Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements
<p>Bottom pressure observations on both sides of the Atlantic basin, combined with satellite measurements of sea level anomalies and wind stress data, are utilized to estimate variations of the Atlantic Meridional Overturning Circulation (AMOC) at 11<span class="inline-formula">...
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doaj-f164a5c686da4cbab3816363d56f742c2021-02-10T14:48:16ZengCopernicus PublicationsOcean Science1812-07841812-07922021-02-011726528410.5194/os-17-265-2021Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurementsJ. Herrford0P. Brandt1P. Brandt2T. Kanzow3R. Hummels4M. Araujo5J. V. Durgadoo6J. V. Durgadoo7GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyKiel University, Kiel, GermanyAlfred Wegener Institute, Bremerhaven, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyDepartment of Oceanography, Federal University of Pernambuco, Recife, BrazilGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyKiel University, Kiel, Germany<p>Bottom pressure observations on both sides of the Atlantic basin, combined with satellite measurements of sea level anomalies and wind stress data, are utilized to estimate variations of the Atlantic Meridional Overturning Circulation (AMOC) at 11<span class="inline-formula"><sup>∘</sup></span> S. Over the period 2013–2018, the AMOC and its components are dominated by seasonal variability, with peak-to-peak amplitudes of 12 Sv for the upper-ocean geostrophic transport, 7 Sv for the Ekman and 14 Sv for the AMOC transport. The characteristics of the observed seasonal cycles of the AMOC and its components are compared to results from an ocean general circulation model, which is known to reproduce the variability of the Western Boundary Current on longer timescales. The observed seasonal variability of zonally integrated geostrophic velocity in the upper 300 m is controlled by pressure variations at the eastern boundary, while at 500 m depth contributions from the western and eastern boundaries are similar. The model tends to underestimate the seasonal pressure variability at 300 and 500 m depth, especially at the western boundary, which translates into the estimate of the upper-ocean geostrophic transport. In the model, seasonal AMOC variability at 11<span class="inline-formula"><sup>∘</sup></span> S is governed, besides the Ekman transport, by the geostrophic transport variability in the eastern basin. The geostrophic contribution of the western basin to the seasonal cycle of the AMOC is instead comparably weak, as transport variability in the western basin interior related to local wind curl forcing is mainly compensated by the Western Boundary Current. Our analyses indicate that while some of the uncertainties of our estimates result from the technical aspects of the observational strategy or processes not being properly represented in the model, uncertainties in the wind forcing are particularly relevant for the resulting uncertainties of AMOC estimates at 11<span class="inline-formula"><sup>∘</sup></span> S.</p>https://os.copernicus.org/articles/17/265/2021/os-17-265-2021.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
J. Herrford P. Brandt P. Brandt T. Kanzow R. Hummels M. Araujo J. V. Durgadoo J. V. Durgadoo |
spellingShingle |
J. Herrford P. Brandt P. Brandt T. Kanzow R. Hummels M. Araujo J. V. Durgadoo J. V. Durgadoo Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements Ocean Science |
author_facet |
J. Herrford P. Brandt P. Brandt T. Kanzow R. Hummels M. Araujo J. V. Durgadoo J. V. Durgadoo |
author_sort |
J. Herrford |
title |
Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements |
title_short |
Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements |
title_full |
Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements |
title_fullStr |
Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements |
title_full_unstemmed |
Seasonal variability of the Atlantic Meridional Overturning Circulation at 11° S inferred from bottom pressure measurements |
title_sort |
seasonal variability of the atlantic meridional overturning circulation at 11° s inferred from bottom pressure measurements |
publisher |
Copernicus Publications |
series |
Ocean Science |
issn |
1812-0784 1812-0792 |
publishDate |
2021-02-01 |
description |
<p>Bottom pressure observations on both sides of the
Atlantic basin, combined with satellite measurements of sea level anomalies
and wind stress data, are utilized to estimate variations of the Atlantic
Meridional Overturning Circulation (AMOC) at 11<span class="inline-formula"><sup>∘</sup></span> S. Over the
period 2013–2018, the AMOC and its components are dominated by seasonal
variability, with peak-to-peak amplitudes of 12 Sv for the upper-ocean
geostrophic transport, 7 Sv for the Ekman and 14 Sv for the AMOC transport.
The characteristics of the observed seasonal cycles of the AMOC and its
components are compared to results from an ocean general circulation model,
which is known to reproduce the variability of the Western Boundary Current
on longer timescales. The observed seasonal variability of zonally
integrated geostrophic velocity in the upper 300 m is controlled by pressure
variations at the eastern boundary, while at 500 m depth contributions from
the western and eastern boundaries are similar. The model tends to
underestimate the seasonal pressure variability at 300 and 500 m depth,
especially at the western boundary, which translates into the estimate of
the upper-ocean geostrophic transport. In the model, seasonal AMOC
variability at 11<span class="inline-formula"><sup>∘</sup></span> S is governed, besides the Ekman transport, by
the geostrophic transport variability in the eastern basin. The geostrophic
contribution of the western basin to the seasonal cycle of the AMOC is
instead comparably weak, as transport variability in the western basin
interior related to local wind curl forcing is mainly compensated by the
Western Boundary Current. Our analyses indicate that while some of the
uncertainties of our estimates result from the technical aspects of the
observational strategy or processes not being properly represented in the
model, uncertainties in the wind forcing are particularly relevant for the
resulting uncertainties of AMOC estimates at 11<span class="inline-formula"><sup>∘</sup></span> S.</p> |
url |
https://os.copernicus.org/articles/17/265/2021/os-17-265-2021.pdf |
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