for heat content or changing concentrations of salinity and dissolved inorganic carbon. Estimates of ice extent are based on overall changes and not total sea ice production, therefore underestimating ice extent because some areas, such as polynyas form ice continuously from autumn to late spring. Despite these limitations, the authors express that the model quantifies the expected perturbations of the air-sea CO2 flux resulting from the sea-ice carbon pump.
CONCLUSION
This paper reviewed the processes behind the sea-ice carbon pump, a mechanism that inputs carbon into the ocean that is unique to high latitude oceans. Although biological communities play a role, the sea-ice pump is driven by the physical and chemical dynamics of sea-ice brine (both brine drainage and the precipitation/dissolution of ikaite). During autumn, as sea ice forms, impurities get rejected from the ice forming front, and accumulate in pore spaces within the ice column. Within the brine is a concentration of dissolved CO2 that enters the ocean via gravity drainage and sinks into the intermediate and deep ocean waters. During the winter, ikaite precipitates within the brine solution, further uptaking CO2. When the sea ice melts, the water column becomes stratified with the less dense, less saline water from the melt staying at the surface, the lower salinity increases the solubility of CO2, and further enhancing the CO2 flux into the ocean. Sea-ice algae uptakes CO2 via photosynthesis during the spring and summer and by producing EPS during the winter that enter the water during the spring ice melt. Although global estimates of the sea-ice carbon pump are varied and limited, they show that sea ice does not simply impede the exchange of gases between the ocean 70 | WARD
and atmosphere but instead plays an active role that is complex and should be included in global carbon models. The field of research concerning the sea ice carbon pump is still relatively new with the bulk of the research being carried out within the last decade. There are still many unknowns that need to be studied before an accurate estimation of the sea ice carbon pump can be included in global models. First, carbon flux estimates need to be completed on all types of sea ice (e.g. compact ice, open and closed pack ice, and consolidated ice) because all ice types have different thickness and horizontal extents, thus changing the amount of CO2 in flux between the atmosphere and ocean (Rysgaard et al., 2011). Secondly, the model by Rysgaard et al. (2011; see table 1) demonstrates that ikaite plays a larger role in the uptake of carbon into the ocean than previously thought. Having a better understanding of the mechanisms of the precipitation and dissolution of ikaite minerals within sea ice will provide better estimates of its role within global carbon models. Climate change will greatly impact the magnitude of the carbon flux into the ocean by the sea-ice carbon pump, particularly in changing the annual extent of sea ice. Increasing climate temperatures are expected to decrease sea ice extent, thus decreasing the magnitude of carbon taken up by the sea ice carbon pump. This will be largely felt in the Antarctic, where the majority of sea ice is first year ice (NSIDC, 2012). The effects in the Arctic will not be felt right away since a greater share of ice is multiyear-ice in comparison to the Antarctic. This ice will become first-year ice so the magnitude of the seaice carbon pump will be maintained, but only until a threshold is reached and sea ice extent becomes reduced. Quantifying the differences of carbon uptake between