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185
T Jan Mayen Ilenden skyder sig i alle Dybder en
kold Tunge ned østenfor Island.
Over Islands Banker strømmer varmt Vand i
anti-cyclonisk Retning.
Mellem Island og Færøerne føres i den sydlige Del
atlantisk Vand over til det norske Hav. I den vestlige
Del af dette Strøg strømmer Atlanterhavets Vand
nordover og vestover. Denne Strøm har paa sin højre Side
Tungen fra Jan Maven Renden (Tversnit V. Pl. IX). hvis
Vand strømmer sydover. I de øverste Lag skylle Vindene
den sidstes koldere Vand udover den førstes varmere. I de
dybere Lag trænger den varmere Strøm frem under den
koldere, idet den følger Bankens Indbojninger.
Dybets Trykmaximum i Station 52, østenfor Island,
gjør sig gjældende ogsaa i de øvre Lag. Der synes at
foregaa en Sugning af varmt Vand østenfra derhenimod.
I 200 Favnes Dyb gjenfinde vi de ovenfor beskrevne
Træk i det hele taget. Kun de enkelte nye behøve derfor
her at beskrives.
Landkuldens Virkning er ophørt. Det varmeste Vand
ligger paa Havets Østside lige ved Bankerne. Under 66°
40’ N. Br., 7°—8° E. Lgd. gjør Isobathen for 200 Favne
en pludselig Bøjning mod Øst. Ligesaa i 300 Favnes Dyb.
Som PI. XLIV viser, føres her Vandet tvers udover Banken,
med nedstigende Tendens. Det er omtrent lignende
Tilfulde som paa Wyville Thomson-Ryggen. Idet Vandet i
sin nordgaaende Bevægelse forlader Banken, fører det det
nærmeste Underlag med sig. Dette erstattes nedenfra, og
koldere Vand suges saaledes ind over Banken. Man ser
dette i Karterne PI. XVIII og XIX, i Tversnit XII, Pl. X.
i Profilet Pl. XXVI og i Bundteinperaturkartet Pl. XXV,
hvor Isothermerne for 5° og 6° have betydelige
Inclsænk-ninger mod Syd.
Den tidligere Side 68 beskrevne kolde Bundstrøm
fra Storfjorden nedover Spidsbergbanken træder frem i
200 og 300 Favnes Dyb, og sees bedst paa Bundkartet
Pl. XXV. Dens Motiv finde vi i Trykfordelingen, PI.
XLIII, der giver en Gradient directe ud af Storfjorden i
Retning af det iskolde Vands Bevægelse.
Af Tversnittene og Karterne fremgaar det, at det
varme Vand paa Kystbankerne af disse beskyttes mod
Afkjøling fra neden, i Modsætning til den sterke Afkjøling,
som finder Sted der, hvor varmt og iskoldt Vand grændse
ind til hverandre, som østenfor Jan Mayen, paa
lsland-Færø-Ryggen (her i horizontal Retning),
Fan-ø-Shetland-Renden, paa Yderskraaningen af de norske Banker, med
flere Steder. I Overfladen har Strømmen sin storste
Hastighed. Den aftager nedover til 300 Favnes Dyb.
I 500 Favnes Dyb (PI. XLV) er Isobarsystemet
meget ligt det i 300 Favne. Nordhavet er ganske afspærret
In the Jan-Mayen Channel, a cold tongue shoots
down in all depths east of Iceland.
Over the banks of Iceland, warm water flows in an
anticyclonic direction.
Between Iceland and the Færoes, in the southern
part of this tract, Atlantic water is carried over to the
Norwegian Sea. In the western part water from the Atlantic
flows northward and westward. On its right side, this
current has the tongue from the Jan-Mayen Channel
(Transverse Section V, Pl. IX), whose water sets southward.
Throughout the uppermost strata, the winds sweep the
colder water of the latter over the warmer water of the
former. In the deeper strata, the warmer current forces
its way under the colder, following, as it does so, the
sinuosities of the bank.
The pressure-maximum of the deep at Station 52.
east of Iceland, asserts its influence also in the upper strata.
A suction of warm water from the east, would appear to
proceed towards that part.
At a depth of 200 fathoms, we again, on the whole,
meet with the features described above. Hence, only the
new characteristics need be set forth here.
The effect of the land-cold has ceased. The warmest
water lies on the east side of the ocean, close to the banks.
In lat. 66° 40’ N, long. 7° to 8° E, the isobath for 200
fathoms makes a sudden bend toward the east. The same
is the case at a depth of 300 fathoms. As shown in PI.
XLIV, the water here is carried straight across and past
the bank, with a downward tendency. This is much the
same as on the Wyville-Thomson Ridge. As the water,
when setting north, leaves the bank, it carries with it the
nearest substratum. For this, compensation is given from
below, colder water being drawn ill over the bank. This
is shown in the maps Pis. XVIII and XIX, in transverse
section XII, Pl. X, in the profile, Pl. XXVI, and in the
Bottom-Temperature Map, Pl. XXV, where the isotherms
for 5° and 6° form distinct loops towards the south.
The cold bottom-stream, described on page 68,
flowing down from the Storfjord over the Spitzbergen Bank,
makes its appearance in depths of 200 and 300 fathoms,
and is best seen on the Bottom-Map, Pl. XXV. Its
motive we find in the distribution of pressure, PI. XLIII,
which shows a gradient pointing straight out of the
Storfjord in the direction taken by the ice-cold water.
From the transverse sections and the maps, it appears
that the warm water on the coast banks is protected by
the latter against cooling from below, in contrast to the
very considerable cooling that results where warm and
ice-cold water border on each other, as for example east of
Jan Mayen, on the Iceland-Færoe Ridge (there
horizontally), the Færoe-Shetland Channel, on the outer
slope of the Norwegian banks, as also in several other
localities. At the surface, the current has its greatest
velocity. This decreases downwards to a depth of 300
fathoms.
At a depth of 500 fathoms (PI. XLV), the
isobar-system resembles that at a depth of 300 fathoms.
Don norske Nordhavsexpedition. II. Mohn: Nordhavets Dybder, Temperatur og St:
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