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KSI)
I Tversnit XIX so vi disse Forhold igjen. Ved
Bækkenets ostlige Skraaning, hvor Trykket er mindst, se
vi Bundvandet, stige op med lavere Temperatur og
Saltholdighed.
I Tversnitteno XXII, XXIII, XXIV og XXV
iagttage vi fremdeles, hvorledes det samme Trykkets Maximum
sender koldt Polurvand ned i Dybet. Ved Spidsborgens
Hanker ligger Tætlledsmaxima med synkende varmere og
saltere Vand.
Vi have saaledes i vort Nordhav to Trykmaxima,
deisende koldt, paa Overfladen afkjolet, og ved Issmeltniiig
tort jadet Vand, Polarvand, ifra Polarstromnien i
Grøulauds-havet og veil Jan Mayen, lied i Bækkenets dybe Partier.
Vi have andre Trykmaxima, ved Bækkenets Sydrand og
under 70° Bredde ved dets Østrand, dor senile varmere
og saltere Vand ned i Dybet. Vi have Trykniiiiima, i 1(8»
og i 74" Bredde, der bringe det koldere og saltfattigere
Dybvand op imod Overfladen. Disse forskjellige
Strømninger ville, paa Grændserne mellem dem, paavirke hverandres
Vandmasser ved Afkjøling eller Opvarmning, ved
Udspæd-ning eller Saltning. Moll saalænge Stamlinene bestaa,
blive deres iboende Egenskaber vedligeholdt i dell
Udstrækning, Iagttagelserne vise, og med don Virkning til at
holde Strømningerne vedlige, som Trykfordelingen antyder.
Efter at have studeret de vertieale Bevægelser i
Nord-havets Dyb kunne vi nu gaa over til at granske de
horisontale Bevægelser i XiveauHadornc i ile forskjellige
Dybder. Overfladens Strømninger have vi allerede tidligere
studeret og paavist deres Forbindelse med Temperaturens
og Saltholdighedens Fordeling.
I 300 Favnes Dyb have vi et Minimum af Tryk i en
Strækning fra Sydvest mod Nordost melk.....Ian Mayen og
Norge (Pl. XLI V). Denne Trykfordeling betinger en
cyclo-nisk Bevægelse omkring Minimum. Paa Østsiden bliver
Strømmen nordgaaemle, paa Vestsiden sydgaaeude. Den
torste fører Vand ind fra Atlanterhavet, dell sidste fra
Polarhavet, Trykkets Minimum ligger ikke centralt i Ha vet.
Polarstrømmens Omraade bliver større end den atlantiske
Strums. Men Kartet PI XLIV viser, at ialfald den største
Del af det under Grønlands Østkyst fra ilet indre
Polarhav indstrømmende Vand finder sit Afløb gjennem
Danmarkstrædet i Lagene mellem Overfladen og 300 Favnes
Dyb, som er Strædets mindste Dybde. Herved afgrændses
den vestligste Del af Polarstrømmen fra Circnlationen i
Nordhavet, og denne kan foregaa omkring et nogenhinde
centralt Trykiuinimum.
Langs Norilsøbanken og de norske Kystbanker ligge
Isobarerne for dot meste paa skraa mod Isobathen for 300
Favne. I dot væsentlige maa Bevægelsen nordover foregaa
langs Isobathen. Hvor Trykket langs denne er aftagende,
kan man vente en opstigende Bevægelse, altsaa med
Tcni-peraturforringelse; hvor Trykket er voxende, en nedstigende
Bevægelse med Temperaturstigning. Saadant se vi virkelig
In Transverse Section XIX. we again meet with
these conditions. On the eastern declivity of flu- basin,
where the pressure is least, the bottom-water is seen to
rise, with a lower temperature and a less amount et’ salt.
In Transverse Sections XXII. XXIII. XXIV, and
XXV, we observe the same maximum of pressure, sending
down cold Polar water into the deep. On the Spitsbergen
banks occur density-maxima, with sinking water, warmer
and salter.
We have thus in our North Ocean two
pressure-niaxima sending down cold water, cooled at the surface and
diluted by the melting of ice — Polar water — from the
Polar current in the Greenland Sea and off Jan Ma ven, into
file deep parts of the basin. (Itliel- pressure-maxima occur,
at the southern margin of the basin and, in lat. 7(1» N, at
its eastern margin, that send down warmer aml salter
water into the deep. We have pressure-minima in lat. «8"
and 74» X. bringing up the water of the deep, colder and
less salt, towards the surface. These different currents
will act at their several limits on the mass of each other’s
water, by cooling or by heating, by diluting or by
increasing the amount of salt. But, as long as the currents
exist, their inherent characteristics are maintained to the
extent shown bv the observations, together with the effect
to maintain the currents indicated by the distribution of
pressure.
Heaving studied the vertical motions in the deep
of the North Ocean, we can now pass on to examine the
horizontal motions at tile surfaces of level at the several
depths. The currents of the surface we have previously
investigated, and shown their connexion with tin-
distribution of temperature and the proportion of salt.
At a depth of 300 fathoms, we have a minimum of
pressure throughout a tract stretching from south-west to
north-east, between Jan Mayen and Norway (PI. XUYi.
This distribution of pressure determines a cyclonic motion
around tin- minimum. On the east side, the current sots
northward, on the west southward. The former branch
carries in water from the Atlantic Ocean, the latter
from the Polar Sea. The minimum of pressure does not
occupy a central position in the sea. The area of the
Polar current exceeds that of the Atlantic current. But
the map PI. XLIV shows that at all events the greater part
of the water flowing in along the east coast of Greenland
from the inner tracts of the Polar Sea, has its outlet
through Denmark Strait in the layers between tile surface
and 300 fathoms beneath, tile least depth in the Strait.
Thus the western part of the Polar current is bounded off
from the circulation of the North Ocean, and this can
take place round a comparatively central pressure-minimum.
Along the North-Sea Bank and the Norwegian Coast.
Banks, the isobars have in great part an oblique position
towards the isobath for 300 fathoms. The motion
northward must chiefly proceed along the isobath. Wherever
the pressure along the isobath is found to decrease, an
upward tendency may lie expected, accordingly with a
diminution of temperature; where the pressure is found to
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