Couette vs. Langmuir circulations: Comment on “On the helical flow of Langmuir circulation — Approaching the process of suspension freezing” by Dethleff, Kempema, Koch and Chubarenko

This comment suggests that flow structures observed in the laboratory work of Dethleff et al., [Dethleff, D.E. Kempema, W., Koch, R. and Chubarenko, I., 2009. On the helical flow of Langmuir circulation — approaching the process of suspension freezing. Cold Regions Sci. and Tech., 56, 50–57.] and identified by the authors as Langmuir circulations may actually be Couette circulations, structures characteristic of the primary flow instability of a sheared channel flow. The difference between the two circulations has implications for the field conditions in which “dirty ice” forms.