|The authors have added some word of caution regarding the lack of inclusion of other proven halogen activation mechanisms, which will be valuable to the community as we explore the relative roles of blowing snow activation versus snowpack and/or other mechanisms. |
These other mechanisms were cited, in the introduction, but the citation didn't really explain that snowpack mechanisms have been shown to activation halogens. The sentence in which relevant papers are cited is:
"Proposed candidates for reactive bromine release include e.g., frost flowers (Kaleschke et al. 2004), first-year sea ice (Skov et al., 2004; Simpson et al., 2007b), sea salt aerosol (SSA) produced from blowing snow (Yang et al., 2008; 2010), snowpack (e.g., Pratt et al., 2013; Custard et al., 2017), SSA from open leads (Kirpes et al., 2019). "
It is true that those authors had proposed these "candidates", but they did it based upon solid field evidence that snowpack produces reactive halogens. Pratt et al. 2013 showed that snowpack does in fact produce reactive halogens. Custard et al. 2017 provided further evidence that snowpack activation happens. Kirpes et al. 2019 shows field evidence for SSA from open leads. The authors should state explicitly in this section that these manuscripts indicate that other forms of halogen activation other than blowing snow have been demonstrated in the field and that SSA can be produced by leads. They have also been modeled (e.g. Toyota et al., Thomas et al. citations). In the end, a critical question will be what the balance of halogen activation via blowing snow versus other mechanisms is. Scaling of one mechanism or the other is likely to be able to match monthly averages, but that doesn't mean that we have actually determined which process is more important.