gdz: dp-2øsingV,dy

The y-axis is parallel

to

the section, the r-axis vertical

to

the section. This

formula

shows

that

Hnr-r,aNn-HeNsnx's statement

is

correct

only if V, :

O at the bottom (or

if it

has a very unlikely distribution along the bottom). The

Aø

distribution

at the

bottom

is not

uniform, and consequently

the

integral [a dp not unique, but dependent on the path of integration.

Dynamic depths determined

by

this method should therefore be ^considered

only in

connection

with the

section along

which the

integrations have been performed.

A

trench more than 300

m

deep extends eastward

from

Gael Hamke Bay, separating st. 20 from the previous stations. There are, however, no observations

from

this trench and the differences

of

dynamic depth between

st.

18

(or

19)

and 20 have therefore been determined

in

the following

way: The

integration la ^{dp has been} performed along a straight line connecting the point of intersection between the station vertical at st.

lB

(or 19) and the bottom

with

the

correspond-ing point at

st. 20, and

from

there vertically

to the

surface. This procedure is equivalent

to

Hor,r.nqo-HeNsnr's method of integrating along the bottom line, and is of course subject to the same limitations, mentioned above. The dynamic depth

at

st. 20 is computed relative

to

the depth

at

st. 21, being 177

m

deep.

The bottom has been taken as reference surface between these two stations.

Geostrophic

current

components

are then

computed, applying

the

above mentioned methods and formulae.

It

should be emphasized that the components are all relative to those at the reference surface. There ^is no reason to believe that the current components at the reference surface are equal in the different sections, and the components are therefore not directly comparable. The surface velocity components are shown

in

the maps Figs.

3 and

16. The isovels

in

the vertical section "Conrad Holmboe"

II

are presented

in Fig.

17.

Fig. 3 shows a weak surface current towards south-west

in

the eastern part of section "Conrad Holmboe"

II. In

the deeper layer between st.

9 and 1l

a

minor

north-easterly current

is

seen, probably

due to

the

Jan

^{Mayen Polar} current, (Hnr,r,aNo-HANsEN and NeNsEN 1909). The currents on, and near, the shelf are quite irregular and complicated (Figs.

3,

¹⁶

and

^17).

No 15, f963 THE "coNRAD HoLMBoE" ExpEDrrIoN

IN

lg2g 25

Fig. 16. Geostrophic surface current components, . Conrad lfolmboe', st. 14-21.

Fig. 17. Section "Conrad Ffolmboe"

II,

current components vertical to the section incm.sec.-l

on

the continental slope, between

st.

12

and

14, relatively strong current components are present, directed parallel to the isobaths. Strong current compo-nents are also found

in the

sections between the stations

17-20, lB-20,

and

19-20.

The sections

st. 14-15,

st.

14-17

and

st. L7-lB,

are situated on the slope, running more

or

^less parallel

to

the isobaths. The corresponding current components are

all

relatively weak.

The

strongest current components are found

on

the shelf

in

the section st.

+5+4 +l +2

r1

^f

As es 4 :l 4

26 TOR KVINGE Mat.-Naturv. serie

15-16,

amounting

to

8.2 cm/sec.

in the

surface layer.

Fig. 1l

shows

that

at these stations

the

section

is

crossing

the

border between

Atlantic and

Polar waters.

The

lines ^seem

to

be nearly parallel

to

the interface between the two watermasses. Consequently, the geostrophic current is closely related to the ^steep inclination of the border separating the water ^masses. We may therefore conclude as follows:

Current conditions are closely related to the bottom topography and to bor-ders between the water masses.

On

the

right

side,

the

current approximately follows the slope.

On

the shelf, however, the direction of the current is parallel to the border ^between the two water masses; here the highest velocities are found.

The

components

are

computed

from the

available observations,

and

the conclusions are given on the assumption that the components are approximately reliable. The smaller components are, however, doubtful, because minor errors of observation may have a relatively great effect of these values.

Neither tidal nor frictional

forces are taken

into

account.

Friction at

the bottom is probably most important on the shallow shelf. The areas dealt with are

partly

covered

by

ice floes, and

friction at

the ice cover may therefore ^also be of importance.

The

effect

of tidal

^forces is probably more significant

in

the narrow, deep trenches.

On

the basis oI the present data, however, a closer ana-lysis

ol

such ellects is

not

^possible.

Transport.

The transport ^values given below, are volume transport values, i.e. the volume oI water which, due to geostrophic current, flows through a vertical section per

unit

time.

Section.

st. l0- 9: llTT0mssec-l

Section.

st. 17-14:

67290m3sec-1

st. 1l-10:

-25230 ^st. 18-17:

¹⁵⁶⁸⁰⁰

st. l2-l

^t

: 67420

^st.

20-18:

²³²⁸⁸⁰

st. 14--12: 224890

^st.

20-17:

³⁸⁸²⁷⁰

st. 15-14: 24870 ^st. 20-19:

¹⁹¹⁰³⁰

st. 16-15: 256600

^st.

2l-20:

¹⁰⁴⁸⁶⁰

st. 19-16:

³⁵⁰⁶⁰

Transport towards south

is

considered positive.

The isotransport diagram Fig. lB shows a large transport through the ^sections st.

12-14

and st.

15-16.

A conspicuous feature is the negative transport extend-ing from the reference level to about 90 m depth between st. ¹⁴ and 15. Negative transport is also encountered

at

about

73'N

latitude

in

the section st.

9-l

^1.

This is probably due

to

the above mentioned

Jan

^Mayen Polar current.

The net

transport through the section

"Conrad

Holmboe"

II

^st.

9-19

^is

estimated to about 0.6

mill.

mssec-1.

No 15, 1968 THE "coNRAD HoLMBoE" ExpEDITToN

rN

1923 27

Fig. lB. Section "Conrad llolmboe"

II,

isotransport curves and transport histogram; mssec-l.

Compaison.

As very few expeditions have previously worked

in

these areas,

only

a few observations are available

for

comparison. Observations carried

out on "Nat-horst" in

lB9B,

"Frithjof" in

^{1900 and}

"Fram" in

^1910, indicate a west-going current

of Atlantic

water

at

about

77"40'N to

7Bo

N.

HBr,r,eNr-HeNsnN and NaNsew (1912) conclude

that the

Svalbard-Atlantic

current

splits

into

two branches. One continues north-wards

into

the Polar basin, the other bends to the west

at

77"-7Bo

N

latitude, forming an intermediate layer under the Polar water

in

the East-Greenland current.

In

the horizontal sections from the

"Fram"

it

is seen

that

the isohalines have

a

tongue-like extension west-ward along the 78"

N

latitude. The 35.00 ^0/oo isohaline thus reaches 100 m depth ^as far west as

beyond 4o

W. In

the

"Veiding"

section the 35.00 ^0/oo isohaline reaches 5o30' W, situated

at

about 200

m

depth.

In

this area (between

st.

186

and

lB7) the

At-lantic water becomes an intermediate layer

in the

East-Greenland current.

Al-together, the observations from

"Veiding"

^{obviously agree well}

^with

^{those from}

the previous expeditions.

Before the observations on the "Conrad Holmboe" ^{sections are} discussed,

it will

be convenient to examine an intermediate section carried out on "Belgica"

in

1905 (Hnr.r.lNo-HexsnN and Konrono 1909). The "Belgica" ^{section st.}

30-25

^runs

in

a north-westerly direction from 75o39'

N,

12'00'W to 76'00' N, 3o55'W, alter having ^crossed the continental ^slope. The warm layer, limited by the 1o isotherm,

02550

NAUI. l,ltLEs

28 TOR KVINGE Mat.-Naturv. ^serie

has a configuration similar to that lound in the section "Conrad Holmboe"

II,

but in

a less developed form. The

q

curves incline steeply, indicating current at the slope.

On the "Polarbjørn" expedition in 193 I and l932 a few sections were carried out

in the

areas close

to

"Conrad Holmboe" ^section

II

and

III (Jernnu.N

^1936a).

According

to

these observations, the core of

Atlantic

water is characterized by a salinity o134.97 ^o/oo and a temperature of 2.10'.JAKHELLN ^suggests that ^these values are very high, as previous investigations do not show temperatures above 1.50' and salinities above 34.95 _oioo. Maximum values

in "Conrad

Holmboe"

sections are found at st. 12

at

¹⁵⁰ m depth, where the temperature is 1.90o, and the salinity 34.95 ^0/oo. Polar water in its original state is, according to Jernnr-r.N, characterized by the salinity 3+.07 ^oloo and the temperature

-1.85'.

^{The lowest}

minimum

temperature

found on the "Polarbjørn"

expedition

is

-1.80o

^and the corresponding salinity 33.55 ^0/oo. These values agree

well with

those from

"Conrad Holmboe" ^section

II,

where lowest minimum temperature is

-1.85'

and the salinity 3+.0201oo found

at

100

m

depth.

As mentioned above, the Polar water in the East Greenland current ^is probably

not

a

well

defined and uniform water type. Consequently,

to

speak

of a

well-defined

T-S

relation

for

Polar water

in

its original state is meaningsless. Based upon observations from the "Belgica" ^{and the} "Polarbjørn" expeditions, current components and water transport have been determined

by

dynamical compu-tations. According to

Jerunr,lN

^no components above 14 cm/sec are present on the

"Polarbjørn"

^{sections. He suggests}

that

the

total

current

in

the section st.

26

to

27 is about 20 cm/sec

at

the surface.

The current velocities

in

the northern areas have been estimated

to 25-30

cm/sec

at the

surface (Hnr.r-eNu-HANsEN

and Korrono

1909).

In the

above mentioned computations the 200

db

surface has been used as reference depth.

The

transport through the section "Belgica" ^{st. B23}

to

836 is estimated to 1.6

mill.

m3/sec (Jernnr.r.n, 1936a).

By applying the method suggested by

Jernrlr-N

^(1936b), the transport ^east of "Polarbjørn" ^{st. 20,1932, is} determined ^{as 1.32} mill. m3/sec (Jexnnr.r.N 1936b).

This

transport has, however, been computed

by

using

the

300

db

surface as

reference depth.

The above mentioned current and transport values are about twice ^as high as those

in the

"Conrad Holmboe" ^sections. Most

of the

"Conrad Holmboe"

sections were, however, situated on the slope, running more

or

^less parallel to the isobaths and consequently also parallel

to

the current.

The values

from

"Conrad Holmboe" should therefore be considered

in

re-lation to the bottom topography, and to the direction of the sections.

The "Conrad Holmboe" expedition ^was carried out late in the summer season,

and the ice had already started to form. This may have had an influence on cur-rent conditions as well. Considerable current and transport may also be present

In document TO IN (sider 24-28)