data at different depths and sites for field sampling in the Arctic fjord Kongsfjorden

Kelps act as ecosystem engineers and foundation species on many polar rocky shore coastlines. The main driver for their vertical and latitudinal distribution is the underwater light climate and temperature. Both are changing drastically in the Arctic in the course of global climate change. It was the aim of this study to analyse the effects of rising temperature and deteriorating underwater light climate on the potential habitat of kelps in the Arctic. The analyses of the underwater light climate in Arctic Kongsfjorden, Svalbard in July 2021. We divided Kongsfjorden in three areas, which are influenced by the run-off of sea-terminating glaciers (station A–J), the run-off of a land-terminating glacier (station K–O) and mostly clear water (control, station P–Q). In each area, we measured the spectrally resolved underwater light climate in the UV-B radiation (280-320 nm), UV-A radiation (320-400 nm) and photosynthetically active radiation (PAR, 400-700 nm) with a RAMSES-ACC-UV/VIS radiometer (TriOS Optical Sensor, Oldenburg, Germany) from 0–12.5 m. UV-B, UV-A and PAR were calculated by integrating the irradiance over the respective wavelengths.