Observational data assimilation in the problem of Black Sea circulation and sensitivity analysis of its solution

The problem of the variational data assimilation of the sea-surface temperature for the model of the Black Sea dynamics has been formulated and numerically studied to reproduce surface heat fluxes. An analysis of sensitivity of the optimal solution to errors in observation data has been conducted. The results of numerical experiments have been presented.     

Gelatinous macroplankton in the Black Sea in the autumn of 2010

In October and November of 2010, the gelatinous macroplankton in the northwestern Black Sea and at the Crimean shelf was represented by the scyphozoan jellyfish Aurelia aurita, three species of ctenophores (Beroe ovata, Mnemiopsis leidyi, and Pleurobrachia pileus), and three species of hydromedusae. A. aurita was more common at the shelf, M. leidyi and P. pileus prevailed at the deeper sea stations, and B. ovata was almost ubiquitous with a biomass from below 1 to 49 g/m² A. aurita, which had an average biomass of 82–224 g/m², was dominant at all the stations. M. leidyi, which had a biomass from below 1 to 115 g/m², was recorded in October at only 14 of the 52 stations and in November at 20 of the 46 stations. The highest biomass of M. leidyi in October (105 to 116 g/m²) was recorded in the deep sea areas; in November, it was also the highest in these areas, but it reached at most 100 g/m². The average daily ration of Aurelia ranged from 19.4 to 27.3 mg/m² in October and from 7.0 to 17.2 mg/m² in November; in both cases, it was insufficient to provide for the minimal physiological requirements. The average daily ration of the Mnemiopsis population (2.8–20.5 mg of zooplankton per m²) was invariably more than sufficient to provide for the minimal physiological requirements. Both predatory species together consumed less than 5% of the daily zooplankton production of the sea.     

The effects of beach nourishment on the sandy-beach amphipod Exoediceros fossor: impact and recovery in Botany Bay, New South Wales, Australia

Beach nourishment is increasingly being implemented to address problems of erosion. However, the ecological consequences of nourishment are poorly understood, especially in Australia. In Botany Bay, sand was piped from an intertidal borrow area at Elephant's Trunk to nourish the nearby eroding beach at Towra Point. The effects on an intertidal exoedicerotid amphipod, Exoediceros fossor (Stimpson, 1856), were examined using a beyond-BACI (Before–After, Control–Impact) sampling design. Sampling was conducted before and after engineering operations at sites within the borrow and nourishment locations and multiple control locations. Hypotheses concerning impact and recovery were tested using asymmetrical ANOVAs and two-tailed F-tests. These examined the effects on abundance and spatial variability, respectively. The impact of the engineering operations on abundance was very large at both borrow and nourishment locations. However, recovery started within several weeks and, using space × time interactions as a criterion, appeared to be complete within a year. This conclusion is made cautiously because of low statistical power and because other criteria for recovery suggest that it was not complete at some sites. As beach erosion is likely to increase in severity with rising sea levels and greater storm surges associated with climate change, management authorities will need a better understanding of the ecological effects of beach nourishment.     

Interactions between sediment chemistry and frenulate pogonophores (Annelida) in the north-east Atlantic

The small frenulate pogonophores (Annelida: Pogonophora a.k.a. Siboglinidae) typically inhabit muddy sediments on the continental slope, although a few species occur near hydrothermal vents and cold seeps. We present data on the distribution and habitat characteristics of several species on the European continental shelf and slope from 48°N to 75°N and show how the animals interact with the chemistry of the sediments. The environments inhabited include: shallow (30 m), organic-rich, fjord sediments; slope sediments (1000–2200 m) and methane seeps at 330 m depth. All the species studied obtain nutrition from endosymbiotic bacteria. They take up reduced sulphur species, or in one case, methane, through the posterior parts of their tubes buried in the anoxic sediment. We conclude that most species undertake sulphide ‘mining’, a mechanism previously demonstrated in the bivalves Lucinoma borealis and Thyasira sarsi. These pogonophores participate in the sulphur cycle and effectively lower the sulphide content of the sediments. Our results show that the abundance of frenulate pogonophores increases with increasing sedimentation and with decreasing abundance of other benthos, particularly bioturbating organisms. The maximum sustainable carrying capacity of non-seep sediments for frenulate pogonophores is limited by the rate of sulphate reduction.     

Influence of chemical composition and microstructure on the hygroscopic growth of pyrogenic aerosol

The hygroscopic properties of a model smoke aerosol series including ammonium sulfate, levoglucosan, and oxalic and humic acids were investigated. The condensation growth of particles and the relative humidity of direct and inverse particle-droplet phase transitions were measured with a tandem differential mobility analyzer. The data were obtained in the range of relative humidity from 4 to 95% at 298 K. Experimental growth factors were compared to the results of Koehler theory by using contemporary models of water activity in particles. It was shown that the hygroscopic properties of the aerosols were substantially different from the hygroscopic properties of the corresponding bulk phases. It was found that a complex microstructure of nanoparticles resulted in excess volume absorption of water, in some cases causing their full deliquescence at lower relative humidities than in macrosystems of identical composition. From the measurement data, a parametrization of hygroscopic particle growth was performed. The results of parametrization can be used to construct refined models of a smoke aerosol.     

Concentration and Diffusion of Nutrients in the Interpore–Bottom Water System of the Ob River Estuary

Oceanology - On cruise 76 in 2019, the R/V Akademik Mstislav Keldysh completed the Gulf of Ob–Kara Sea slope transect. Samples of bottom water and two sediment layers 1 cm thick were obtained...     

Field Research in the Baltic Sea on Cruise 55 of the P/V Akademik Ioffe

Oceanology - New data on the structure of the water column, upper layer of bottom sediments, and biological communities of the Gdansk and Gotland deeps and the Gulf of Finland in the Baltic Sea...     

Vertical Variability of Primary Production and Chlorophyll a in the Kara Sea in the Middle of Summer: Contribution of Subsurface Maxima to the Water Column Values

Oceanology - Spatial and vertical variability of primary production (PP) and Chl a were studied in the framework of the 76th cruise of R/V Akademik Mstislav Keldysh to the Kara Sea from July 7 to...     

Potential Vorticity in the Ocean: Ertel and Rossby Approaches with Estimates for the Lofoten Vortex

Izvestiya, Atmospheric and Oceanic Physics - The potential vorticity (PV) in the ocean is considered, including the history of the term. Various aspects and basic formulas used to calculate the PV...