Variability in sea ice carbonate chemistry: a case study comparing the importance of ikaite precipitation, bottom-ice algae, and currents across an invisible polynya

Abstract. The carbonate chemistry of sea ice is known to play a role in global carbon cycles, but its importance uncertain part due disparities reported results. Variability physical and biological drivers usually invoked explain differences between studies. In the Canadian Arctic Archipelago, “invisible polynyas” – areas strong currents, thin ice, potentially high productivity are examples extreme spatial variability. We used an invisible polynya as natural laboratory study effects inferred initial formation conditions, growth rate, algal biomass on distribution species by collecting enough cores perform statistical comparison sites located within, just outside of, near Iqaluktuttiaq (Cambridge Bay, Nunavut, Canada). At both sites, uppermost 10 cm horizon showed evidence CO2 off-gassing, while distributions middle bottommost horizons largely followed salinity distribution. polynya, upper had significantly higher bulk total inorganic (TIC), alkalinity (TA), freeze-up conditions that favoured frazil production. were statistically indistinguishable suggesting rate not important factor for under mid-winter conditions. thicker (non-polynya) site experienced biomass, TIC, TA bottom horizon. Carbonate could be explained distribution, with currents at playing desalinization; biology appeared exert only minor control, some algae community was net heterotrophic. did see calcium precipitation little impact TIC:TA ratio difference sites. Because constrained relatively layers top bottom, vertically averaged values TA, especially meaningfully different This provides justification using single value each parameter when modelling ocean coarse resolution. Exactly what use (particularly ratio) likely varies region approximated from knowledge source seawater salinity. Further insights await rigorous intercomparison existing data.