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THEME SESSION on North Atlantic Processes (L) THEME SESSION on North Atlantic Processes (L) ICES CM 2000/L:01 The relation between long-term variations of water temperature in the North Atlantic and Nordic Seas Yu. Bochkov, E. Sentyabov, and A. Karsakov The paper presents the results of estimation of the character and value of the relation between long-term variations of the water thermal state in the North Atlantic and the adjacent Nordic Seas. A close relation is found between large-scale variations of the water thermal state over the study area from the Labrador Sea to the Barents Sea. These long-range relations are of both synchronous and asynchronous character, which permits us to use them with the purpose of forecast. Using data on the sea surface temperature in the North Atlantic (1982–2000), as well as data on the water temperature at the depth of 0–200 m in the Kola Section (the Barents Sea) as the base, a close synchronous relation between interannual variations of the temperature in the Barents Sea and the Gulf Stream areas (positive relation) and the Labrador Current (negative relation) is found. An important factor of formation of the large-scale and long-term variations in climatic systems of the North Atlantic and adjacent seas is the North Atlantic Oscillation. The other character of the relation is revealed when comparing interannual (1959–1999) variations of temperature of the Atlantic waters in the Faeroe-Shetland Channel (Northeast Atlantic) and in the Kola Section (The Barents Sea). Here a close asynchronous relation is found. Temperature variations in the Kola Section are 10–12 months behind those in the Faeroe-Shetland Channel. Based on these grounds, a model is developed to make a long-term forecast of water temperature in the Barents Sea long in advance. Yu. Bochkov, E. Sentyabov and A.. Karsakov: Polar Research Institute of Marine Fisheries and Oceanography (PINRO), 6 Knipovich Street, 183763 Murmansk, Russia [tel./fax: +47 78 910 518, e-mail: [email protected]] ICES CM 2000/L:02 Interannual variations in the transport of the Labrador Current on the Newfoundland Shelf E.B. Colbourne During the past several decades' climate conditions in the Northwest Atlantic have been characterised by several extremes, from the warm 1960s and late 1990s to cold conditions of the early 1970s, mid-1980s and early 1990s. The magnitude of these variations is measured by the strength of the winter atmospheric pressure fields in the north Atlantic or the NAO index. Variations in the baroclinic component of the volume transport of the Labrador Current on the Newfoundland Shelf during these events are presented. The historical (1950–1999) summer temperature and salinity data along standard transects on the Newfoundland Shelf were used to compute geostrophic currents and to construct time series of baroclinic transports. The results generally show large interannual variations in transport, but the trend indicates higher-than-average transport during the warm 1960s (low NAO index) and lower than average values during the cold early 1970s and the mid-1980s (high NAO index). During the late 1980s the transport increased to above average values that continued into the mid-1990s, a period of high NAO index anomalies. The results are consistent with earlier work based on data up to the mid-1980s and with the hypothesis that increased transport of Labrador Current Water around the south-east Grand Bank during the warm 1960s on the Newfoundland Shelf resulted in colder ocean conditions further south on the Scotian Shelf. However, the higher-than-average transport for the high NAO index period of the early 1990s is not consistent with previous studies. Eugene Colbourne: Northwest Atlantic Fisheries Centre, Department of Fisheries and Oceans, Physical Oceanography, P.O. Box 5667, St. John's NF. A1C 5X1 Canada [tel: +1 709-772-6106, fax: +1 709-772-5315, e-mail: [email protected]] 1 ICES CM 2000/L:03 Seasonal variations in the Atlantic water inflow to the Nordic Seas B. Hansen, S. Jónsson, W.R. Turrell, and S. Østerhus The inflow of warm and saline Atlantic water to the Nordic Seas occurs through three separate branches. The westernmost of these, the North Icelandic Irminger Current, has been monitored since 1985 with moored Anderaa current meters and regular CTD cruises. The other two branches that flow through the Iceland-Faeroe and the Faeroe- Shetland gaps respectively have been monitored by moored ADCP's and CTD sections since 1994 within the Nordic WOCE and VEINS programmes. Although there are gaps in the observations, they allow a consistent picture of the total inflow to be constructed and they allow an estimate of the seasonal variation of fluxes. This has implications for the possible driving mechanisms that can be considered for the Atlantic inflow. Bogi Hansen: Faeroes Fisheries Laboratory, P.O. Box 3051, FO-110 Torshavn, Faeroe Islands [tel: +298 31 5092, fax: +298 31 8264, e-mail: [email protected]]. Steingrimur Jonsson: Marine Research Institute, University of Akureyri, P.O. Box 224, 602 Akureyri, Iceland [tel: +354 463 0948, fax: +354 463 0998, e-mail: [email protected]]. William R. Turrell: Marine Laboratory, P.O. Box 101, Aberdeen AB9 8DB, Scotland, UK [tel: +44 1224 295 349, fax: +44 1224 295 511, e-mail: [email protected]]. Svein Østerhus: Geophysical Institute, Allegaten 70, N-5007 Bergen, Norway [e-mail: [email protected]] ICES CM 2000/L:04 First results of upper ocean variability in the North Atlantic between the North Sea and Greenland from repeat ADCP measurements onboard the container vessel ‘Nuka Arctica’ P. Jaccard, G. Reverdin, H. Svendsen, S. Østerhus, and T. Rossby The advection of warm subtropical waters east- and northward along the Sub-polar Front plays a central role in moderating the climate of the European subcontinent, reflecting the fact that the northern North Atlantic is much warmer than any other ocean at corresponding latitudes. Further, it is known that there exist low frequency (seasonal to inter-annual) variations in the circulation and hence pole-ward transport of mass and heat, but the lack of accurate information on currents has made this variability difficult to define and quantify. In order to improve our ability to elucidate the spatial and temporal variability of the fluxes of North Atlantic Waters in the northern North Atlantic, a thermosalinograph (TSG) and an acoustic Doppler current profiler (ADCP) were installed on the Royal Arctic Lines' container vessel, the Nuka Arctica, in 1998 and 1999, respectively. In this paper we report on the results from about 15 transects the first year of operation with the 150 kHz ADCP. The ADCP reaches to 300 – 400 meters depth, depending upon weather and biomass/backscatter conditions. At this stage we focus our attention on the eddy activity with emphasis on the Iceland Basin, the Irminger Sea and the waters around Greenland. Pierre Jaccard: Geophysical Institute, University of Bergen, N-5007 Bergen, Norway [tel: +47 55 582 692, fax: +47 55 589 883, e-mail: [email protected]]. Gilles Reverdin: LEGOS, UMR556 CNRS/CNES/UPS, 14 Av. E. Belin, 31000 Toulouse, France [tel: +33 561 333 003, fax: +33 561 253 205, e-mail: [email protected]]. Harald Svendsen: Geophysical Institute, University of Bergen, N-5007 Bergen, Norway [tel: +47 55 582 644, fax: +47 55 589 883, e- mail: [email protected]]. Svein Østerhus: Geophysical Institute, University of Bergen, N-5007 Bergen, Norway [tel: +47 55 582 607, fax: +47 55 589 883, e-mail: [email protected]]. Tom Rossby: Graduate School of Oceanography, University of Rhode Island, Kingston, RI 02881, USA [tel: +1 401 874 6521 (office), fax: +1 401- 874-6728, e-mail: [email protected]] ICES CM 2000/L:06 On influence of long-term variability of temperature regime in the Gdansk Deep of the Baltic Sea on the sprat reproduction and the offspring survival E.M. Karasiova and A.S. Zezera Based on the long-term hydrographic data the peculiarities of temperature vertical distribution during the sprat- spawning season in cold and warm years were considered and discussed in relation to sprat spawning timing and 2 offspring survival. It was assumed that while the temperature conditions in warm years are only one of prerequisites among others for successful survival, the temperature regime of cold years was possibly a key factor for sprat recruitment. E.M. Karasiova and A.S. Zezera: Scientific Research Institute of Marine Fisheries and Oceanography (AtlantNIRO), 5, Dm. Donskoy St., Kaliningrad 236000, Russia [tel: +7 112 225 265, fax: +7 112 219 997; e-mail: [email protected]] ICES CM 2000/L:07 Formation and propagation of temperature anomalies in the North Atlantic Current G. Krahmann, M. Visbeck, and G. Reverdin A general circulation ocean model has been used to study the formation and advection mechanisms of North Atlantic Oscillation-generated temperature anomalies in the North Atlantic Current. In a set of experiments we have applied patterns of NAO-regressed windvector, windspeed and windstress anomalies modulated by fixed-frequency NAO- amplitudes. This idealised forcing generates temperature anomalies in the upper 440~m of the North Atlantic which spread similarly to observed temperature anomalies along the pathway of the North Atlantic Current (NAC). The analysis of individual components of the ocean heat budget reveals that anomalies in the upper 440~m heat content are primarily generated by anomalies of the oceanic heat transport divergence. The surface heat fluxes contribute only 1/3 of the total changes. The anomalous divergences result, both from anomalous currents created by the windstress anomalies, and from the advection of temperature anomalies from further upstream. Along the pathway of the North Atlantic Current temperature anomalies of opposite sign are formed in the first and second halves of the pathway in response to both the surface heat flux and the windstress anomalies.
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