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106
axe. Dot ev ikke den varme Strom trå Syden, der dukker
under, men den samme, der afkjøles paa sin Overflade.
Observationerne fra den norske Kyst, navnlig fra
Lødingen og Alteuf jorden. samt fra Grønlandshavet have
vist os, hvorledes Temperaturens aarlige Vandring her
foregaar under Lufttemperaturens Indflydelse. Vi kunne ogsaa
forstaa, hvorledes Vinterkulden lægger sig ud over Havets
Overflade og gjør denne koldere end Dybet. Men hvorledes
Overgangen ude i det aabne Hav sker fra Vinter til Sommer,
derom kunne vi være i Tvivl. Vi kunne tænke os, at Luften
om Vaaren opvarmer de ovre Lag, hvorved der vilde
fremkomme et Minimum af Varme under Overfladen, der,
efterhaanden som Opvarmningen skred frem, vilde synke dybere
ned. indtil Temperaturen, som om Sommeren, aftog stadig fra
Overfladen til 100 Favnes Dyb. Dette vilde svare til, hvad
der finder Sted under Kysten. Eller vi kunne tænke os,
at det fra Syden tilstrømmende Vand tiltog i Varme i
Vaarens Lob, og saaledes, forende den højeste Temperatur i
Overfladen, afløste Vandlagene fra Vinteren. Paa et og
samme Sted vilde om Vinteren Isothermernes øverste Del
være bøiet tilbage mod Syd (som mellem 70° og 73" N. Br.
i Tversnit XXVIII); om Vaaren vilde efterhaanden
Iso-therinerne rette sig op, idet de antog sydligere Egnes
Character (62° til (57° X. Br. i Tversnit XXVIII), og ende
med om Sommeren at pege med sin øverste Del mod
Nord. Eller Teinperaturcurvcn for Stedet, der om Vinteren
skraanede med sin øvre Ende mod Kuldegraderne, vilde om
Vaaren efterhaanden blive niere og mere vertical, overskride
denne Stilling og helde om Sommeren med sin øvre Ende
mod de højere Varmegrader, uden at frembyde
Inflexions-punkter. Den sidste Betragtningsmaade antager jeg
kommer Virkeligheden nærmest, da Luftens Temperatur om
Vaaren og idethele over Havet er lavere end
Havoverfladens, og da Strømninger, udgaaende fra varmere Egne,
kunne paavises at være tilstede i de Dele af Nordhavet,
hvorom her er Spørgsmaal.
Over det norske Hav ligger i alle Maaneder
gjennemsnitlig et Minimum af Lufttryk. Sterkest udpræget er
dette i Vinteriiiaanederne1. I disse ligger et Maximum af
Lufttryk over den centrale Del af den skandinaviske Halvø.
Ifølge den bariske Vind-Lov blive de herskende Vinde
Landvinde. Fra alle Kanter, fra Øst-Island, fra Norge,
fra Spidsbergen, fra Grønlandsisen strømme disse Vinde
ud over Nordhavet. Disse Egne have om Vinteren en
Luft-Temperatur, der er meget lavere end den over Havet-;
de herskende Vinde bringe den kolde Landluft ud over
de Stra’kninger af Havet, der ligge ved Kysterne (Isgrændsen).
De afkjole Havets Overflade, sterkest Ved Kysten, mindre i
større Afstand fra denne, hvor de opvarmes af det varmere
Hav. Dette er Land kuld en, som lægger sig over Havet,
1 Ocstr. Zeitschrift fur Meteorologis 188:5.
2 Sammesteds. Kart over Luftens Temperatur i Januar.
least sensibly over the thermal axis for the air and the
sea. It is not the warm Current from the south dipping
down, but this current cooled off at its surface.
The observations from the coast of Norway, in
particular Lødingen and the Altenfjord, together with those
from the Greenland Sea, have shown us the annual
variation of the temperature lie re as affected by the
temperature of the air. We can, too, comprehend how the cold
of winter extends over the sea-surface, making it colder
than the water of the deep. But in what manner the
transition from winter to summer proceeds out in the open sea,
we have reason to question. The air in spring might
be assumed to warm the upper strata, and thus give
rise to a minimum of heat beneath the surface, which, by
degrees, as the warming progressed, would sink deeper down,
till the temperature, as in summer, was found to steadily
diminish from the surface to a depth of 100 fathoms. This
mode of propagation would agree with that observed at the
coasts. Or, we might imagine the flux of water from the
south to increase in heat during the course of spring, and
thus, with the highest temperature at the surface, to
supplant the winter-strata. In one and the same place, the
uppermost part of the isotherms would curve back
towards the south during winter (as between lat. 70" and
73° N, in section XXVIII); in spring the isotherms would
gradually rise up, assuming the character peculiar to more
southern regions (lat. 02° to 1)7° N, in section XXVIII),
and terminate with their uppermost extremity pointing in
summer towards the north. Or the temperature-curve for
the place in question, which during winter sloped with its
upper end towards the lower temperatures, would in spring
gradually become more and more vertical, then pass on and
incline during summer with its upper extremity pointing
towards the higher degrees without exhibiting any points
of inflexion. The last view of the subject comes, 1
opine, the true conditions nearest, since the temperature
of the air in spring, and generally above the sea, is lower
than that of the sea-surface, and as currents flowing from
warmer regions can be shown to exist in those parts Of
the North Ocean we have to deal with here.
Over the Norwegian Sea extends during all months of
the year, on an average, a minimum of atmospheric pressure.
Most prominent, this is found to be in winter, 1 During
that season a maximum of atmospheric pressure lies over
the central part of the Scandinavian peninsula. According
to Buijs Ballot’s Law, the prevailing winds are land-winds.
From all points of the compass — East-Iceland, Norway.
Spitzbergen, the ice of the Greenland Sea — these winds blow
out over the North Ocean. The said regions have in winter
a much lower atmospheric temperature than that observed
over the sea;2 the prevailing winds bring with them the cold
land-air and spread it over the tracts of ocean approximating
the coast (ice limit). They cool down the surface of the sea.
inshore most, less at a greater distance from land, where
1 Ocstr. Zeitschrift fiir Meteorologic, ISS.5.
- Ibid. Map of Atmospheric Temperature for January.
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