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79
ker det iskolde Vand ved Bunden til Tærskelen mellem
G ion land og Island; söndenfor er Varmegrader ved Bunden.
Det er til et Niveau af c. 300 Favnes Dyb, at det iskolde
Vand rækker op ved Grændsen mod Atlanterhavet. ^
Den isotherme Flade for 0° ligger i Nordhavet paa
temmelig forskjellig Dybde paa de forskjellige Steder. I
Grønlandshavet og i Østhavet er der Kuldegrader allerede i
Overfladen. Deres Øst- og Syd-Grændse angives ved
Iso-thermen for 0° paa Kartet Pl. XVI. Østenfor og
söndenfor denne Linie ligger det varme Vand i de øvre Lag.
Dets horisontale Begrændsning sees paa Kartet Pl. XXV.
dets verticals paa Snittene Pl. IX til XV. I den søndre
Del af vort Nordhav række, i de øvre Lag, Varmegrader
over hele Strækningen fra Danniai’kstrædet til Norge, .lo
længere man kommer nordover, desto mere indsnevres
Bredden af det varme Vandlag. Allerede noget nordenfor
.Ian Mayen er den vestre halve Bredde iskold, og kun den
ostre har Varmegrader. Fra 74° Bredde er Bredden
betydelig indskrænket og bliver stadig mindre, indtil det
varme Vand ophører ved Nordvestspiclsbergen. I Østhavet
holder derimod Bredden sig temmelig jevn og stor.
Den Dybde, til hvilken Varmegraderne naa. er i
Almindelighed noget større ude i Havet end inde ved
Banken, og i end højere Grad er dette Tilfældet med
Isother-liien for — 1°. Den sænker sig i det søndre Bassin dybt
ned mod dets Midte, i det nordre ligger dens Iiidsæiikning
henimod den østre Skraaning. For tydeligere at vise dette
Forhold har jeg paa Kartet Pl. XXIX afsat en bred
skygget Linie, der gaar gjennem de dybeste Punkter af
Isothermerné for — 1°. Paa PI. XXVI er afsat
Isothor-niernes verticale Fordeling, projiceret paa en Meridian langs
den østlige Rand af Nordhavet. Mellem Spidsbergen og
Nordkap er sat et Grændsesnit over Beeren-Eiland, og fra
Stad til Shetland et lignende, i hvilke Isothernierne ere
optegnede i Verticalsnit. Ellers ere kun
Bundteinperatu-rerne paa Bankernes Skraaninger benyttede, og Linierne
indpassede efter Verticalsnittene og Isothermkarterne for
de forskjellige Dybder. Man vil gjenkjende Virkningen af
Landkulden i de øvre Lag. Söndenfor Vesteraalen (09°
N. Br.) ligge Isothermerne 0° til 5° meget tæt sammen.
Den følgende Tabel, hvis Tal ere tagne efter Profilet, viser
Isothermernes Dybde ved Banken og deres
Maximuins-Dybdc ude i Havet for 0° og for — 1° for de forskjellige
Breddegrader.
— in a single locality perhaps a little over — the crest
of the Wyville-Thomson Ridge. The Iceland-Færoe Ridge
lies higher. In Denmark Strait, the ice-cold water at the
bottom reaches, so to speak, the threshold between
Greenland and Iceland; farther south, water above 0" occurs at
the bottom, ft is to a level of close upon 300 fathoms
from the surface, that the ice-cold water rises up at the
boundary towards the Atlantic.
The isothermal surface for 0° lies in the Xortli Ocean
at very different depths in the various localities. In the
Greenland Sea and the Barents Sea water below 0"
occurs at the surface even. The limit to the east and
south is indicated by the isotherm for 0° in the maps,
Pl. XVI. To the east and south of this line, the warm
water occurs in the upper strata. Its horizontal limit
is shown in the map, Pl. XXV. its vertical in the sections,
Pis. IX to XV. In the south part of the North Ocean,
temperatures above 0° extend over the upper strata
throughout the whole tract, from Denmark Strait to Norway. The
farther north you go, the less becomes the breadth of the
warm water. Even a little to the north of .Tan Mayen,
half the breadth — the western — consists of ice-cold
water, the eastern only exhibiting degr ees above 0°. From
lat. 74° N, the breadth becomes considerably diminished,
and steadily lessens, till, off the north-west coast of
Spitsbergen, the warm water altogether disappears. In the
Barents Sea. on the other hand, the breadth keeps
comparatively equal and considerable.
The depth down to which a temperature above 0°
is found to reach, is generally somewhat greater out at sea
than close to the bank; and this refers in a stall higher
degree to the isotherm for — 1°. It sinks in the southern
basin to a great depth towards the middle; in the
northern, its lowest point lies towards the eastern declivity. In
order to illustrate this relation with greater distinctness. I
have drawn on the map, Pl. XXIX. a broad, shaded line
passing through the deepest points of the isotherms for — 1°.
Pl. XXVI shows the vertical disposition of the isotherms
projected on a meridian - along the eastern margin of the
North Ocean. Between Spitsbergen and the North Cape, I
have traced a boundary-section, passing over Beeren-Eiland,
and another from Stad to Shetland, in which the isotherms
are shown in vertical sections. With this exception, the
bottom-temperatures only, on the slopes of the banks, have
been used, and the lines made to agree with the
vertical sections and the maps of isotherms for the different
depths. The effect of the land-cold will be seen in the
upper strata. South of Vesteraalen (lat. 651° N) the isotherms
for 0° to 5° lie very close. The following Table, in which
the figures have been taken from the profile, gives the
depths of the isotherms on the bank and their
maximum-depth out at sea for 0° and — 1° on the different latitudes.
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