Extreme wind waves in the Black Sea

Boris V. Divinsky ^a,, Vladimir V. Fomin ^b, Ruben D. Kosyan ^a, Yuri D. Ratner b

^a Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

^b Marine Hydrophysical Institute, Russian Academy of Sciences, Sevastopol, Russia

Results of the analysis of a long-term data set, including fields of significant waveheights of the surface wave components, and mixed (total) wave field in the Black Sea arepresented. The data set was collected on the basis of retrospective calculations using the MIKE21 SW spectral wave model with the atmospheric forcing based on the ERA-Interim data in theperiod from 1979 to 2017. A criterion is used to isolate the swell waves from the initial wave dataset that takes intoaccount the wave age. We used the experimental data to develop a regressionrelationshipshowing that the maximum possible wave height can exceed the significant waveheightapproximately one and a half times. Analysis of the spatial distribution of wave heights intheBlack Sea suggests that a possibility exists that significant wave height of storm waves can beas high as 12 m. This result indicates that the actual heights of maximum waves in the Black Seacan reach 18—19 m. Three regions are distinguished on the basis of the wave potential. Thetimesof manifestation of extreme situations in these regions are different: in the southwestern part ofthe sea, extreme storm situations occur, as a rule, in December—January; in the region south ofthe Crimea Peninsula this happens in February; in the northeastern part of the sea they occur inNovember. It was also found that the south-southeastern and eastern parts of the sea are mostaffected by swell.

https://doi.org/10.1016/j.oceano.2019.06.003

Maximum waves in the Black Sea

Divinskii B¹., Fomin V²., Kosyan R^1,3., Lazorenko D².

¹Shirshov Institute  of Oceanology RAS, Moscow, Russia

²Marine Hydrophysical Institute RAS, Sevastopol, Russia

In this paper, a comparison of the wind waves parameters calculations in the Black and Azov seas, using two common spectral wave models: DHI MIKE 21 SW and SWANwas made. The fields of the wind waves main parameters (wave heights, periods, directions of propagation) were obtained for a climatic period of time from 1979 to 2018. Comparison of the calculation results shows that with the accepted model settings, the SWAN model, compared with MIKE, overestimates the values of wave heights with weak and moderate waves and underestimates with the extreme ones. Estimation of the maximum wave heights on the Black Sea, possible once in a given number of years, performed on two different models, was made. It showed that for the conditions of the Black Sea the difference between the calculated values of significant wave heights of rare frequency for the MIKE and SWAN models does not exceed 12%. The maximum significant wave heights, possible once in a hundred years, in the Black Sea can reach 11-12 m.

Chamelea gallina in the coastal waters of the Anapa bay bar (the Black Sea) as a carbonate sediment producer

Kosyan A.R^a., Divinsky B.V^b

^aSevertsov Institute of Ecology and Evolution RAS, Moscow, Russia

^bShirshov Institute  of Oceanology RAS, Moscow, Russia

The paper presents preliminary results of monitoring the population of the bivalveChamelea gallina, which is the main source of biogenic carbonates for the Anapa bay bar beaches(the Black Sea). It is shown that by 2017, the biomass of the clams decreased more than twicecompared to 2010, but began to increase in 2018. The average sizes of C. gallina are clearlydivided in terms “year” — “section” — “age”. At the same time, interannual variations of theaverage size are very strong in all age groups. The average shell length of C. gallina significantlyincreased in 2018 compared to 2016, and especially — to 2017. This may be caused by thepopulation decline of the predator Rapana venosa feeding on clams. Geographic differences inthe shell length between sections are not directly related to the distribution of biogenic elements(nitrogen and phosphorus). The differences in longevity and shell size between C. gallina fromtheAnapa region and distant populations from the other parts of the distribution area are likelyrelated to its significant negative correlation with the growth rate, which in turn negativelycorrelates with latitude.

https://doi.org/10.1016/j.oceano.2019.04.003