Influence of underwater light fields on pigment characteristics in the Baltic Sea – results of statistical analysis**This work was carried out within the framework of the SatBałtyk project funded by the European Union through the European Regional Development Fund, (contract No. POIG.01.01.02-22-011/09 entitled ‘The Satellite Monitoring of the Baltic Sea Environment’), research project NN 304 275235 and also as part of IO PAS’s statutory research.

AbstractChanges in phytoplankton pigment concentrations in Case 2 waters (such as those of the Baltic Sea) were analysed in relation to the light intensity and its spectral distribution in the water. The analyses were based on sets of empirical measurements containing two types of data: chlorophyll and carotenoid concentrations obtained by HPLC, and the distribution of underwater light fields measured with a MER 2040 spectrophotometer – collected during 27 research cruises on r/v ‘Oceania’ in 1999–2004. Statistical analysis yielded relationships between the total relative (to chlorophyll a concentrations) concentrations of major groups of phytoplankton pigments and optical depth τ, between the total relative concentrations of major groups of photosynthetic pigments (chlorophylls b (Cchl b tot/Cchl a tot), chlorophylls c (Cchl c tot/Cchl a tot) and photosynthetic carotenoids (CPSC tot/Cchl a tot)) and the spectral fitting function (the ‘chromatic acclimation factor’), and between the total relative concentrations of photoprotective carotenoids (CPPC tot/Cchl a tot) in Baltic waters and the potentially destructive radiation (PDR), defined as the absolute amount of energy in the blue part of the spectrum (400–480nm) absorbed by unit mass of chlorophyll a. The best approximations were obtained for the total chlorophyll c content, while the relative estimation errors were the smallest (σ−=34.6%) for the approximation to optical depth and spectral fitting function. The largest errors related to the approximation of chlorophyll b concentrations: σ−=56.7% with respect to optical depth and 57.3% to the spectral fitting function.A comparative analysis of the relative (to chlorophyll a content) concentrations of the main groups of pigments and the corresponding irradiance characteristics in ocean (Case 1) waters and Baltic waters (Case 2 waters) was also carried out. The distribution of Cchl b tot/Cchl a tot ratios with respect to optical depth reveals a decreasing trend with increasing τ for Baltic data, which is characteristic of photoprotective pigments and the reverse of the trend in oceans. In the case of the Cchl c tot approximations, the logarithmic statistical error is lower for Baltic waters than for Case 1 waters: σ−=34.6% for Baltic data and σ−=39.4% for ocean data. In relation to photoprotective carotenoids (CPPC), σ− takes a value of 38.4% for Baltic waters and 36.1% for ocean waters. The relative errors of the approximated concentrations of different pigment groups are larger than those obtained for ocean waters. The only exception is chlorophyll c, for which the logarithmic statistical error is about 8.8% lower (σ−=34.6% for Baltic waters and 38.2% for ocean waters). Analysis of the errors resulting from the approximations of the photoprotective carotenoid content, depending on the energy characteristics of the underwater irradiance in the short-range part of PAR, showed that the relative errors are 1.3 times higher for Baltic waters than for ocean waters: σ−=38.4% for Baltic waters and 32.0% for ocean waters

Inherent optical properties and particulate matter distribution in summer season in waters of Hornsund and Kongsfjordenen, Spitsbergen

Two Spitsbergen fjords, Hornsund and Kongsfjorden, are known for being under different hydrological regimes. The first is cold, separated from warm Atlantic water by East Spitsbergen Current, while Kongsfjorden is frequently penetrated by relatively warm Atlantic water. On the other hand, both are under strong influence of water discharge from glaciers and land freshwater input. During the period of observation in both fjords a dominant water mass was Surface Water, which originates mainly from glacial melt. The presence of suspended matter introduced with melt water in Surface Water is reflected by highest values of light attenuation and absorption coefficients recorded in areas close to glacier both in Hornsund and Kongsfjorden. In Hornsund the maximum light attenuation coefficient cpg(555) was 5.817 m−1 and coefficient of light absorption by particles ap(676) = 0.10 m−1. In Kongsfjorden the corresponding values were 26.5 m−1 and 0.223 m−1. In Kongsfjorden suspended matter of the size class 20–200 μm dominated over fractions smaller than 20 μm while in Hornsund dominating size fraction was 2–20 μm. The results provide an evidence of considerable range of variability of the optical properties mainly due to glacial and riverine runoff. The scale of variability of particulate matter in Kongsfjorden is bigger than in Hornsund. Most of the variability in Hornsund can be attributed to glaciers discharge and a presence of particles of mineral origin, while in Kongsfjorden the organic and mineral particles contribute almost equally to defining the optical properties of water

Characterization of the Light Field and Apparent Optical Properties in the Ocean Euphotic Layer Based on Hyperspectral Measurements of Irradiance Quartet

Although the light fields and apparent optical properties (AOPs) within the ocean euphotic layer have been studied for many decades through extensive measurements and theoretical modeling, there is virtually a lack of simultaneous high spectral resolution measurements of plane and scalar downwelling and upwelling irradiances (the so-called irradiance quartet). We describe a unique dataset of hyperspectral irradiance quartet, which was acquired under a broad range of environmental conditions within the water column from the near-surface depths to about 80 m in the Gulf of California. This dataset enabled the characterization of a comprehensive suite of AOPs for realistic non-uniform vertical distributions of seawater inherent optical properties (IOPs) and chlorophyll-a concentration (Chl) in the common presence of inelastic radiative processes within the water column, in particular Raman scattering by water molecules and chlorophyll-a fluorescence. In the blue and green spectral regions, the vertical patterns of AOPs are driven primarily by IOPs of seawater with weak or no discernible effects of inelastic processes. In the red, the light field and AOPs are strongly affected or totally dominated by inelastic processes of Raman scattering by water molecules, and additionally by chlorophyll-a fluorescence within the fluorescence emission band. The strongest effects occur in the chlorophyll-a fluorescence band within the chlorophyll-a maximum layer, where the average cosines of the light field approach the values of uniform light field, irradiance reflectance is exceptionally high approaching 1, and the diffuse attenuation coefficients for various irradiances are exceptionally low, including the negative values for the attenuation of upwelling plane and scalar irradiances. We established the empirical relationships describing the vertical patterns of some AOPs in the red spectral region as well as the relationships between some AOPs which can be useful in common experimental situations when only the downwelling plane irradiance measurements are available. We also demonstrated the applicability of irradiance quartet data in conjunction with Gershun’s equation for estimating the absorption coefficient of seawater in the blue-green spectral region, in which the effects of inelastic processes are weak or negligible

Supporting marine environment research by modeling

The Centre of Informatics – Tri-City Academic Supercomputer and Network (CI TASK) was founded over twenty-five years ago, in 1994. It was a very important initiative undertaken as a result of rapid development of computer technology and one of its main goals was to integrate the computer resources of scientific communities in the Tri-City. CI TASKstarted to provide computing resources and the first steps in the world of high-performance computing must have been proved to be a significant challenge. The scientific community of the Institute of Oceanology has been cooperating with that computing centre since the very beginning.Currently, CI TASKprovides the widest set of tools and hardware that can be used for ocean modeling purposes. The main goal of this work is expression of appreciation and gratitude for the people who have contributed to the developing of this institution and helped in the work using their tools.CI TASK has been helpful in a great number of past and present tasks, however, in this paper we would like to present only three results of our work – a coupled ice-ocean model of the Baltic Sea, assessment of contamination for potential leak age from chemical munition dumped after the Second World War, and the currently operating SatBaltic system

Empirical Formulas for Estimating Backscattering and Absorption Coefficients in Complex Waters from Remote-Sensing Reflectance Spectra and Examples of Their Application

Many standard methods used for the remote sensing of ocean colour have been developed, though mainly for clean, open ocean waters. This means that they may not always be effective in complex waters potentially containing high concentrations of optically significant constituents. This paper presents new empirical formulas for estimating selected inherent optical properties of water from remote-sensing reflectance spectra Rrs(λ), derived, among other things, for waters with high concentrations of dissolved and suspended substances. These formulas include one for estimating the backscattering coefficient bb(620) directly from the magnitude of Rrs in the red part of the spectrum, and another for estimating the absorption coefficient a(440) from the hue angle α. The latter quantity represents the water’s colour as it might be perceived by the human eye (trichromatic colour vision); it is easily calculated from the shape of the Rrs spectrum. These new formulas are based on a combined dataset. Most of the data were obtained in the specific, optically complex environment of the Baltic Sea. Additional data, taken from the NASA bio-Optical Marine Algorithm Dataset (NOMAD) and representing various regions of the global oceans, were used to widen the potential applicability of the new formulas. We indicate the reasons why these simple empirical relationships can be derived and compare them with the results of straightforward modelling; possible applications are also described. We present, among other things, an example of a simple semi-analytical algorithm using both new empirical formulas. This algorithm is a modified version of the well-known quasi-analytical algorithm (QAA), and it can improve the results obtained in optically complex waters. This algorithm allows one to estimate the full spectra of the backscattering and absorption coefficients, without the need for any additional a priori assumptions regarding the spectral shape of absorption by dissolved and suspended seawater constituents

Relationships between inherent optical properties in the Baltic Sea for application to the underwater imaging problem**This work was supported by the Russian Foundation for Basic Research project No. 10-05-00311. Partial support for this study was also provided by the Satellite Monitoring of the Baltic Sea Environment – SatBałtyk project, funded by the European Union through European Regional Development Fund contract No. POIG 01.01.02-22-011/09 and statutory research funds from the Institute of Oceanology PAS, Sopot

AbstractStatistical relationships between coefficients of light attenuation, scattering and backscattering at wavelength 550nm derived from series of optical measurements performed in Baltic Sea waters are presented. The relationships were derived primarily to support data analysis from underwater imaging systems. Comparison of these relations with analogous empirical data from the Atlantic and Pacific Oceans shows that the two sets of relationships are similar, despite the different water types and the various experimental procedures and instrumentation applied. The apparently universal character of the relationships enables an approximate calculation of other optical properties and subsequently of the contrast, signal/noise ratio, visibility range and spatial resolution of underwater imaging systems based on attenuation coefficients at wavelength 550nm only

Daily Radiation Budget of the Baltic Sea Surface from Satellite Data

Recently developed system for assessment of radiation budget for the Baltic Sea has been presented and verified. The system utilizes data from various sources: satellite, model and in situ measurements. It has been developed within the SatBałtyk project (Satellite Monitoring of the Baltic Sea Environment - www.satbaltyk.eu) where the energy radiation budget is one of the key element. The SatBałtyk system generates daily maps of the all components of radiation budget on every day basis. We show the scheme of making daily maps, applied algorithms and empirical data collection within the system. An empirical verification of the system has been carried out based on empirical data collected on the oil rig placed on the Baltic Sea. This verification concerned all the components of the surface radiation budget. The average daily NET products are estimated with statistical error ca. 13 Wm-2. The biggest absolute statistical error is for LWd component and equals 14 Wm-2. The relative error in relation to the average annual values for whole Baltic is the biggest for SWu and reaches 25%. All estimated components have correlation coefficient above 0.91

Influence of Dispersed Oil on the Remote Sensing Reflectance—Field Experiment in the Baltic Sea

Remote sensing techniques currently used to detect oil spills have not yet demonstrated their applicability to dispersed forms of oil. However, oil droplets dispersed in seawater are known to modify the local optical properties and, consequently, the upwelling light flux. Theoretically possible, passive remote detection of oil droplets was never tested in the offshore conditions. This study presents a field experiment which demonstrates the capability of commercially available sensors to detect significant changes in the remote sensing reflectance Rrs of seawater polluted by six types of dispersed oils (two crude oils, cylinder lubricant, biodiesel, and two marine gear lubricants). The experiment was based on the comparison of the upwelling radiance Lu measured in a transparent tank floating in full immersion in seawater in the Southern Baltic Sea. The tank was first filled with natural seawater and then polluted by dispersed oils in five consecutive concentrations of 1–15 ppm. After addition of dispersed oils, spectra of Rrs noticeably increased and the maximal increase varied from 40% to over three-fold at the highest oil droplet concentration. Moreover, the most affected Rrs band ratios and band differences were analyzed and are discussed in the context of future construction of algorithms for dispersed oil detection