Rapp. P.-v. Réun. Cons. int. Explor. Mer, 188: 23-35. 1989

Climatic fluctuations in the Barents Sea

Lars Midttun

Midttun, Lars. 1989. Climatic fluctuations in the Barents Sea. Rapp. P.-v. Réun. Cons. int. Explor. Mer, 188: 23—35.

The circulation system of the Barents Sea is described. Warm water flows into the sea from the west and is gradually transformed into Arctic water, which then flows out of the sea, partly as surface currents, partly as dense bottom water. The climatic conditions of the Barents Sea are determined both by the variations in the inflow and by processes taking place in the sea itself. The great variations in temperature and salinity observed along standard sections crossing the inflowing water masses are examined, and possible explanations are discussed.

Lars Midttun: Institute of Marine Research, P.O. Box 1870 - Nordnes, N-5024 Bergen, Norway.

Introduction The main purpose of this paper is to present and discuss been the most intensively studied area, and several stan­ the rather marked climatic variations observed in the dard sections have been established in order to investi­ Barents Sea. However it may be worth while first to gate variations in the inflowing water masses. Measure­ give a short description of the circulation system as ments in the Kola section were started as early as 1900 known from the literature. by Dr N. Knipowich and have been regularly continued Based on early observations, Knipowich (1905) gave since 1920. Bochkov (1976) studied temperature var­ a description of the water masses of the Barents Sea, iations in relation to solar activity. Three sections ob­ and Nansen (1906) devised theories on the formation of served by the Institute of Marine Research were ana­ bottom water in the northern seas, including the Bar­ lysed by Blindheim and Loeng (1981) and later by ents Sea. Nansen also believed that dense water formed Loeng and Midttun (1984). The section Fugløya- in the eastern Barents Sea could supply the bottom Bjørnøya (Bear Island) was studied by Dickson and water of the Arctic Ocean through the channel between Blindheim (1984). Variability at the fixed station Nord- Novaya Zemiya and Franz Josef Land, as indicated by kapp was analysed by Midttun (1969), while Blindheim Admiral Makaroffs temperature observations in that et al. (1981) compared the climatic variations in Norwe­ area. Recently. Midttun (1985) has confirmed Nansen’s gian coastal water with the observations from the Kola hypothesis. Mosby (1938) studied the waters between sections. Dickson et al. (1970) presented results from Svalbard and Franz Josef Land. This area is mainly the hydrographic work done during the joint 0-group dominated by Atlantic water masses, although some fish surveys in the Barents Sea from 1965 to 1969. The outflow from the Barents Sea may take place near Franz climatic variations in the Barents Sea were studied by Josef Land. Midttun and Loeng (1987). The majority of the contributions to the oceanog­ raphy of the Barents Sea are presented by scientists from the USSR. Tantsiura (1959) made a comprehen­ sive analysis of the currents in the Barents Sea. Agene- General description of physical rov (1946) studied a large number of current observa­ conditions tions. The detailed work by Novitskiy (1961) dealt with the currents of the northern Barents Sea. Sarynina Principally on the basis of the above-mentioned litera­ ( 1972) was concerned with the bottom water of the Bear ture, Loeng (1987) gave a brief review of the main Island Channel, and Kislyakov (1964) studied the condi­ circulation and water masses of the Barents Sea. This tions at the western inlet to the Barents Sea. review is summarized below. Naturally, the southern part of the Barents Sea has

23 Figure 1. Bottom topography of the Barents Sea.

The current systems The Norwegian Coastal Current flows along the west­ The bottom topography is given in Figure 1. Figure 2 ern and northern coast of Norway. Outside, and parallel shows a simplified picture of the surface current system, to, the coastal current flows the Norwegian Atlantic based mainly on current maps made by Tantsiura (1959) Current along the Norwegian continental shelf. Off the and Novitskiy (1961). Only minor corrections have been coast of northern Norway the Atlantic Current splits made as a result of some recent observations. The map into two branches, one continuing northwards along the indicates two main current directions. In the southern continental slope as the West Spitsbergen Current, and part, the currents are towards the east, while the current the other entering the Barents Sea along the Bear Island directions in the north are westwards and southwest- Channel as the Nordkapp Current. wards. The southern part of this current continues eastwards

24 FRANZ JOSEFS LAND

K VITÖYA

\ NORDAUSTLANDET

/ KONG KARLS LAND

VEST - SPITSBERGEN

HOPEN

SENT KAL Bk

THOR IVERSEN Bk

NORDKAPP Bk

J FUG LOY 4*

Figure 2. Surface currents in the Barents Sea. Arctic currents (------>), Atlantic currents (—>), and coastal currents (• • •>). (Simplified after Tantsiura, 1959; and Novitskiy, 1961). Locations of sections discussed are indicated.

together with the Norwegian Coastal Current and pro­ parallel to the Murmansk Current, turning northeast­ ceeds along the Murmansk coast as the Murmansk Cur­ wards along the axis of the eastern basins. A much less rent. The northern part of the Nordkapp Current di­ important inflow of Atlantic water to the Barents Sea vides along three major routes at about 30°E. One arm takes place along the Storfjordrenna between Bjørnøya turns northwards between Hopen Island and the Great and Spitsbergen. Bank where it submerges under the lighter Arctic wa­ The influx of Arctic water to the Barents Sea takes ter. The second branch continues eastwards in the place along two main routes: between Spitsbergen and deeper area between the Great Bank and the Central Franz Josef Land, and through the opening between Bank as an intermediate current. The third part turns Franz Josef Land and Novaya Zemlya (Dickson et al., southeastwards, south of the Central Bank, and flows 1970). The main part of the first-mentioned current

25 Figure 3. Distribution of salinity (left) and temperature (right) at 100-m depth, autumn 1984.

flows as the East Spitsbergen Current southwards along and temperature in the core from 1966 to 1977 were the coast of Spitsbergen. The current flowing south- 35.13 and 6.2°C, respectively (Blindheim and Loeng, westwards south of Franz Josef Land, called the Persey 1981). Farther east in the Barents Sea the salinity and Current, splits north of the Central Bank. According to temperature were lower, as shown in Figure 3, and as Tantsiura (1959), one branch turns southwards to the clearly demonstrated by Loeng and Midttun (1984). As Central Bank, but this part is probably small. The main will be discussed later, there are also great long-term part of the Persey Current goes southwestwards along variations in the properties of the Atlantic inflow to the the eastern slope of the Svalbard Bank as the Bear Barents Sea, which again may influence the properties Island Current. The current turns around Bear Island of the locally formed water masses. and goes northeastwards around the Storfjordrenna. The coastal water is characterized by low salinity (S < The details of the current system are poorly known. 34.7) and relatively high temperature (t > 3°C). This Hydrographic observations indicate an anticyclonic vor­ mass is also most easily traced by the salinity (Fig. 3). tex above some of the bank areas, such as the Central The light coastal water spreads out in a wedge-shaped Bank and probably also the Svalbard Bank. This implies form above the heavier Atlantic water. The seaward a long residence time for the water masses and possibil­ extent of this wedge of coastal water varies seasonally ities for vertical mixing during the winter season (Nan­ and has its minimum in the winter (Sætre and Liøen, sen, 1906). Current measurements indicate almost the 1971). same direction from surface to bottom in areas with During the summer the Arctic water (or Barents Sea only one water mass (Blindheim and Loeng, 1978; winter water) is mainly found in the intermediate layer, Helle, 1979). However, in areas where the Atlantic between 20 and 150 m, in the northern Barents Sea. The water submerges beneath the lighter Arctic water, as it core is usually found between 30 and 60 m, with temper­ does west and south of the Great Bank, one must expect atures below — 1.5°C and the salinity between 34.4 and different current directions with depth. Also in areas 34.6. In the horizontal map (Fig. 3) most of the water with outflowing dense bottom water, the current direc­ with a temperature below 0°C is Arctic water. tions probably differ from surface to bottom. Therefore The area between the Atlantic and the Arctic water Figure 2 represents the current systems in intermediate masses is called the Arctic Front. In this area Arctic and and bottom layers only to a certain extent. Atlantic water mix. In the area west of the Central Bank, the Arctic Front is sharp and has features typical of the bottom topography. In the eastern Barents Sea the front area is less distinct, and a mixed water mass Water masses covers great areas. Following Helland-Hansen and Nansen (1909), Atlantic Bottom water of different kinds may be formed in water is defined by a salinity higher than 35.0. At the various places in the Barents Sea. Dense bottom water entrance to the Barents Sea, the mean autumn salinity is formed through brine rejection when ice freezes and

26 ^ MINIMUM EXTENSION ^ MAXIMUM EXTENSION

Figure 4. Southern limit of sea ice at the end of the months February, April, June, August, October, and December during the period 1971-1980 (after Vinje, 1983). is a more or less regular phenomenon, particularly on water of the Bear Island Channel, however, may also be the shelf of Novaya Zemlya, but sometimes also on the formed in the frontal zone (Arctic Front area) during Svalbard Bank (Midttun, 1985). Bottom water with a the period of vertical winter circulation on the south­ somewhat lower salinity is formed on the Central Bank eastern slope of the Svalbard Bank (Sarynina, 1972). during the winter season (Midttun, 1961). The bottom The winter and summer situations differ with respect

27 25° 30° 35° 40° 45° 50° Figure 5. Maximum ice coverage in the Barents Sea in winter during the period 1979-1986.

to the vertical structure of the water masses. During water masses may be homogeneous to more than 200 m. winter, vertical mixing takes place throughout the Bar­ In the ice-covered areas, the temperature will be homo­ ents Sea. Over shallow bank areas, convection may geneous, while a salinity gradient may maintain a weak reach the bottom and contribute to bottom-water for­ vertical stability. Ice-freezing with brine rejection may mation as already mentioned. In the deeper areas, the break down the salinity gradient.

28 t°c s

5

4 -

3-

2

'76177'78 '79' 80'81182'83 '8^ '85 '86 I Figure 6. Temperature (left) and salinity (right) of the 50—200-m layer in the three sections A, B, and C, and temperature in the 50-200-m layer in the Kola section (K) in August-September 1970-1986.

variations of three to five years in the sea-ice conditions Sea-ice conditions (Kissler, 1934; Lunde, 1965). Long-term variations, not The variation in the position of the ice edge, based on necessarily of a cyclic nature, are also well known from satellite images over a period of ten years (1971 — 1980), other marginal areas of the Arctic, e.g., the west coast is shown in Figure 4 for the months February, April, of Greenland (Dunbar, 1972). June, August, October, and December (Vinje, 1983). The figure shows considerable variations in ice exten­ sion, which may take place from year to year. In some Climatic variations months, especially in summer and autumn, these var­ General description iations may exceed 500 km. Generally, the seasonal variations of the sea-ice extension are, in their broad Climatic variations can be recorded in sections crossing features, similar from one year to another, with the the inflowing water masses. Figure 6 shows temperature maximum and minimum extensions in March—May and and salinity variations in the three Norwegian sections August-September, respectively (Loeng, 1979; Loeng A, B, and C, and the corresponding temperature ob­ and Vinje, 1979). The formation of ice usually starts in served in the Kola section, the latter taken from Anon. late September or in October, and the ice border moves (1986). The curves represent mean values in the rapidly southwards to the Arctic Front during No­ 50—200-m layer observed in late August—early Septem­ vember and December. The melting of ice starts in ber each year. Locations of sections can be seen in May-June, but in the beginning the melting is very Figure 2. slow. The retreat of the ice border is usually most rapid The salinity curves have similar trends in all three in July and early August. sections, A, B, and C. The salinity gradually decreased Figure 5 shows the variations of maximum ice cov­ from 1970 until 1978/1979, when the lowest values were erage in the years 1979-1986. In the vicinity of Bear observed. Later on the salinities generally increased, Island, there is almost no variation from one year to reaching normal values in 1983. another. In the eastern Barents Sea, however, the var­ The variations are greatest in the east (section C), iations are considerable. where the standard deviation for the period 1970—1986 Some authors have suggested the presence of cyclic is 0.07, compared with 0.05 in the west (section A).

29 1900, 01 , 02 , 03 , OU . 05 , 06 , 07 , 06 , 09 , 10 , 11 , 12 , 13 , U , 15 , 16 , 17 , 1B , 19 , 20 , 21 , 22 , 23 , Z- , 25 , 26 , r , 28 ^

-0,5

- 1,0

1,5

O O . C L

-0,5

- 1,0

-15

X LU

<_) -0,5

- 1,0 -10

-1.5- -15

-20 Figure 7. Temperature anomalies in the Kola section for the period 19(X) — 1985 (continuous line) and ice index for the Barents Sea (dotted line).

30 Figure 8. Depth of the o, surfaces 28.0 and 28.1 in 1977. Dotted lines indicate area limitations.

The temperature curves also show parallel trends. Midttun et al. (1981), using the Kola section, calcu­ Most pronounced is the cold period 1977-1981, which lated monthly mean temperatures on the basis of data in the Kola section is the longest period with negative from the period 1921 — 1980, and anomalies from those anomalies observed since 1920. means have been calculated for the whole period up to 1987 (Fig. 7). 31 77“ N 75° N 73" N i_ — i— O

4 ^

100 -

200 -

--1.5

300 - Sep. 1962

0

100 -

2 0 0 -

300- Sep.1903

Figure 9. Temperature in the meridional section of 45°E in September 1982 (top) and 1983 (bottom).

Figure 7 shows that the years up to 1906 were cold. 1970—1976 was warm, while the second half of the According to Sætersdal and Loeng (1984), almost the decade was characterized by low temperatures. whole missing period, 1907—1920, was also cold. After Throughout the early 1980s, temperatures increased. some years with higher temperatures in the beginning of An ice index for the period after 1970 shows similar the 1920s, the years up to 1930 had lower temperatures trends, indicating a close relationship between variation than normal. The longest period with a warm regime in sea temperature and ice conditions (Fig. 7). was between 1930 and 1939, with a maximum in 1938. As early as 1909 Helland-Flansen and Nansen (1909) The years after 1945 are characterized by fluctuations suggested that climatic variations in the Barents Sea are with a duration of three to five years. These periods probably of an advective nature. They observed a time coincide with cyclic variations in sea-ice conditions, as lag of one year between the Lofoten and the Kola proposed by Kissler (1934) and Lunde (1965). A period sections. Loeng et al. (1983) showed that temperature of 11 years, which coincides with the solar activity cycle, changes in the eastern part will most often occur about has also been suggested both for temperature and ice one year later than in the western part. Also in the conditions (Bochkov, 1976). Norwegian Sea, climatic variations seem to be due to During the 1970s, great variations in climatic condi­ advective processes in the Atlantic inflow (Blindheim, tions were observed in the Barents Sea. The period 1987).

32 LAT. NORTH 74' BJØRNØYA FUGLØYA

, - 4 100

200

x 300 Q- o

400

Figure 10. Mean current component (cm s ) through the Fugløya-Bjørnøya section from measurements at mooring stations in September-October 1978. The observation depths are indicated by + (Blindheim, 500 1989).

inflowing water; that is, the current system of constant Discussion of possible causes velocity and volume brings in a water mass with chang­ The notable variations observed in the physical envi­ ing temperature and salinity. But the variations could ronment of the Barents Sea have a great effect on the just as well be a result of variations in the current system biological conditions for the large fish stocks in the sea. itself. Since both temperature and salinity increase in It is therefore important to discuss possible explanations the direction of the countercurrents, high velocity and to try to understand the physical causes behind the should result in high temperature and salinity, and low climatic variations observed in the inflowing water velocity in low temperature and salinity. In the last case masses. The variations are seen in the long series of the variation in the current system has to be explained. temperature observations in the Kola section crossing Again, the variation in the current activity could be the main branch of the Murmansk Current (Fig. 2). The forced upon the sea from outside, but it could just as temperature alternates, with successive warm and cold well be a result of processes taking place in the Barents periods of about three to five years (Fig. 7). Similar Sea itself. variations are observed in other sections of the Barents Water of high density is formed during the winter as a Sea (Fig. 6), and are also reflected in the ice coverage. result of cooling and ice formation, and then draining It may be seen from Figures 3 and 4 that the winter ice from the sea in bottom currents. The process of ice coverage has the greatest variations over the Central formation is also the source of the light surface water Bank and in the eastern part of the Barents Sea. carried by the Arctic currents. The process is described The variations may be hypothetically explained as in detail by Midttun (1985) and can be regarded as a arising from similar variations in the properties of the separator, transferring salt from the surface water to

33 3 Rapports et Procès-Verbaux deep water and in this way gradually building up dense bottom water and light surface water. The bottom water Acknowledgements forms bottom currents along the right side of the chan­ My appreciation to H. Kismul for preparing the figures nels leading from the Barents Sea to the Norwegian Sea and to Ms I. Byrkjedal for typing the manuscript. Ha­ through the Bear Island Channel and to the polar seas rald Loeng has contributed to this paper. through the Novaya Zemlya-Franz Josef Land Chan­ nel. The water volume, which in this way leaves the sea, has to be replaced by inflowing water from the west. The activity in building up dense bottom water may vary from one year to another, followed by variations in the References outflow with corresponding changes in the inflow. After a large inflow it may take more than one year to build Anon. 1986. Preliminary report of the International 0-Group Fish Survey in the Barents Sea and Adjacent Waters in up the required conditions again to initiate the next August-September 1986. ICES CM 1986/G: 78, 27 pp. dense water outflow. To some degree the rate of dense Agenerov, V. K. 1946. On the dynamics of the Barents Sea water formation will depend on the salinity of the in­ water. Gidrometeoizdat. 130 pp. flowing water since density is a function of salinity. Blindheim, J. 1987. Ecological features of the Norwegian Sea. Proceedings from the 6th International Conference of Co­ Figure 8 shows that areas with formations of high- mité Arctique: Marine living systems of the Far North. Fair­ density water are located near the Central Bank and on banks, Alaska, May 1985. 41 pp. the Novaya Zemlya Bank. This is the same area where Blindheim, J. 1989. Cascading of Barents Sea bottom water the interannual changes of winter ice coverage are into the Norwegian Sea. This volume, pp. 49-58. Blindheim, J., and Loeng, H. 1978. Strømmålinger i området greatest (Fig. 5). Troms-Bjørnøya i 1970, 1971 og 1975. Fisken Hav. Ser. B, Figure 9 shows the effect of the extensive water ex­ 1978 (2): 1-46. changes between 1982 and 1983. The inflow and outflow Blindheim, J., and Loeng, H. 1981. On the variability of At­ between the Norwegian Sea and the Barents Sea have lantic influence in the Norwegian and Barents Seas. FiskDir. Skr. Ser. HavUnders., 17: 161-189. been measured in the section between Fugløya and Blindheim. J., Loeng, FI., and Sætre, R. 1981. Long-term Bjørnøya from a series of anchored current meters temperature trends in Norwegian coastal waters. ICES CM (Blindheim, 1989). Results are presented in Figure 10. 1981/C: 19, 13 pp. Transport calculations indicate about 3 Sv into, and Bochkov, Yu. A. 1976. On the effect of solar activity of various periodicity on the thermal regime of the Barents Sea. ICES around 1 Sv out of, the section. This would require CM 1976/C: 2, 19 pp. another outflowing current, most likely located in the Dickson, R., and Blindheim, J. 1984. On the abnormal hydro- channel between Novaya Zemlya and Franz Josef Land. graphic conditions in the European Arctic during the 1970s. The outflow of high-density water in this area has re­ Rapp. P.-v. Réun. Cons. int. Explor. Mer, 185: 201-213. Dickson, R. R., Midttun, L., and Mukhin, A. I. 1970. The cently been described by Midttun (1985). hydrographic conditions in the Barents Sea in August-Sep- The above considerations lead to the following hy­ tember 1965 — 1968. International 0-group fish surveys in the potheses: Barents Sea 1965-1968. Coop. Res. Rep. Cons. int. Explor. Mer, Ser. A, No. 18: 3-24. 1. The mechanisms behind the climatic variations in the Dunbar, M. 1972. Increasing severity of ice conditions in Baf­ fin Bay and Davis Strait and the effects on the extreme limits Barents Sea might be described as the result of dense of ice. In Sea ice. Proceedings of an international confer­ water formation during cooling and ice formation. ence, Reykjavik, Iceland, May 10-13, 1971, pp. 87-93.Ed. This process transforms the inflowing water mass by T. Karlsson. Setberg, Reykjavik. into two outflowing types, viz. bottom water of high Hclland-Hansen, B., and Nansen, F. 1909. The Norwegian Sea. FiskDir. Skr. Ser. HavUnders., 2 (2): 1-360. density and surface water of low density. Helle, H. B. 1979. Oceanographic measurements in the Bar­ 2. The transforming process is time dependent on the ents Sea between Fugløya (Norway) and Bear Island. Vass- properties and quantity of the influx. After a period drags- og Havnelaboratoriet ved NTH. S1NTEF rapport STF60A79003: 1-12+289 pp. with tables and figures. of high influx, the transformation requires more than Kislyakov, A. G. 1964. Horizontal circulation of water on the one year of cooling before the density of the bottom watershed of the Norwegian and Barents Seas. Trudy po- water is high enough to initiate a new outflow. lyar. nauchno-issled. Inst, morsk. ryb. Khoz. Okeanogr., 3. The bottom water outflow takes place mainly in the 16: 215-225. (In Russian). Kissier. F. 1934. Eisgrensen und Eisverschiebungen in der Ark­ northern Bear Island Channel and along the south­ tis zwischen 50°West und 105°0st im 34-jährigen Zeitraum ern part of the Novaya Zemlya — Franz Josef Land 1898-1931. Beitr. Geophys., 42 (1): 12-55. Channel. Knipowich, N. 1905. Hydrologische Untersuchungen im Eu­ 4. To confirm these hypotheses, direct current observa­ ropäischen Eismeer. Annaln Hydrogr. Berl., 33 (1905): 193-205, 241-260, 289-308, 337-346. tions in the above-mentioned areas of outflow are Loeng, H. 1979. A review of the sea ice conditions of the strongly recommended. Barents Sea and the area west of Spitsbergen. Fisken Hav., 1979 (2): 29-75. (In Norwegian, abstract in English). Loeng, H. 1987. Ecological features of the Barents Sea. Pro­ ceedings from the 6th International Conference of Comité Arctique: Marine living systems of the Far North. Fairbanks, Alaska, May 1985. 54 pp.

34 Loeng, H., and Midttun, L. 1984. Climatic variations in the stocks in the Barents Sea, pp. 13-28. Ed. by H. Loeng. Barents Sea during the 1970s. ICES CM 1984/Gen: 15, 10 Proc. Third Soviet-Norwegian Symposium, Murmansk, May pp. 1986. Loeng, H., Nakken, O., and Raknes, A. 1983. The distribu­ Mosby, H. 1938. Svalbard waters. Geofys. Publr, 12(4): 1-86. tion of capelin in the Barents Sea in relation to water tem­ Nansen, F. 1906. Northern waters: Captain Roald Amundsen’s perature in the period 1974—1982. Fisken Hav., 1983 (1): oceanographic observations in the Arctic seas in 1901. Skr. 1-17. (In Norwegian, abstract in English). VidenskSelsk. Christiania, 1906 (3): 1-145. Loeng, H., and Vinje, T. E. 1979. On the sea ice conditions in Novitskiy, V. P. 1961. Permanent currents of the northern the Greenland and Barents Seas. In POAC 79. Proceedings Barents Sea. Trudy gos. okeanogr. Inst., 64: 1—32 (In Rus­ of the Fifth International Conference on Port and Ocean sian). Engineering and Arctic Conditions, pp. 163-176. The Nor­ Sarynina, R. N. 1972. Conditions of origin of cold deep-sea wegian Institute of Technology, Trondheim, 1979. waters in the Bear Island Channel. Rapp. P.-v. Réun. Cons, Lunde, T. 1965. Ice conditions at Svalbard 1946-1963. Norsk int. Explor. Mer, 162: 300. Polarinst. Ârb., 1963: 61-80. Sætersdal, G., and Loeng, H. 1984. Ecological adaptation of Midttun, L. 1961. Norwegian hydrographical investigations in reproduction in Arctic cod. In Proc. of the Soviet-Norwe­ the Barents Sea during the international geophysical year. gian Symp. Reproduction and Recruitment of Arctic Cod, Rapp. P.-v. Réun. Cons. int. Explor. Mer, 149: 25-30. pp. 13-35. Ed. by O. R. Godø and S. Tilseth. Inst. Mar. Midttun, L. 1969. Variability of temperature and salinity at Research, Bergen. some localities off the coast of Norway. Prog. Oceanogr., 5: Saetre, R., and Ljøen, R. 1971. The Norwegian Coastal Cur­ 41-54. rent. In Proceedings from the First International Conference Midttun, L. 1985. Formation of dense bottom water in the on Port and Ocean Engineering under Arctic Conditions, Barents Sea. Deep-Sea Res., 32 (10): 1233-1241. Volume II, pp. 514-535. Technical University of Norway, Midttun, L., Nakken, O., and Raknes, A. 1981. Variation in Trondheim. the geographical distribution of cod in the Barents Sea in the Tantsiura, A. I. 1959. About the current in the Barents Sea. period 1977-1981. Fisken Hav., 1981 (4): 1-16. (In Norwe­ Trudy polyar. nauchno-issled. Inst.morsk.ryb. Khoz. Okea­ gian, abstract in English). nogr., 11: 35-53. (In Russian). Midttun, L., and Loeng, H. 1987. Climatic variations in the Vinje, T. E. 1983. Sea ice conditions in 1982. Norsk Polarinst. Barents Sea. In The effect of oceanographic conditions on Arb., 1982: 49-53. distribution and population dynamics of commercial fish

3 * 35