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339
E. R. Gunther. "A Report on Oceanographical Investigations in the
Peru Coastal Current." Discovery Rep., Vol. 13, pp. 107—276, Plates
XIV—XVI, 71 Fig. Cambridge, 1936.
"Variations in Behaviour of the Peru Coastal Current." Geograph.
Journ., Vol. 88, No. 1, pp. 37—65, 6 Fig. London, 1936.
In the report on oceanographical investigations in the Peru Coastal
Current which were undertaken by the R.R.S. "William Scoresby" in 1931,
G u n t h e r has dealt in great detail with the temperature and salinity of
the waters and has discussed the phosphate distribution and certain features
of the life of the sea. By making use of all available information concerning
the character of the waters and currents off the coast of Peru he has been
able to generalize a number of his important conclusions.
G u n t h e r discusses the name of the current in considerable length and
decides in favour of the name "The Peru Coastal Current", discarding the
name "The Humboldt Current" which recently was revived by W ii s t.
Since the work of the "William Scoresby" was limited to the coastal region
and since most sections run only to a distance of 100 to 200 miles out
from the coast, the discussion has been limited to the coastal region. Within
this region the distances between the stations which have been occupied
are small, for which reason many sections show a number of interesting
details which throw light on the processes of upwelling.
The upwelling has previously attracted great interest and it is natural that
emphasis is placed on this phenomenon. G u n t h e r's discussion reveals two
interesting features. It is evident that the upwelling does not take place
to the same extent in every region. Certain preferred areas exist between
which tongues of warm water appear to approach the coast. The observations
of the "William Scoresby" indicate the presence of two such tongues, one
approaching Callao from the north-west and one approaching the Bight of
Arica • from the same direction. Temperature observations indicate that
similar tongues are found in more southerly latitudes. G u n t h e r interprets
these tongues as showing the existence of anticyclonic swirls. He explains
the appearance of aguaje, accompanied by disastrous destruction of fish and
lesser forms of life by warm water, as the result of the convergence of the
wedge of warm water with the coastal water.
The observations lead G u n t h e r to the conclusion that the upwelling
has an intermittent character. Under the influence of strong southerly winds
the light surface water is transported away from the coast and replaced by
cold water of higher salinity and high phosphate content, but when the
wind dies off or reverses the cold and heavy water masses subside and lighter
water spreads towards the coast. During the upwelling, water is drawn to
the surface from depths not exceeding 300 metres and generally less than
150 metres. Below the upper layer water of high salinity and relatively
high temperature appears to flow towards the south. G u n t h e r is able
to show a remarkably close correlation between the physico-chemical
characteristics of the water and a number of biological phenomena.
G u n t h e r's conclusions concerning the character of the complicated
Peru Coastal Current are corroborated by reports from earlier expeditions
and by incidental observations of southerly currents in the regions where
G u n t h e r supposes that the tongue of warm water approached the coast.
Several such observations have previously been discarded as erroneous, but
they fit remarkably well in the picture at which G u n t h e r arrives. His
system, showing intermittent upwelling followed by subsidence, and indicating
quasi-stationary horizontal swirls of great dimensions, is in striking contrast
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to the schematic picture which D e f a n t recently has given of the region
of upwelling off south-west Africa, but it is noteworthy that recent work
off the coast of Southern California indicates conditions which are quite
similar to those described by G u n t h e r from the area off the coast of
Chile.
When discussing the possibility of mixing leading to formation of water
of greater density than both components and thus to sinking, G u n t h e r
appears to have made a mistake which has influenced his conclusion. On
page 140 he states that if surface water from stations WS 617 and WS 615
were mixed in the ratio 5:8, the mixture would have a density of 25-94
and would not be in equilibrium with surrounding water until it had sunk
to a depth of about 40 metres. The correct value of the density is,
however, 25-52, and this water would be in equilibrium with surrounding
water directly below the surface. This is a minor point since G u n t h e r
supposes only in one instance that processes of mixing may lead to sinking.
On the whole he has undertaken a most careful discussion of the data and
arrived at conclusions which, in the opinion of the reviewer, will find
application within other areas.
H. U. S.
E. E. Watson. "Mixing and Residual Currents in Tidal Waters as
Illustrated in the Bay of Fundy." Journ. Biol. Board Canada, Vol.
II, No. 2, pp. 141—208, 26 Fig. Toronto, 1936.
The paper presents the hydrographic part of an investigation carried
out by the International Passamaquoddy Fisheries Commission in order to
determine the probable effect on the fisheries of a proposed tidal-power
construction involving the damming of Passamaquoddy and Cobscook bays.
The Bay of Fundy is well known for its great tidal range. Another
important hydrographic factor is the freshwater discharge. On an average
60°/o of this comes from the Saint John river. The yearly variations of
the watershed have a considerable influence on the distribution of temperature and salinity in the bay.
Owing to the predominance of the tidal currents the residual currents
are difficult to detect. The author discusses the different methods available
for the determination of them and shows why no one has been able to
give a satisfactory solution. After an introductory part, dealing with the
topography of the bay, freshwater discharge, tidal effects and wind effects,
the author gives a detailed analysis of the observations of temperature and
salinity. The water movements in the different parts of the Bay of Fundy
at different times of the year are considered. In Part III the hydrological
phenomena, studied in connexion with the Bay of Fundy are discussed
from a more general point of view, viz., estuarial mixing, the formation
and maintenance of homogeneous water, the conditions for the occurrence
of permanent residual currents and the effect of shoaling bottom on tidal
waters.
It appears that the Saint John estuarial water flows out to sea as a
strongly stratified layer, about 10 metres thick, retaining its lower boundary
as far as Grand Manan island (74km.). This is due to the features of
the river estuary and the adjoining sea. The turbulent influence of bottom
friction in gradually shoaling waters is found to extend upwards to
20—50 metres. Stratified regions are found, where tidal mixing causes
an outflow of mixed water at an intermediate depth with an inflow at
both the surface and bottom, and regions where the fresh water is mixed