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Open AccessArticle

Influence of Tropical Instability Waves on Phytoplankton Biomass near the Marquesas Islands

1
University of Brest, Ifremer, CNRS, IRD, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, 29200 Brest, France
2
IRD, UPF, ILM, Ifremer, Écosystèmes Insulaires Océaniens (EIO), 98702 Tahiti, French Polynesia
3
Laboratoire de Géosciences du Pacifique Sud, Université de la Polynésie française, 98702 Tahiti, French Polynesia
*
Author to whom correspondence should be addressed.
Remote Sens. 2018, 10(4), 640; https://doi.org/10.3390/rs10040640
Received: 21 March 2018 / Revised: 13 April 2018 / Accepted: 16 April 2018 / Published: 20 April 2018
(This article belongs to the Special Issue Remote Sensing of Ocean Colour)
The Marquesas form an isolated group of small islands in the Central South Pacific where quasi-permanent biological activity is observed. During La Niña events, this biological activity, shown by a net increase of chlorophyll-a concentration (Chl, a proxy of phytoplankton biomass), is particularly strong. It has been hypothesized that this strong activity is due to iron-rich waters advected from the equatorial region to the Marquesas by tropical instability waves (TIWs). Here we investigate this hypothesis over 18 years by combining satellite observations, re-analyses of ocean data, and Lagrangian diagnostics. Four La Niña events ranging from moderate to strong intensity occurred during this period, and our results show that the Chl plume within the archipelago can be indeed influenced by such equatorial advection, but this was observed during the strong 1998 and 2010 La Niña conditions only. Chl spatio-temporal patterns during the occurrence of other TIWs rather suggest the interaction of large-scale forcing events such as an uplift of the thermocline or the enhancement of coastal upwelling induced by the tropical strengthening of the trades with the islands leading to enhancement of phytoplankton biomass within the surface waters. Overall, whatever the conditions, our analyses suggest that the influence of the TIWs is to disperse, stir, and, therefore, modulate the shape of the existing phytoplankton plume. View Full-Text
Keywords: tropical instability waves; La Niña; chlorophyll-a concentration variability; ocean colour; island mass effect; Marquesas islands; oceanography; satellite observations tropical instability waves; La Niña; chlorophyll-a concentration variability; ocean colour; island mass effect; Marquesas islands; oceanography; satellite observations
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MDPI and ACS Style

Martinez, E.; Raapoto, H.; Maes, C.; Maamaatuaihutapu, K. Influence of Tropical Instability Waves on Phytoplankton Biomass near the Marquesas Islands. Remote Sens. 2018, 10, 640.

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