Articles | Volume 19, issue 1
https://doi.org/10.5194/os-19-43-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-19-43-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
17 Jan 2023
Research article |
| 17 Jan 2023
| 17 Jan 2023
Fortnightly variability of Chl a in the Indonesian seas
Edward D. Zaron
CORRESPONDING AUTHOR
College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, Oregon, USA
Tonia A. Capuano
Laboratory for Studies in Geophysics and Spatial Oceanography (LEGOS), Université de Toulouse, Toulouse, France
Ariane Koch-Larrouy
Laboratory for Studies in Geophysics and Spatial Oceanography (LEGOS), Université de Toulouse, Toulouse, France
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We examine temperature (T) variability at two semidiurnal and one fortnightly frequencies in North Brazil using satellite-observed and modeled temperatures. Semidiurnal T variability is weak offshore but peaks over the shelf due to barotropic mixing. Below 100 m, internal tide (IT)-driven mixing causes strong T variability (0.6–2 °C). T fortnightly maximums (~0.15 °C) appear along IT pathways, showing their key role.
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In the ocean off the Amazon shelf, internal waves caused by tides move water layers up and down and mix them. Using an underwater glider and satellites, we found internal tides redistribute chlorophyll from the deep chlorophyll maximum upward to the surface and downward to depth. Turbulent chlorophyll fluxes supply about 38 % of surface chlorophyll, and total chlorophyll increases by 14–29 % during strong tides, potentially affecting the marine food web.
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Using high-resolution satellite measurements, we observed how eddies off the Amazon shelf modify internal solitary waves. The results show that these waves can be deflected from their path, even split into two branches, and change their geometry when interacting with different types of eddies. This work provides new insight into the ocean’s complex dynamic interactions and could help guide future predictions of ocean behavior and its effects on coastal and marine ecosystems.
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MIOST24 (Multivariate Inversion of Ocean Surface Topography 2024) annual and monthly internal tide (IT) atlases, based on 25 years of altimetry data and an updated wavelength database, are presented for the Indo-Philippine archipelago and the Amazon shelf. The atlases show monthly IT variability and a better correction of IT in altimetry data than with MIOST22 (MIOST 2022) and HRET (High-Resolution Empirical Tide). The results support the development of a global MIOST24.
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We investigated how ocean tides influence marine phytoplankton along the North Brazilian coast. Using satellite data from 2005 to 2021, we found that tides can either enhance or reduce phytoplankton growth on the continental shelf. Offshore, internal tides stimulate primary production along their pathways. These results improve our understanding of how tidal processes shape marine life in tropical coastal regions.
Fernand Assene, Ariane Koch-Larrouy, Isabelle Dadou, Michel Tchilibou, Guillaume Morvan, Jérôme Chanut, Alex Costa da Silva, Vincent Vantrepotte, Damien Allain, and Trung-Kien Tran
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Twin simulations, with and without tides, are used to assess the impact of internal tides (ITs) on ocean temperature off the Amazon mouth at a seasonal scale. We found that in the surface layers, ITs and barotropic tides cause a cooling effect on sea surface temperature, subsequently leading to an increase in the net heat flux between the atmosphere and ocean. Vertical mixing is identified as the primary driver, followed by vertical and horizontal advection.
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Ocean Sci., 19, 1357–1374, https://doi.org/10.5194/os-19-1357-2023, https://doi.org/10.5194/os-19-1357-2023, 2023
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We focus on the internal solitary waves (ISWs) off the Amazon shelf, their velocity, and their variability in seasonal and tidal cycles. The analysis is based on a large remote-sensing data set. The region is newly described as a hot spot for ISWs with mode-2 internal tide wavelength. The wave activity is higher during spring tides. The mode-1 waves located in the region influenced by the North Equatorial Counter Current showed a velocity/wavelength 14.3 % higher during the boreal summer/fall.
Michel Tchilibou, Ariane Koch-Larrouy, Simon Barbot, Florent Lyard, Yves Morel, Julien Jouanno, and Rosemary Morrow
Ocean Sci., 18, 1591–1618, https://doi.org/10.5194/os-18-1591-2022, https://doi.org/10.5194/os-18-1591-2022, 2022
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This high-resolution model-based study investigates the variability in the generation, propagation, and sea height signature (SSH) of the internal tide off the Amazon shelf during two contrasted seasons. ITs propagate further north during the season characterized by weak currents and mesoscale eddies and a shallow and strong pycnocline. IT imprints on SSH dominate those of the geostrophic motion for horizontal scales below 200 km; moreover, the SSH is mainly incoherent below 70 km.
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Short summary
Phytoplankton in the upper ocean are food for fish and are thus economically important to humans; furthermore, phytoplankton consume nutrients and generate oxygen by photosynthesis, just like plants on land. Vertical mixing in the ocean is responsible for transporting nutrients into the sunlit zone of the surface ocean. We used remotely sensed data to quantify the influence of tidal mixing on phytoplankton through an analysis of ocean color, which we interpret as chlorophyll concentration.
Phytoplankton in the upper ocean are food for fish and are thus economically important to...
