Seasonal dynamics and regional distribution patterns of CO<sub>2</sub> and CH<sub>4</sub> in the north-eastern Baltic Sea
<p>Significant research has been carried out in the last decade to describe the CO<span class="inline-formula"><sub>2</sub></span> system dynamics in the Baltic Sea. However, there is a lack of knowledge in this field in the NE Baltic Sea, which is the main fo...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2024-10-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/21/4495/2024/bg-21-4495-2024.pdf |
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| Summary: | <p>Significant research has been carried out in the last decade to describe the CO<span class="inline-formula"><sub>2</sub></span> system dynamics in the Baltic Sea. However, there is a lack of knowledge in this field in the NE Baltic Sea, which is the main focus of the present study. We analysed the physical forcing and hydrographic background in the study year (2018) and tried to elucidate the observed patterns of surface water CO<span class="inline-formula"><sub>2</sub></span> partial pressure (<span class="inline-formula"><i>p</i></span>CO<span class="inline-formula"><sub>2</sub></span>) and methane concentrations (<span class="inline-formula"><i>c</i></span>CH<span class="inline-formula"><sub>4</sub></span>). Surface water <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula"><sub>2</sub></span> and <span class="inline-formula"><i>c</i></span>CH<span class="inline-formula"><sub>4</sub></span> were continuously measured during six monitoring cruises onboard R/V <i>Salme</i>, covering the Northern Baltic Proper (NBP), the Gulf of Finland (GoF), and the Gulf of Riga (GoR) and all seasons in 2018. The general seasonal <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula"><sub>2</sub></span> pattern showed oversaturation in autumn–winter (average relative CO<span class="inline-formula"><sub>2</sub></span> saturation 1.2) and undersaturation in spring–summer (average relative CO<span class="inline-formula"><sub>2</sub></span> saturation 0.5), but it locally reached the saturation level during the cruises in April, May, and August in the GoR and in August in the GoF. The <span class="inline-formula"><i>c</i></span>CH<span class="inline-formula"><sub>4</sub></span> was oversaturated during the entire study period, and the seasonal course was not well exposed on the background of high variability. Surface water <span class="inline-formula"><i>p</i></span>CO<span class="inline-formula"><sub>2</sub></span> and <span class="inline-formula"><i>c</i></span>CH<span class="inline-formula"><sub>4</sub></span> distributions showed larger spatial variability in the GoR and GoF than in the NBP for all six cruises. We linked the observed local maxima to river bulges, coastal upwelling events, fronts, and occasions when vertical mixing reached the seabed in shallow areas. Seasonal averaging over the CO<span class="inline-formula"><sub>2</sub></span> flux suggests a weak sink for atmospheric CO<span class="inline-formula"><sub>2</sub></span> for all basins, but high variability and the long periods between cruises (temporal gaps in observation) preclude a clear statement.</p> |
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| ISSN: | 1726-4170 1726-4189 |