Evolution of Physical and Biological Patterns Along the Tropical and South Atlantic Western Boundary: A Satellite Perspective
We investigate the spatial and temporal patterns of satellite‐derived sea surface temperature, salinity and chlorophyll‐a concentration along the eastern South American coast. Two decade‐long time series (2002–2019; except for the salinity) allowed us to investigate changes from seasonal to interann...
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| Published in: | Journal of geophysical research. Oceans Vol. 127; no. 3 |
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| Main Authors: | , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Washington
Blackwell Publishing Ltd
01-03-2022
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | We investigate the spatial and temporal patterns of satellite‐derived sea surface temperature, salinity and chlorophyll‐a concentration along the eastern South American coast. Two decade‐long time series (2002–2019; except for the salinity) allowed us to investigate changes from seasonal to interannual time scales on an array that stretches from the south (42°S) to the north (10°N) of the continent and from isobaths ranging from −50 to −1000 m away from the coast. The novelty of our approach is to assess comparatively the magnitude, variability, and spectrum of these variables following the same isobaths and using the same methodology. This allowed us to examine the influence of large scale ocean circulation patterns entangled with the local forcing systems such as river discharge and coastal currents, and to quantify to what extent these patterns are spatially and temporally consistent. The seasonal cycle of the temperature explains more variance than that of salinity and chlorophyll on average. Comparatively, salinity has a weak seasonal signal, except near major rivers. Significant long‐term trends were observed in specific regions in the salinity time series. Our study revealed distinct interannual changes at 2‐ and 4‐year period in the whole array with the largest spectral peaks near the La Plata and the Amazon Rivers. Within this period band, thermal signals propagate northward along the whole array. Statistical correlations between satellite‐derived variables and several climate indices suggest remote forcing.
Plain Language Summary
Studies based on satellite data are useful to assess surface ocean properties on a continuous and regular basis, with global coverage and consistent methodology. In this article we analyzed sea surface temperature and salinity, and chlorophyll‐a concentration retrieved from satellite measurements along the eastern South American coast with 20‐year satellite data (except for the salinity). That allowed us to investigate how those variables are affected by regional and coastal circulations, major river discharges and oceanic source input of properties, helping us to understand their propagation patterns and connection with atmospheric remote processes. The seasonal cycle dominated the fluctuation patterns of the variables, but distinct interannual signal could also be identified in specific regions like the Amazon or La Plata river mouths. In some regions, the salinity presented significant long‐term trends. We found significant correlations between the interannual signal of some regions to atmospheric climate indices, like the Niño 3.4. Our work could be used as a reference for future studies that aim to quantify the connectivity of physical and biological parameters in the region. This is the first study aiming to assess comparatively the magnitude, variability, and spectrum of these variables following the same isobaths and using the same methodology.
Key Points
Large‐scale interannual temperature signals consistently propagate northward along the whole western boundary
The Amazon region shows a local maxima in intra‐annual chlorophyll signals
Salinity has no dominant seasonal cycle away from major rivers |
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| ISSN: | 2169-9275 2169-9291 |
| DOI: | 10.1029/2021JC017714 |