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71
Kartet over Havoverfladens aarlige Middeltemperatur
(Pl. XVI) viser, at dennes Fordeling er afhængig, foruden
af Bredden, i højeste Grad af Kysternes Retning. Paa
mange Steder lobe Isothermerne nærmere langs
Meridianerne end langs Parallelerne. Det characteristiske for
Iso-thermernes "Lob er deres Tungeform, og Tungernes
Spidser pege paa forskjellige Steder i forskjellige Retninger.
Den højeste Temperatur tindes i Kartets sydvestlige Hjørne,
hvor Isothermen for 11° optræder. Den laveste
Temperatur findes i Grønlandshavet, hvor Isothermen for 0° løber
parallel med dettes omtrentlige Grændse, og i den nordre
Del af Østhavet mellem Spidsbergen og Novaja
Semlja-I begge Have betegner Nulgrads-Isothermen den omtrentlige
midlere Isgrændse. Isotherm-Tungernes concave Parti an.
giver ved sin Rækkefølge i Almindelighed den Egn,
hvorfra Stedets Temperatur har sit Udspring, forsaavidt den er
et Resultat af Strømninger. Man kan saaledes tale om
varme og kolde Isotherm-Tunger. En Linie, der forbinder
de successive Tungespidser, bliver en Varme-Axe eller en
Kulde-Axe, der har den Egenskab, at i begge Retninger
tvers paa Axen, saavel til Højre som til Venstre, er
Temperaturen i Overfladen respective synkende eller stigende.
En Varme-Axe kan forfølges fra Atlanterhavet vesten
-for Skotland, mod Færø-Island-Ryggen, langs denne mod
Islands sydostlige Hjørne. Som dens Fortsættelse kunne
vi betragte den langs Islands Vestkyst og Nordkyst gaaende
Række af varme Tunger.
En anden Varme-Axe udgaar fra den forrige
vestenfor Færøerne og tager Vejen nordenom disse Øer mod Øst
ved den 63. Breddegrad, hvor den slutter sig til den næst
følgende.
Denne udgaar fra samme Sted som den første, bøjer
mod Øst nordenfor Orkenøerne, passerer Shetland og gaar
herfra udenfor den norske Vestkyst. Udenfor Lofoten
sender den en Arm mod Vest henimod Jan Maven; under den
70. Breddegrad sender den en Arm nordover, der løber
langs Spidsbergens Vestkyst helt op til den 80.
Breddegrad, og en tredie Arm følger Norges Kyst østenfor
Nordkap og den Murmanske Kyst til det Hvide Hav og Novaja
Semlja.
En Varme-Axe sees ogsaa i Syd for Jan Maven,
gaaende mod Nordvest op paa Vestsiden af denne 0.
En Kulde-Axe er antydet fra den nordlige Del af
Østhavet henimod Spidsbergens Sydkap og Beeren-Eiland.
En anden fra Grønlandshavet mod Sydost omtrent
midtvejs mellem Spidsbergen og Jan Mayen.
En tredie østenfor Jan Mayen.
En fjerde fra Grønlandshavet mellem Jan Mayen og
Island, udenfor Islands Østkyst og videre mod Sydost til
The Map giving the Mean Annual Temperature of the
Sea-Surface (Pl. XVI), shows the distribution to be
dependent, not only on the latitude, but also, in the highest
degree, on the direction of the coast. In many localities,
the isotherms run closer along the meridians than they do
along the parallels. The most prominent characteristic
distinguishing the course taken by the isotherms, is their
linguiform shape, and the tip of the tongue points in
different places in different directions. The highest temperature
is seen to occur in the south-western corner of the map,
together with the isotherm for 11°. The lowest
temperature occurs in the Greenland Sea, where the isotherm for 0°
runs parallel to the approximate limit of the latter, and
in the northern tract of the Barents Sea, between
Spitsbergen and Novaja Semlja. In both seas, the isotherm for 0°
marks the approximate mean limit of ice. The concave
part of the linguiform isotherms generally points towards
the tract from which the local temperature has its origin,
provided it result from the action of currents. Hence, we
can speak of warm and cold isothermal tongues. A line
connecting the successive extremities of the linguiform
parts, constitutes an axis of heat or of cold, with the
property, that in both directions perpendicular to such an
axis, alike to the right and to the left, the temperature
at the surface is respectively falling or rising.
An axis of heat may be traced from the Atlantic,
west of Scotland, to the Færoe-Iceland Ridge, and along
the latter towards the south-eastern extremity of Iceland.
As its continuation, we may regard the series of warm
isothermal tongues extending along the west and north
coasts of that island.
Another axis of heat strikes off from the preceding,
west of the Færoes, and makes its way north of those
islands towards the east, at the 03rd parallel of latitude,
where it joins that next in succession.
This axis extends from the same point as the first,
makes a bend to the east north of the Orkney Islands,
and passes Shetland, proceeding thence towards the
West Coast of Norway. Off Lofoten it sends off an arm
westward, in the direction of Jan Mayen; at the 70th
parallel of latitude it sends off an arm northward, which
extends along the west coast of Spitzbergen, as far as the
80th parallel of latitude; and a third arm follows the coast
of Norway, east of the North Cape, and the Murman
coast, to the White Sea and Novaja Semlja.
An axis of heat also extends south of Jan Mayen,
passing towards the north-west up along the west side of
that island.
An axis of cold is found to proceed from the
northern part of the Barents Sea towards South Cape,
Spitzbergen, and Beeren Eiland.
Another extends from the Greenland Sea towards
the south-east, about midway between Spitzbergen and
Jan Mayen.
A third occurs east of Jan Mayen.
A fourth passes from the Greenland Sea between
Jan Mayen and Iceland, off the east coast of the lat-
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