Abstract:
The distribution of dissolved oxygen in the sea is controlled by a combination of its
physical, chemical and biological characteristics; on the one hand, the chemical and biological
activities tend to vary the content of the dissolved gas whereas, on the other, the
circulatory agencies tend to redistribute the oxygen and bring about equilibrium. The
fact that there is a constant consumption of dissolved oxygen in the depths and that frequent
supersaturation with oxygen occurs at or near the surface of the ocean was observed
on the "Challenger" expedition (Dittmar, 1884). An explanation of the cause of
supersaturation of oxygen, however, was not forthcoming until 1899 when Martin
Knudsen suggested that it was caused by photosynthetic activities of vegetable plankton.
The original oxygen content of ocean waters has been obtained from a-thin surface
layer in contact with the atmosphere and as a product of photosynthetic activity. In
modern concepts of oceanography it is a generally accepted fact that the water masses of
the depths of the oceans have at some time and place been at the surface where under the
influence of climatic conditions they acquired distinct temperature, salinity and oxygen
characteristics. The sinking of the surface layers in the so-called regions of convergence
and their ultimate distribution by means of quasi-horizontal and convectional currents
results in the whole of the ocean basins being filled with water which has acquired its
fundamental characteristics while under the influence of atmospheric conditions.
From general knowledge of oceanic circulation, based on researches of Nansen (1912),
Jacobsen (1929), Wüst (1928), etc., the water of the western basin of the North Atlantic
is probably of several origins and consequently of different ages and oxygen contents.
Thus, the deepest part of the whole basin, up to depths of 2000-1500 meters appears to
contain water which, for the most part, originated at the surface in high North Atlantic
latitudes. Lying on top of this deepest water there is, in the northern half of the region,
what appears to be a mixture of it and other North Atlantic water, while in the southern
half of the region there is at intermediate depths a mass of water which apparently originated
at the surface in high latitudes of the South Atlantic.
