Comment on cp-2021-44

Seasonal cycles in ice core parameters depend on the seasonal variations of the chemical species at their source. The Introduction section of the paper seems to imply that as along as there is a source seasonal variation, seasonal cycles can be found in ice cores. However, that is not the only dependency that may determine whether seasonal cycles can be identified and utilized for dating. Tow other factors are also important in determining whether a seasonal cycle in a paramter can be found in ice cores. One is the transport process from the source area to the ice core site. Seasonal variations in source may be moderated or even erased by differences in transport efficiency during different time periods of a year. One example is sea-salt components such as Na and Mg ions. Seasalt aerosols may not be particularly more abundant in winter to many Antarctic locations; but stronger winds in winer and spring may bring higher levels of sea-salt aerosols to a site, resulting in a winter-high and summer-low seasonal pattern. The second factor is preservation of seasonal signals in snow. Water oxyegn isotope composition is an example: vapor diffussion can graually even out the difference between summer and winter, eventually smoothing out seasonal cycles completely. Another such example is nitrate: Even through nitrate is primarily produced in summer with photochemical reactions in the atmosphere, significant post-depositional change (reemission of nitrate as NOx) make the nitrate annual cycle in snow or ice unrecognizeable, such that nitrate is not a good annual layer indicator in in many places in Antarctica.