Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system
Persistent hypoxic bottom waters have developed in the Lower St Lawrence Estuary (LSLE) and have impacted fish and benthic species distributions. Minimum dissolved oxygen concentrations decreased from ∼ 125 µ mol L −1 (38 % saturation) in the 1930s to ∼ 65 µ mol L −1 (21 % saturation) in 1984. Minim...
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ftdoajarticles:oai:doaj.org/article:5b9862e4e32145e1afc53875985ac1d0 2023-05-15T17:31:39+02:00 Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system M. Jutras A. Mucci G. Chaillou W. A. Nesbitt D. W. R. Wallace 2023-02-01T00:00:00Z https://doi.org/10.5194/bg-20-839-2023 https://doaj.org/article/5b9862e4e32145e1afc53875985ac1d0 EN eng Copernicus Publications https://bg.copernicus.org/articles/20/839/2023/bg-20-839-2023.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 doi:10.5194/bg-20-839-2023 1726-4170 1726-4189 https://doaj.org/article/5b9862e4e32145e1afc53875985ac1d0 Biogeosciences, Vol 20, Pp 839-849 (2023) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2023 ftdoajarticles https://doi.org/10.5194/bg-20-839-2023 2023-02-26T01:32:17Z Persistent hypoxic bottom waters have developed in the Lower St Lawrence Estuary (LSLE) and have impacted fish and benthic species distributions. Minimum dissolved oxygen concentrations decreased from ∼ 125 µ mol L −1 (38 % saturation) in the 1930s to ∼ 65 µ mol L −1 (21 % saturation) in 1984. Minimum dissolved oxygen concentrations remained at hypoxic levels ( < 62.5 µ M = 2 mg L −1 or 20 % saturation) between 1984 and 2019, but in 2020, they suddenly decreased to ∼ 35 µ mol L −1 . Concurrently, bottom-water temperatures in the LSLE have increased progressively from ∼ 3 ∘ C in the 1930s to nearly 7 ∘ C in 2021. The main driver of deoxygenation and warming in the bottom waters of the Gulf of St Lawrence and St Lawrence Estuary is a change in the circulation pattern in the western North Atlantic, more specifically a decrease in the relative contribution of younger, well-oxygenated and cold Labrador Current Waters to the waters of the Laurentian Channel, a deep valley that extends from the continental shelf edge, through Cabot Strait, the gulf and to the head of the LSLE. Hence, the warmer, oxygen-depleted North Atlantic Central Waters carried by the Gulf Stream now make up nearly 100 % of the waters entering the Laurentian Channel. The areal extent of the hypoxic zone in the LSLE has varied since 1993 when it was first estimated at 1300 km 2 . In 2021, it reached 9400 km 2 , extending well into the western Gulf of St Lawrence. Severely hypoxic waters are now also found at the end of the two deep channels that branch out from the Laurentian Channel, namely, the Esquiman Channel and Anticosti Channel. Article in Journal/Newspaper North Atlantic Directory of Open Access Journals: DOAJ Articles Cabot ENVELOPE(-54.600,-54.600,-63.383,-63.383) Biogeosciences 20 4 839 849 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
spellingShingle |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 M. Jutras A. Mucci G. Chaillou W. A. Nesbitt D. W. R. Wallace Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
description |
Persistent hypoxic bottom waters have developed in the Lower St Lawrence Estuary (LSLE) and have impacted fish and benthic species distributions. Minimum dissolved oxygen concentrations decreased from ∼ 125 µ mol L −1 (38 % saturation) in the 1930s to ∼ 65 µ mol L −1 (21 % saturation) in 1984. Minimum dissolved oxygen concentrations remained at hypoxic levels ( < 62.5 µ M = 2 mg L −1 or 20 % saturation) between 1984 and 2019, but in 2020, they suddenly decreased to ∼ 35 µ mol L −1 . Concurrently, bottom-water temperatures in the LSLE have increased progressively from ∼ 3 ∘ C in the 1930s to nearly 7 ∘ C in 2021. The main driver of deoxygenation and warming in the bottom waters of the Gulf of St Lawrence and St Lawrence Estuary is a change in the circulation pattern in the western North Atlantic, more specifically a decrease in the relative contribution of younger, well-oxygenated and cold Labrador Current Waters to the waters of the Laurentian Channel, a deep valley that extends from the continental shelf edge, through Cabot Strait, the gulf and to the head of the LSLE. Hence, the warmer, oxygen-depleted North Atlantic Central Waters carried by the Gulf Stream now make up nearly 100 % of the waters entering the Laurentian Channel. The areal extent of the hypoxic zone in the LSLE has varied since 1993 when it was first estimated at 1300 km 2 . In 2021, it reached 9400 km 2 , extending well into the western Gulf of St Lawrence. Severely hypoxic waters are now also found at the end of the two deep channels that branch out from the Laurentian Channel, namely, the Esquiman Channel and Anticosti Channel. |
format |
Article in Journal/Newspaper |
author |
M. Jutras A. Mucci G. Chaillou W. A. Nesbitt D. W. R. Wallace |
author_facet |
M. Jutras A. Mucci G. Chaillou W. A. Nesbitt D. W. R. Wallace |
author_sort |
M. Jutras |
title |
Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system |
title_short |
Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system |
title_full |
Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system |
title_fullStr |
Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system |
title_full_unstemmed |
Temporal and spatial evolution of bottom-water hypoxia in the St Lawrence estuarine system |
title_sort |
temporal and spatial evolution of bottom-water hypoxia in the st lawrence estuarine system |
publisher |
Copernicus Publications |
publishDate |
2023 |
url |
https://doi.org/10.5194/bg-20-839-2023 https://doaj.org/article/5b9862e4e32145e1afc53875985ac1d0 |
long_lat |
ENVELOPE(-54.600,-54.600,-63.383,-63.383) |
geographic |
Cabot |
geographic_facet |
Cabot |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Biogeosciences, Vol 20, Pp 839-849 (2023) |
op_relation |
https://bg.copernicus.org/articles/20/839/2023/bg-20-839-2023.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 doi:10.5194/bg-20-839-2023 1726-4170 1726-4189 https://doaj.org/article/5b9862e4e32145e1afc53875985ac1d0 |
op_doi |
https://doi.org/10.5194/bg-20-839-2023 |
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Biogeosciences |
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20 |
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4 |
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839 |
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849 |
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