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68
afgrændser sig mod det indenfor flydende meget ferskere
Vand. Forøvrigt, holder Grændsen for det saltere
Overfladevand sig meget langt tilhavs med Undtagelse af, at
den ved den 70de Breddegrad paa en ganske kort
Strækning kaster sig tæt ind under Kysten.
Denne Fortynding af Overfladevandet, som overalt
ytrer sig ved den norske Kyst, er intetsteds ledsaget af
nogen væsentlig Forrykkelse af Overfladetemperaturen.
Salt-gehaltens Formindskelse skyldes her aabenbart det fra
Kysterne udstrømmende Flodvand, der om Sommeren besidder
en ikke ringe Varmegrad, saaledes at man i den mest
fremtrædende Kyststrøm langs Norges Vestkyst endog
linder en noget høiere Overfladetemperatur end paa
nærliggende Puncter. ’• Ganske anderledes stiller Sagen sig paa
den mod den østgrønlanske Polarstrøm vendende Side,
•hvor Overfladevandet fortyndes ikke ved Flodvand men
ved det ved Havisens Smeltning dannede, stærkt afkjølede
Ferskvand, og det viser sig derfor, at en Synken i
Saltge-halten her bestandig er ledsaget af en tilsvarende
Formindskelse af Overfladetemperaturen. Grændsen for clet saltere
Vand i Overfladen følger derfor paa denne Side ofte
Polarstrømmens Grændse, og selv der, hvor den forlader
denne, optræder der dog’ samtidig meel Overgangen fra
saltere til ferskere Vand altid meget tydelige Variationer
i Temperaturen, der gaa i samme Retning som
Saltgehal-tens. At Overfladetemperaturen synker, naar man enten
nærmer sig eller overskrider Grændsen for 3.50 °./0 Salt,
vise Observationerne No. 115 til 120 og No. 207 til 209.
I selve Polarstrømmen er Saltgehalten i Overfladen i
nogen Afstand fra Grændsen oftest fundet meget lav. kun
paa et Sted optræder i saa Henseende en Undtagelse fra
den almindelige Regel, idet der omtrent paa den 75de
Breddegrad skyder sig en smal Tunge med Vand af høiere
Saltstyrke ind over Polarstømmen, uden at der dog derved
bevirkes nogen væsentlig Forhøielse af
Overfladetemperaturen. En Mærkelighed, som fortjener at omtales, er den,
at Professor Dr. G. O. Sars, som paa Expeditionens
Togter jevnlig undersøgte Dyrelivet i Overfladen, netop paa
dette Punct langt inde i Polarstrømmen har gjenfundet de
for det varmere Atlanterhavsvand eiendommelige
Dyreformer, der forresten intetsteds ellers ere fundne i den
østgrønlandske . Koldvandsstrøm.
Med Hensyn paa Saltmængderne i de større Dyb •
henvises til Kartet No. II, hvori paa samme Maade som
ovenfor lindes indtegnet Saltgehalten ved Havbunden samt
i de intermediære Dyb. forsaavidt Observationerne refererer
sig til Puncter saa dybt under Overfladen, at
Temperaturen der ligger under 0°. Hvor en Observation hidrører
fra et intermediært Dyb, er Tallet i Kartet understrøget.
Naar man bortser fra enkelte i Nærheden af
Kysterne og paa grundt Vand optagne Vandprøver, varierer
Saltgehalten paa de store Dyb mellem 3.59 og 3.45 %,
of the salt ocean-water of the,Atlantic, distant but a few
miles from land, its boundary being distinctly marked by
the limits of the brackish water flowing along the shore.
Except in this region, and a locality bordering the 70th
parallel of latitude, where, for a short distance, it runs
close to the coast, the boundary of the salt surface-water
lies far out at sea.
This dilution of the surface-water on all parts of the
Norwegian coast is not anywhere found to exert a material
influence on the surface-temperature. The decrease in the
amount of salt must be obviously ascribed to the influx of
river-water, the temperature of which during the summer
months is relatively high, — so high indeed, that the
principal coastal current, flowing along the western shores
of Norway, lias a somewhat higher surface-temperature than
that observed in its immediate vicinity. Phenomena the
reverse of these prevail in the tract of ocean exposed to
the influence of the Arctic, or East Greenland, current.
There, the surface-water is not diluted by an influx of
river-water. but with freshwater of a low temperature, produced
by the. melting of drift-ice; and hence a decrease in the
percentage of salt is invariably attended with a
corresponding -reduction of the surface-temperature. The salt
surface-water borders, therefore, not infrequently the Arctic current;
and even where its boundary diverges from it, the
transition from salt to comparatively fresh water is always
ac-compained by a very considerable variation in temperature,
proportionate to the variation in the amount of salt. That
the surface-temperature becomes gradually lower on
approaching the limits of the section in which the proportion
of salt is 3.50 per cent, will be seen from the series of
observations Nos. 115—120 and Nos. 207—209.
In the Arctic current, some distance from its extreme
boundary, the proportion of salt at the surface was found
to be very small, except in one locality, near the 75th
parallel of latitude, where a narrow strip of salter water
flows into the current, without, however, causing an
appreciable rise in the surface-temperature. It is a remarkable
fact, which must not be passed by unnoticed, that
Professor G. O. Sars, naturalist to the Expedition, found here
in the surface-water, which he examined from day to day,
forms of animal life peculiar to the warm area of the
Atlantic water, which he never met with in any’other part
of the cold East Greenland current.
As regards the amount of salt observed at great
depths, the reader is referred to Pl. II, in which, as in
PI. I, will be found the percentage both at the bottom
and at intermediate depths, provided the observations were
taken with samples of water the temperature of which in
situ was below 0". Observations with water from
intermediate depths are denoted by underlining the figures
expressing their results.
Disregarding a few samples of water collected near
the coast and in shallow spots, the proportion of salt,
where the depth is great, ranges from 3.59 to 3.45 per
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