Total inorganic carbon, alkalinity, total organic carbon, and salinity measured in melted ice core sections. Full core profiles with 10-cm resolution taken weekly at Takatuk. Partial pressure of CO2 measured 2-3 times per week through peepers at three depths at each of 6 locations, 3 at Takatuk and 3 at Bruney Island. Total inorganic carbon measured coulometrically, alkalinity by potentiometric titration, organic carbon by high temperature catalytic combustion, and salinity by diffraction. pCO2 measured by gas chromatograph.

An incubation experiment was conducted on board of the Canadian research icebreaker CCGS Amundsen between 6 and 15 August 2015. The water was collected near the nitracline at 38 m depth in Baffin Bay using 12-L Niskin-type bottles deployed on a CTD rosette system. A natural Arctic plankton community in a pre-bloom stage (initial high nutrient-low Chl a concentrations) was exposed over 9 days to reduced pH conditions under two contrasting light regimes. The two light regimes were designed to simulate the mean irradiance in an ice-free 5-m thick surface mixed layer (HL, marginal ice bloom conditions) and the mean irradiance at 5 m depth under a melting ponded ice pack (LL, under-ice bloom/ subsurface chlorophyll maximum conditions). The pH gradient comprised 6 levels covering the range of pH expected between the present and the year 2300. During the incubation, a phytoplankton bloom developed in every incubation bag and diatoms dominated the biomass (Chaetoceros spp.). Temporal variations of pH, dissolved inorganic carbon, total alkalinity, chlorophyll a, macronutrients, DMS(P), flow cytometry (nano- and pico-phytoplankton, bacteria, virus), taxonomy, salinity and incubator's temperature are available.