A mooring consists of steel wire or synthetic rope which holds instruments at selected depth and likewise flotation glass or foam buoys which provide buoyancy to keep the construction upright. The mooring is anchored at a fixed location by a bottom weight.
Close to the bottom, but above the anchor, an acoustic release device is installed and which allow the controlled release of the instrumented part of the mooring in order to recover the instrumentation. The buoyant flotation brings the instruments plus the steel wire to the sea surface to be recovered by the attending research vessel. Most of the data are immediately retrieved from the instrumentation while on the ship, the instruments are checked, calibrated and refurbished, if necessary, and then redeployed after just a few days in order to obtain longer, uninterrupted time series of oceanic parameters.
Typical instrumentation included sensors for temperature, salinity, and current speed and direction, but also oxygen, chlorophyll, pCO2, or turbidity is recorded. Today’s technology permits long-term records of even more than 2 years while sampling at intervals of 5 to 10 minutes.
The time series records from the instrumentation permits analysis of fluctuations on many time scales, from tidal to decadal. Quality assessment of instruments and data is necessary to ensure that any observed trends or long-term fluctuations, for example, are true indicators of climate-relevant changes.
These moorings must be able to withstand the highly corrosive environment and extreme pressure and forces caused by the sea. MOSES profits from the many years of experience and expertise in the installation and maintenance of complex mooring platforms in the Physical Oceanography division. Technicians, engineers and scientists at GEOMAR work continuously on optimizing the mooring systems. Under constant development is the remote data access in near-real time of sensors.
Indispensable for this type of work is the capable and effective support at sea through the German fleet of research vessels.
The image on the right-hand side shows the principle design of a mooring with a small surface buoy to transmit data via satellite communication. The instruments include physical sensors to measure current speed and direction (yellow) as well as temperature and salinity (silver grey). The bottom anchor and the acoustic releases above it are also shown. Biogeochemical measurements are frequently included in these moorings, such as a sediment trap (collecting floating material) and carbon dioxide sensors near the sea surface.