In order to properly forecast the effects of climate change, general circulation models need to adequately account for sources and sinks of CO2. The global marine system plays a major role in cycling CO2 and presently absorbs about 2.2 PgC year−1 [Denman et al., 2007], which offsets about 30% of present anthropogenic emissions. However, the rate of CO2 uptake is not consistent across all oceans. On an annual basis a given region may behave anywhere on the spectrum from a strong source of CO2 to a strong sink, and significant inter- and intra-annual variability may also exist [Takahashi et al., 2009]. This spatiotemporal variability arises from variability in the processes controlling CO2 fluxes.
 For the open ocean, research has advanced to the point where these processes are known well enough to make reasonable flux estimates at a wide range of scales (see review by Wanninkhof et al. ). Typically, estimates of CO2 flux are computed using a form of the bulk flux equation:
where α is the solubility of CO2 in water, pCO2sw is the partial pressure of CO2 in the surface seawater, pCO2air is the partial pressure of CO2 in the atmosphere and k is the gas transfer velocity. Using this approach, the air-sea gradient of CO2 (pCO2sw − pCO2air, commonly denoted ΔpCO2) determines the potential for exchange, while the transfer velocity encompasses the processes that control the rate at which the exchange can occur. The main determinant of transfer velocity is water-side turbulence, which itself is mainly determined by wind velocity through its relationship with momentum flux [Jähne, 1987]. Many other factors influence water-side turbulence, such as wave state [Bock et al., 1999; Zappa et al., 2004], surface films [Jähne, 1987; Frew et al., 2004; Frew, 1997], rain [Ho et al., 2004; Takagaki and Komori, 2007; Zappa et al., 2009], tides [Zappa et al., 2007], and buoyancy [McGillis et al., 2004]. In addition, several processes not directly related to turbulence also affect transfer velocity, such as chemical enhancement [Bolin, 1960; Kuss and Schneider, 2004] and bubbles from breaking waves [Asher et al., 1996; Woolf, 1997; Woolf et al., 2007]. Despite the myriad processes affecting gas exchange, wind velocity alone is typically used to estimate transfer velocity in the open ocean with mature wavefields [Wanninkhof et al., 2009]. As such, numerous parameterizations to estimate k from wind speed have been created based on tank experiments [Liss and Merlivat, 1986], modeling exercises [Wanninkhof, 1992; Sweeney et al., 2007], and field studies conducted primarily at low and midlatitudes [Ho et al., 2006; Nightingale et al., 2000; Wanninkhof and McGillis, 1999].
 At high latitudes (e.g. the Arctic), the processes that control CO2 fluxes are not well known. Depending on the season and location, a given region of the Arctic Ocean may be ice free or it may be covered by sea ice of variable concentration, thickness and thermodynamic state. During the open water season it is reasonable to assume that what we understand about open-ocean fluxes would be applicable, but as soon as sea ice is present existing parameterizations of transfer velocity are likely invalid. Although sea ice is permeable to gas exchange under certain conditions [Gosink et al., 1976], the mechanisms that control the rate of exchange are very different from the open ocean. Furthermore, the open water that does remain in an icescape experiences different controls on near-surface turbulence; fetch limitations [Woolf, 2005] imposed by surrounding ice floes and the generation of turbulence due to ice formation [McPhee and Stanton, 1996] are two examples of those unique controls.
 The initial freezeup and growth of sea ice has generated considerable interest, since the process significantly modifies the chemistry of the surface ocean and because dissolved inorganic carbon (DIC) may be driven down from the surface with rejected brines in what has been termed a sea ice CO2 pump [Rysgaard et al., 2007, 2009; Anderson et al., 2004]. A water column study by Anderson et al.  in Svalbard found high DIC and elevated chlorofluorocarbon levels in deep waters, which they hypothesized originated from enhanced air-sea exchange of CO2 during ice formation. Some support for this enhanced exchange was recently presented in a tank study by Loose et al. . In this paper, we describe the first eddy covariance observations of such flux enhancements over a natural sea ice surface.