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
By saving cost and energy, the lighting revolution may increase light pollution
23.11.2017 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
Frictional Heat Powers Hydrothermal Activity on Enceladus
23.11.2017 | Universität Heidelberg
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
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