Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea
Summary: The aim of this study was to investigate the light transfer through sea ice with a focus on bio-optical substances both in fast ice and in the drift ice zones in the northern Baltic Sea. The measurements included snow and ice structure, spectral irradiance and photosynthetically active radi...
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doaj-047926f1e24c44b2937985a7d7e8da362020-11-25T02:54:30ZengElsevierOceanologia0078-32342020-07-01623347363Measurements of light transfer through drift ice and landfast ice in the northern Baltic SeaElina Kari0Arttu Jutila1Anna Friedrichs2Matti Leppäranta3Susanne Kratzer4Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden; Present: Institute for Atmospheric and Earth System Research (INAR), P.O. Box 64, 00014 University of Helsinki, Finland; Corresponding author at: Institute for Atmospheric and Earth System Research (INAR), P.O. Box 64, 00014 University of Helsinki, Finland.Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Helsinki, Finland; Present: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany.Institute for Chemistry and Biology for the Marine Environment, Carl von Ossietzky University of Oldenburg, Oldenburg, GermanyInstitute for Atmospheric and Earth System Research (INAR), University of Helsinki, Helsinki, FinlandDepartment of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, SwedenSummary: The aim of this study was to investigate the light transfer through sea ice with a focus on bio-optical substances both in fast ice and in the drift ice zones in the northern Baltic Sea. The measurements included snow and ice structure, spectral irradiance and photosynthetically active radiation below the sea ice. We also measured the concentrations of the three main bio-optical substances which are chlorophyll-a, suspended particulate matter, and coloured dissolved organic matter (CDOM). These bio-optical substances were determined for melted ice samples and for the underlying sea water. The present study provides the first spectral light transfer data set for drift ice in the Baltic Sea. We found high CDOM absorption values typical to the Baltic Sea waters also within sea ice. Our results showed that the transmittance through bare ice was lower for the coastal fast ice than for the drift ice sites. Bio-optical substances, in particular CDOM, modified the spectral distribution of light penetrating through the ice cover. Differences in crystal structure and the amount of gas inclusions in the ice caused variation in the light transfer. Snow cover on ice was found to be the dominant factor influencing the light field under ice, confirming previous studies. In conclusion, snow cover dominated the amount of light under the ice, but did not modify its spectral composition. CDOM in the ice absorbs strongly in the short wavelengths. As pure water absorbs most in the long wavelengths, the light transfer through ice was highest in the green (549–585 nm).http://www.sciencedirect.com/science/article/pii/S0078323420300324Light transferSea iceDiffuse attenuation coefficientColoured dissolved organic matterScattering |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Elina Kari Arttu Jutila Anna Friedrichs Matti Leppäranta Susanne Kratzer |
spellingShingle |
Elina Kari Arttu Jutila Anna Friedrichs Matti Leppäranta Susanne Kratzer Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea Oceanologia Light transfer Sea ice Diffuse attenuation coefficient Coloured dissolved organic matter Scattering |
author_facet |
Elina Kari Arttu Jutila Anna Friedrichs Matti Leppäranta Susanne Kratzer |
author_sort |
Elina Kari |
title |
Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea |
title_short |
Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea |
title_full |
Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea |
title_fullStr |
Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea |
title_full_unstemmed |
Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea |
title_sort |
measurements of light transfer through drift ice and landfast ice in the northern baltic sea |
publisher |
Elsevier |
series |
Oceanologia |
issn |
0078-3234 |
publishDate |
2020-07-01 |
description |
Summary: The aim of this study was to investigate the light transfer through sea ice with a focus on bio-optical substances both in fast ice and in the drift ice zones in the northern Baltic Sea. The measurements included snow and ice structure, spectral irradiance and photosynthetically active radiation below the sea ice. We also measured the concentrations of the three main bio-optical substances which are chlorophyll-a, suspended particulate matter, and coloured dissolved organic matter (CDOM). These bio-optical substances were determined for melted ice samples and for the underlying sea water. The present study provides the first spectral light transfer data set for drift ice in the Baltic Sea. We found high CDOM absorption values typical to the Baltic Sea waters also within sea ice. Our results showed that the transmittance through bare ice was lower for the coastal fast ice than for the drift ice sites. Bio-optical substances, in particular CDOM, modified the spectral distribution of light penetrating through the ice cover. Differences in crystal structure and the amount of gas inclusions in the ice caused variation in the light transfer. Snow cover on ice was found to be the dominant factor influencing the light field under ice, confirming previous studies. In conclusion, snow cover dominated the amount of light under the ice, but did not modify its spectral composition. CDOM in the ice absorbs strongly in the short wavelengths. As pure water absorbs most in the long wavelengths, the light transfer through ice was highest in the green (549–585 nm). |
topic |
Light transfer Sea ice Diffuse attenuation coefficient Coloured dissolved organic matter Scattering |
url |
http://www.sciencedirect.com/science/article/pii/S0078323420300324 |
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