The oceans have their desert zones, in other words areas poor in nutrients and unfavourable for phytoplankton to develop. Half of the southern Pacific thus consists of great expanses of warm water with an average temperature of 28 °C (a greater surface area than Europe), which receives no input of deep-source cold water, rich in nutrient salts.
However, in 2000 analyses of satellite observations on the colour of the ocean conducted by American scientists revealed unusually high concentrations of chlorophyll -the green pigment carried by phytoplankton- in these unfertile areas. These accumulations were associated with the movement of Rossby waves and variations in ocean height they generate (2). An initial hypothesis proposed that Rossby waves induce an intermixing which prompts intermingling between the layers of warm water at the surface and the deep cold nutrient-rich water levels. This mixing wouls generate surface influx of nitrates, favourable for phytoplankton development. This hypothesis cannot explain, however, why the chlorophyll concentration peaks are always observed at the warmest spots where the water accumulates under the effect of the passing waves.
The IRD oceanographers and their co-workers investigating these effects (1) consider rather that the Rossby waves act like a rake over the ocean surface, in this way concentrating all floating particles or debris in these places where warmer water accumulates owing to greater sun exposure. This excludes the possibility of nutrients ascending from the deep cold waters by mixing. In the convergence zones produced by wave movements, there would not be any new production of phytoplankton as had been suggested, but rather an accumulation of floating organic particles of a different origin. This floating material’s optical properties are similar to those of chlorophyll, so it gives the same effect as captured by satellite observation of ocean colour, in a way misleading the calculation systems which use these satellite colour data to estimate the chlorophyll concentration.
Marie Guillaume | IRD
Further information:
http://www.ird.fr/us/actualites/fiches/2003/190.htm
http://www.ird.fr/sais/cgi/TrSaS?nomPopulation=unites&procedure=POPULATION.AfficherObjets&action=ArPAGE&nomObjet=R086
http://www.ird.fr
Clear as mud: Desiccation cracks help reveal the shape of water on Mars
20.04.2018 | Geological Society of America
Hurricane Harvey: Dutch-Texan research shows most fatalities occurred outside flood zones
19.04.2018 | European Geosciences Union
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
Anzeige
Anzeige
Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"
13.04.2018 | Event News
Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018
12.04.2018 | Event News
IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur
09.04.2018 | Event News
Magnetic nano-imaging on a table top
20.04.2018 | Physics and Astronomy
Start of work for the world's largest electric truck
20.04.2018 | Interdisciplinary Research
Atoms may hum a tune from grand cosmic symphony
20.04.2018 | Physics and Astronomy