220
J. A. KITCHINB AND a. J. EBLINO
still further by the rays of the sun, so that a higher temperature is msintained there. It is to be expected that the deeper waters of the Western
Trough will become better oxygenated with the postulated autumnal
mixing, and that conditions may become much more favourable for
animals in respect of oxygen than they were during the summer. We
might expect a new onset of stagnation and oxygen depletion with the
re-establishment of a thermocline in early summer. However, all this
remains to be investigated.
3. Renewal of Water
might approach :
There are three different extreme situations which the South Basin
(a) that all the water which comes in during inflow leaves again
during outflow without mixing with the South Basin water;
(b) that all the water which flows in remains within the South Basin,
and that only old South Basin water flows out;
(c) that all the water which comes in mixes with the South Basin
water, and that mixed water flows out.
We have already provided evidence to suggest that the actual state of
affairs approximates to (c), and we shall assume that (c) obtains.
We must also assume that the hypolimnion of thc Western Trough,
which in summer is at a temperature well below that of any inflowing
water, is almost completely cut off during that season from the epilimnion. We may, therefore, regard the thermocline as forming a false
bottom, as in some Norwegian fjords (Strom, 1936). Disregarding water
below the thermocline, the average depth of the South Basin, including
the south end of the Western Trough, is about 15 m. The surface area
of the North Basin is about twice that of the South Basin, and the rise
and fall of the tide in the lough is about 1 m. We shall express volumes
of water in terms of the depth which they would occupy in the South
Basin. During inflow 3 m of new water enter the South Basin from the
Rapids, and 2 m of South Basin water are displaced into the North
Basin, giving a general rise of 1 m. During outflow 3 m of water, again
in terms of the South Basin, leave the lough, of which something less
than 2 m come from the North Basin and something more than 1 m
from the South Basin. In effect, about 50% of the South Basin water is
replaced by water from outside the Rapids in three tides; and there is
also some exchange with the North Basin. Some of the water entering
during the first hour of inflow may be old South Basin water, but it is
J. A. KITCHINB AND a. J. EBLINO
still further by the rays of the sun, so that a higher temperature is msintained there. It is to be expected that the deeper waters of the Western
Trough will become better oxygenated with the postulated autumnal
mixing, and that conditions may become much more favourable for
animals in respect of oxygen than they were during the summer. We
might expect a new onset of stagnation and oxygen depletion with the
re-establishment of a thermocline in early summer. However, all this
remains to be investigated.
3. Renewal of Water
might approach :
There are three different extreme situations which the South Basin
(a) that all the water which comes in during inflow leaves again
during outflow without mixing with the South Basin water;
(b) that all the water which flows in remains within the South Basin,
and that only old South Basin water flows out;
(c) that all the water which comes in mixes with the South Basin
water, and that mixed water flows out.
We have already provided evidence to suggest that the actual state of
affairs approximates to (c), and we shall assume that (c) obtains.
We must also assume that the hypolimnion of thc Western Trough,
which in summer is at a temperature well below that of any inflowing
water, is almost completely cut off during that season from the epilimnion. We may, therefore, regard the thermocline as forming a false
bottom, as in some Norwegian fjords (Strom, 1936). Disregarding water
below the thermocline, the average depth of the South Basin, including
the south end of the Western Trough, is about 15 m. The surface area
of the North Basin is about twice that of the South Basin, and the rise
and fall of the tide in the lough is about 1 m. We shall express volumes
of water in terms of the depth which they would occupy in the South
Basin. During inflow 3 m of new water enter the South Basin from the
Rapids, and 2 m of South Basin water are displaced into the North
Basin, giving a general rise of 1 m. During outflow 3 m of water, again
in terms of the South Basin, leave the lough, of which something less
than 2 m come from the North Basin and something more than 1 m
from the South Basin. In effect, about 50% of the South Basin water is
replaced by water from outside the Rapids in three tides; and there is
also some exchange with the North Basin. Some of the water entering
during the first hour of inflow may be old South Basin water, but it is