Argonautica data

Argos locations

- Num.:	Beacons are registered by a number in the Argos system, not by a name.
- cl.:	This index (1, 2 ou 3) classifies the location quality; 3 is the best. For animal tracking, more difficult than buoys, you have alos 0, A and B.
- date:	The date is given in year / month / day.
- h.:	The hour of the location in hour, minutes UT (Universal Time)
- lat.:	latitude, in degrees and thousandths of degree (from -90° at the South Pole to +90° at the North Pole)
- lon.:	longitude, in degrees and thousandths of degree (from 0 to -180° (westward), from 0 to 180° (eastwards)).
- press.:	atmospheric pressure, in HectoPascal (HPa).
- temp.:	temperature, in Celsius degrees (°C).

What is shown on the map?

Bathymetry

Water depth (sea floor relief in negative). This depth is measured locally by oceanographic vessels, or computed from satellite altimetry measurements.

Mean Ocean topography

The permanent relief of ocean surface due to the great currents. This mean ocean topography was computed from altrimetric and gravimetric satellite measurements, and from in situ (i.e. made in the ocean from an oceanographic vessel or from automated buoys) measurements.

Ocean topography

Relief of ocean surface due to the currents with their variations. Ocean eddies can be observed as "trenches" (cold eddies) or "peaks" (warm eddies) on this relief.

Geostrophic currrents

Geostrophic currrents are currents computed from ocean topography (and thus from altimetric measurements): the steepest the slopes, the strongest the currents, perpendicular to the slope, are.

Surface currrents

Surface currrents are either computed from geostrophic currrents and surface winds, or from ocean forecasting models like Mercator.

Surface temperature

Surface temperature can be measured from buoys, or by satellites, or are computed by ocean forecasting models like Mercator.

Salinity

Quantity of salt in sea water is an important information: the saltier is the sea, the densest the water is, and this has a role in the way it moves. Salinity can be measured from buoys, computed from other measurements, or by ocean forecasting models like Mercator.
Salinity is expressed in "psu" (practical salinity unit), i.e. part per thousand in weight (weight of the salts with respect to 1000 grammes (1 kg) of water)

Surface winds

Winds are one of the things that make the drifting buoys move, directly, or by its effects on surface currents. They can be measure by sensors called "scatterometers", onboard satellites, or computed from weather forecasting models.

Ocean color

The phytoplankton is the vegetal part of the plankton, the micro-organisms of the seas, that constitute the first of the food chain in the ocean. Measuring the quantity of phytoplankton is thus essential to understand marine ecosystems. The presence of phytoplankton changes the colour of the water in the oceans, since it contains chlorophyll, which makes all plants on Earth green. Those measurements are sensitive to clouds, thus maps often include blank areas, where the clouds were when the satellites flew over.

Data sources

Argos

Argos sensors are onboard several satellites. They allow the locations of beacons on the Earth (ocean included)

Altimeters

Altimeters are radars onboard satellites that measure sea surface height.
Three satellites are currently operating are are all used together to computed the maps: Jason-1 (Cnes/Nasa), but also Envisat (Esa) and GFO (Geosat Follow-On, US Navy).

Mercator

Mercator Ocean develops and runs ocean forecasting models, and distributes these forecasts.
Before October 2005, those data were "only" available over North and Tropical Atlantic and over the Mediterranean Sea. Since then, they have been available over the whole ocean (see Mercator Ocean web site)

Scaterrometers

Scaterrometers are radars onboard satellites that measure wind at the surface of the sea.
The satellites used here is Quikscat (Nasa)

Sea Surface Temperature Satellites

Sea Surface Temperature is estimated by satellites from the radiation emitted by the sea surface, either infrared (high-resolution, but sensitive to cloud cover) or microwave (lower resolution, but less sensitive to clouds).
The satellites used here are Aqua (Nasa, AMSR-E microwave sensor) and TRMM (Nasa/Nasda, TMI microwave sensor)

Ocean color

By observing the sea surface with instruments looking the greens and blues of the oceans, we can deduce the phytoplankton concentration in the water (in fact, chlorophyll concentrations). Those measurements are sensitive to clouds, thus maps often include blank areas, where the clouds were when the satellites flew over.
The satellites used here are Aqua and Terra (Modis sensor)

Armor

These data are computed from satellites measurements (altimetry and sea surface temperature) and in situ measurements
They are computed in the Mercator Ocean project frame, but are not forecasts.

Surcouf

"Surcouf" surface currents are computed from geostrophic currents from altimetric satellite measurements and from surface winds from scatterometer satellites
These data are computed in the Mercator Ocean project frame, but are not forecasts.