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Screencast tutorial for the new LAS version

Tue, 14 Aug 2012 13:57:00 +0000

New Lively Data as a screencast tutorial, where each step is directly described by markers on the...

Keops2: Plankton blooms modeled

Fri, 10 Feb 2012 13:31:00 +0000

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 79Â°E 51Â°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.

(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:

Special issue Biogeosciences, 2014
Smetacek V. et al. (2012), Deep carbon export from a Southern Ocean iron-fertilized diatom bloom, Nature 487, pp 313-319
Buesseler (2012), The great iron dump, Nature 487, p 305
Centre d'OcÃ©anologie de Marseille website: Keops-2 Objectives
IPEV website: Keops-2, des nouvelles du terrain (in french).
Club des Argonautes: PrÃ©voir la floraison planctonique (in french)
Image of the month, April 2009: Cruise around Kerguelen Island
Access to Ssalto/Duacs data delivered for Keops-2 : first subscribe by filling in the form.

Keops2: plankton bloom

Thu, 17 Nov 2011 12:55:00 +0000

One of the goals of Keops-2 is to better understand the biogeochemical mechanisms at the beginning of the biological activity season. To do this, samplings are done in specific areas, especially around the ocean eddies. The regional altimetry products (SSALTO/DUACS) made for this occasion help by giving locations where to take the bio-chemical samples with respect to the ocean dynamics for the best results.
In November, a plankton bloom can be seen in ocean color data (see the animation). Good correlation can be observed between those data and absolute dynamic topography.

Regional Absolute Dynamic Topography on 2011-11-15 and ocean color for the same day. A plankton bloom is ongoing, with nutrient-rich eddies clearly visible.

Keops-2 Background and objectives

Wed, 19 Oct 2011 09:17:00 +0000

This is "News from the cruise Keops-2", which during the southern spring, aims to give news from scientists embarked on this research cruise, to explain their objectives and present their results. Fifty scientists are preparing to board the research vessel Marion Dufresne for the cruise Keops-2, which will cross the Kerguelen Plateau in the Howling Fifties, in the Southern Ocean. Keops-2 is a project funded by the Agence Nationale de la Recherche (ANR), the Centre National de la Recherche Scientifique / Institut National des Sciences de l'Univers (CNRS / INSU) and the Institut Polaire Paul-Emile Victor (IPEV). The first campaign (Keops-1) took place during the austral summer in 2005. Its purpose was to measure the biological activity (including phytoplankton) depending on the chemical composition (including iron) and the impact on the biogeochemical cycles (especially the carbon cycle, including CO₂). The atmospheric CO₂, key component for its role of greenhouse gas and its impact in global warming, is partly assimilated into the ocean by the biological "pump". Photosynthetic organisms (including phytoplankton) within the upper ocean's sunlit zone, transform CO₂, which "residues" are transported to the ocean deep layers. The ocean biological pump is thus a major process in controlling the content of CO₂ and hence the Earth's climate.

This new campaign, Keops-2 occurs at the beginning of the biological activity season (in 2005, it was at the end of this season), in deeper waters, at the East of the Kerguelen Plateau. Its purpose is to better understand the biogeochemical mechanisms that we have just described. New analysis tools are implemented, such as profiling floats and satellite data in real time.

A specific support from CNES allows to deliver the satellite data in real-time and delayed-time, specifically processed for this area. These data include Ssalto / Duacs sea level heights, a new mean dynamic topography (MDT) over the area, geostrophic currents and the currents induced by wind (Ekman currents). Others data from satellite sensors (Modis and Meris) measured the ocean color (and thus biological activity) are also distributed.
In return, in situ data collected during the campaign will contribute to calibrate the satellite measurements and to improve the models.

Examples of Ssalto/Duacs products processed and delivered for the Keops-2 project: new Mean Dynamic Topography (MDT) over the Kerguelen area (above) and absolute dynamic topography with absolute geostrophic velocities in near-real time (bottom). Credits Ssalto/Duacs.

Further information:

IPEV website: Keops-2, des nouvelles du terrain (in french).
Image of the month, April 2009: Cruise around Kerguelen Island
Access to Ssalto/Duacs data delivered for Keops-2 : first subscribe by filling in the form.

High Mediterranean Sea Level Anomalies

Thu, 10 Feb 2011 13:33:00 +0000

High positive Sea Level Anomalies are currently observed in Mediterranean Sea. Consequence of...

Cold winter and negative NAO

Fri, 17 Dec 2010 15:00:00 +0000

Comparison of the ocean situation in 2009-2010 and the situation today where the winters are...

Benguela current, an Atlantic NiÃ±o ?

Tue, 30 Nov 2010 15:58:00 +0000

Some warm events in the South Atlantic Ocean have been named Benguela NiÃ±os, because of the...

Surface circulation in the Eastern Mediterranean

Thu, 22 Jul 2010 15:07:00 +0000

Currents and eddies are numerous in the Levantine basin. They shift along the islands or disappear...

Gulf Stream variability

Thu, 10 Jun 2010 15:25:00 +0000

The Gulf Stream is a turbulent western boundary current with strong variations caused by an intense...

Ocean circulation in the Solomon Sea

Fri, 16 Apr 2010 14:10:00 +0000

The Solomon Sea is a key area where currents redistribute water from the subtropics to the equator....

Eddy activity in South China Sea

Fri, 26 Mar 2010 16:57:00 +0000

The South China Sea is a large semi-enclosed sea where the seasonal circulation is driven by the...

Navidad current and North Atlantic Oscillation

Thu, 25 Feb 2010 15:49:00 +0000

The LAS is used to map the typical eddies (called swoddies) of the Navidad current. For this...

Seasonal reverse in the Somali current

Fri, 29 Jan 2010 09:50:00 +0000

Along the Somali coast, the seasonal circulation changes drastically with a spectacular reverse in...

On the borders of the Gulf Stream

Tue, 29 Dec 2009 08:41:00 +0000

Along the northern boundary of the Gulf Stream, where the subtropical and subpolar gyres meet...

Meeting the Mindanao and the Kuroshio currents

Tue, 24 Nov 2009 16:08:00 +0000

The western equatorial Pacific Ocean is an area with a complex circulation. The geostrophic...

Cold waters and wet African monsoon

Mon, 21 Sep 2009 14:20:00 +0000

The LAS illustrates the negative SLA (cold waters) occuring this summer in the Gulf of Guinea,...

Severe typhoon Morakot in the western Pacific

Tue, 18 Aug 2009 16:45:00 +0000

Wind and wave near-real time data deduced from altimetry and integrated in the LAS can help to...

Prelude to El NiÃ±o

Fri, 17 Jul 2009 08:59:00 +0000

While current observations indicate El NiÃ±o conditions are increasing across the equatorial...

Meddies in the Atlantic Ocean

Thu, 18 Jun 2009 13:43:00 +0000

'Meddies' are defined as warm and salty eddies of Mediterranean water sinking in the Atlantic...

Drawing formal mapping error maps

Wed, 20 May 2009 09:09:00 +0000

A comparison on maps of merged SLA before/after the Jason-2 integration shows a formal error...