Category: Lively data

The Keops-2 oceanographic cruise ended last November. The strategy developed at sea with a new regional altimetry product to help to predict the extension of the blooms has been successful.

The possibility of predicting the extension of a plume with altimetry data is very important for cruise campaigns, because ocean color data are not available in the presence of clouds. In that case, the position of a sampling station can only rely on altimetry data. During the Keops2, a model of the plume extension ran in near-real time on board the Marion-Dufresne research vessel. The model was fed by the Ssalto/Duacs regional product and allowed to test a novel adaptive sampling strategy, by which the position of the sampling stations were adjusted day-by-day to the position of the plume. This strategy allowed to monitor the development of the bloom and its biogeochemical dynamics with a unprecedented precision for more than one month with more than 300 biophysical operations. Such detailed observations will serve to better quantify the role of the Southern Ocean on the carbon cycle. The nice fit between modeled and observed patterns highlights the key role of horizontal transport in structuring in space and time phytoplankton abundance and the possibility of studying this mechanism by satellite altimetry.
Although both altimetric products do a good job, the regional one is clearly better in predicting the southern flank of the bloom extension (see in particular the pattern centered in 79°E 51°S, highlighted by the black ellipses on the figures below). Note that a difference in the plume extension corresponds to differences in the regional primary production and carbon export.

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(A-B) Ocean color image from MODIS / MERIS for the 11/11/2011. (A) shows the expected Chlorophyll concentration, (B) provides the pattern of the chlorophyll plume (obtained by setting a threshold on (A)). (C-D) Prediction of thebloom extension by a model driven by Ssalto/Duacs altimetry data. Panel C uses the global product, panel D the regional one. Credits LOCEAN/ F. d'Ovidio.

Further information:

• <link http: www.obs-vlfr.fr keops2 _blank external-link-new-window>Special issue Biogeosciences, 2014
• Smetacek V. et al. (2012), Deep carbon export from a Southern Ocean iron-fertilized diatom bloom, <link http: www.nature.com nature journal v487 n7407 full nature11229.html _blank external-link-new-window>Nature 487, pp 313-319
• Buesseler (2012), The great iron dump, <link http: www.nature.com news dumping-iron-at-sea-does-sink-carbon-1.11028 _blank external-link-new-window>Nature 487, p 305
• Centre d'Océanologie de Marseille website: Keops-2 <link http: www.com.univ-mrs.fr keops_2.html _blank external-link-new-window>Objectives
• IPEV website: <link http: www.institut-polaire.fr ipev actualites tout_public des_nouvelles_du_terrain keops_ii _blank external-link-new-window>Keops-2, des nouvelles du terrain (in french).
• Club des Argonautes: <link http: www.clubdesargonautes.org faq keops.php _blank external-link-new-window>Prévoir la floraison planctonique (in french)
• Image of the month, <link http: cms-dev.cls.fr internal-link>April 2009: Cruise around Kerguelen Island
• Access to Ssalto/Duacs data delivered for Keops-2 : first subscribe by filling in the <link http: cms-dev.cls.fr internal-link>form.