Integrated net primary production during POLARSTERN cruise ARK-XXVII/3 (IceArc) in 2012

Depth-integrated in situ rates were calculated for each environment as a function of the available photosynthetically active radiation (PAR). Irradiance profiles were calculated for each environment (sea ice, melt pond, water under the ice and open water) from the daily average incoming solar shortwave irradiance measured by a pyranometer (Kipp & Zonen, Delft, Netherland) mounted on the ship. We used light attenuation coefficients of 10 m**-1 for snow, 1.5 m**-1 for sea ice (Perovich, 1996) and 0.1 m**-1 for Atlantic-influenced Arctic seawater, based on literature values and observations during the cruise. Planar irradiance was transformed to scalar irradiance according to Ehn and Mundy (2013) and Katlein et al., (2014). Water column production was integrated over the euphotic zone (1% of incoming irradiance) and sea ice production over the ice core thickness. Melt pond coverage and sea ice concentration were taken into account when calculating the total primary production per area.