Scientific research
How does the 'ocean machine' work?
Research is at the heart of Mercator. Understanding and explaining the intimate equilibria of the thermohaline environment, its internal dynamics and variability, its interactions with submarine relief and the atmosphere … Understanding and explaining the variations observed or predicted in living species, according to the seasons and the regions … Understanding and explaining the capacity of the ocean to absorb certain chemical species … Mercator was conceived from advances in research, it was nurtured on them and in return it has given us the means to advance our understanding of ocean physics. This is why the Mission Group was set up. The models, as well as the assimilation techniques used by the operational systems, have all come from research laboratories, as will future advances in this area (read the interview with Herlé Mercier, the GMMC President).
For its scientific users, Mercator is an operational ocean observatory: by systematically combining, over several years, all the information yielded from observations (measurements reflecting reality) with that provided by the model (a three-dimensional view and a memory of past states), it can produce a view of the ocean that is continuous in both space and time. This integrated view is extremely valuable, as it exists nowhere else. It provides a reference state which can be examined or enriched … as well as the raw materials to do it.
Mercator is involved in several areas of research:
Physical oceanography
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This is Mercator's 'parent' discipline … It explains the ocean's movements at the Earth's surface. Navier-Stokes, forcing, Ekman, Coriolis, turbulence, instability, Rossby, Kelvin, convection, stratification ... These words are the keys to understanding and modelling the thermo-dynamic behaviour of the ocean. To use physics, mathematics … and a lot of computing; such is the destiny of the physical oceanographers, or at least those 'modellers' and 'assimilators' responsible for assimilating everything that happens in the air (using satellites) or in the water (using in situ measurements). We should also not forget those oceanographers who literally get their feet wet, by going out on boats to get a close-up view of what is happening. They bring back the precious 'truths' from the field which enable us to describe the key areas of the ocean: sink zones, the great gyres, freezing zones, the great western currents, modal waters, etc. |
Coastal oceanography
Half of the world's population lives within 100 km of the coasts! Tourism, coastal development, port industries, prevention of pollution and unforeseeable climatic disasters, aquaculture, etc. These are just some of the many activities where there is an increasing demand for precise, real time information about sea conditions. Coastal models can now respond to this demand. These models, which describe and forecast small-scale coastal phenomena (from a kilometre down to around one hundred metres), require large-scale (ie: oceanic basin, global) operational models such as Mercator to provide their initial and boundary conditions. Mercator thus aids several coastal modelling teams, not only for the French members of the public interest group (CNRS, Ifremer, IRD, Shom) but also elsewhere in Europe (Spain, Portugal, Denmark, Ireland) and even one American university. |
 Source : Legi/S. Cailleau |
Biogeochemical modelling
Source : Nasa |
Just as atmospheric chemistry was able to benefit twenty years ago from numerical weather forecasting models, biogeochemistry is now growing rapidly due to the arrival of systems like Mercator. However, biogeochemical models are particularly difficult to implement, as they aim to model nothing less than living organisms! By including phytoplankton or primary productivity as variables, just like temperature or salinity, one day these models will be able to predict 'blooms' of chlorophyll in any part of the ocean. We are not there yet, but the first steps have already been taken. This is how Mercator became a partner in an experiment combining Mercator output with biogeochemical models developed by Legos within the Bionuts programme. These models can implement between one and five chemical constituents, including chlorophyll. The latter is is particularly interesting, not only due to its importance in determining the general health of the sea (chlorophyll indicates the presence of phytoplankton, which comprise the first links in the food chain), but also because of its value to the fishing industry (wherever phytoplankton is found, fish are found …). In addition, it constitutes data which can be observed in real time by satellite, thus enabling the validation of chlorophyll evolution models. |
Halieutic research
This is the study of how marine resources are affected by the fishing industry. Marine ecosystems are characterised and explained in many ways, including the thermal and dynamic conditions of the ocean. It is not difficult to see how a system like Mercator, which offers a consistent description of the evolution of oceanic parameters, in particular for temperature, salinity and current, can be viewed as a precious source of information. Today, two laboratories are using Mercator products for this purpose:
- Ifremer, for simulating sea current conditions in order to study the performance of fish concentration devices in the Caribbean,
- A Scottish university, for simulating the influence of currents on jellyfish transport and hatching in Scottish waters (the European Eurogel project).
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 Source : NOAA/DoC |
Supporting sea campaigns
Source : Ifremer/O. Dagornay |
Mercator analyses and forecasts are used during certain sea campaigns to obtain prior knowledge about the thermosaline structures a ship will encounter, in order to determine the best course it should take, ie: the one that leads to maximum benefit for any research. In this area, Mercator is a regular contributor to the Ovide and EGYPT-MC programmes. |
Climatology and seasonal weather forecasting
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Currently the focus of scientific and political attention, the climate is determined by interactions between the atmosphere and the ocean: the atmosphere triggers phenomena in the ocean through the actions of wind, precipitation and solar radiation. The ocean responds by warming or cooling the atmosphere through the combined effects of temperatures and ocean currents. Climate research advances through the study of past climate indicators (polar caps, marine sediment, etc) as well as through developments in climate modelling. However, climate models are based on coupled atmospheric and ocean modelling, thus making ocean models essential for climate modelling. The prototype version of Mercator's global low-resolution model (Minipog) is currently being used on a routine basis for Météo-France's seasonal forecast model. There is no doubt that the forthcoming high-resolution global system will attract other users. |
 Source : NOAA/DoC |
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