PD-41
Fertilization of the sea with Deep Ocean Water Upwelling Machine
Dr Kazuyuki Ouchi
Ouchi Ocean Consultant, Inc.
Miyamae 5-17-22, Suginami-ku, Tokyo 168-0081, Japan
1. INTRODUCTION
In a stratified low latitude ocean area, the surface layer of the sea is warmed up by the sunlight and the high temperature air, and there is no vertical circulation between the warm surface layer and the cold bottom layer. Therefore, the sea of the low latitude area is always stratified with the temperature and density.
The mankind, wishing the sea of fertility, hopes the increase of primary production in the layer of sunlight where the photosynthesis can be done by the phytoplankton. But the primary production in the stratified sea area is very little, because the Deep Ocean Water (DOW) which includes very much nutrient-salt such as nitrogen and phosphorus etc. does not upwell to come in the layer of sunlight. Therefore, the low latitude, sea area is called "the sea of desert", and the primary production is much less than that in middle or high latitude sea area. But we have some exceptions, for example in the sea of offshore Peru, a large amount of DOW upwelling is occurred by the steady wind, so that the sea area is one of the richest fishing ground in the world, and the water temperature in the surface is lower than another equatorial sea.
If we are able to make such a large amount of DOW upwelllng artificially, we can expect to create and control the new fishing ground in "the sea of desert", and the increase of fish production is a very important issue toward the 21st century whose population will be in excess of 10 billion.
In addition of creation of the fishing ground, we can also expect the fixing carbon with photosynthesis done by the phytoplankton. But, to estimate the CO2 absorption from the air into the sea, we have to account also the amount of dissolved CO2 in the DOW in which the CO2 have been generated by bacteria in the course of decomposing the organic matter into the inorganic. 3)
In this paper, we propose, the Deep Ocean Water upwelling machine which make "the sea of desert" into "the rich fishing ground" using the technology of density current diffusion and the ocean thermal energy conversion (OTEC), and we also report the feasibility study of the machine operation.
2. DENSITY CURRENT
The main feature of the DOW upwelling machine is utilizing a density current diffusion. Owing to this property, the machine is able to affect very wide sea area with very little energy. The outline of the density current is stated in this chapter.
In the liquid stratified with density, we can see the phenomenon that the fluid of a certain density tend to flow into the layer of identical density and then spread over great distances along the layer horizontally. This kind of current has long been known as a density current.
For example, it has been confirmed that when comparatively cold water from a river flows into a lake, the river water sinks for a while within the lake until it reaches the layer of equal density and then starts flowing, changing its direction of flow to horizontal, along the layer. Also in the vicinity of a river mouth where the water from the river enters the sea, high density sea water flows into the bottom layer of the river water during rising tide, while conversely during ebb tide, low density fresh water from the river spreads over the surface of the sea water. These phenomena are caused by the density currents, which can be observed through the nature.
Fig.1 shows a schematic drawing of a density current. Here, a liquid of a certain density enters a layer of identical density in form of a wedge, and as long as there. is a supply of this liquid from behind, it moves forward, separating the liquid layers of higher and lower density like driving a wedge between them to create a density current.
In this way, gravity induces the density current through the difference of density potential between the upper and lower liquid layers. Thus the gravity provides the energy source for this movement, so that induction of this flow does not require any energy cost. This feature conceivably recommends an extensive use of this phenomenon.
