Oceanologia No. 40 (3) / 98





Finding the aerosol optical thickness over the Baltic Sea – comparison of two methods
Oceanologia 1998, no. 40 (3), pp. 165–182

Anna Rozwadowska, Jolanta Kuśmierczyk-Michulec
Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81–712 Sopot, Poland; ania@iopan.gda.pl

Keywords: Aerosol optical thickness, Retrieval methods, Baltic atmosphere Manuscript received June 29, 1998, in final form July 30, 1998
The results of two methods used to estimate the aerosol optical thickness over the Baltic Sea are compared. The standard method is based on measurements of the direct component of the downward irradiance at the sea surface in 8 spectral bands (412, 443, 490, 510, 555, 670, 765, 865 nm – the same as SeaWiFS). In the pyranometric method, Baltic aerosols are assumed to be a mixture of model aerosol types with strictly defined optical properties, i.e. maritime, continental and stratospheric types. Their proportion in the Baltic aerosol is found from broadband spectral downward irradiance measurements (VIS, IR) using the radiative transfer model. Simultaneous measurements of the spectral downward irradiance and its direct component on cloudless days in the southern Baltic were used in the comparison. The pyranometric method of estimating the aerosol optical thickness proved to be a satisfactory tool. Depending on the wavelength, the statistical errors in it are not in excess of plus_min.gif - 0.07 K0.06 to plus_min.gif - 0.07 K0.08.
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Inter-annual oscillations of Baltic water volumes and sea levels:
Oceanologia 1998, no 40 (3), pp. 183–203

Andrzej Wróblewski
Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81–712 Sopot, Poland; wroblew@iopan.gda.pl

Keywords: Baltic volume, Long-term oscillations, Sea level Manuscript received July 2, 1998, in final form August 28, 1998.
In spite of the existence of recent long-term sea level measurement series, these have not been applied to compute the long-term characteristics of Baltic water volume changes. To deal with the problem, the mean annual volume changes in the Baltic basin were computed for the measurement period 1896–1986 on the basis of mean monthly sea levels at six tide gauges. EOFs were applied to obtain the averaged sea level characteristics for the entire basin. The results were compared with those of calculations based on the readings of the Stockholm tide gauge, regarded as representative of the whole Baltic, and on geodetic measurements. The differences were found to be minimal. Following computation of the mean annual water volumes, the time series obtained was subjected to a Finite Fourier Transform. The resulting amplitude spectrum was worked up with the bootstrap technique at the 5% significance level, yielding oscillations with periods of 5.6, 4.5 and 3.6 years and corresponding volume change amplitudes of 7.9, 8.7 and 8.7 km3. The fundamental statistical characteristics of the Baltic water volume changes were determined together with the application of stochastic parametric processes. A forcing study of the long-term water volume oscillations in the Baltic is included.
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Maximum-entropy probability distribution of wind wave free-surface elevation
Oceanologia 1998, no 40 (3), pp. 205–229

Witold Cieślikiewicz
Institute of Hydro-Engineering, Polish Academy of Sciences, Kościerska 7, 80–953 Gdańsk, Poland; witold_c@bryza.ibwpan.gda.pl

Keywords: Maximum-entropy principle, Maximum-entropy probability distribution, Random water waves, Wind waves, Free-surface elevations Manuscript received June 16, 1998, in final form July 23, 1998.
The probability density function of the surface elevation of a non-Gaussian random wave field is obtained. The derivation is based on the maximum entropy (information) principle with the first four statistical moments of the surface elevation used as constraints. The density function is found by the use of the Lagrangian multipliers method and it is shown that only two of four Lagrangian multipliers are independent. The applied method of numerical solution is described in detail and the useful nomograms that give the Lagrangian multipliers as functions of skewness and kurtosis are calculated and incorporated in the paper.
For slightly nonlinear waves the approximate maximum-entropy probability distribution is developed. The condition of the existence of this approximate distribution agrees with the empirical criterion for small deviations from the Gaussian distribution of random water waves.
The theoretical results compare well with field experiment data of Ochi and Wang (1984), even in the strongly non-Gaussian case.
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Energy value of the mud crab Rhithropanopeus harrisii ssp. tridentatus (Crustacea, Decapoda) in relation to season, sex and size
Oceanologia 1998, no 40 (3), pp. 231–241

Anna Wiszniewska, Agata Rychter, Anna Szaniawska
Institute of Oceanography, Gdańsk University, Al. Marszalka J. Pilsudskiego 46, 81–378 Gdynia, Poland; oceasz@univ.gda.pl

Keywords: Crustacea, R. harrisii tridentatus, Energy value, Vistula Lagoon Manuscript received June 10, 1998, in final form August 7, 1998.
The energy value of male and female Rhithropanopeus harrisii tridentatus of various carapace width classes was determined. Crab samples were collected in the Vistula Lagoon from April to November 1995. The population of R. harrisii tridentatus from the Vistula Lagoon was characterised by a very low energy value 7.97 [SD] plus_min.gif - 0.07 K1.5 J mg-1DW, (12.69 [SD] plus_min.gif - 0.07 K 2.1 J mg-1 AFDW). The average amount of ash in this population was 37.66% of dry weight (organic matter was 62.44%). In each month (except September) the calorific value of the females exceeded that of the males; this value also varied seasonally. The calorific value of the population dropped to a minimum in August, whereas the maximum level was recorded in September.
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Meiobenthic communities of the Pomeranian Bay (southern Baltic): effects of proximity to river discharge
Oceanologia 1998, no 40 (3), pp. 243–260

Joanna Rokicka-Praxmajer, Teresa Radziejewska, Halina Dworczak
Department of Oceanography, Agricultural University, Kazimierza Krolewicza 4, 71–550 Szczecin, Poland; tr@iom.gov.pl

Keywords: Meiobenthos, Baltic Sea, Estuary, River discharge, Organic enrichment Manuscript received April 29, 1998, in final form July 13, 1998.
The Pomeranian Bay (southern Baltic Sea) is a component of the river Oder (Odra) estuarine system. It receives the Oder's discharge once it has passed through the Szczecin Lagoon, a eutrophic and polluted water body. The discharge has been documented as affecting the hydrography of the pelagic domain as well as the sedimentary environments and the macrozoobenthos of the Bay. This study focused on the distribution of meiobenthic communities in the Bay as investigated with the use of a suite of uni- and multivariate analyses applied to data collected at 14 stations in September 1993. Meiobenthic community characteristics (composition and abundance) are presented in relation to sediment properties (grain size, silt/clay and organic matter content), changing with distance from the major riverine discharge site. The communities studied showed a clear distinction between those associated with organic matter-enriched sediments close to the discharge site and the assemblages living in clean sands, away from the discharge. We conclude that the meiobenthos can be regarded as another compartment of the Pomeranian Bay system responding to the River Oder discharge.
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The hydrological and hydrochemical division of the surface waters in the Gulf of Gdańsk
Oceanologia 1998, no 40 (3), pp. 261–272

Jacek Nowacki
Institute of Oceanography, Gdańsk University, Al. J. Pilsudskiego 46, 81–378 Gdynia, Poland; ocejn@univ.gda.pl

Ewa Jarosz
Louisiana State University, Baton Rouge, LA 70803, USA

Keywords: Gulf of Gdańsk, Surface water, Temperature, Salinity, Nutrients, Surface layer division, Cluster analysis, Ward's method Manuscript received May 8, 1998, in final form July 15, 1998.
The objective of this work was to define regions in the surface layer of the Gulf of Gdańsk that are characterised by different natural (temperature, salinity, total water depth) and anthropogenic (concentrations of major nutrients) factors. Additionally, approximate boundaries between the regions distinguished were delineated. To find regions of different hydrological and hydrochemical properties, Ward's method, an agglomerative hierarchical cluster technique, was applied to a data set containing measurements of temperature, salinity, total depths and nutrient concentrations.
Cluster analysis divided the surface waters of the Gulf of Gdańsk into seven regions. The surface waters in the shallow water part of the Gulf of Gdańsk, where six out of the seven regions were located, displayed a distinct diversity which was probably associated with the morphometry of the Gulf, nutrient sources and freshwater input. The last region encompassed the deep-water part of the Gulf of Gdańsk and Puck Bay.
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Transfrontal exchange of mass and heat in the region of the Arctic front (review by Jerzy Cyberski)
Oceanologia 1998, no 40 (3), pp. 273–275

Waldemar Walczowski
Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81–712 Sopot, Poland; walczows@iopan.gda.pl

Ph. D. thesis in physical oceanography supervised by Professor Jan Piechura
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