| 02 Apr 2026
High current speed events in a harbor channel driven by resonant sub-hourly sea level dynamics: an example from Varna, Black Sea
Abstract. Current and sea-level observations in the 2.4-km-long, 300-m-wide channel between Varna Lake and the Black Sea, conducted by three novel Hydromast stations with a 1-minute resolution, revealed that moderate sub-hourly dynamics were occasionally interrupted by high-amplitude oscillations with a period of a few tens of minutes. The resonant excitation of the events was studied using barotropic 1D analytical and numerical models. Basic features of high-intensity sub-hourly variations can be interpreted as linear barotropic long waves in a sea-channel-lake system with resonant and damped forcing. The observed 37-minute oscillations, identified from the power spectra, spectrogram, and wavelet analysis, can be explained as the first mode of the channel-lake system. Another period of 19 minutes resembles the zero, quarter-wave mode of the channel and the second mode of the channel-lake system. During the measurement period, two high-amplitude events were highlighted. One of the events is interpreted as having been caused by a meteotsunami; moderate meteorological conditions prevailed; strong channel oscillations began abruptly and lasted for a few cycles. The second event occurred more than 5 h after landward winds up to 20 m s−1. The observed maximum changes in current and sea level – up to 0.8 m s−1 and 0.8 m, respectively, over 10 minutes – are harmful to ship navigation, harbor operations, and coastal management. Building on these observations, approaches for detecting and forecasting strong sub-hourly oscillations are discussed.
This paper presents a good and worthy study of sub-hourly sea-level oscillations and currents along channels in Varna Bay. The study implements novel data, measured with novel instruments alongside existing data. Furthermore, it studies the system via analytic and numeric methods proving the characteristics of specific events of interest. It highlights the importance of theses sub-hourly oscillations and presents a theoretical framework for future prediction system.
Although the study looks valuable, some issues need to addressed before the final decision on publication is made. Most are only of technical nature. I attach the pdf file with my in-text comments for various parts of the manuscript. Below I add my general comments which you can find scattered around the pdf as well. Because some comments will likely need a change in Figure, or change in some parts of paragraphs, I propose major revision.
Before the comments I want to make clear that if you disagree with any comment or my comment is just wrong, just say it and I will accept that. For most of the in-text comments I just need an explanation on why is something done a certain way.
First bigger comment is in regards to Figures. I don't know why, but most, if not all, Figures have really low quality. Maybe that is the rendering which is made after your submission and you have uploaded higher quality Figures, I don't know but that should be changed. Additionally, a lot of Figures have really small font values and are hard to read, if not impossible. Furthermore, most Figures have titles for subplot which are not needed if the y-axis says the same thing or the caption in good clarity. On top of that, a lot of times x-axis is shared between subplots which can be the reason to omit ticks on some subplots and leave them only on the bottom ones for creating extra space. The spaces between subplots are also large for most Figures. It is better to name subplot as follows: (a) than caption for (a); (b) than caption for (b). Not stating the caption and at the end the letter of the subplot.
Link for the data repository is not working. I do not know if that an error from my side or is it wrong.