CLIMATIC VARIATIONS IN THE BARENTS SEA DURING THE 1970'S.

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1 This paper not to be cited without prior refernce to the authors nternational council for the Exploration of the sea C.M.. l984gen:l5 Mini-Symposium CLMATC VARATONS N THE BARENTS SEA DURNG THE 197'S. by Harald Loeng and Lars Midttun nstitute of Marine Research Bergen, Norway

2 2 ~ Recently three small reports were presented by members of the nstitute of Marine research viz: Midttun, Nakken and Raknes (1981), Loeng, Nakken and Raknes (1983) and s~tersdal and Loeng {1934) all describing biological reactions to climatic variations in the Barets Sea. The biological reactions were in the two larger fish stocks of the area, the Arctic Cod and the Barents Sea Cape1in. t is of considerable interest to study the nature of the biological reaction proc~sses, and equally important is it to try to understand the mechanisms causing the climatic variations. The latter is however beyond the scope of this paper which is merely just a of climatic variations observed in the Barents Sea in the period The paper may be seen as an to the two papers dealing with some biological variables observed in Capelin (Gj~s~ter and Loeng 1984) and Cod (Nakken and Raknes 1984) during recent years. 2. Climat in the Barents Sea. The Barents Sea is in the north and east covered with Arctic water masses, where ice is formed in winter and melts again during the surruner season~ n the south and west the inflowing Norwegian Coastal Current and the Barents Sea branch of the Atlantic Current form the Sub-Arctic water masses bordered from the Arctic area by the Polar Front (Fig. l) The climatic conditions in the Barents Sea are therefore determined both by effects from variation in the inflow from the west and by processes place in the sea itself. Several authors have studied the climatic conditions of the Barents Sea, among others He11and-Hansen and Nansen (199), Lee (1963), Kislyakov (1964), Midttun (19691, Dickson, Midttun and Mukhin (197)Q Buchkov (1976) r B1indhe.im and Loeng (1981), ( ) Dickson and Blindheim (1984).

3 ~r--- l ; )f STDR Bk ~ 1 t f l, t " t : ~ - t 68 so 1 15 ' 2 5,ig. 1. Location of the four sections A, B, K, and C seen in relation to the circulation pattern of the Barents Sea.----> : Atlantic water, --- -> : Arctic water, > : Coastal water. The polar front is indicated by a broken line. A general conclusion is that the climatic conditions of the Barents Sea depend mainly on the activity and property in the inflowing water from the west. Climatic variations can therefore be recorded in the sections crossing the inflowing water masses. 3. Variations in standard sections The locations of the standard sections dealt with below are shown in Fig 1. The three sections A, B, and C have been observed by Norwegian reserach vessels since the early 195's,

4 but at late are more 4 (1981), in sal the) Se ar observations have been taken in since From 1977 the sections (section A: 6 times, section B: s yearly) Blindheirn and Loeng Loeng (1984) have studied the and salinity in the three sections, ions of the sections containing the reflecting the Atlantic influence. Kola , 7 3 N clrtd of Mar:'ine nsti tt:li:e Midttun 6 anomali the whole of artoma1 (1984) " at seed: ion shows the location of the famous of the two neriods and are recorded back to 19 for the depth layer -2 m between been made available to the nstitute the Knipowich Polar Research s and Oceanog-raphy, Murmansk. (1981} have calculated monthly for the periods and mean values have been calculated for up to The complete series in a paper by S~tersdal and Loeng crossing the eastward flowing current temperature, therefore t.he Kola exactly the same watermasses as the. But as is shown below, in all the series. 4. Var Ficr 2. shows and salinity variations in the~three Norweqian sections A, B and C and the corresponding temperature the Kola, the latter taken from Anon. (1983). The curves mean values in the layer 5-2 m, observed in late each vear. The 9al A, B C ini imilar trends in all the three secti.ons is gradually decreasing from 127Q until

5 5 S%o Fig. 2. Temperature (left) and salinity (right) of the 5-2 m layer in the three sections A, B, C and temperature in 5-2 m in the Kola section. August-September, when values are observed. Later on the salinities are generally increasing up to normal values in The variations are greatest Ln the east (section CJ where the standard deviation for the perlod is.7 compared to.5 in the west (section A) e Also the temperature curves show parallell trends, most pronounced is the cold period , which in the Kola section is the longest period with negative anomalies observed after 192s The curves of Fige 2 are all based on only one observation per year and may therefore be encumbered with accidental short term variationss Since 1977 the sections A, B and C have been more frequently observed n order to eliminate the seasonal changes anomalies have been calculated for the period (Fig 3-5)_ The thres curve sets show the same trends in the climatic variations as was described aboveo The salinity was decreasing

6 - 6-1 s.15 t.12.lll 7 B B 1 j Jg_j_fu.1 '<!- Vl <l.}f!! vv" 1 Fig. 3. Anomalies in temperature (left) and salinity (right) in the depth layer 5-2 m in section A (71 3' 'N)in the period ti u t 1. rv '. ~ ' 'J' ~. <! <l v -.5 A! Vl j1 A Fig. 4. Anomalies in t.emperature (left) and salinity (right) in the depth layer 5-2 m in section B (72 15' 'N)in the period

7 ~ 1. t L os.5.1 ' L.J ~ ~ V1 <J <J Fig. 5. Anomalies in temperature (left) and salinity (right) in the depth layer 5-2 m in section C (71 15' 'N) in the period w..._ <J n 1"11 z ~ X ~ -15 Fig. 6. Temperature anomalies of the -2 m layer in the Kola section (continuous line) together with the ice index (broken line).

8 - 8 - in the beginning of this period until lowest value in Later on the salinity have been increasing. There seems to be a lag in the alteration from west to east as would be expected. The relative high salinity value in section C observed in August 1981 is difficult to explain. The temperature curves as well have similar trends. The lowest values were observed in , some warming through 198, but again lower values in Since early 1982 the temperature has generally been increasing~ The best description of the climatic variations in the period is presented in Fig. 6 which shows the temperature anomalies observed in the Kola section (section K). The normal in the -2 m layer are monthly means for the period n the same figure is also indicated the variation in the ice coverage in the Barents Sea taken from s~tersdal and Loeng (1984). s. Concluding remarks. Large variations have been observed in the climatic conditions in the Barents Sea during the 197's. The second half of the decade was characterized by low temperature, low salinity anq large ice coverage. Through the beginning of the 198's temperature and salinity are generally increasing and the ice coverage becomes smaller. The climatic variations are mainly determined by variation in the Atlantic inflow to the Barents Sea.

9 - 9 - References Anon Preliminary report of the nternational -group fish survey in the Barents Sea and adjacent waters in August-September Coun. Meet. nt Coun. Explor. Sea, 1983 (G 35): (Mimeo.) Blindheim, J. and Loeng, H On the variability of Atlantic influences in the Norwegian and Barents Seas Fisk. biro Skr. Ser. HavUnders. 17: Buchkov, Yu.A On the effect of solar activity of various periodicity on the termal regime of the Barets Sea. Coun Meet. nt. Coun. Explor. Sea, (C 2) :l-19. (Mimeo.) Dickson, R.,Midttun, L. and Mukhin, A The hydrographic conditions in the Barents Sea in August-September in Dragesund,. (Ed.) nternational -group survey in the Barents Sea CES Cooperativ Research Report A (18). Dickson, R. and Blindheim, J On the abnormal hydrographic conditions in the European Arctic during the 197's. Jens Smed Volume, Rapoorts et p~oces-verbeaux. (n press). Helland-Hansen, B and Nansen, F The Norwegian Sea. Fisk. Dir. Skr. Ser. HavUnders. 2 (2): Kislyakov, A.G Horizontal circulation of water on the Watershed of the Norwegian and Barents Sea. Trudy polyar. nauchno-issled. nst. morsk. ryb. khoz. Okeanogr 16 : (n russianj. Lee, A The hydrography of the European Arctic and Subarctic Seas. Oceanogr. Mar.!!!_ Biol., 1:

10 - 1 - Loeng, H Climatic variations in three hydrographic sections in the Barets Sea during the period Fisken Hav (3) : (n Norwegian, abstract in English). Loeng, H The climate in the Barets Sea in Fisken Hav (1): (n Norwegian, abstract in English). Loeng, H, Nakken,. and Raknes, A The distribution of capelin in the Barents Sea in relation to the water temperature in the period , Fisken Hav., 198~ (1): 1-17 (n Norwegian, abstract in English o) Midttun, L Variability of temnerature and salinity at some localities off the coast of Norway. Prog Oceanogr. 5: Midttun, L. f Nakken, o. and Raknes, A Variations in the geographical distribution of cod in the Barents Sea in the period Fisken Hav., 1981 (4): 1-16 (n Norwegian, abstract in English.) S~tersdal, G. and Loeng H Ecological adaption of reproduction in Arctic Cod. P in God~, O.R. and Tilseth, S. ed. Proc. of the Soviet-Norwegian Symp Re?roduction and Recruiternent of Arctic Cod, Leningrad, September nstitute of Marine Research, Bergen 1984.