- Project Runeberg -  Den Norske Nordhavs-expedition 1876-1878 / The Norwegian North-Atlantic Expedition 1876-1878 / 2. Bind /
102

(1880-1901) [MARC]
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02

Til0 N. Br., 14° E. Lgd.. en Temperatur i Havfladen af
over 4°. Her var aabenbart en Tungespids for
4"-Iso-thermen. Samtidig var Temperaturen ved Fruholm 4°.
hvilket er omtrent den normale Temperatur for Aarstiden.
Ved Fruholm er den normale Temperatur for Marts 2°.4,
eller 2°.0 lavere end Normaltemperaturen for den 24.
November. En ligefrem Reduction giver Temperaturen for
Marts paa "Alberts" ovennævnte Plads lig lidt over 2°.
Imidlertid fandt Ca.pt. Otto den 7. December under 71° N. Br.
16ljt E. Lgd. en Temperatur af (>".5, hvilket er 0°.5 højere
end Aarets Medium paa dette Sted. Aarsniediet for
Fruholm er 5°.0, og Mediet for den 7. December 4".(>, altsaa
skulde den observerede Temperatur paa "Alberts"
sidstnævnte Sted være 1°.5 for højt eller den normale
Temperatur her for den 7. December 5°.0 og for Marts (4"—2°.4)
1°.G lavere eller 3°.4, et Tal, som stemnior godt med mit
endelige Kart. Jeg sætter derfor Temperaturen før Marts
under Sydkap lavere end 2°. og lægger Tungespidsen for
Isothermen for 2° paa lavere Bredde, paa 75°.5. Forøvrigt
har jeg ladet Isothermen for 2° danne en Tunge, hvis Axe
falder sammen med den af "Alberts’" Observationer
frcm-gaaende Tunge for 4".

Til Constructionen af Marts-1 sothermerne for Østhavet
Og Daninarkstrædet har jeg, da,Observationer ganske mangle,
maattet benytte en anden Fremgangsmaade. Idet jeg har
støttet mig til Observationerne fra Kyst-stationerne og
Betragtningen af IsgraMidserne tidlig om Taaren, samt efter
Analogi med Temperaturens Fordeling i Havets Overflade
om Sommeren og i Luften om Vinteren, har jeg først gjort
et Udkast til Havisotherniernes Løl) i Marts. Efter dette
Udkast og August-Isothermerne beregnedes den aarlige
Variation. og bleve Linier for ligestor aarlig Variation forsøgt
op-construerede i Kartet. Det noget uregelmæssige og mindre
sandsynlige Lob af disse Linier corrigeredes saaledes, at
Variationslinierne lik et regelmæssigt Lob (se Pl. XXIX).
Ved Hjelp af disse nye Linier for ligestor aarlig Variation
kunde jeg derpaa gaa directe over fra August-Isothermerne
til de paa Kartet PI. XXVIII fremstillede Isothermer for
Havoverfladen i Marts.

Til Isothermerne for Nordsoen har jeg benyttet
Observationer fra norske Handelsfartøjer.

Aarets Middeltemperatur har jeg beregnet paa
følgende Maade. Kaldes Middeltemperaturen for August M,
for Marts m og for Aaret A. saa kan man sætte
A = i (il/+Mi) — f (M—m)

hvor f er en constant Factor og il/—m den aarlige
Variation fra Marts til August, fra den koldeste til den varmeste
Maaned. Factoren f udledes af Observationerne fra
Kyst-stationerne. Hver af disse giver en Ligning af ovenstaaende
Form, og man faar, naar betyder Sunimationstegn,

2 A = 2 } (M+m) — f 2 (M—vi)

Cape, Spitzbergen, lat. 7(i() N, long. 14° E, a temperature at
the sea-surface reaching upwards ol’4°. This was clearly the
extremity of the tongue formed by the 4° isotherm. The
temperature at the same time at Fruholni was 4°. which is
about the normal temperature for that time of year. At
Fruholni, the normal temperature for March is 2°.4. or
2°.0 lower than the normal temperature for the 24tli of
November. A direct reduction of the temperature at the
forestated position of the "Albert," gives for March a trifli’
over 2°. Meanwhile, Capt. Otto found, on the 7th ol’
December, in lat. 71° N, long. 16°.5 E, a temperature ol’ (>°.5.
or 0°.5 higher than the annual mean determined for that
locality. The annual mean for Fruholni reaches 5°.0.
and the mean for the 7th of December 4°.0: hence the
temperature observed by the "Albert" at the last-mentioned place
should be 1 °.5 too high, or the normal temperature here
lor the 7th of December be 5°.() and for March (4°—2°.4)
l°.l) lower, or 3°.4, a result exhibiting very satisfactory
agreement with my finally constructed map. Hence, 1 put
the temperature for March, in close proximity to South
Cape, lower than 2°, and draw the point of the isothermal
tongue for 2° on a lower parallel of latitude, viz., 75°.f>.
For the rest, I have let the isotherm for 2° form a tongue
the axis of which is congruent with the tongue for 4°
resulting from the observations of tin* "Albert,"

In order to construct the March-isotherms for the
Barents Sea and Denmark Strait, I had necessarily,
observations being wholly wanting, to adopt another mode of
operation. Taking regard to the observations from the
Coast-Stations, as also to the ice-limit early in the spring, and
in accordance with analogy as shown by the distribution of
temperature at the surface of the sea in summer and in
the atmosphere during winter, I first drew a rough sketch
of the course taken by the sea-isotherms in March. From
this sketch and the August-isotherms, I computed the
annual range, and drew lines for an equal annual range on
the ma]). The somewhat irregular, and comparatively
improbable, run of these lines was corrected by giving tlie
lines of range a regular course (See Pl. XXIX). With
these new lines for an equal yearly range, I could then pass
directly over from the August-isotherms to the isotherms
drawn on Pl. XXVIII lor the sea-surface in March.

When constructing the isotherms for the North Sea,
I made use of the observations taken by Norwegian
merchant vessels.

Now, calling the mean temperature for August -71/.
that for March m, and that for the whole year A. we
can put

A = A (M-\-m) — f (M—m),

in which formula f is a constant factor and M—m the
annual range from March to August, from the coldest to
the warmest month. The factor f is determined from the
observations taken at the Coast-Stations. Each of these
gives an equation of the above form; and we get, with 2:
as the sign of summation,

2 A = 2 A (il/-f»n) — / 2 [M m),

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