Causes of Abnormally Low Concentrations of Dissolved Oxygen on Decadal Time Scales in the Northwestern Black Sea

Biomass and Size Composition of the Comb Jelly Mnemiopsis sp. in the North-western Black Sea During Spring 1997 and Summer 1995

The Atlantic Meridional Overturning Circulation (AMOC) variability is suggested to be incoherent between the subpolar and subtropical gyres in the Atlantic on interannual and even decadal time scales, questioning the representativeness of AMOC variability at a single latitude in modern observation and paleoreconstruction. Paleoreconstructions of the Florida Current transport suggest that Florida Current variability is associated with the AMOC on the millennial time scale, but the Rapid Climate Change (RAPID) mooring array suggests a weak correlation between the Florida Current and the AMOC. In this study, we investigate the meridional coherence of AMOC variability and the relationship between the Florida Current variability and the AMOC variability on different time scales in a transient 20,000‐year simulation. We find that with the increase of time scales, the meridional coherence of the AMOC increases. On decadal and longer time scales, the coherent subtropical and subpolar AMOC is caused by the coherent buoyancy forcing in the subpolar gyre. Also, the Florida Current transport is highly correlated with AMOC variability on decadal and longer time scales, suggesting that observations of the Florida Current can be used to indicate AMOC variability on long time scales.

Features of decadal–multidecadal variations of the Asian summer rainfall are revealed by analysis of the reconstructed Asian summer precipitation (RAP) dataset from 1470 to 2013. Significant low-frequency periodicities of the all-Asian rainfall (AAR) index (AARI) are found on decadal (8–10 yr), quasi-bidecadal (22 yr), and multidecadal (50–54 yr) time scales, as well as centennial time scales. The decadal and multidecadal peaks are mainly from the “monsoon Asia” area and the Maritime Continent, while the 22-yr peak is from the “arid Asia” area. A remarkable change of leading frequency from multidecadal to decadal after AD 1700 is detected across the entire Asian landmass. The leading empirical orthogonal function (EOF) modes on the decadal and multidecadal time scales exhibit a uniform structure similar to that on the interannual time scale, suggesting a cross-time-scale, in-phase variation of the rainfall across continental Asia and the Maritime Continent. Enhanced AAR on a decadal time scale is found associated with the mega-La Niña sea surface temperature (SST) pattern over the Pacific. The AARI–mega-ENSO (El Niño–Southern Oscillation) relationship is persistently significant except from 1820 to around 1900. Enhanced decadal AAR is also found to be associated with extratropical North Atlantic warming. The AARI–AMO (Atlantic multidecadal oscillation) relationship, however, is nonstationary. On the multidecadal time scale, the AAR is significantly related to the AMO. Mechanisms associated with the decadal–multidecadal variability of AAR are also discussed.

Upper Quaternary water level history and sedimentation in the northwestern Black Sea

Interannual–decadal variability of tropical cyclone (TC) track density over the North Atlantic (NA) between 1979 and 2008 is studied using observations and simulations with a 25-km-resolution version of the High Resolution Atmospheric Model (HiRAM) forced by observed sea surface temperatures (SSTs). The variability on decadal and interannual time scales is examined separately. On both time scales, a basinwide mode dominates, with the time series being related to variations in seasonal TC counts. On decadal time scales, this mode relates to SST contrasts between the tropical NA and the tropical northeast Pacific as well as the tropical South Atlantic, whereas on interannual time scales it is controlled by SSTs over the central–eastern equatorial Pacific and those over the tropical NA. The temporal evolution of the spatial distribution of track density is further investigated by normalizing the track density with seasonal TC counts. On decadal time scales, two modes emerge: one is an oscillation between track density over the U.S. East Coast and midlatitude ocean and that over the Gulf of Mexico and the Caribbean Sea and the other oscillates between low and middle latitudes. They might be driven by the preceding winter North Atlantic Oscillation and concurrent Atlantic meridional mode, respectively. On interannual time scales, two similar modes are present in observations but are not well separated in HiRAM simulations. Finally, the internal variability and predictability of TC track density are explored and discussed using HiRAM ensemble simulations. The results suggest that basinwide total TC counts/days are much more predictable than local TC occurrence, posing a serious challenge to the prediction and projection of regional TC threats, especially the U.S. landfall hurricanes.

There is growing interest on whether changes in the Atlantic meridional overturning circulation (AMOC) may have an impact on regional sea surface height (SSH) variability. In this study, we investigate the impact of differing AMOC strengths and trends and their effect on SSH anomalies on decadal variability and centennial model drift. We use a series of six experiments with the 1/20° VIKING20X model configuration, repeatedly and subsequently following the atmospheric forcing from 1958 to 2019 under the Ocean Model Intercomparison Project (OMIP)-II protocol yielding 372 model years in total. Consistent across all experiments, the decadal variability of AMOC is associated with a tripole pattern of SSH variability. A weaker AMOC correlates with a local SSH increase along the Northeast U.S. coast and western subpolar gyre (SPG). In our simulation, this is related to an increased ocean heat and salt content, where thermosteric changes dominate over halosteric variations. On longer time scales, the same tripole pattern emerges but predominantly caused by the halosteric effect. Although a strong linear relationship exists between AMOC and SSH, the regression slope differs between decadal and longer time scales. This challenges the suggested use of SSH as a potential fingerprint of AMOC strength, particularly on longer than decadal time scales. Significance Statement With this study, our aim is to understand how basin-scale circulation variations of the Atlantic Ocean are related to changes in regional sea level on decadal time scales. This is of major importance to better constrain the expected future evolution of sea level along the coasts and vice versa to infer knowledge of circulation changes from sea level estimates. In contrast to ocean currents, sea level can be observed basinwide by satellites and tide gauge records along the Atlantic coast date back much further than direct ocean current measurements.

Water Constituents in the North-western Black Sea from Optical Remote Sensing and In situ Data

The Indian Ocean has received increasing attention for its large impacts on regional and global climate. However, sea surface temperature (SST) variability arising from Indian Ocean internal processes has not been well understood particularly on decadal and longer time scales, and the external influence from the tropical Pacific has not been quantified. This paper analyzes the interannual-to-decadal SST variability in the tropical Indian Ocean in observations and explores the external influence from the Pacific versus internal processes within the Indian Ocean using a linear inverse model (LIM). Coupling between Indian Ocean and tropical Pacific SST anomalies (SSTAs) is assessed both within the LIM dynamical operator and the unpredictable stochastic noise that forces the system. Results show that the observed Indian Ocean basin (IOB)-wide SSTA pattern is largely a response to the Pacific ENSO forcing, although it in turn has a damping effect on ENSO especially on annual and decadal time scales. On the other hand, the Indian Ocean dipole (IOD) is an Indian Ocean internal mode that can actively affect ENSO; ENSO also has a returning effect on the IOD, which is rather weak on decadal time scale. The third mode is partly associated with the subtropical Indian Ocean dipole (SIOD), and it is primarily generated by Indian Ocean internal processes, although a small component of it is coupled with ENSO. Overall, the amplitude of Indian Ocean internally generated SST variability is comparable to that forced by ENSO, and the Indian Ocean tends to actively influence the tropical Pacific. These results suggest that the Indian–Pacific Ocean interaction is a two-way process.

Piebaldism is one of three types of hypopigmentation of animals, when some areas on the skin have no pigments. Anomalously white cetaceans are rare, although they have been reported in more than 20 different cetacean species, including the common bottlenose dolphin, which in the Black Sea is recognized as an endangered endemic subspecies — the Black Sea bottlenose dolphin (Tursiops truncatus ponticus Barabash-Nikiforov, 1940). Its main habitat in the north-western Black Sea region is the coastal waters, however, these dolphins also occur offshore. Thirty cases of anomalously white bottlenose dolphins have been reported from the Black Sea, which were unevenly distributed, and only a few sightings have been reported from the north-western Black Sea. Cetacean observations were conducted in the Ukrainian part of the north-western Black Sea waters in April 2017, onboard the research vessel "Auguste Piccard". All encountered cetaceans were photographed, and individual distinctiveness of dorsal fin images was used for their photo-identification. On 13 April 2017, four groups of up to four individuals of bottlenose dolphins were encountered in the same area at a distance of 61 km south of Odesa (34 km from the nearest coast). The depth at the observation site was about 20 m. The initially observed type of dolphins’ behavior was feeding. However, two groups changed their behavior and followed the vessel by 5–6 individuals for approximately 18 minutes. The joint group consisted of adults and one juvenile individual. Among the adults, there was one piebald specimen with white patches on its dorsal fin, peduncle, and tail fluke. The piebald dolphin was photographed and photo-identified. Our research has shown that piebald Black sea bottlenose dolphins occur not only in the coastal waters, but also in offshore waters of the north-western Black Sea. However, the frequency of such hypopigmentation in local populations remains unknown. Further intensive photo-identification and genetic sampling of local stocks of the Black Sea bottlenose dolphins are necessary for the assessment of their population genetic structure and its divergence.

Изучение таксоцена Annelida (Polychaeta), эпибионтов брюхоногого моллюска — вселенца Rapana venosa, продолжает цикл по описанию состава консорции самого крупного брюхоногого моллюска черноморского бентоса. Консорция R. venosa до сих пор является мало исследованной и неучтённой компонентой в структуре биоценозов шельфа Чёрного моря. Цель данной работы — изучить комплекс полихет консорции R. venosa. Задачи этого этапа: составление списка таксонов Annelida (Polychaeta) — эпибионтов рапаны; изучение биогеографической и трофической структуры таксоцена; исследование экологических связей полихет с ядром консорции. Для изучения консортного сообщества рапаны были осуществлены сборы в семи районах северной части Чёрного моря: 1 — Мамайя, Румыния; 2 — северо-западная часть Чёрного моря, Крымский сектор; 3 — Севастополь; 4 — Алупка; 5 — Ялта — Алушта; 6 — Карадаг; 7 — Керченский пролив. Сбор R. venosa в прибрежной зоне до глубины 15 м проводили тотально с использованием легководолазного оборудования, в более глубоководной зоне (до 40 м) — дночерпателем «Океан-50» с борта НИС «Профессор Водяницкий». Каждый экземпляр (пробу) рапаны помещали в отдельный пластиковый пакет с указанием района, глубины и биотопа. Всего отобрано и проанализировано 2411 проб, из них 977 — скальной рапаны и 1434 — песчаной. Покрытие эпибионтами раковины R. venosa (интенсивность обрастания) оценивали в процентах от общей площади внешней поверхности раковины. Таксоцен Polychaeta консорции R. venosa включает 31 вид, представляющий 31 род 15 семейств 2 подклассов. Бόльшая часть видов (18) относится к Errantia, половину из них составляют представители семейств Nereididae и Syllidae. К Sedentaria относятся 13 видов; наибольшее их количество (4) принадлежит семейству Serpulidae. Таксоцен Polychaeta консорции рапаны представлен тремя биогеографическими группами: аборигенные виды средиземноморско-атлантического генезиса (84 %), эндемики Чёрного моря (10 %) и современные виды-вселенцы различного географического генезиса (6 %). На песчаной рапане обнаружен 31 вид полихет, а на скальной — только 5. Показатели развития фауны полихет значительно различаются по глубинам и районам исследований. Наиболее разнообразны полихеты в бухтах г. Севастополя (район № 3) на глубинах 2–10 м; максимальная глубина обнаружения полихет (40 м) соответствует наибольшей глубине отбора рапаны. Площадь покрытия раковины рапаны полихетами достигает 70 %, встречаемость в отдельных районах составляет до 95 %. Максимальное число видов, обнаруженных на отдельном экземпляре рапаны, — 8; в среднем на особях R. venosa отмечено 2–4 вида полихет. Таксономическое разнообразие и обилие Polychaeta определяют их значимость в консорции R. venosa. Благодаря инвазионному хищному моллюску R. venosa полихеты получают дополнительные возможности для распространения на шельфе Чёрного моря.

Biogeochemical Transformations of Inorganic Nutrients in the Mixing Zone between the Danube River and the North-western Black Sea

The ichthyofauna of the Black Sea is comparatively poor and includes about 200 species (Boltacev 2003). The gobiid fishes (Actinopterygii: Gobiidae) are a large group of approximated by 28 species inhabiting coastal habitats of the Black Sea (Miller 1986, Smirnov 1986, Rass 1993). Five Black-Sea gobiid species are important commercially (Smirnov 1986) and they have also been targeted by anglers. In the north-western Black Sea (NWBS), gobiids can be found in different salinities ranging from fresh water (0.5‰ salinity off the Dniester River mouth) to full-salinity sea water (30‰–35‰ in the Tuzly group of lagoons). These fish make up two groups according to their origin: 1) Ponto-Caspian relict species that are endemics of the Sarmatic and Pontic basins; typical representatives of this group are: Mesogobius batrachocephalus (Pallas, 1811); ACTA ICHTHYOLOGICA ET PISCATORIA (2005) 35 (2): 103–110

Establishment of “Zernov’s Phyllophora field” marine reserve: Protection and restoration of a unique ecosystem

Man induced change in community control in the north-western Black Sea: The top-down bottom-up balance

Two new fish species were recorded while monitoring the fish fauna of Sukhyi Lyman (or Sukhyi Estuary), an estuary in the northwestern Black Sea (Ukraine) close to the marine port of Chornomorsk. A single pumpkinseed, Lepomis gibbosus (Linnaeus, 1758), was observed in May 1999, followed by numerous observations in May 2021, while a single peacock blenny, Salaria pavo (Risso, 1810), was photographed during snorkeling observations in September 2021. The estuary is a known hub for invasive alien species and other neobionts due to the presence of the marine port. The new population of pumpkinseed, a North American invasive species, in the estuary represents the next stage in the species’ ongoing expansion along the Ukrainian Black Sea coast. Likewise, the appearance of the peacock blenny represents the latest stage in the “Mediterranization” of the Black Sea, a process that has been ongoing over the last several thousand years.