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drev store Ismasser udenfor Finmarkens Kyst. Men paa
den anden Side synes Temperaturen i 100 Fa vnes Dyb ved
Lødingen i 1879 og 1880 og i Altenfjorden 1882—83 at
være saa temmelig upaavirket af de vexlende Varmetilstande
i Atmosfæren og i Havets Overflade. Det foreliggende
Materiale strækker ikke til for at udrede den nærmeste
Aarsag til de gjennem Iagttagelserne paaviste Variationer af
Temperaturen paa Bankerne og i Fjorddybene. Det
positive Resultat er, at der existerer Variationer, der synes at
være af uperiodisk Natur.
I Fjorddybene og i Dybbassiner paa Bankerne finde
vi i de større Dyb en i vertical Retning constant
Temperatur. Det er det samme Fænomen, som er fundet i
indelukkede Have, som Middelhavet, Banda Søen, Sulu Søen,
m. fl. Dersom den constante Dybtemperatur væsentlig
hidrørte fra Atmosfærens Varme, skulde den nærmest {svare
til den midlere aarlige Lufttemperatur. Thi saavel Vinter
som Sommer forblive de af Luften directe paavirkede
Vandlag øverst, paa Grund af deres i Modsætning til Dybet
ringere Saltholdighed, et Forhold, der om Vinteren ikke
rokkes ved, at Overfladens Temperatur er lavest, og som om
Sommeren understøttes af Overfladens højere Temperatur.
Varmens eller Kuldens Forplantning foregaar nedad kun
ved Ledning. Noget anderledes turde Forholdet stille sig
om Vinteren i længere Afstand fra Land. hvor
Overfladevandet er saltere, idet dette ved Afkjøling kan faa en
Tendents til at synke ned i do underliggende varmere og derfor
lettere Lag og saaledes forplante Vinterkulden ved
Strømninger nedad i Dybet. I saa Fald vil Vinterens
Lufttemperatur faa en overvejende Indflydelse paa Dybets
Temperatur, som f. Ex. Tilfældet er i Middelhavet. Skageraksdybet
turde være under lignende Indflydelse af Vinterens
Lufttemperatur.
Sammenstille vi Dyb-Temperaturen i vore Fjorde og
andre Dybbassiner paa Bankerne med Luftens normale
Temperatur for Aaret og for Vintermaanederne (December,
Januar, Februar), faa vi den i den følgende Tabel givne
Oversigt, I denne er medtaget Dybtemperaturer, maalte
med Miller-Casella-Thermometre, der have vist en stadig
Aftagen af Temperaturen med Dybden. 1
1 Potermanus (reographisclie Mittheilungeu 187(i. S. 4:52—433.
tober 1880 to June 1881 was 2°.5 to 4°.0 below the normal
temperature, and when vast masses of ice kept drifting
during the spring off the coast of Finmark. But, on the
other hand, the temperature, in depths of 100 fathoms, at
Lødingen during 1879 and 1880 and in the Altenfjord
during 1882 and 1883, would appear to have been
well-nigh uninfluenced by the varying thermal conditions in the
atmosphere and at the surface of the sea. The material
before me will not suffice to explain the proximate cause of
the variation in temperature on the banks and in the depths
of the fjords shown by the observations to have occurred
there. Meanwhile, the positive result proves the existence
of variations apparently unperiodical in character.
In the depths of the fjords and in the deep
basins on the banks, we meet in greater depths, a
vertically constant temperature. This is the same
phenomenon observed in inland seas, e. g. the Mediterranean, the
Banda Sea, the Sulu Sea. Were the constant
deep-temperature mainly the result of atmospheric heat, it
should most nearly correspond with the mean annual
temperature of the air. For, both in winter and summer, the
layers of water exposed to the direct action of the
atmosphere remain uppermost, by reason of their inconsiderable
amount of salt as compared to that of the deep, a
distribution not affected in winter by the surface-temperature
being lowest, and supported in summer by the higher
temperature of the surface. The heat or cold is propagated
downward by conduction only. Wholly different, however,
may this relation prove during winter at a distance
from land, where the surface-water is salter, since the
latter, when cooled, may acquire a tendency to sink down
into the warmer, and hence lighter, subjacent strata, thus
propagating downward by convection the winter-cold
throughout the deep. In such case, the atmospheric temperature of
winter would exert a paramount effect on the temperature
of the deep — as, for example, in the Mediterranean. The
Skagerak Dee]) may, perhaps, in like manner be subject to
the atmospheric temperature of winter.
If we compare the deep-temperatures in our fjords
and other deep basins on the banks with the normal
temperature of the air for the whole year, and for the
winter-months (December, January and February), we shall obtain
the general result given in the following Table. In this
synopsis are comprised the deep-temperatures registered
with the Miller-Casella thermometer that have shown a
steady diminution of temperature with depth.1
1 Petermanns Goographische Mittheilungen 187(i; pp. 432. 433.
I)eii norske Nordliavsexpeditioii. II. Mohn: Nordhavets Dybder, Temperatur og Strømninger. 12
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