Methane fluxes in the southeastern Baltic Sea

New data from surveys of gas-bearing mud areas in the Gdansk Deep (southeastern Baltic Sea) were collected during four research cruises in 2009–2011. These revealed the presence of seven large pockmarks apart from the three already known, and enabled significant improvement of the existing digital map of gassy mud distribution. Based on geochemical sediment analyses, calculated diffusive methane fluxes from the upper (0–5?cm) seabed layer into near-bottom waters were highest—3.3?mmol/(m²?day)—in pockmark mud, contrasting strongly with the minimum value of 0.004?mmol/(m²?day) observed in typical, background mud. However, fluxes of less than 0.1?mmol/(m²?day) were observed in all sediment types, including pockmarks. In a newer attempt to roughly estimate budgets at a more regional scale, diffusive methane venting amounts to 280?×?10⁶?mmol/day for southeastern Baltic Sea muddy sediments. Elongated pockforms in the southern Gotland Deep, known since the end of the 1980s as pockmarks, had methane concentrations that were similar to those of gassy mud from the Gdansk Basin, and there was no geo-acoustic evidence of considerably increased gas levels.     

Development of barrier-lagoon systems in the southeastern Baltic Sea

A comparative study of the geological structure and evolution of the Curonian and Vistula spits representing large barrier-lagoon systems in the southeastern Baltic Sea reveals some geological and geomorphologic differences against the background of their general similarity. It is shown that morphological structures in the Vistula Spit are smaller. The grain-size analysis of the spit sediments demonstrates that eolian sands constitute all the structures of the spits down to the water level and below it (down to depths of 2 m), except for beaches and low lagoonal terraces. This means that the eolian relief on the maritime plain started forming when the sea level was approximately 4 m below its present-day position. Subsequently, they were growing beyond the wave influence. The sea-level rise resulted in the erosion of the coasts of the spits on both the sea and the lagoon sides and provided an intense landward transport of eolian material.     

Aliphatic hydrocarbons in particulate matter from the Baltic Sea

During May 1980, particulate matter was collected at an anchor station from different depths by two methods. In the separated hydrocarbon fraction the most abundant component was the highly unsaturated hydrocarbon n-heneicosahexaene (HEH). Also present was a series of mono- and di-unsaturated olefinic hydrocarbons with an uneven number of carbon atoms, starting with n-C₁₇. The alkane pattern was characterized by a maximum in the range between n-pentadecane and n-heptadecane, with a strong uneven to even carbon number predominance. The peculiar composition of the aliphatic hydrocarbons was compared with literature data given for aliphatic hydrocarbons, whether produced by different marine organisms or derived from crude oil of other anthropogenic sources. A suggestion is made for using a set of conditions as indicators for pollution by fossil hydrocarbons.     

Peculiarities of the currents field in the north-western part of the Black Sea

On the basis of the results derived by theoretical analysis [1] and laboratory physical modelling [2] of the circulation seawater and stratification, induced by buoyancy fluxes, the suggestion has been made that, possibly, the Black Sea currents system is three-layered. It has been supposed that an anticyclonic current flows in the basin. To verify this deduction, the data from MHI's archived dataset have been treated, and results from twoad hoc expeditions are submitted here. Analysis of the vertical structure of currents, based on thein situ velocity measurements, using various means and calculations of the geostrophic circulation, has confirmed that a flow with the theoretically predicted parameters may exist in the Black Sea. Translated by Vladimir A. Puchkin.     

Large accumulative forms of relief on the southeastern coast of the Baltic Sea

The paper describes the conditions of formation of large accumulative forms on the southeastern coast of the Baltic Sea and presents the results of a comparative analysis of these structures. It has been established that Baltic barrier–lagoon systems have a complex geological and geomorphologic structure. Sandy barriers, which are, in general, marine accumulative formations, often comprise various fragments of different genesis (moraine remnants, glaciolacustrine and deltaic plains, etc.). The formation and development of large accumulative forms in the southeastern Baltic occurred against the background of sea level fluctuations in the Littorina time following a unified scenario for the entire coast.     

The relative distribution of non-aromatic hydrocarbons in the Baltic in September 1971

The relative distribution of the total non-aromatic (saturated and olefinic) hydrocarbons and of the total saturated hydrocarbons, was determined for the central Baltic in September, 1971. Only l litre of sample was required. The hydrocarbons were removed with liquid-liquid extraction, purified with liquid chromatography, and then determined by means of a micro-adsorption detector. Since hydrocarbons in nature are a very complicated mixture, it was impossible to determine their absolute concentration. The results therefore give the concentrations in respect to a standard, consisting of water extracted from the Kiel Bight.Even with this limitation one can see from the data that the hydrocarbons at that time of year originated largely in situ at the sediment-water interface, presumably synthesized by anaerobic bacteria. Low hydrocarbon values appeared in regions that would favor the presence of aerobic bacteria. A large amount of hydrocarbons was released by what was presumably a small plankton bloom, but there is reason to believe that they were relatively labile. The net result is that the dissolved hydrocarbons that enter into the sediment have most likely been produced at the sediment-water interface.     

The impact of salt water inflows on the distribution of polycyclic aromatic hydrocarbons in the deep water of the Baltic Sea

Salt-water inflows into the Baltic Sea are important events for renewing the deep and bottom waters of the deep basins of the Baltic Sea. These events occur only at irregular intervals. The last strong event was in January 1993 followed by minor inflows in winter 1993/1994. As a result of these inflows, the deep water of the central Baltic basins was completely renewed.Based on extensive observations of polycyclic aromatic hydrocarbons (PAHs) in water, fluffy layer material and surface sediments between 1992 and 1998, the transformation of PAHs and the modification of their distribution in the Baltic deep water is discussed in connection with the spreading of the inflowing highly saline and oxygen-rich water along its pathway from the sills into the central basins. In the course of the inflows in 1993/1994, the PAH concentration in the deep water of the different basins increased significantly. The concentrations were elevated, at least by a factor of 2 and as much as seven to eight times (for the four-ring PAHs) compared to the previous and the following years. Two hypotheses for the causes were discussed: the inflowing salt water may have entrained more highly polluted surface water in the western Baltic Sea, or it may have entrained contaminated fluffy layer material or sediment particles along the route of transport.     

Peculiarities of distribution of oil polution in the Southeastern Baltic by satellite data and in situ measurements

The results of satellite monitoring of oil pollution of the sea surface and field measurements of the concentration of oil products in the water column and bottom sediments for the first time allowed the establishment of a relation between the surface pollution from ships and the general characteristics of spatial and temporal distribution of oil products in the Southeastern Baltic Sea. Areas with increased concentrations of oil products in the surface and bottom layers were determined in the southeastern Baltic Sea. The basic directions of pollution spread, which are consistent with the main direction of annual mean transport of substances in the Gdansk Basin, are determined.     

Observation and modeling of upwelling in the southeastern Baltic

The specific features of the upwelling in the southeastern Baltic have been studied by comparing the field observations and numerical simulations. The upwelling registered in October 2005 (when a gale caused by a northeastern wind with a velocity of 15 m/s continued for about three days after a period of relatively calm weather during which the thermohaline structure was in the state close to the summer one) has been considered in detail. The gale caused a decrease in the temperature by approximately 4°C in the along-shore belt with a width of about 8 km in the region with depths of about 25 m located at a distance of approximately 8 km from the shore. The changes in the thermohaline structure that originated as a result of this gale were simulated using a 3D numerical model based on the Princeton Ocean Model (POM). This made it possible not only to consider the variability of the thermohaline fields at the observation region but also to study a rather wide region and to consider the field of velocity in addition to the fields of temperature and salinity. Subsequently, the numerical model made it possible to estimate the upwelling effect during cooling of the upper layer, which was more intense than the effect of turbulent mixing by an order of magnitude. It was confirmed that the specific features of the upwelling spatial structure depend on the geographic position of the upwelling observation region and on the velocity and duration of the wind that causes the upwelling.     

Depositional conditions and organic matter distribution in the Bornholm Basin,Baltic Sea

Information on grain-size distribution and total organic carbon (TOC) content of surface sediment and cores from the Bornholm Basin, together with dating of cores using the ²¹⁰Pb method and shallow seismic chirp profiling, has been analysed to elucidate long-term accumulation patterns. The presence of non-depositional areas with lag sediments and low TOC content below the wave base indicates that inflows of dense bottom water originating in the North Sea and associated near-bottom currents have strong influence on the depositional patterns of bulk sediment and organic matter in this deep basin. The general fining in mean grain size towards the northeast corresponds to the direction of inflow currents and prevailing winds. Recent and previously found ²¹⁰Pb-based mean accumulation rates vary greatly within the basin, between 129 and 1,144 g m⁻² year⁻¹. The accumulation rate may vary by a factor of three even between stations located only 3–4 km apart. Rates recorded close to a seismic profile are consistent with the variation in Holocene sediment thickness. This variation reflects a depositional system controlled by near-bottom inflow currents, consisting of a large-scale channel and a wedge-formed sediment package. The spatial variation in TOC content depends partly on water depth, presumably due to generally poorer degradation in the deepest part of the basin because of less frequent oxygen supply by inflow water. Moreover, there is a tendency of higher TOC contents in the southern part of the basin, which may be due to the input of sediments originating from the Oder River. Compared to values for the central, deep Baltic Sea, TOC contents show lower values of 4–6% and insignificant temporal variations. This may be due to the Bornholm Basin being located much closer to the source of the more oxic inflow water, resulting in more favourable degradation conditions.     

Tidal oscillations in the Baltic Sea

Long-term hourly data from 35 tide gauge stations, including 15 stations in the Gulf of Finland, were used to examine tidal sea level oscillations of the Baltic Sea. High-resolution spectral analysis revealed the well-defined fine structure of tidal peaks with diurnal peaks at most stations being higher than semidiurnal. At some stations (e.g., Narva, Daugava, and Wladyslawowo), high frequency radiational tidal peaks with periods multiple of the solar day (3, 4, 5, 6, and 8 cpd) were detected; the respective oscillations are supposed to be caused by seabreeze winds. Harmonic analysis of tides for individual yearly sea level series followed by vector averaging over the entire observational period was used to estimate the amplitudes and phases of 16 tidal constituents. The maximum tidal oscillations of 17–19 cm were found to be observed in the Gulf of Finland and, first of all, in Neva Bay (in the head of the gulf). Diurnal or mixed diurnal tides are predominant in almost the entire Baltic Sea. The comparison of the observed tides with those theoretically computed showed that the existing numerical models of the main tidal harmonics generally quite accurately reproduce the structure of the tides in the Baltic Sea except for some regions of the Gulf of Bothnia.     

Dissolved uranium in the Baltic Sea

Filtered water from the Baltic Sea was analysed for uranium concentration and ²³⁴U/²³⁸U activity ratio with alpha-ray spectrometry. The uranium concentration shows a strong correlation to salinity, the correlation coefficient being close to 0.98. Consequently, the uranium concentration increases from 0.15 μg kg⁻¹ in the northern part, dominated by fresh water, to above 1.0 μg kg⁻¹ in the Belt Sea. However, the data also show that dissolved uranium is not strictly conservative in the Baltic. In deeper intermittently anoxic basins of the Baltic Proper, the element is removed from the water phase and incorporated into the sediment. This is most evident in the Gotland Deep, which has been anoxic below 200 m depth since 1979.     

Pole tide in the Baltic Sea

The pole tide, which is driven by the Chandler Wobble, has a period of about 14 months and typical amplitudes in the World Ocean of ～0.5 cm. However, in the Baltic Sea the pole tide is anomalously high. To examine this effect we used long-term hourly sea level records from 23 tide gauges and monthly records from 64 stations. The lengths of the series were up to 123 years for hourly records and 211 years for monthly records. High-resolution spectra revealed a cluster of neighboring peaks with periods from 410 to 440 days. The results of spectral analysis were applied to estimate the integral amplitudes of pole tides from all available tide gauges along the coast of the Baltic Sea. The height of the pole tide was found to gradually increase from the entrance (Danish Straits, 1.5–2 cm) to the northeast end of the sea. The largest amplitudes—up to 4.5–7 cm—were observed in the heads of the Gulf of Finland and the Gulf of Bothnia. Significant temporal fluctuations in amplitudes and periods of the pole tide were observed during the 19th and 20th centuries.     

波罗的海地震的危险性

俄罗斯等国积累了地震分区和评价地震高危地区的重要经验。地台属于地震程度较小的地区,更不用说在地台范围内的海区了。但波罗的海及其东部,实际上处于专家们的视线之外。在2004年9月21日,加里宁格勒强度(I)为6·5的4·9级(M)地震发生之后,这个工作上的不到位特别明显地暴露出     

Spatiotemporal distribution of copepod populations in the Gulf of Gdansk (southern Baltic Sea)

In the present study, we used a 3D Coupled Ecosystem Model of Baltic Sea version 1 (3D CEMBSv1) coupled with a copepod model to examine the spatiotemporal distribution of two representative copepod populations in the Gulf of Gdansk (southern Baltic Sea) including Acartia spp. and Pseudocalanus minutus elongatus. The annual cycles simulated for 2000 under realistic weather and hydrographic conditions were studied with the three-dimensional version of the coupled ecosystem-copepod model in the south-eastern Baltic Sea. The paper presents the comparison of simulated and observed copepod development at two stations in the Gulf of Gdansk. A validation of influential state variables gives confidence that the model is able to calculate reliably the stage development of dominant species in the southern Baltic Sea. The number of generations was one for P. m. elongatus and 3?C5 for Acartia spp.. A mean of five generations for the latter species per year were estimated in the coastal region and ca. three generations at the Gdansk Deep (in the open sea). Food concentration and temperature as the main factors controlling the development of the investigated copepods as well as salinity as a masking factor (i.e. salinity modifies the rate of their development) in the case of Pseudocalanus minutus elongatus are included in the present study.     

Dissolved organic carbon in the southern Baltic Sea: Quantification of factors affecting its distribution

During a cruise of r/v ‘Oceania’ in May 2006, seven vertical dissolved organic carbon (DOC) concentration profiles were produced against a background of CTD, chlorophyll a (chl a) and phaeopigment concentration profiles. The results indicate distinct vertical and spatial DOC fluctuations, ranging from 248 ± 7 μmol C dm⁻³ at 70 m depth at the westernmost station G/06 to 398 ± 5 μmol C dm⁻³ at 5 m depth at station A/06 in the western Gulf of Gdańsk. DOC concentrations were the highest at 10 m depth, where phytoplankton activity was relatively intensive, as reflected by the active chl a concentration distribution. DOC concentrations decreased towards the sea bottom.     

Variations in the Baltic Sea wave fields

The surface waves in the Baltic Sea are hindcast with the spectral wave model HYPAS during a 12-month period. The model results show a strong temporal and spatial variation in the wave field due to the physical dimensions of the different basins and the predominant wind field. The highest waves in the area are found in the outer part of Skagerrak, as well as in the central and southern parts of the Baltic Proper. To get significant waves above 6 m high, strong winds (15–20 m/s) must have been blowing for 6 to 24 h from a favourable direction over a deep area.     

The vertical distribution of the fluorescence of the photosynthetic pigments in Kaliningrad Bay of the Baltic Sea

The annual (2004–2006) series of probing using a multichannel filter-fluorimeter from the water’s surface to the bottom at fixed sites in Kaliningrad Bay and the adjacent areas were carried out. The following parameters were recorded: the water turbidity and temperature, the intensity of the fluorescence of the photosynthetic pigment (excitation at 450 nm, detection band 675–820 nm), and the intensity of the background fluorescence of the dissolved organic matter. The high levels of “red fluorescence” presumably related to the presence of photosynthetic bacterioplankton, live phytoplankton, or their mixture (which demands further biological identification) annually registered in the aphotic zone of the water column represent specific feature of the obtained data.