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ICES/CM 1999/1 L: 1 4 Theme Session Nordic Seas Exchanges ICES 1999 Hydrographic conditions in North Icelandic waters and annual air temperature in Iceland by Svend-Aage Malmberg Marine Research Institute 121 Reykjavik Skulagata 4 Fax: +354 5623790 e-mail: [email protected] and Julie Desert ENSIETA 29806 Brest 2rue Francois Verny Fax: 029 834 8846 Abstract Iceland is situated at fronts, i.e. at the meeting place of wann (Inninger current) and cold (East Greenland and East Icelandic Current) ocean current1. These different hydrographic conditions in Icelandic waters are refleted in the atmospheric or climatic conditions in and over the country and the surrounding seas, mainly through the Iceland Low and Greeland High. The paper deals with hydrographic conditions in North Icelandic waters - Siglunes section - in comparison to annual air temperature in Akureyri - North Iceland - and Reykjavik - Southwest Iceland - since 1950. The results show the hydrographic conditions in North Icelandic waters are coherent with air temperature both in North and South Iceland. The forcing of the atmospheric pressure systems involved ("North Atlantic Oscillation") is also considered. Keywords: hydrographic conditions, air temperatures, annual and decadal variations; NAO. Introduction Iceland is situated at the meeting place of wann and cold sea and air flows (Fig. 1). To the south is the Inninger Current with temperature of 4-8°C and a transport of about 2 Sv or at this outpost of the North Atlantic Current only 2% of the volume of the "birth" of the North Atlantic current system in the south and west. To the north, the sea is cold, the East Greenland Current with temperature of O°C or less and a transport of 1-2 Sv, and the East Icelandic Current with temperatures of 0-2°C and still an unknown transport. These diffelient hydrographic conditions in Icelandic waters are reflected in the atmosphere or clim~tic conditions in the country itself and its surrounding waters, than mainly through the Icel~d Low and Greenland High. I The wann Inninger Current flows from the south northwards along the west coast of Iceland and from there with one branch westwards to Greenland and another branch eastwards into North Icelandic waters. The latter branch is sometimes called the North Icelandic Inninger Current. This branch has a distinct seasonal variability, it is in general strengthening in spring and summer (Stefansson 1962, Kristmannsson 1998). Since the sixties the inflow into North Icelandic waters also had a strong annual variability when the cold currents from the north took over at least in the upper layers (Malmberg and Kristmannsson 1992, Malmberg and Blindheim 1994, Malmberg et al. 1996, Malmberg and Jonsson 1997; Fig.2b). The Siglunes section As described in Malmberg et al. -paper L: 13 in this Session on Nordic Seas Exchanges - a selected station in North Icelandic waters (8/3 - Siglunes section -50m as well as the whole section 8/1-5/0-200m, Fig.l) has been used to show interannual variability in spring in the area during the period 1952-1999 (Figs.2b and 10). Most outstanding are the changes in hydrographic conditions in the latter part of the sixties (upstream years of the "Great Salinity Anomaly" (GSA) in the seventies; Dickson et al. 1988). At this time the hydrographic conditions in North Icelandic waters changed from being Atlantic ( t>4°C; S>35.0) to Polar conditions ( t~O°C; S as low as 34.0) after decades of Atlantic conditions even since the twenties (Stefansson 1969). After the sixties the conditions have shifted between Atlantic and Polar conditions and furthennore even with one more characteristic of Arctic water with moderate cold temperatures of I-3°C and salinities around 34.8 (downstream "tail" of the GSA's) in the seventies (Dickson et al. 1988) and eighties (Belkin et al. 1998). Besides, the salinity of the inflowing Atlantic waters since the eighties up to 1998 never reached the high values prior to the mid sixties (Fig.3). This low salinity may even in general reveal a tendency to arctic conditions during this period, which came to an abrupt end in 1999. At last the relation between temperature and salinity for all data in spring 1952-1999 at 50 m depth at the selected station in question (FigA) indicates the different water masses in question Atlantic, Polar and Arctic water - the last mentioned is very close to be even North Icelandic Winter water (Stefansson 1962), fonned in winter by cooling and mixing in the North Icelandic shelf area. Summarized, -the extreme variations in temperature and salinity between years in the surface layers of the Siglunes section 1952-1999 were as large as 7-8°C in temperature and one 8U in salinity (Figs.2 and 4). 2 Sea surface temperature at Grimsey Grimsey is a small island in the neighbourhood of station S-3 in North Icelandic waters (Fig. 1). Since 1987 sea surface temperature readings are available throughout the years to present time (1998/99), though with a few interruptions (Fig.S). Three months means for the seasons (jan.-march, april-june, july-sept., oct.-dec.; Fig.6) show the annual variations being largest in spring. Thus the cold periods of Polar conditions (1988) and Arctic conditions (1989-1990, 1995) are outlined in the recordings (Fig.7a). Comparison between the Grimsey spring data and those from the nearby S-3 station -SOm (Fig.7b) gives a satisfying result supporting the overall data set used. Further the positive relationship between the Grimsey temperature and the salinity maximum in the upper 300m at S-3 (Fig.8) supports a view that the continuous Grimsey data may be used to indicate conditions at S-3 and even in the whole Siglunes section throughout the years, than referring to the close relationship between the hydrographic conditions at S/3/S0m and SIl-S/0-200m (Anon.1999,Fig.11a,b). Furthermore, not only annual air temperatures in Reykjavik and Akureyri and hydrographic conditions in spring in the waters north of Iceland should be studied, but seasonal conditions in both cases as well to obtain more detailed results. The NAO index and the hydrographic variability in North Icelandic waters The normalized atmospheric difference between the Azores High and the Iceland Low is known as the North Atlantic Oscillation (NAO; Hurrell 1995; Fig.9). The variable forcing of these atmospheric conditions on the westerlies has an impact on the oceanic circulation through variable wind forcing and heat and vapour exchange between atmosphere and ocean. Positive NAO indices are thus in general followed by relatively strong, warm and humid westerlies in the eastern North Atlantic, bp.t with cold and dry winds in the western North Atlantic. Negative NAO indices are on the other hand followed by cold and dry northerly winds in the eastern part and warm and humid southerly winds in the western part of the North Atlantic (McCartney 1996). As seen in figure 10a,b the S years running means of both NAO and salinity and temperature in surface layers (S-3/S0m) in North Icelandic waters as well as integrated over the whole Siglunes section (SIl-S/0-200m; Anon.1999 see Fig.11) agree fairly well with each other as regards timing of periods, especially in the late sixties and the seventies as well as in the nineties, but not so in the eighties. This disagreement in the eighties coincide with the GSA's arrivals into the waters north of Iceland (Iceland Sea) in 1982-1983 (Dickson et al. 1988) and in 1989-1990 (Belkin et al. 1996) contributing to Arctic conditions in North Icelandic waters ( a.o. Malmberg et al. 1998). Curry and McCartney (1996) have as well related irregularities between thickness of the Labrador water in the Labrador'Sea and a positive NAO to impact of the GSA's in the western part of the North Atlantic in the early seventies and eighties (during the years 1970-1972 and 1982-1984). Annual air temperature in Reykjavik and Akureyri Comparing the variations in annual air temperature in Akureyri, North Iceland, and Reykjavik, SQuthwest Iceland, 19S2-1998 (Fig.2) with the annual spring temperature and salinity in the sea north of Iceland (Siglunes 3 /SO m), the coherence between these time series is obvious. Cold and low saline respectively warm and high saline conditions in North Icelandic waters generally coincide with "low" and respectively "high" annual air temperature both in Reyjavik and Akureyri. The positive temperature relationship between Reykjavik and 3 ----.--- Akureyri (Fig.12) as well as temperature and salinity relationships are further demonstrated in x-y plots (Fig.13). The poor relationship of the time series may though indicate a positive relationship of climate both in North as well as South Iceland with hydrographic conditions in North Icelandic waters. Also noteworthy is the variability in the air temperature difference between Reykjavik and Akureyri (Fig.14), being around 1°C prior to the cold ice-years in the sixties, than increasing up to 2°C during the ice-years and decreasing again after that to values frequently below 1°C, some years even to· almost no difference. Further, the annual air temperature in Akureyri reached the same level after the ice-years in the sixties as before (34°C; Fig.2), but in Reykjavik less so where the late seventies and early eighties with 3-4°C were even colder than the sixties with 4°C compared to 5°C before. This is even also true for many of the cold years early in the century (1900-1920; Fig.15). These low temperatures in Reykjavik in the seventies-eighties and occasionally later may seem to coincide with the observed hydrographic arctic conditions in North Icelandic waters which again were related to the GSA's in the northern North Atlantic and Nordic Seas (Dickson at al. 1988, Belkin et al. 1998). It may also be noted that a general cooling and "freshening" found place during the same period in the Norwegian Sea and the eastern part of the Nordic Seas ( Blindheim et al. 1999), a "freshening" related to the conditions in the East Icelandic Current in the Iceland Sea. Summarized (Fig.2), the annual air temperature in Reykjavik respectively Akureyri was around 5°C respectively 3-4°C prior to 1965, but decreased after that to 4°C respectively almost 2°C during the extreme ice-years when also the difference between Reykjavik and Akureyri was up to 2°C (Fig. 14). After the ice-years 1965-1971 the temperatures in Akureyri rose again to the former values of 3-4°C but in Reykjavik it was frequently even lower than during the cold ice-years. Noteworthy is the extreme cold year 1979 in Reykjavik respectively Akureyri with annual air temperatures of 3°C respectively 1.5°C. This year was indeed the coldest one in the 20th century (see Einarsson 1989; Fig.15), both in Reykjavik and Akureyri. Sea and air temperatures As the annual variations in temperature in North Icelandic waters in spring more or less coincide with the annual air temperatures in Reykjavik and Akureyri, the difference between temperatures in the sea and in the air must as well coincide in time (showing up with a few years periodicity of -4 years) (Fig.16). This difference might from first sight due to different distances and locations generally be larger for Reykj avik than the corresponding Akureyri difference. This is in general true, especially for the cold ice-years 1965-1971, but after that the differences are only slightly larger (negative) for Reykjavik than Akureyri. Also during the period 1973-1998 the differences had an indication of a negative trend and smaller annual amplitudes, it is a relative cooling in Reykjavik and Akureyri compared with the sea temperatures. Summerized, during the warm period prior to the ice-years in the late sixties the air temperatures in Reykjavik were near-by to those of the sea north of Iceland but relatively colder (2°C) in Akureyri (Fig.16). During the cold ice-years Reykjavik air temperatures on the other hand did not cool as much down (1°C) as those in Akureyri (2°C) and in the sea (5°C); and after that the differences were similar or slightly negative. These three different periods may refer to the three different hydrographic conditions in Icelandic waters during 4 the time - Atlantic, Polar and Arctic conditions - which than are reflected in the climatic conditions in Iceland. Discussion and conclusions The different locations of Reykjavik and Akureyri on each side of the Icelandic highlands may account for the different response to "warm" and "cold" periods. Akureyri in the north is located at the bottom of a fjord - Eyjafjorour - intrusing far into the country (50 km) whereas Reykjavik in the southwest is much more open to the open ocean. "Warm" periods with southerly winds - low pressure in the Iceland Low and positive NAO - and "warm" inflow into North Icelandic waters give Reykjavik and Akureyri as well heat input, for Akureyri also including the effect of fohn-winds (Einarsson 1984). On the other hand "cold" periods with northerly winds (high pressure over Greenland and Iceland, ice-years and negative NAO) and less inflow of warm water into North Icelandic waters have a direct cooling effect in Akureyri and also in Reykjavik but less so than in Akureyri due to the southerly location with additional effect of northerly dry and bright weather. The connection between the annual air temperatures both in North as well as in South Iceland with hydrographic conditions in North Icelandic waters reveal the fight between the Iceland Low and the Greenland High. The former is in simplest terms related to "warm" air and sea flows northwards but the latter to "cold" southwards flows. It should though be born in mind that the different tracks of the Iceland Low from the northern North Atlantic into the Nordic Seas complicate this simple sceme. The northerlies in Iceland are not only due to the Greenland High but also due to the track of the Iceland Low east and northeast of Iceland into the Norwegian Sea. These different tracks of the Low pressure include than also different weather types in Iceland (Einarsson 1984). These ocean/atmospheric conditions are steering the climate or air temperatures in Iceland, both in the south and north, conditions which than are intensified or modified by the fohn-winds of the mountainous inland of Iceland. During "warm" periods the annual air temperature in Reykjavik is closer to the spring temperature in North Icelandic waters than that in Akureyri, but during "cold" periods it is the opposite, the annual air temperature in Akureyri being closer to sea temperature than in Reykjavik. Variability in annual air temperature both in Akureyri in the North and in Reykjavik in the Southwest is thus after all related to the hydrographic variability in North Icelandic waters and all three to the principal atmospheric circulation. At last, the most extreme variations for the period studied were observed during the so-called ice-years in the late sixties. During those years exceptional atmospheric conditions seem to have been observed (Figs.9 and 17), the atmospheric pressure being higher along the East coast of Greenland than at all other times in the 20th century along with the strong negative NAO indices observed (Fig.9). The pressure was continously increasing since around 1920 when the well-known mild period in the Northern North Atlantic and in nearby countries started (Rodewald 1967, Striibing 1968, Smed 1975; Einarsson 1989; Fig.15). Thus the cold period during the ice-years in North Icelandic waters in the late sixties may not have been quite of the same character in the atmosphere as that prior to 1920 as frequently directly or indirectly stated (a.o. Dickson et al. 1988). The exceptional high pressure over Greenland which gave rise to the extreme negative NAO and ice-years in North Icelandic waters in the late sixties and far reaching effect in wide areas in the northern North Atlantic (GSA of the seventies, Dickson et al. 1988) as well as on the living conditions in the sea (Jakobsson 1992) seemed to come to an abrupt end in the early seventies (c.f. Climatic reversale in the North 5 Atlantic; Dickson et al. 1975). But new decadal periods of high pressure in the north occurred into the nineties along with variable NAO indices. To close this discussion a diagram of the NAO (Fig.9) and a reversed pressure over East (Fig.17)Greenland could be shown to demonstrate the outstanding conditions observed in the sixties which gave rise to exceptional response in the northern North Atlantic including Icelandic waters and climate in Iceland. REFERENCES Anon. 1999. prettir Ur vistfrreoi sjavar 1994. Environmental conditions in Icelandic waters 1997 and 1998. Hafrannsoknastonunin. Fjolrit Nr 73; 111 pp. Blindheim, J., Borokov, V., Hansen, B., Malmberg, S.A, Turrell, W.R, and Osterhus, S. 1999. Upper layer cooling and freshening in the Norwegian Sea in relation to Atmospheric Forcing. Deep Sea Research(in press). Belkin, I.M., Levitus, S., Antonov, l, and Malmberg, S.A. 1998. "Great Salinity Anomalies" in the North Atlantic. Progress in Oceanography, 41:1-68. Curry, RG., and McCartney, M.S. 1996. Labrador Sea Water Carries Northern Climate Signal South. Oceanus, 39,2:24-28. Dickson, RR, Meincke, J., Malmberg, S.A, and Lee, AJ. 1988. The "Great Salinity Anomaly" in the northern North Atlantic, 1968-1982. Progress in Oceanography, 20,2:103-151. Einarsson, M.A. 1984. Climate of Iceland. World survey of World Climatology 15. Ed. H. van Loon. Elsevier. Einarsson, M.A. 1989. Hitafar a islandi apessari old. Veourstofa islands, 65 pp. Hurrell, lW. 1995. Decadal trends in the North Atlantic Oscillation: Regional temperatures and precipitation. Science 296:676-679. Jakobsson, Jakob 1992. Recent Variability in the fisheries in the North Atlantic. ICES Marine Science Symposium 195:291-315. Kristmannsson, S.S. 1998. Flow of Atlantic water into. the northern Icelandic shelf area, 1985-1989. North Atlantic-Norwegian Sea Exchanges : ICES NANSEN project. ICES Coop. Res. Rep. 225:124-135. Malmberg, S.A., and Kristmannsson, S.S. 1992. Hydrographic conditions in Icelandic waters, . 1980-1989. ICES Marine Science Symposium 195:76-92. Malmberg, S.A, and Blindheim, J. 1994. Climate, cod and capelin in northern waters. ICES Marine Science Symposium 198:297-310. 6 Malmberg, S.A., Valdimarsson, H., and Mortensen, J. 1996. Long time series in Icelandic waters in relation to physical variability in northern North Atlantic. NAFO Scientific Council Studies 24:300-309. Malmberg, S.A., and Jonsson, S. 1997. Timing of deep convection in the Greenland and Icelandic Seas. ICES Journal of Marine Science 54:300-309. Malmberg, S.A., Mortensen, J., and Valdimarsson, H. 1999. Decadal-Scale climate and hydro-biological variations in Icelandic waters in relation to large scale oceanatmospheric conditions in the northern North Atlantic. ICES 1999. CM. Theme Session Nordic Seas Exchanges, L:13, and International Symposium - 100 years of oceanographic observations in the Kola section in the Barents Sea. Murmansk. McCartney, M.S. 1992. North Atlantic Oscillation. Oceanus 39,2:13. Rodewald, M. 1967. Recent variations of North Atlantic temperature and "type tendencies" of the atmospheric circulation. ICNAF Redbook 1967, part IV:6-23. Smed, J. 1975. Monthly anomalies of the sea surface temperature in the areas of the northern North Atlantic in 1972. Annales Biologiques 30:15-17. Stefansson, U. 1962. North Icelandic waters. Rit Fiskideildar 3:269 pp. Stefansson, U. Temperature variations in the North Icelandic coastal area during recent decades. Jokull19:17-28. Strobing, K. 1968. Uber Zusammenhange zwichen der Eisfiihrung des Ostgronlandstroms und der atmospharische Zirculation tiber dem Nordpolarmeer. Deutsche Hydrographische Zeitschript, 20,6. FIGURE CAPTIONS Fig. 1 Topography, nomenclature and locations referred to. Fig. 2 a) Mean annual air temperature in Reykjavik, SW Iceland and Akureyri, N Iceland 1950-1998. b) Temperature and salinity at 50m in spring at station S-3 in North Icelandic waters 1950-1999. For location see Fig.1 Fig. 3 Maximum salinity in the upper 300m at station S-3 in North Icelandic waters in spring 1950-1999. For location see Fig.1 7 Fig. 4 Temperature-salinity relationship at station S-3/50m in North Icelandic waters in spring 1950-1999 and main water masses. AW: warm and saline Atlantic water (S>34.8) PW: cold and low-saline Polar water (S<34.5) AIW: medium warm and saline Arctic water (34.5<S<34.8) Fig. 5 Monthly average of continuous recording of sea surface temperature (SST) at Grimsey, North Icelandic waters 1987-1999. For location see Fig.1 Fig. 6 Seasonal three months averages of SST at Grimsey 1987-1999. For location see Fig.1 Fig. 7 a) Spring SST at Grimsey and station. S-3/50m 1987-1999 and b) their relationship. Fig. 8 The relation between spring SST at Grimsey and salinity maximum at station S3/O-300m 1987-1999. Fig. 9 The annual and 5 years running means ofthe winter NAO index a) 1870-1999 and b) 1959-1999 using normalized sea level pressure differences between Lisbon, Portugal, and Stykkish6lmur, Iceland (Hurre11995 and pers. comm.). Fig. 10 Five years running means of the winter NAO and temperature and salinity in spring 1950-1999 at a) station S-3/50m and b) five stations on the Siglunes section integrated over 0-200m. Fig. 11 Temperature and salinity relationships in spring 1950-1999 at a) station S-3/50m and b) stations SIl-5/0-200m. Fig. 12 Relationship between mean annual temperature in Reykjavik and Akureyri 19501998. Fig. 13 Relationship between temperature .and salinity at S-3/50m and annual aIr temperatures in a) Reykjavik and b) Akureyri 1950-1998. Fig. 14 Difference between mean annual air temperature in Reykjavik and Akureyri 1950-1998. 8 Fig. 15 Annual mean air temperature in Reykjavik and Akureyri 1900-1988 (Einarsson 1989). Fig. 16 Differences between sea-temperature at S-3/50m and annual air temperatures in Reykjavik and Akureyri 1952-1998. Fig. 17 Winter mean sea level pressure, Dec-Mar 5 years running means, hPa 10, -190019LJ0 (Blindheim, pers. comm.). GREENLAND 6r II" ...c III Z C ...iI i; &I: 0 z ~ "I <I W II> II: w C> Z ~ 6Z· II: RIDGES NORTH ATLANTIC 1"land Ba" n 3Z· Z~· Fig. 1 20" Topography, nomenclature and locations referred to. ... / \ ' Mean Air Temp. 1950-1998 7 ---,-_. °c --,--_._---------- 6-t---=----t-=~-l----+--- - - - - - - - ·--r---I-----~- 5 -+--I-C-~p...~~-J 4~~~'~~~_+1~~~~~-Ar~~-j~ 3~~~--_+--~~~--~~ 24---~---+--~~--+----1 1---+----- - Akureyri 1+ - - - - 1 - - - 1 - - - ------ -- ---.--- - - - - - - ----- --- ------ -- - -- -- ---- --- Heimild: Veourstofa islands o 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 North Icelandic Waters spring 50 m st.Siglunes 3 10,---~--~--~----T-~~--~-----.----~---,--- Sjavarhiti 0C 35,0 %0 34,5 -1---+----+--11--\--+-1---11 f--"'---\--..+-\---,f--1--V--l---:+----'~34,O+--+--..,---f-~-I-'---I_____l~:-...::.:2iI:..:....:...:.:::...=:..:j.I=-:.:.::==+-:~ 1950 Fig. 2 1955 1960 1965 1970 1975 1980 1985 1990 1995 -a) Mean annual air temperature in Reykjavfk, 8W Iceland and Akureyri, N Iceland 1950-1998. b) Temperature and salinity at 50m in spring at station 8-3 in North Icelandic waters 1950-1999. For location see Fig.1 Salinities at Siglunes 3 35,15 35,10 35,05 35,00 UJ 34,95 34,90 34,85 34,80 34,75 f\ ) '-1 r. V " 1\ II r0J jJ I,.... 1/ '\ v \J A h ~JA ,. \~ ~ rrv~ ~ V I I I 1940 1950 1960 1970 19801990 2000 2010 i 1 year 1- S max Fig. 3 - 5 years running mean I Maximum salinity in the upper 300m at station S-3 in North Icelandic waters in spri ng 1950-1999. For location see Fig.1 Siglunes 3 T-S diagram ~ E :::l (1) c.. E ~ . .1 l I Fig. 4 8,00 7,00 6,00 5,00 4,00 3,00 2,00 1,00 000 , -1,00 -2,00 /,/ AW :,t: . •• • z.. · •• AIW ~.-.- .. /~: • .. Yo .-/ .. - /PW ./ • I I 33,50 I 34,00 34,50 Salinity 35,00 35,50 ! Temperature-salinity relationship at station S-3/50m In North Icelandic waters in spring 1950-1999 and main water masses. AW: warm and saline Atlantic water (S>34.8) PW: cold and low-saline Polar water (S<34.5) AIW: medium warm and saline Arctic water (34.5<S<34.8) Monthly SST averages at Grimsey 9 a ~ 1 J 7 I \ 6 5 • • 4 3 J 2 • . ~ ~ • f 1 iI' o , ~ ¥ ~ ~ I , ~ _.' , I j-a6 j-a7 j-aa j-a9 j-90 j-91 1 J I I .f.t. 1 V I ~ I , j-92 j-93 j-94 j-95 j-96 j-97 j-98 j-99 j-OO I i Fig. 5 Monthly average of continuous recording of sea surface temperature (SST) at Grlmsey, North Icelandic waters 1987-1999. For location see Fig.1 Seasonal SST temperatures at Grimsey 9 ~----------------------------------------~ 8 +---------------~=-------------------------~ 7 +-____~~~~------~--~L-~~-===~----~ 6 5 +-------~------------~~----------------~ 4 +-----~--~~--~~~~--~==~~~------~ 3 +-----~~~--~~----~--~--~~~-=----~ T-----------~--~~----------~~--_I 2-+---~~~~~~------~~~~~~----~ 1 o ~------------~------------~------------~ i I 1985 1-- winter T --- spring T 1 Fig. 6 1995 1990 -tr- 2000 summer T -- fall T I Seasonal three months averages of SST at Grfmsey 1987-1999. For location see Fig.1 I -- - - - - - - - - - - - - - - - - ; i 6 5t---------------~--------------------_J 2t---~~~==~---------~~~--------- I1 I ~----~--~----~--~----~--~. 10L-__ I 1986 ' 1988 1990 1992 1994 1996 1998 I 2000 I I-T Grimsey ---T S3! 6 . . • . ~ E . ~ . .~ . .... v = O,7795x + 0,6842 . R2 = 0,6673 5 I- .-" 4 >. Q) 3 ;:: (!) 2 o , o 2 1 4 3 5 S-3 T Fig. 7 a) Spring SST at Grimsey and station S-3/S0m 1987-1999 and b) their relationship. 34,98 34,96 34,94 34,92 34,90 34,88 34 ,86 34 1 ,84 y /. 1 Fig. 8 a . =0,0247x + 34,821 R2 =0 ,6616 1 ~ 2 ~ ~ ~ . . I ! 3 4 5 The relation between spring SST at Grimsey and salinity maximum at station S-3/0-300m 1987-1999. NAO winter indices and 5year running means 6 4 A 2 o W II JI ~ II V -2 -4 i -6 ~ ~N V' )a1 f\ ~ \, r~ A oo~ ~l~\ ~J V'VIJ ~\J v ~ H \ ; ~ V 1 1 1850 1900 1- NAO index - 2000 1950 5years running mean I NAO winter indices and 5year running means 6,00 - , - - - - - - - - - - - - - - - - - - - - - - - , 4,00 -f--------------i--\----,r----_l 2, 00 -f------~--____+'I___,H+-A~_++_---_l 0, 00 -f----t--t\-='I-Hr-t'rl-t---++---+-~'---_+l++---++_---l -2,00 -I-----+-I------.,h-f'lf-=t-t------'<I---¥------++--------l -4,00 -I----------+/---------''----_l -6,00 +,--~-______,,...__-----,---_:__-_....,.----___l 1940 1950 1960 1970 1980 1990 2000 2010 1- NAO index Fig. 9 5years running mean! The annual and 5 years running means of the winter NAO index a) 18701999 and b) 1950-1999 :-:-~'.;'-i using normalized sea level pressure differences between Lisbon, Portugal, and Stykkish6lmur, Iceland (Hurrel 1995.and pers. comm.). NAO, T and 5 5year running means at 5-3 -Sam 7,00 35,2 6,00 35 5,00 4,00 34,8 3,00 0 < z . '"c: I- 34,6 2,00 ., 1,00 34,4 0,00 34,2 _:1,00 -2,00 34 -3,00 33,8 -4,00 . ",'1,. ~ year I--NA05rm --.T5rm __ SSrm: NAO, T and 5 at 5 1-5 a-200m;" 5year running means 6r-------------------------~--------------------------------------~ 35,1 35 34,9 34,8 34,7 I- ; "C 1+-------------------~------~_.~y__*----.r--~c_~----------~~~ ~ 34,6 z '" 34,5 .1+-------~--~--------------+_------------------------------------~ ~+---------------~~L-~------------------------------------------~ 34,4 .3+-________________________________________________________________--1 34,3 -4~.--~~__~----~--~~~~__~~~+__ _ _ _~--~_ _~~~~~--~_r~~. 34,2 ##~~##~~~##~####~~~##~~# year Fig, 10 Five years running means of the winter NAO and temperature and salinity in spring 19S0-1999 at a) station S-3/S0m and b) five stations on the Siglunes section integrated over 0-200m. - - - - - - - - - - Temperature at Siglunes : -50m at station 3 and means of 0-200m at stations 1-5 6 y = 0,6046x + 1,3301 R = 0,8889 5 E 4 o . ~ 3 o I- 2 I • • •• •• ~ ~ ~ • .~. ... •• • • / : .....-: 1 ° • • • • I -200 , 0,00 2,00 4,00 6,00 8,00 T-50m I Salinity at Siglunes : -50m at station 3 and means of 0-200m at stations 1-5 35,2 35,1 35 34,9 E o 34,8 o ~ 34,7 ~ 34,6 34,5 34,4 34,3 34,2 33,50 • '", /' y = 0,6151x + 13,42 R = 0,936 .... • .~ ./. 9/ ~9 /' Y I I 34,00 34,50 35,00 35,50 S -SOm Fig. 11 Temperature and salinity relationships in spring 1950-1999 at a) station S-3/50m and b) stations S/1-5/0-200m. Annual air temperature 1950-1998 6 , 5 y =0,9403x - 0,7944 R2 =0,~896 4 • *~• • • • ~ .. .J . "i: ~ • * /H •• • ! 3 ~ .:.::: <C • 2 • •• •• • / • 1 O~----~--~-----,----,-----.----,-----,~--~ o 1 2 3 4 5 6 7· 8 Reyjavik Fig. 12 Relationship between mean annual temperature in Reykjavik and Akureyri 1950-1998. ---------------- Temperature at Siglunes 3 and Reykjavik 6 _. 5 • -- • • • . • •• • • • • • •• • •• • • .-:-----:-;• . I. • • • -. - • • y • =0,1902x + 3,8188 R" =0,3465 1 0· -200 , I 0.,00 2,00 6,00 4,00 8,00 53 Salinity at Siglunes 3 and Temperature in Reykjavik 6 5 • ... . 4 ~ ~ • • 3 • • . ••• •• .. _... .:. • • • =1 nnJ:;Lt.v _ "-n Lt."-&:: 2- R2 = 0,22,14 1 ° I 33;-50 Fig. 13 34,00 34,50 35,00 I I 35,50 I Relationship between temperature and salinity at S-3/50m and annual air temperatures in a) ReykjavIk and b) Akureyri 1950-1998. Temperature at Siglunes 3 and Akureyri 5 • •• •• • •• 4 • •• • .. .. . .. ~ • • ~ •• •. • • • •• • • 'y = 0,2645x + 2,4949 • R2 = 0,4356 1 ° 1 -200 , • , , 0,00 2,00 , 4,00 6,00 8,00 S3 Salinity at Siglunes 3 and Temperature in Akureyri 5 • 4,5 • 4 •• 3,5 3 2,5 2 I • ~ • ~ ~ • •• 1 ,5 1 • • • • • • •• ~ • • • • • •• •• y = 1,5959x - 52,013 R" - 0,3627 0,5 o 33,50 Fig. 13 , I 34,00 34,50 35,00 I 35,50 I Relationship between temperature and salinity at S-3/50m and annual air temperatures in a) Reykjavik and b) Akureyri 1950-1998. Difference of Annual Air Temperature between Reykjavik and Akureyri 2,5 ,--------------------------------------, 2 +-------------~~------------------------~ 1,5 +---------+t---tt-t---4--\---------1~----___+_-----1 1 0,5 -t-------------++,-------t--t---++--------I o +-------------------~------~--------------~ -0 ,5 +,--------,--------:------,----------.,.---------;------,-----~ 1940 , Fig. 14 1950 1960 1970 1980 1990 2000 2010 Difference between mean annual air temperature in Reykjavik and Akureyri 1950-1998. "C 7 ARSHITi 1901-1988 1900 Fig. 15 Annual mean air temperature in Reykjavik and Akureyri 1900-1988 (Einarsson 1989). Differences of Temperatures between Siglunes 3 and Reykjavik and Akureyri 4,00 ,., '11 2,00 .~ 0,00 v: .('1 V 7\ I ft. ~ • .~~N -200 , ¥ ~ ~' -4,00 -6,00 1940 h I\tIt ~ R~~J~ • N .... ¥ ~ - I 1950 1960 1970 1980 1990 1-- S3-R -- S3-A Fig. 16 2000 2010 I Differences between sea-temperature at S-3/50m and annual temperatures in· Reykjavik and Akureyri 1952-1998. air 10200.-------------------------------, Winter MSLP, Dec - Mar S-year moving averages, hPa 10 10150 .. Scoresoysund iGiGO "'-Si·~ \) t , AmmaS!i2J:k A 10000 . 9950 ·v j f\ . L -_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ";890 Fig. 17 1900 1910 i 540 ;9S0 1960 1~70 1980 1990 Winter mean sea level pressure, Dec-Mar 5 years running means, hPa 10, -1900-19t0 (Blindheim, pers. comm.). I I ~! 2000