ICES Journal of
Marine Science
ICES Journal of Marine Science (2012), 69(5), 833 –840. doi:10.1093/icesjms/fss075
Atlantic water temperature and climate in the Barents Sea,
2000 – 2009
Vladimir D. Boitsov, Alexey L. Karsakov, and Alexander G. Trofimov*
Knipovich Polar Research Institute of Marine Fisheries and Oceanography (PINRO), 6, Knipovich Street, Murmansk 183038, Russia
*Corresponding author: tel: +7 8152 473280; fax: +7 8152 473331; e-mail: trofi[email protected]
Boitsov, V. D., Karsakov, A. L., and Trofimov, A. G. 2012. Atlantic water temperature and climate in the Barents Sea, 2000– 2009. – ICES Journal
of Marine Science, 69: 833 – 840.
Received 25 May 2011; accepted 26 March 2012
Year-to-year variability in the temperature of Atlantic water (AW), which has a strong influence on the marine climate and ecosystem
of the Barents Sea, was analysed using data from the Kola Section. With a positive trend in mean annual temperature during the late
20th century, only positive anomalies were registered during the past decade. In nine of those years, the temperature was warmer than
the 1951 – 2000 long-term mean by 0.5 –1.28C, and in 2006, the historical maximum for the 110-year period of observations along the
section was recorded. High air and water temperature coincided with reduced sea-ice cover, especially between October and April,
when there is seasonal enlargement of the ice-covered area. An integral climate index (CI) of the Barents Sea based on the variability
in temperature of AW, air temperature, and ice cover is presented. A prediction of future Barents Sea climate to 2020 is given by
extrapolating the sixth degree polynomial approximating the CI.
Keywords: Barents Sea, climate, water temperature.
Introduction
The Barents Sea is a shelf sea of the Arctic Ocean situated between
northern Europe and the archipelagos of Spitsbergen, Franz Josef
Land, and Novaya Zemlya (Figure 1). Being a transitory area
between the North Atlantic and Arctic Basins, it plays a key role
in water exchange between them.
Advection of Atlantic water (AW) is one of the main sources of
heat and salt in the Eurasian part of the Arctic Ocean (Nikiforov
and Shpaikher, 1980; Alekseev et al., 1997; Schauer et al., 2002;
Gerdes et al., 2003). AW masses arrive there mainly through the
Barents Sea and the eastern Greenland Sea past the Spitsbergen
archipelago. They are carried by the eastern branch of the
Norwegian Atlantic Current, which then splits into two branches
before entering the Barents Sea. The first branch enters the
Barents Sea, crosses its southern and eastern parts, then flows
into the Kara Sea through the strait between Franz Jozef Land
and Novaya Zemlya. This modified AW then flows from the
Kara Sea into the deep Arctic Ocean. The second branch proceeds
north as the Spitsbergen Current, continuing as the West
Spitsbergen Current, which flows along the continental shelf
break through the Fram Strait west of Spitsbergen. The transformed AW rounds the northern tip of the archipelago and continues east along the continental slope, joining with modified
AW flowing from the Kara Sea (Figure 1). In ice-covered areas,
this water submerges under the cold surface layer and penetrates
# 2012
far into the eastern Arctic Ocean (Treshnikov and Baranov,
1976; Rudels et al., 1994).
Interaction of Atlantic and Arctic waters increases the vertical
mixing of water masses and warming of their upper layers, hampering ice-formation in winter and enhancing ice-melting in
summer in the Arctic Ocean areas occupied by AW (Polyakov
et al., 2010). A combination of these processes has an impact on
climate and climate variability in high-latitude areas (Polyakov
et al., 2004; Alekseev et al., 2007), which means that variations
in volume, temperature, and salinity of AW can affect oceanographic conditions in both the Barents Sea and the Arctic
Ocean. Studies of variability of these factors in the Barents Sea
are therefore important for investigating climate variability in
large areas of the Arctic Ocean.
Material and methods
Knipovich Polar Research Institute of Marine Fisheries and
Oceanography (PINRO) has over the years accumulated a large
array of oceanographic data on the Barents Sea and adjacent
waters. Fluctuations in temperature and salinity of AW passing
through the Barents Sea are studied at standard oceanographic sections. The longest dataseries are available for the Kola Section
running along the 33830′ E meridian from 69830 to 77800′ N
(Figure 1). Observations along the Kola Section started in May
1900 and are more frequent (6–15 times a year) than at other
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834
Figure 1. Main flows of AW in the Barents Sea (arrows; after Rudels
et al., 1994, and Ozhigin et al., 2000) and the Kola Section (black
dots). 1, eastern branch of the Norwegian Atlantic Current;
2, Spitsbergen Current; 3, West Spitsbergen Current; 4, Murmansk
Current; 5, Bear Island; 6, Vardø Island; 7, Cape Kanin Nos.
standard sections. The Kola Section has been so far occupied more
than 1100 times, and the PINRO database contains data on
.11 000 oceanographic stations. It is one of the world’s longest
oceanic time-series.
Long-term variations in the Barents Sea climate and features of
hydrographic conditions from 2000 to 2009 were analysed using
the following data: annual mean air temperature at Vardø
(70822′ N 31806′ E) and Kanin Nos (68839′ N 43818′ E) coastal stations, 1900–2009; annual mean air temperature at Bear Island
coastal station (74830′ N 19800′ E), 1950–2009; annual mean temperature in the 0 – 200-m layer of the Kola Section, 1900–2009;
monthly mean temperature in the 0 –200-m layer of the Kola
Section, 1951–2009; May–July averaged ice cover (the percentage
of area covered by ice) of the Barents Sea, 1900– 2009 (provided by
the Murmansk Department for Hydrometeorology and
Environmental Monitoring); and monthly mean ice-covered area
calculated by data from satellite observations, 1980–2009. The
water temperature observations were carried out with both
bottles and CTDs, but the temperature data stored in the
PINRO database and used here have the same accuracy of
0.018C for the whole period.
The spatial distribution of temperature in the Barents Sea was
analysed using data from the joint Norwegian – Russian ecosystem
survey in 2000–2009 as well as data from hydrographic observations in the strait between Franz Josef Land and Novaya Zemlya
in September of 2007 and 2008.
Results and discussion
Over the past two decades, water and air masses in the Barents Sea
have been warmer than normal (Boitsov, 2006; Karsakov, 2009).
Mean annual AW temperature in the 0–200-m layer of the
Murmansk Current in the Kola Section in the first decade of the
21st century was 4.78S (Figure 2a), the highest for the entire
period of instrumental observations in the Barents Sea since 1900.
V. D. Boitsov et al.
During 2000–2009, the mean annual temperature exhibited positive
anomalies of 0.5–1.28C relative to the 1951–2000 mean, being close
to the long-term mean in 2003 only, with an anomaly of 0.38S.
There were anomalously high positive anomalies in 2000 and
2004–2009, with a historical maximum in 2006 (positive anomaly
of 1.28S relative to the 1951–2000 mean) for the entire 110-year
period of observations along the Kola Section (Figure 2b). In
some months in 2006–2009, positive anomalies were the highest
since 1951. In 2006, anomalies were extremely high from May to
October (Figure 2c). Positive anomalies in 2000–2009 were generally 0.18C higher in the cold season than during summer.
The first decade of the 21st century was characterized not
only by warmer water temperature, but also by warmer air temperature (Figure 3), with the highest annual mean values in
2006/2007. In particular, air temperature off the Bear Island
in those 2 years reached 0.8 –1.28S, vs. the long-term (1951 –
2000) mean of – 1.48S. Similar to AW temperature in the
Kola Section, positive air temperature anomalies in winter
were higher than in summer. From 2000 to 2009, air temperature anomalies off Bear Island in November– February were
2.4 times higher than in June–August, and those off the west
coast of Spitsbergen along 788N were 3.6 times higher in
winter than in summer.
Ice cover of the Barents Sea (the area covered with ice in relation to the entire marine area) is strongly correlated with air and
water temperature (Boitsov, 2006), because ice conditions
depend mainly on heat exchange between the sea and the atmosphere (Doronin and Kheysin, 1975; Bengtsson et al., 2004;
Johannessen et al., 2007). The formation and melting of ice in
the Barents Sea is seasonally and interannually variable (Malinin
and Gordeeva, 2003; Boitsov, 2007). Long-term observations
show that from May to July during the ice-melting season, there
are two periods with extensive ice cover and two periods with
little cover (Figure 4). The periods were identified based on the cumulative curve of ice cover anomalies, which shows the years of the
transition from one period to the other. From 2000 to 2009, higher
air and water temperatures in the Barents Sea resulted in little ice
cover. Mean ice extent in the period 2000–2009 was 10% less than
in the previous decade, and 19% less than in the cold decade
1960–1969. The least mean annual ice cover, 22 –23% below the
1900–2000 long-term mean, was observed in the Barents Sea in
2006/2007.
The mean annual ice-covered area calculated using data from
satellite observations in 2007 was 200 000 km2 smaller than the
1980–2008 long-term mean. Data for 2000–2009 show that in
February –April, when the extent of drifting ice is greatest, it
was 13% lower than the 1980–2008 normal. In August –
September of the same period, when ice extent is least, it was
7% less than the 1980–2008 normal. This suggests that winter
processes, principally heat exchange between the atmosphere
and the sea causing ice formation, had a greater impact on
the decrease in annual ice extent than summer processes
during ice-melting. The formation and melting of ice depended
on air temperature, which had higher positive anomalies in
winter than in summer. From 2000 to 2009, the air temperature
anomalies off Bear Island were 2.78C from December to
February and 1.18C from June to August (relative to the
1951–2000 long-term means), whereas those in the northern
Kara Sea were 2.68C in winter and 0.38C in summer.
Air temperature, water temperature and ice cover serve as indicators of marine climate. Their combination provides more
Atlantic water temperature and climate in the Barents Sea
835
Figure 2. Temperature in the 0– 200-m layer in the Murmansk Current of the Barents Sea: (a) mean decadal temperature, 1900 – 2009 (the
long-term average is for the years 1900– 2009); (b) mean annual temperature anomalies, 1951 – 2009 (grey columns indicate anomalously high
positive anomalies); (c) seasonal variations in mean monthly temperature anomalies, 2006 – 2009 (absolute maxima for the period since 1951
are shown as circles).
accurate estimates of long-term climate variability than each used
separately, because combining these parameters smoothes shortterm climate variability and therefore allows better estimation of
long-term climate variability (Boitsov, 2006). As a result, a new
climate index (CI) for the Barents Sea was introduced and calculated for the period 1900–2009. It was derived as a sum of mean
annual anomalies of air temperature, water temperature, and
ice-free area normalized by their standard deviations:
CI =
Ta − MTa Tw − MTw L − ML
+
+
,
sTa
sTw
sL
where Ta, Tw, and L are the mean annual air temperature (at
Vardø and Kanin Nos coastal stations), water temperature (0 –
200 m layer of the Murmansk Current in the Kola Section), and
ice-free area in the Barents Sea (May–July), respectively, MTa,
MTw, and ML are the long-term mean air temperature, water temperature, and ice-free area, respectively, and sTa, sTw, and sL are
the standard deviations of air temperature, water temperature,
and ice-free area, respectively. The individual contributions of
air temperature, water temperature, and ice-free area to the CI
were 20, 62, and 18%, respectively.
Analysis of interannual variations in the CI and its sixth degree
polynomial approximation demonstrated that, since 1900, long
836
Figure 3. Mean decadal anomalies of air temperature off Bear Island,
1950 –2009.
V. D. Boitsov et al.
cold periods twice alternated with long warm periods (Figure 5a).
Vertical arrows in Figure 5b show years of the transition from cold
to warm periods and vice versa. Currently observed steady
warming of air and water masses in the Barents Sea began in the
late 1980s. The CI was negative only from 1997 to 1999, because
air and water temperature in that period were lower than the
1900–2009 average. In 2006, mean annual water temperature in
the Murmansk Current was the highest and ice cover in May–
July the lowest for the entire history of observations, which
resulted in the highest CI.
From 2000 to 2009, the CI for the Barents Sea was positive, with
the largest inclination of cumulative curve compared with other
decades (Figure 5b). However, since 2006, this index has been decreasing; in 2009, it was only half its historical maximum (2006).
Extrapolation of the sixth degree polynomial approximating the CI
Figure 4. Anomalies of ice cover in the Barents Sea, May – July 1900 – 2009, and the corresponding non-linear trend (dotted line). Horizontal
lines show the mean ice cover in specific periods.
Figure 5. (a) CI for the Barents Sea 1900– 2009 (solid line), its sixth degree polynomial approximation (dotted line), and the forecast up to
2020. (b) Cumulative curve of the Barents Sea CI, where 1929, 1961, and 1988 are years of the transition from cold to warm periods and vice
versa.
837
Atlantic water temperature and climate in the Barents Sea
Figure 6. Bottom temperature (8C) in the Barents Sea, August– September 2000– 2009.
has shown that the index is expected to decrease further soon
(Figure 5a), and transition through the zero point will probably
take place after 2025 (Boitsov, 2008). The predicted decreasing
CI should coincide with decreasing air temperature, water temperature, and ice-free area, because the index is formed from
these parameters and is related directly to them.
Thanks to low ice extent in the Barents Sea in August –
September 2000– 2009, oceanographic observations during the
joint Russian –Norwegian ecosystem survey covered almost the
entire northern part of the sea (Figure 6), providing an opportunity to study the interannual variability of the area occupied by
bottom waters of different temperature. Figure 7 shows the area
838
Figure 7. Areas (%) of the Barents Sea (68 – 778N 20– 558E)
occupied by bottom water of different temperature, August–
September 2000 – 2010.
V. D. Boitsov et al.
occupied by bottom water of different temperature in the Barents
Sea (68– 778N 20 –558E) in August–September 2000–2010. As
mentioned above, the water temperature in the Kola Section in
summer 2006 was extremely high. The value demonstrates that
in August–September 2006, 51% of the study area was occupied
by bottom water of temperature .28S. During the subsequent 3
years (2007–2009), that area was reduced by 5 – 6%, and in
2000–2005, just 32 –39% of the area was occupied by water
.28S (Figure 7).
The area occupied by bottom water with temperature ,08S
was smallest in August–September of 2007 (5%) and 2008
(4%). In August –September 2006, it was three times larger than
in the two subsequent years, despite the historical maximum of
water temperature in the Kola Section and the largest area occupied by bottom water with temperature .28S in summer 2006.
This was because rather cold water remained in the eastern
Barents Sea in August–September 2006 (Figure 6). However, in
the first half of 2007 and 2008, the temperature in the 150–
200-m layer of the Kola Section remained anomalously warm
(1.1–1.28S warmer than the 1951–2000 normal), and in
Figure 8. Temperature (8S) in the section between Franz Josef Land and Novaya Zemlya in September of 1991, 1992, 2007, and 2008.
Atlantic water temperature and climate in the Barents Sea
August–September of 2007 and 2008, the temperature of the
bottom water was ,08S only in several small areas of the
Barents Sea. In other years (2000–2005 and 2009), the area occupied by bottom-water masses with ,08S temperature was 3 –8
times larger than in 2007/2008. The greatest extent of cold
bottom water was observed in 2003 (Figure 7). Lower temperature
in the 150 –200-m layer of the Kola Section in winter was correlated with larger areas occupied by bottom water with ,08S temperature in August–September (r ¼ 20.77, n ¼ 11, p ¼ 0.05) and
smaller areas occupied by bottom water with temperature .28S
(r ¼ 0.74, n ¼ 11, p ¼ 0.05), and vice versa.
Oceanographic conditions in August–September of 2007 and
2008 differed from those in other years of that decade, because
positive bottom temperature anomalies were observed in almost
90% of the study area, exceeding the historical (since 1951)
maximum in 35% of the area. Record high anomalies were
mainly in the eastern Barents Sea. Bottom temperature in the
entire Barents Sea was 1.0 –1.58S above the 1951–2000 normal.
Positive anomalies in the areas occupied by the main AW flows
reached 28S.
In recent years, Arctic regions have also experienced stronger
heat advection by atmospheric and ocean currents from the
North Atlantic (Zhang et al., 1998; Alekseev et al., 2007;
Rozhkova et al., 2008). Field observations and simulations indicate
that the major outflow from the Barents Sea is in the strait between
Novaya Zemlya and Franz Josef Land (Loeng et al., 1997;
Rozhkova et al., 2008). In 2007/2008, PINRO and the Institute
of Marine Research (Bergen, Norway) conducted oceanographic
observations in the strait under the BIAC (Bipolar Atlantic
Thermohaline Circulation) project of the International Polar
Year 2007/2008. The investigations revealed a complex thermohaline structure in water of Atlantic and Arctic origin (Trofimov et al.,
2010). Comparison of the results obtained in 2007/2008 with data
from investigations performed in the same area in 1991/1992
(Loeng et al., 1993) showed that in September 2007/2008, the temperature of the surface waters in the strait between Novaya Zemlya
and Franz Josef Land was .08S, i.e. considerably warmer than in
1991/1992 (Figure 8). In September 2007/2008, the temperature
of water flowing from the Barents Sea above the southern slope
of the St Anna Trough was also .08S, whereas in the less warm
years of 1991/1992 it was ,08S.
Conclusions
The decade 2000– 2009 was the warmest of the record starting
in 1900. Throughout the year, air and water temperature in
the Barents Sea was higher than the 1951–2000 average.
Temperature peaked in 2006/2007, and during the subsequent
years (2008–2009), the proposed Barents Sea CI almost halved.
Based on the extrapolation of the sixth polynomial approximation,
the CI is expected to decrease between 2010 and 2020. The related
decreasing trend in air and water temperature of the Barents Sea is
predicted to continue into the near future, which will result in
increased ice cover.
References
Alekseev, G. V., Bulatov, L. V., Zakharov, V. F., and Ivanov, V. V. 1997.
Inflow of unusually warm Atlantic waters into the Arctic Basins.
Contributions of the Russian Academy of Sciences, 356: 401– 403
(in Russian).
Alekseev, G. V., Frolov, I. E., and Sokolov, V. T. 2007. Observations in
the Arctic do not confirm weakening of thermohaline circulation
839
in the North Atlantic. Contributions of the Russian Academy of
Sciences, 413: 92– 95 (in Russian).
Bengtsson, L., Semenov, V. A., and Johannessen, P. N. 2004. The early
twentieth-century warming in the Arctic—a possible mechanism.
Journal of Climate, 17: 4045 –4057.
Boitsov, V. D. 2006. Variability of Temperature in the Barents Sea and
its Forecasting. PINRO Press, Murmansk. 292 pp. (in Russian).
Boitsov, V. D. 2007. Seasonal variability in ice edge position in the
Barents Sea. Problems of Fisheries Oceanography, 4: 206 –220 (in
Russian).
Boitsov, V. D. 2008. Long-period fluctuations of air temperature in the
North Atlantic and the North-European region. News of the
Russian Geographical Society, 140: 6 – 11 (in Russian).
Doronin, Ju. P., and Kheysin, D. E. 1975. Sea Ice. Gidrometeoizdat
Press, Leningrad. 318 pp. (in Russian).
Gerdes, R., Karcher, M. J., Kauker, F., and Schauer, U. 2003. Causes
and development of repeated Arctic Ocean warming events.
Geophysical Research Letters, 30: 1980, doi:10.1029/
2003GL018080.
Johannessen, O. M., Alexandrov, V. Yu., Frolov, I. Ye., Sandven, S.,
Pettersson, L. H., Bobylev, L. P., Kloster, K., et al. 2007. Remote
Sensing of Sea Ice in the Northern Sea Route: Studies and
Applications. Springer– Praxis, Chichester, UK. 472 pp.
Karsakov, A. L. 2009. Oceanographic Investigations along the Kola
Section in the Barents Sea in 1900– 2008. PINRO Press,
Murmansk. 139 pp. (in Russian).
Loeng, H., Ozhigin, V., and Aadlandsvik, B. 1997. Water fluxes
through the Barents Sea. ICES Journal of Marine Science, 54:
310– 317.
Loeng, H., Sagen, H., Aadlandsvik, B., and Ozhigin, V. 1993. Current
measurements between Novaya Zemlya and Frans Josef Land
September 1991 – September 1992. Institute for Marine
Research, Report 2. 23 pp. ISSN 0804-2128.
Malinin, V. N., and Gordeeva, S. M. 2003. Physicostatistical Method of
Forecasting Oceanographic Parameters (for the North-European
Region). PINRO Press, Murmansk. 164 pp. (in Russian).
Nikiforov, Ye. G., and Shpaikher, A. O. 1980. Typical Features in the
Formation of Large-Scale Fluctuations of the Hydrological
Regime of the Arctic Ocean. Gidrometeoizdat Press, Leningrad.
269 pp. (in Russian).
Ozhigin, V. K., Trofimov, A. G., and Ivshin, V. A. 2000. The Eastern
Basin Water and currents in the Barents Sea. ICES Document
CM 2000/L: 14. 19 pp.
Polyakov, I. V., Alekseev, G. V., Timokhov, L. A., Bhatt, U. S., Colony,
R. L., Simmons, H. L., Walsh, D., et al. 2004. Variability of the
intermediate Atlantic water of the Arctic Ocean over the last 100
years. Journal of Climate, 17: 4485 – 4495.
Polyakov, I. V., Timokhov, L. A., Alexeev, V. A., Bacon, S., Dmitrenko,
I. A., Fortier, L., Frolov, I. E., et al. 2010. Arctic Ocean warming
contributes to reduced polar ice cap. Journal of Physical
Oceanography, 40: 2743– 2756.
Rozhkova, A. Yu., Dmitrienko, I. A., Bauch, D., and Timokhov, L. A.
2008. Changes in the properties of the Barents Sea branch of
Atlantic waters in the Nansen Basin caused by atmospheric circulation above the Barents Sea. Contributions of the Russian
Academy of Sciences, 418: 401– 406 (in Russian).
Rudels, C., Jones, E. P., Anderson, L. G., and Kattner, G. 1994. On the
intermediate depth waters of the Arctic Ocean. In The Polar Oceans
and their Role in Shaping the Global Environment, pp. 33– 46. Ed.
by O. M. Johannessen, R. D. Muench, and J. E. Overland.
Geophysical Monograph, 85. American Geophysical Union,
Washington, DC.
Schauer, U., Rudels, B., Jones, E. P., Anderson, L. G., Muench, R. D.,
Bjork, G., Swift, J. H., et al. 2002. Confluence and redistribution of
Atlantic water in the Nansen, Amundsen and Makarov basins.
Annales Geophysicae, 20: 257– 273.
840
Treshnikov, A. F., and Baranov, G. I. 1976. Structure of circulation and
dynamics of the water budget of the northern region. Problemy
Arktiki i Antarktiki, 47: 93 – 100 (in Russian).
Trofimov, A. G., Titov, O. V., Karsakov, A. L., Loeng, H., Ingvaldsen,
R., and Lien, V. 2010. Studies of thermohaline structure and water
circulation along the north-eastern border of the Barents Sea (joint
Russian – Norwegian project BIAC). In Proceedings of the
V. D. Boitsov et al.
International Conference on Marine Investigations of Polar
Areas of the Earth in International Polar Year 2007/2008,
St Petersburg, Russia, 21 – 23 April 2010, pp. 50 – 51. Ed. by I. M.
Ashik. AARI Press, St Petersburg. 256 pp. (in Russian).
Zhang, J., Rothrock, D. A., and Steele, M. 1998. Warming of the Arctic
Ocean by a strengthened Atlantic inflow: model results.
Geophysical Research Letters, 25: 1745– 1748.
Handling editor: Bill Turrell