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179
Meridiansnittet XXVIII, Pl. XLI. der viser
Tiet-hedens Fordeling, er særdeles oplysende med Hensyn til
Motivet for de opstigende og nedstigende Bevægelser.
Under 64° Bredde have vi et Maximum af Tæthed
og Maximum af Tryk. Det tungeste Vand synker ned
gjennem det mindre tunge.
Under 68° Bredde have vi et Minimum af Tæthed.
Her, hvor ogsaa Trykket har sit Minimum, stiger det
lettere Vand tilvejrs.
Under 70° Bredde have vi et Maximum af Tæthed,
og der er et Maximum af Tryk. Det tungere Vand
synker ned, omgivet af lettere.
Under 74° til 75° Bredde have vi et Minimum af
Tæthed. Her er. ved Trykkets Minimum, det lettere Vand
i Opstigning.
Og under 76° til 77° Bredde have vi et Maximum af
Ta’thed, et Maximum af Tryk og det tungere Vand
synkende nedad.
Sammenligne vi dernæst Tversnittene. der vise
Temperaturens, Saltholdighedens og Tæthedens Fordeling tvers
paa Meridianerne, med Trykkenes Fordeling i de dybere
Lag, saa er følgende at bemerke.
I Tversnit X kommer paa Vestsiden koldt og noget
mindre salt Vand ned fra Jan Mayen Benden. Paa
Østsiden drages det kolde Bundvand opad langs Bundens
Skraaning, henimod Trykminimet under (58° Bredde. I
Midten udover Dybets Trykmaximum sin nedadforende
Virkning paa Temperatur og Saltholdighed.
I Tversnit XIII se vi paa vestre Side Virkningen af
Vandet fra Jan Mayen Benden, der er varmest og saltest
ved selve Jan Maven-Banken. Paa Østsiden løfte
Tsother-rnerne og Isosalinerne sig under Indflydelse af Trykkets
Minimum under 08° Bredde. Tæthedernes Fordeling her
(Pl. XXXIX) give Billedet af opstigende Bobler af lettere
Vand.
I Tversnit XV sees Virkningen af Trykkets Maximum
i Isothermernes og Isosalinernes Sænkning mod Dybet.
Under Jan Mayen, hvor det er Polarstrømmens kolde Vand,
der er i Synkende under Trykmaximum, frembringes
Kuldegrader fra øverst til nederst. Det tætteste Vand befinder
sig i Midten af Snittet mellem Jan Mayen og Norge.
I Tversnit XVII se vi Isothermerne mellem
Meridianerne 5° AV og 5° E løfte sig under Trykkets Minimum.
Vestenfor ligger Polarvandets kolde og saltfattigere Lag.
Østenfor ligger varmere og saltholdigere Vand. med
nedstigende Tendents, under et Trykmaximum med absolut
Tæthedsmaxiinuni.
its similar relations. Hence, the stronger vertical motions
in the deep produce corresponding vertical motions in the
upper strata.
The meridional section XXVIII, Pl. XLI, showing
the distribution of density, is remarkably elucidative as
regards the cause of the upward and downward motions.
In lat. 64° N, we have a maximum of density and
a maximum of pressure. The heaviest water sinks through
the lightest.
In lat. G8° N, we have a minimum of density. Here,
where the pressure too has its minimum, the lighter
water ascends.
In lat. 70° N, we have a maximum of density, in
conjunction with a maximum of pressure. The heavier
water sinks, surrounded by lighter.
In lat. 74° to 75" N, we have a minimum of density.
Here, at the minimum-pressure, the lighter water is rising.
And from lat. 76° to 77° N, we have likewise a
maximum of density and a maximum of pressure, with the
heavier water sinking down.
Now, if we next compare the transverse sections,
showing the distribution of the temperature, the amount
of salt, and the density across the meridians, with the
maps showing the distribution of pressure in the deeper
strata, the following remarks are called for.
In Transverse Section X, water both cold and
containing a somewhat less proportion of salt flows down from
the Jan-Mayen Channel. On the east side, the cold
bottom-water is drawn up along the slope of the bed towards
the pressure-minimum, lat. 08° N. In the middle, the
maximum of pressure in the dec]) exerts its downward
effect on the temperature and amount of salt.
In Transverse Section XIII, we observe on the west side
the effect of the water from the Jan-Mayen Channel, which
is warmest and saltest on the Jan-Mayen Bank itself.
On the east side, the isotherms and the lines of equal
specific gravity rise under the influence of the
minimum-pressure lat. 68° N. The distribution of density here (PI.
XXXTX) shows, so to speak, ascending bubbles of lighter
water.
In Transverse Section XV, we see the effect of the
maximum-pressure in the descent of the isotherms and the
lines of equal specific gravity towards the deep. Off
Jan-Mayen, where the cold water of the Polar current
sinks, acted on by the pressure-maximum, degrees below
zero occur from the surface to the bottom. The water
of greatest density occupies the mid-part of the section,
between Jan Mayen and Norway.
In Transverse Section XVII, the isotherms between
the meridians 5° W and 5° E are seen to rise from the
action of the minimum-pressure. Farther west, extend the
cold strata of the Polar current, containing a less amount
of salt. Farther east, there is warmer water, richer in salt,
having a downward tendency, caused by a pressure-maximum
along with an absolute density-maximum.
23*
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