Observations made over the last decade suggest an important role ofsea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice;(ii) a permeable sea ice cover, allowing fluid and gas exchanges at the sea ice interface; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Micro-organisms thrive in sea ice, extending the production season, providing a winter and early spring food source, and significantly contributing to organiccarbon export at depth. Ice retreat can be preceded by pelagic under-ice blooms and followed by so-called ice edge phytoplankton blooms, triggered by increased upper ocean stratification due to freshening and potentially by the release of light limitation, as well as by the release of material from the melting sea ice. Due to brine rejection and relatively small brine volume fractions, nutrients in bulk sea ice are usually not abundant, but their high concentration in brine inclusions and replenishment mechanisms usually maintain quite viable levels of nutrients. Iron, a key micronutrient – limiting phytoplankton growth in high-nutrient, low-chlorophyll areas, such as the North Pacific and Southern Oceans – is peculiar: sea ice can carry large loads of iron, which, when released in the water column by melting ice, can relieve iron limitation of phytoplankton growth. Inorganic carbon transport by brines sinking below the sea ice, calcium carbonate precipitation in sea ice, as well as active ice-atmosphere CO2 fluxes, most likely play a central but poorly understood role in the polar ocean CO2cycle. Additionally, sea ice is a potential major contributor to the sulphur cycle in the Polar oceans through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulfate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet.The sea ice zone is also suspected to be an active source of methane in the Arctic Ocean. Finally, saline ice surfaces activate atmospheric bromine chemistry in spring, responsible for the springtime tropospheric ozone depletion events observed in both Polar Regions. A quantification of polar marine biogeochemical processes at large-scales is of high priority, as Polar Regions will rapidly and significantly change in this century.Earth System models are the most promising tools to evaluate this, but they currently represent sea ice as biologically and chemically inert. Including a better representation of those processes in Earth System models should help us understand the potential responses of the polar oceans to human activities and evaluate their impact on the climate, biogeochemistry and ecosystems at planetary scales. In addition, the analysis of glacial and marine sediment core data should give us information on the past evolution of these processes and help us to assess their importance. Sea ice proxies, integrating information of past sea ice characteristics at long climatological time scales, would not only benefit from but also contribute to a better understanding of polar marine biogeochemistry.
Vancopennolle, Martin ; Meiners , Klaus M. ; Michel, Christine ; Bopp, Laurent ; Brabant, Frederic ; et. al. Large-scale interactions between sea ice and polar marine biogeochemistry: emerging views on the relevant processes and their modelling. In: Quaternary Science Reviews,