Download Hydrographic conditions in North Icelandic waters and annual air

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
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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.
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Anomaly" in the northern North Atlantic, 1968-1982. Progress in Oceanography,
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van Loon. Elsevier.
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and precipitation. Science 296:676-679.
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Malmberg, S.A., and Kristmannsson, S.S. 1992. Hydrographic conditions in Icelandic waters,
.
1980-1989. ICES Marine Science Symposium 195:76-92.
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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
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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
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Stefansson, U. Temperature variations in the North Icelandic coastal area during recent
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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