Sometimes water conditions below ice in the arctic is to be investigated. This task may make it necessary to lower an instrument through a hole drilled in the ice. As the RCM 9 does not have a large vane, as the former RCM 4 and the RCM 7 had, a hole of about only 6 to 8 inches diameter is sufficient. By having the instru- ment at a certain depth below the ice, recording of these water conditions can easily be obtained.
Figure 3. Lowered into the sea through an ice floe
Bottom currents
Besides use for basic oceanographic research, the RCM 9 has many practical uses. One of them is to learn the typical bottom currents at different locations on the continental shelf and in coastal waters. Information on the bottom currents is wanted, for instance, for selecting suitable locations for fish farms. At such sites, uneaten fish fodder and fish excrement should not accumulate underneath the maers used. Such residues if piled up, will consume oxygen from the bottom water and cause harmful gases, to be formed as a result of anaerobic processes. When a suitable bottom current exists, the residues are carried away, spread over a larger area, and made harmless. In other cases, locations with a low current speed are preferred. This is the case for various underwater installations that can be harmed by bottom sediments being accumulated or removed by the action of a strong bottom current. The RCM 9 is well suited for such use as it lends itself to be placed on the sea bed, either upside up or upside down. Data can be recorded internally, be transmitted acoustically or in certain cases be transmitted ashore by use of a cable. Besides current speed, a bottom-placed RCM 9 can report on other basic water parameters near the bottom, as for instance the water temperature, which often is wanted at locations where gas pipelines are placed.
Figure 4. Placed on die sea bed
Surface waters
The conditions at the surface of the sea is usually very different from the conditions near the bottom. Here light and oxygen are plentiful with high algae production which is sometimes harmful at certain times of the year. Here a fresh water layer can exist on top of the sea water which often has an unbalanced content of nutrition elements and high current speed. The RCM 9 is well suited for monitoring many of these conditions in the surface water of the sea.
