Impact of eddies on surface chlorophyll in the South Indian Ocean

Dufois, Francois, Hardman-Mountford, Nick J., Greenwood, Jim, Richardson, Anthony J., Feng, Ming, Herbette, Steven and Matear, Richard (2014) Impact of eddies on surface chlorophyll in the South Indian Ocean. Journal of Geophysical Research C: Oceans, 119 11: 8061-8077. doi:10.1002/2014JC010164

Author Dufois, Francois
Hardman-Mountford, Nick J.
Greenwood, Jim
Richardson, Anthony J.
Feng, Ming
Herbette, Steven
Matear, Richard
Title Impact of eddies on surface chlorophyll in the South Indian Ocean
Journal name Journal of Geophysical Research C: Oceans   Check publisher's open access policy
ISSN 2169-9291
Publication date 2014-11
Year available 2014
Sub-type Article (original research)
DOI 10.1002/2014JC010164
Open Access Status
Volume 119
Issue 11
Start page 8061
End page 8077
Total pages 17
Place of publication Hoboken, NJ, United States
Publisher Wiley-Blackwell Publishing
Collection year 2015
Language eng
Abstract A unique feature of the subtropical South Indian Ocean is the existence of anticyclonic eddies that have higher chlorophyll concentrations than cyclonic eddies. Off Western Australia, this anomalous behavior is related to the seeding of anticyclonic eddies with shelf water enriched in phytoplankton biomass and nutrients. Further off-shore, two mechanisms have been suggested to explain the eddy/chlorophyll relationship: (i) eddies originating from the Australian coast maintain their chlorophyll anomaly while propagating westward; and (ii) eddy-induced Ekman upwelling (downwelling) enhances (dampens) nutrient supply in anticyclonic (cyclonic) eddies. Here we describe the relationship between eddies and surface chlorophyll within the South Indian Ocean, and discuss possible mechanisms to explain the anomalous behavior in light of new analyses performed using satellite chlorophyll data. We show that anticyclonic eddies exhibit higher surface chlorophyll concentration than cyclonic eddies across the entire South Indian Ocean basin (from 20 to 28°S), particularly in winter. Using Self Organizing Maps we analyze the chlorophyll patterns within anticyclonic eddies and cyclonic eddies and highlight their complexity. Our analysis suggests that multiple mechanisms may underlie the observed eddy/chlorophyll relationship. Based on Argo float data, we postulate the relationship may be partly related to seasonal adjustment of the mixed layer depth within eddies. Deeper mixing in anticyclonic eddies is expected to enhance nutrient supply to the mixed layer, while shallower mixing in cyclonic eddies is expected to reduce it. This could explain why the observed winter surface chlorophyll bloom is stronger in anticyclonic eddies than in cyclonic eddies.
Keyword Eddies
Self-organizing map
Convective mixing
Eddy-induced Ekman pumping
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
Official 2015 Collection
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Citation counts: TR Web of Science Citation Count  Cited 6 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 7 times in Scopus Article | Citations
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