The unusual surface chlorophyll signatures of Southern Ocean eddies
Southern Ocean mesoscale eddies play an important role in ocean circulation and biogeochemical cycling, but their biological characteristics have not been well quantified at the basin scale. To address this, we combined a 15‐year tracked eddy data set with satellite observations of ocean color, sea...
| Published in: | Journal of Geophysical Research: Oceans |
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| Main Authors: | , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley-Blackwell Publishing Inc.
2018
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| Subjects: | |
| Online Access: | https://eprints.utas.edu.au/29254/ https://eprints.utas.edu.au/29254/1/130949%20-%20The%20unusual%20surface%20chlorophyll%20signatures%20of%20Southern%20Ocean%20eddies.pdf |
| Summary: | Southern Ocean mesoscale eddies play an important role in ocean circulation and biogeochemical cycling, but their biological characteristics have not been well quantified at the basin scale. To address this, we combined a 15‐year tracked eddy data set with satellite observations of ocean color, sea surface temperature, and autonomous profiling floats to quantify the surface and subsurface properties of eddies. Anomalies of surface temperature and chlorophyll were examined in eddy‐centric composite averages constructed from thousands of eddies. Normalized surface chlorophyll anomalies (chlnorm) vary seasonally and geographically. Cyclones typically show positive chlnorm, while anticyclones have negative chlnorm. The sign of chlnorm reverses during late summer and autumn for eddies between the Subtropical and Polar Fronts. The reversal is most obvious in the Indian sector, and we attribute this to a combination of eddy stirring (deformation of surface gradients by the rotational velocity of an eddy) and deeper winter mixing in anticyclones. Both chlnorm and sea surface temperature anomalies transition from dipole structures north of the Subtropical Front to monopole structures south of the Subantarctic Front. Sea surface temperature and chlnorm composites provide evidence for eddy trapping (transporting of anomalies) and eddy stirring. This research provides a basin‐scale study of surface chlorophyll in Southern Ocean eddies and reveals counterintuitive biogeochemical signals. |
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