Budget of sediments and forecast of long-term coastal changes

A method for predicting the coast evolution based on the calculated estimates of the components of the sediment budget is discussed. The approaches outlined in a series of previous publications of the author [9, 10, 11] are further developed. The prerequisites and concepts used as the basis of the suggested method for forecasting are characterized. The sediment budget parameters under typical conditions are presented. The contributions of natural processes and the anthropogenic impact are compared. Different approaches for calculating the principal sediment budget components, including the cross-shore flux through the lower boundary of the coastal zone, the eolian flux of sand material through the upper limit of the coastal zone, and the alongshore sediment flux gradients, are considered. The examples of forecasting the development of coasts in the Baltic and Kara seas and the Sea of Okhotsk are given for the period from 100 to 500 years. The results obtained show that, in the case of a balanced budget of the sediments, the future behavior of the coast would be mainly governed by the variations in the sea level. This factor is capable of determining the changes in the coastline, whose recession and advancing would depend on the rate of the sea level rise. Under specific conditions, an enhanced sea level rise can trigger destructive processes (for example, the erosion of a coastal bar or the thermal abrasion of a cliff). In the case of a strong imbalance in the sediment budget, sea-level changes play a subordinate role.     

On the reliability of millennial reconstructions of variations in surface air temperature in the Northern Hemisphere

The reliability of the recently published reconstructions of the surface air temperature variability in the Northern Hemisphere over the past 2000 yr is discussed. For this purpose, the power spectra of the two best known reconstructions (Mann et al.[10–12] and Moberg et al. [13]) are calculated and compared to the spectra of the 150-yr temperature series based on instrumental observations and simulated 1000-yr series. It is found that the Mann et al. reconstruction drastically underestimates low-frequency temperature variations, whereas the Moberg et al. reconstruction reproduces them much better, although with a certain underestimation rather than overestimation, as Mann et al. have recently argued.     

The seasonal cycle of surface chlorophyll in the Peruvian upwelling system: A modelling study

The seasonal variability of surface chlorophyll in the northern Humboldt Current System is studied using satellite data, in situ observations and model simulations. The data show that surface chlorophyll concentration is highest in austral summer and decreases during austral winter, in phase opposition with coastal upwelling intensity. A regional model coupling ocean dynamics and biogeochemical cycles is used to investigate the processes which control this apparently paradoxical seasonal cycle. Model results suggest that the seasonal variability of the mixed layer depth is the main controlling factor of the seasonality. In winter, the mixed layer deepening reduces the surface chlorophyll accumulation because of a dilution effect and light limitation. In summer, biomass concentrates near the surface in the shallow mixed layer and nitrate limitation occurs, resulting in a biomass decrease in the middle of summer. Intense blooms occur during the spring restratification period, when winter light limitation relaxes, and during the fall destratification period, when the surface layer is supplied with new nutrients. Model sensitivity experiments show that the seasonal variations in insolation and surface temperature have little impact on the surface chlorophyll variability.     

Enhanced concentrations of dissolved gaseous mercury in the surface waters of the Arctic Ocean

During an almost three months long expedition in the Arctic Ocean, the Beringia 2005, dissolved gaseous mercury (DGM) was measured continuously in the surface water. The DGM concentration was measured using an equilibrium system, i.e. the DGM in the water phase equilibrated with a stream of gas and the gas was thereafter analysed with respect to its mercury content. The DGM concentrations were calculated using the following equation, DGM = Hg_eq / k_H' where Hg_eq is the equilibrated concentration of elemental mercury in the gas phase and k_H' is the dimensionless Henry's law constant at desired temperature and salinity. During the expedition several features were observed. For example, enhanced DGM concentration was measured underneath the ice which may indicate that the sea ice acted as a barrier for evasion of mercury from the Arctic Ocean to the atmosphere. Furthermore, elevated DGM concentrations were observed in water that might have originated from river discharge. The gas-exchange of mercury between the ocean and the atmosphere was calculated in the open water and both deposition and evasion were observed. The measurements showed significantly enhanced DGM concentrations, compared to more southern latitudes.     

Seasonal evolution of the mediterranean water propagation in the north Atlantic

The Climatic variability of the seasonal water exchange in the Strait of Gibraltar and the spatial structure of the tongue of the Mediterranean Waters (MW) in the Atlantic Ocean are studied. The analysis is based on the results of a numerical experiment using a 3D ocean circulation model developed at the Institute of Computational Mathematics (ICM RAS) with a resolution of the dataset over the latitude and longitude equal to 0.25 degree. The seasonal evolution of the salinity and density fields is calculated in the North Atlantic (from 20 °S, including the Mediterranean Sea) and in the Arctic Ocean (including the Bering Sea). The comparison of the model estimates with the results of field observations demonstrated good agreement. The transport of the MW into the Atlantic is close to the observed data (during the year, it varies from 1.8 Sv in the winter to 0.9 Sv in the summer). The complex pattern of the currents in the region of the MW spreading is confirmed. The alternating character of the saline MW tongue at the 1000-m level is shown for the first time. It is found that the zones of maximum salinities in the open part of the ocean coincide with the main trajectories of migration of MW lenses and the regions of their decomposition.     

The timing and reproductive output of the commercial sea cucumber Holothuria scabra on the Kenyan coast

The sea cucumber Holothuria scabra is a widely distributed and economically important species that has been harvested in Kenya for decades. No previous studies have been carried out on the reproduction of this species in Kenya. Standard gonad index methods were used to analyze reproductive patterns of individuals collected monthly in 1998–1999, 2000–2001 and 2006–2007. Morphological characteristics, gonad tubule lengths and fecundity were also measured. Mean monthly gonad indices were significantly correlated between males and females indicating synchronous gonad development between the sexes. Gonad indices showed a biannual pattern that was consistent in all three years with a minor spawning event occurring between August and September and a major spawning event between November and December. The pattern of gonad growth showed significant variability between years and between months. Temporal changes in gonad growth correlated significantly with gonad tubule length and absolute fecundity. Monthly gonad indices also correlated significantly with monthly measurements of air temperature and light suggesting a possible role for both factors in timing gametogenesis and spawning. There was a shift in sex ratio from unity in the 1998–1999 and 2000–2001 samples to significantly more males in the 2006–2007 samples, as well as a significant reduction in mean sizes (body wall weight) and reproductive output (gonad index) which suggests that the reproductive success of this species is potentially negatively affected by fishing.     

Some aspects in the development of dynamic meteorology in Russia in 2003–2006

A brief review of the studies performed by Russian scientists in dynamic meteorology in 2003–2006 is presented. This review is based on the material prepared by the Commission on Dynamic Meteorology of the National Geophysical Committee of the Russian Academy of Sciences and included in the general information report of the Section of Meteorology and Atmospheric Sciences at the 24th General Assembly of the International Union of Geodesy and Geophysics.     

Composition of ferromanganese nodules from Riga Bay (Baltic Sea)

An average sample of ferromanganese nodules from Riga Bay was investigated by analytical electron microscopy coupled with atomic absorption, neutron activation, and ICP-MS methods. It is established that the nodules consist of colloform and poorly crystallized Fe and Mn hydroxides with an admixture of dispersed inclusions of better crystallized particles allowing revealing their mineralogical nature by the microdiffraction method. The major mineral phases are ferroxigite and Fe-vernadite with subordinate magnetite, asbolane, and todorokite. The chemical composition of the nodules is dominated by iron followed by cobalt and lead, while nickel, molybdenum, and tungsten associate with the manganese phase. The concentration of several minor elements in the Riga Bay nodules is slightly lower as compared with their average values for the entire Baltic Sea; some elements such as silver, bismuth, cadmium, niobium, tin, and thallium were never analyzed before.     

Oxidation of copper(I) in seawater at nanomolar levels

The oxidation and reduction of nanomolar levels of copper in air-saturated seawater and NaCl solutions has been measured as a function of pH (7.17–8.49), temperature (5–35 °C) and ionic strength (0.1–0.7 M). The oxidation rates were fitted to an equation valid at different pH and ionic strength conditions in sodium chloride and seawater solutions:

The reduction of Cu(II) was studied in both media for different initial concentrations of copper(II). When the initial Cu(II) concentration was 200 nM, the copper(I) productions were 20% and 9% for NaCl and seawater, respectively. The effect of speciation of copper(I) reduced from Cu(II) on the rates was studied. The Cu(I) speciation is dominated by the CuCl₂⁻ species. On the other hand, the neutral chloride CuCl species dominates the Cu(I) oxidation in the range of 0.1 M to 0.7 M chloride concentrations.