Physical drivers of pelagic sargassum bloom interannual variability in the Central West Atlantic over 2010–2020
Physical drivers of pelagic sargassum bloom interannual variability in the Central West Atlantic over 2010–2020
Since 2011, unprecedented pelagic sargassum seaweed blooms have occurred across the tropical North Atlantic, with severe socioeconomic impacts for coastal populations. To investigate the role of physical drivers in post-2010 sargassum blooms in the Central West Atlantic (CWA), conditions are examined across the wider tropical North Atlantic, using ocean and atmospheric re-analyses and satellite-derived datasets. Of particular consequence for the growth and drift of sargassum are patterns and seasonality of winds and currents. Results suggest that in years of exceptionally large sargassum blooms (2015, 2018), the Intertropical Convergence Zone (ITCZ), an area of maximum wind convergence where sargassum naturally accumulates, shifted southward, towards nutrient-rich waters of the Amazon River plume and the equatorial upwelling zone further stimulating sargassum growth. These changes are associated with modes of natural variability in the tropical Atlantic, notably a negative phase of the Atlantic Meridional Mode (AMM) in 2015 and 2018, and a positive phase of the Atlantic Niño in 2018. Negative AMM in these 2 years is also associated with stronger trade winds and enhanced northwest Africa upwelling, probably resulting in stronger southwestward nutrient transport into the eastern part of CWA. Moreover, in contrast with most years, important secondary winter blooms took place in both 2015 and 2018 in the northern part of CWA, associated with excessive wind-driven equatorial upwelling and anomalously strong northwestward nutrient transport.
Climatic modes, Ocean circulation, Sargassum, Trade winds, Tropical North Atlantic
383-404
Skliris, Nikolaos
07af7484-2e14-49aa-9cd3-1979ea9b064e
Marsh, Robert
702c2e7e-ac19-4019-abd9-a8614ab27717
Addo, Kwasi Appeaning
ba52d61b-153f-4263-bb45-ee23efd2fb58
Oxenford, Hazel A.
29104ad8-b2b9-4678-bba0-ab64032764be
June 2022
Skliris, Nikolaos
07af7484-2e14-49aa-9cd3-1979ea9b064e
Marsh, Robert
702c2e7e-ac19-4019-abd9-a8614ab27717
Addo, Kwasi Appeaning
ba52d61b-153f-4263-bb45-ee23efd2fb58
Oxenford, Hazel A.
29104ad8-b2b9-4678-bba0-ab64032764be
Skliris, Nikolaos, Marsh, Robert, Addo, Kwasi Appeaning and Oxenford, Hazel A.
(2022)
Physical drivers of pelagic sargassum bloom interannual variability in the Central West Atlantic over 2010–2020.
Ocean Dynamics, 72 (6), .
(doi:10.1007/s10236-022-01511-1).
Abstract
Since 2011, unprecedented pelagic sargassum seaweed blooms have occurred across the tropical North Atlantic, with severe socioeconomic impacts for coastal populations. To investigate the role of physical drivers in post-2010 sargassum blooms in the Central West Atlantic (CWA), conditions are examined across the wider tropical North Atlantic, using ocean and atmospheric re-analyses and satellite-derived datasets. Of particular consequence for the growth and drift of sargassum are patterns and seasonality of winds and currents. Results suggest that in years of exceptionally large sargassum blooms (2015, 2018), the Intertropical Convergence Zone (ITCZ), an area of maximum wind convergence where sargassum naturally accumulates, shifted southward, towards nutrient-rich waters of the Amazon River plume and the equatorial upwelling zone further stimulating sargassum growth. These changes are associated with modes of natural variability in the tropical Atlantic, notably a negative phase of the Atlantic Meridional Mode (AMM) in 2015 and 2018, and a positive phase of the Atlantic Niño in 2018. Negative AMM in these 2 years is also associated with stronger trade winds and enhanced northwest Africa upwelling, probably resulting in stronger southwestward nutrient transport into the eastern part of CWA. Moreover, in contrast with most years, important secondary winter blooms took place in both 2015 and 2018 in the northern part of CWA, associated with excessive wind-driven equatorial upwelling and anomalously strong northwestward nutrient transport.
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Skliris2022_Article_PhysicalDriversOfPelagicSargas
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Accepted/In Press date: 30 April 2022
e-pub ahead of print date: 4 May 2022
Published date: June 2022
Additional Information:
Funding Information:
This publication is supported by the UK Economic and Social Research Council through the Global Challenges Research Fund (GCRF) project, Teleconnected sargassum risks across the Atlantic: building capacity for TRansformational Adaptation in the Caribbean and West Africa (SARTRAC), grant number ES/T002964/1. We acknowledge the Optical Oceanography Laboratory at the University of South Florida, for freely providing AFAI images via https://optics.marine.usf.edu .
Funding Information:
This publication is supported by the UK Economic and Social Research Council through the Global Challenges Research Fund (GCRF) project, Teleconnected sargassum risks across the Atlantic: building capacity for TRansformational Adaptation in the Caribbean and West Africa (SARTRAC) , grant number ES/T002964/1. We acknowledge the Optical Oceanography Laboratory at the University of South Florida, for freely providing AFAI images via https://optics.marine.usf.edu.
Funding Information:
The research was funded by the UK’s Economic and Social Research Council through the Global Challenges Research Fund (GCRF) project, Teleconnected sargassum risks across the Atlantic: building capacity for TRansformational Adaptation in the Caribbean and West Africa (SARTRAC), grant number ES/T002964/1.
Publisher Copyright:
© 2022, The Author(s).
Keywords:
Climatic modes, Ocean circulation, Sargassum, Trade winds, Tropical North Atlantic
Identifiers
Local EPrints ID: 457128
URI: http://eprints.soton.ac.uk/id/eprint/457128
ISSN: 1616-7341
PURE UUID: f11ba288-5ee0-477a-813b-ffec2b444348
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Date deposited: 24 May 2022 16:54
Last modified: 17 Mar 2024 03:25
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Author:
Kwasi Appeaning Addo
Author:
Hazel A. Oxenford
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