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Abstract Solute exclusion during sea ice formation is a potentially important contributor to the Arctic Ocean inorganic carbon cycle that could increase as ice cover diminishes. When ice forms, solutes are excluded from the ice matrix, creating a brine that includes dissolved inorganic carbon (DIC) and total alkalinity (A_T). The brine sinks, potentially exporting DIC andA_Tto deeper water. This phenomenon has rarely been observed, however. In this manuscript, we examine a ~1 yearpCO₂mooring time series where a ~35‐μatm increase inpCO₂was observed in the mixed layer during the ice formation period, corresponding to a simultaneous increase in salinity from 27.2 to 28.5. Using salinity and ice based mass balances, we show that most of the observed increases can be attributed to solute exclusion during ice formation. The resultingpCO₂is sensitive to the ratio ofA_Tand DIC retained in the ice and the mixed layer depth, which controls dilution of the ice‐derivedA_Tand DIC. In the Canada Basin, of the ~92 μmol/kg increase in DIC, 17 μmol/kg was taken up by biological production and the remainder was trapped between the halocline and the summer stratified surface layer. Although not observed before the mooring was recovered, this inorganic carbon was likely later entrained with surface water, increasing thepCO₂at the surface. It is probable that inorganic carbon exclusion during ice formation will have an increasingly important influence on DIC andpCO₂in the surface of the Arctic Ocean as seasonal ice production and wind‐driven mixing increase with diminishing ice cover. 

A new special collection in JGR: Oceans presents results from studies of the Beaufort Gyre, an oceanic circulation system in the Arctic that has far-reaching influence on the global climate. 

Several recent field efforts have revealed surprisingly complex and dynamic thermohaline structure in the upper ocean of the Beaufort Sea. Solitary and compact eddies with strong temperature contrasts and currents have been observed in multiple locations and are associated with vigorous mixing, staircase structure and intrusive feature formation. While many of the eddies are primarily found in the upper 300-m of the water column, rare deep eddies with cores near 500 to 1000-m depth have also been observed. Internal waves are generally weak with energies an order of magnitude less than mid-latitude values and they show marked dominance by near inertial waves, intermittency, spatial inhomogeneity, and deviations from the Garrett-Munk model. Strong intrusive structure, termed spice, is observed in the upper 150-m of the water column and is associated with the mixed layer and eddy activity. Acoustic implications of the associated sound speed structure will be discussed. 

A coordinated set of Arctic modeling experiments is proposed which explore how the Arctic responds to changes in external forcing. Our goal is to compute and compare 'Climate Response Functions' (CRFs) – the transient response of key observable indicators such as sea-ice extent, freshwater content of the Beaufort Gyre etc. – to abrupt 'step' changes in forcing fields across a number of Arctic models. Changes in wind, freshwater sources and inflows to the Arctic basin are considered. Convolutions of known or postulated time-series of these forcing fields with their respective CRFs then yields the (linear) response of these observables. This allows the project to inform, and interface directly with, Arctic observations and observers and IPCC models and the climate change community. Here we outline the rationale behind such experiments and illustrate our approach in the context of a coarse-resolution model of the Arctic based on the MITgcm. We conclude by outlining the expected benefits of such an activity and encourage other modeling groups to compute CRFs with their own models so that we might begin to document how robust they are to model formulation, resolution and parameterization.