| 1. |
- Olsen, Are, 1972, et al.
(författare)
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Nordic seas transit time distributions and anthropogenic CO2
- 2010
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Ingår i: Journal of Geophysical Research Oceans. - 0148-0227. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- The distribution and inventory of anthropogenic carbon (DICant) in the Nordic seas are determined using the transit time distribution (TTD) approach. To constrain the shape of the TTDs in the Nordic seas, CO2 is introduced as an age tracer and used in combination with water age estimates determined from CFC-12 data. CO2 and CFC-12 tracer ages constitute a very powerful pair for constraining the shape of TTDs. The highest concentrations of DICant appear in the warm and well-ventilated Atlantic water that flows into the region from the south, and concentrations are typically lower moving west into the colder Arctic surface waters. The depth distribution of DICant reflects the extent of ventilation in the different areas. The Nordic seas DICant inventory for 2002 was constrained to between 0.9 and 1.4 Gt DICant, corresponding to ∼1% of the global ocean DICant inventory. The TTD-derived DICant estimates were compared with estimates derived using four other approaches, revealing significant differences with respect to the TTD-derived estimates, which can be related to issues with some of the underlying assumptions of these other approaches. Specifically, the Tracer combining Oxygen, inorganic Carbon and total Alkalinity (TrOCA) method appears to underestimate DICant in the Nordic seas, the ΔC* shortcut and the approach of Jutterström et al. (2008) appear to overestimate DICant at most depths in this area, and finally the approach of Tanhua et al. (2007) appears to underestimate Nordic seas DICant below 3000 m and overestimate it above 1000 m.
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| 2. |
- Olsen, Are, 1972, et al.
(författare)
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Overview of the Nordic Seas CARINA data and salinity measurements
- 2009
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Ingår i: Earth System Science Data Discussions. - 1866-3591. ; 2, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Water column data of carbon and carbon relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruises in the Arctic, Atlantic, and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have been subject to rigorous quality control (QC) in order to ensure highest possible quality and consistency. The data for most of the parameters included were examined in order to quantify systematic biases in the reported values, i.e. secondary quality control. Significant biases have been corrected for in the data products, i.e. the three merged files with measured, calculated and interpolated values for each of the three CARINA regions; the Arctic Mediterranean Seas (AMS), the Atlantic (ATL) and the Southern Ocean (SO). With the adjustments the CARINA database is consistent both internally as well as with GLODAP (Key et al., 2004) and is suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation. The Arctic Mediterranean Seas includes the Arctic Ocean and the Nordic Seas, and the quality control was carried out separately in these two areas. This contribution provides an overview of the CARINA data from the Nordic Seas and summarises the findings of the QC of the salinity data. One cruise had salinity data that were of questionable quality, and these have been removed from the data product. An evaluation of the consistency of the quality controlled salinity data suggests that they are consistent to at least 0.05.
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| 3. |
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| 4. |
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| 5. |
- Jeansson, Emil, 1972, et al.
(författare)
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Evidence of Greenland Sea water in the Iceland Basin
- 2009
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Ingår i: Geophys. Res. Lett.. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluates the presence of intermediate water from the Greenland Sea in the Iceland Basin deduced from the observed excess of the tracer sulphur hexafluoride (SF6), released in the central Greenland Sea in 1996. The large tracer release experiment has served a unique opportunity to follow the spread of Greenland Sea intermediate water to the adjacent basins of the Nordic Seas and to the areas bordering this region. In the present study, using data from May–June 2001, the released tracer was detected at the sill in the Faroe Bank Channel and at several locations in the Iceland Basin of the North Atlantic, just downstream the sill and southeast of Iceland. The estimated excess of the released tracer at the Icelandic slope combined with reported values of the volume flow at this location suggest an annual transport rate of approximately 1.4 kg excess SF6. The results suggest an upper transit time from the central Greenland Sea to the area southeast of Iceland of approximately 4 years.
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| 6. |
- Jeansson, Emil, 1972, et al.
(författare)
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Recent changes in the Greenland Sea: Tracers and Hydrography
- 2008
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Ingår i: Geophysical Research Abstracts. ; 10
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Konferensbidrag (refereegranskat)abstract
- Time series of chemical and hydrographic parameters from mid-90s to 2006 in the central Greenland Sea are presented. In addition to potential temperature and salinity, oxygen and transient tracers (CFC-12 and CFC-11) have been measured between 1995 and 2006. The lack of deep convection since the 80s has changed the properties of the Greenland Sea Deep Water, which has become more or less continuously warmer and more saline during, at least, the last two decades. The change in temperature and salinity during the 90s has previously been reported as 0.01°C yr−1 and 0.001°C yr−1, respectively. The change from the mid-90s to 2006 shows the same trend, and might now even increase more rapidly. At the same time, the levels of oxygen have decreased while the transient tracer concentrations have more or less levelled out, indicating that the deep water now has a larger contribution of Arctic Ocean Deep Water. The ventilation depth of the Greenland Sea was larger in the 2000s, compared with the 90s. In accordance with this the transient tracer concentrations of the intermediate waters, down to 1500 m, has increased.
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| 7. |
- Jeansson, Emil, 1972, et al.
(författare)
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Sources to the East Greenland Current and its contribution to the Denmark Strait Overflow
- 2008
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611. ; 78:1, s. 12-28
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Tidskriftsartikel (refereegranskat)abstract
- Data from the East Greenland Current in 2002 are evaluated using optimum multiparameter analysis. The current is followed from north of Fram Strait to the Denmark Strait Sill and the contributions of different source waters, in mass fractions, are deduced. From the results it can be concluded that, at least in spring 2002, the East Greenland Current was the main source for the waters found at the Denmark Strait Sill, contributing to the overflow into the North Atlantic. The East Greenland Current carried water masses from different source regions in the Arctic Ocean, the West Spitsbergen Current and the Greenland Sea. The results agree well with the known circulation of the western Nordic Seas but also add knowledge both to the quantification and to the mixing processes, showing the importance of the locally formed Greenland Sea Arctic Intermediate Water for the East Greenland Current and the Denmark Strait.
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| 8. |
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| 9. |
- Jutterström, Sara, 1975, et al.
(författare)
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Evaluation of anthropogenic carbon in the Nordic Seas using observed relationships of N, P and C versus CFCs
- 2008
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611. ; 78:1, s. 78-84
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Tidskriftsartikel (refereegranskat)abstract
- Several methods to compute the anthropogenic component of total dissolved inorganic carbon () in the ocean have been reported, all in some way deducing (a) the effect by the natural processes, and (b) the background concentration in the pre-industrial scenario. In this work we present a method of calculating using nutrient and CFC data, which takes advantage of the linear relationships found between nitrate (N), phosphate (P) and CFC-11 in the Nordic Seas sub-surface waters. The basis of the method is that older water has lower CFC-11 concentration and also has been exposed to more sinking organic matter that has decayed, resulting in the slopes of P versus CFC-11 and N versus CFC-11 being close to the classic Redfield ratio of 1:16. Combining this with the slope in total alkalinity (AT) versus CFC-11 to correct for the dissolution of metal carbonates gives us the possibility to deduce the concentration of anthropogenic CT in the Nordic Seas. This further allowed us to compute the inventory of anthropogenic CT below 250 m in the Nordic Seas in spring 2002, to 1.2 Gt C.
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| 10. |
- Kasajima, Yoshie, et al.
(författare)
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A submesoscale coherent eddy in the Greenland Sea in 2003
- 2006
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Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH. - 0148-0227. ; 111
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Tidskriftsartikel (refereegranskat)abstract
- Submesoscale Coherent Vortices (SCVs) have been observed earlier in the Greenland Sea, but their overall characteristics, the formation and the dissolution mechanisms, and the effects on the large-scale hydrodynamics were not well understood. In order to improve the understanding of these features, a simultaneous investigation of hydrography, chemical tracers, and full-depth velocity profiles in a SCV was employed in September 2003. The observed eddy had a homogeneous cold core from 500 m to 2500 m depth with a radius of 8∼15 km. The velocity field of the eddy was higher than in the previous years, and the eddy was in strong anticyclonic rotation in the intermediate layer (1000∼2000 m). The high velocity field led to the estimate of eddy vorticity twice as high as previous observations, and this was accounted for the eddy migration while the earlier observed eddies were rather stationary around 75°N 0°E. The eddy migrated northeast ward with a speed of 3 km/day driven by the background mean flow under the strong effects of the background shear, which tilted the rotation axis in the upper layer. The concentrations of sulphur hexafluoride (SF6) and chlorofluorocarbons (CFCs) in the eddy provided firm information about the source water end-members. The Greenland Sea Arctic Intermediate Water and winter cold surface water were determined as the principal eddy source waters. This differs from the earlier conception of eddies being sourced from intermediate waters at the periphery of the Greenland Basin.
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| 11. |
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| 12. |
- Marnela, M, et al.
(författare)
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Transports of Nordic Seas water masses and excess SF6 through Fram Strait to the Arctic Ocean
- 2008
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611. ; 78:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- To determine the exchanges between the Nordic Seas and the Arctic Ocean through Fram Strait is one of the most important aspects, and one of the major challenges, in describing the circulation in the Arctic Mediterranean Sea. Especially the northward transport of Arctic Intermediate Water (AIW) from the Nordic Seas into the Arctic Ocean is little known. In the two-ship study of the circulation in the Nordic Seas, Arctic Ocean – 2002, the Swedish icebreaker Oden operated in the ice-covered areas in and north of Fram Strait and in the western margins of Greenland and Iceland seas, while RV Knorr of Woods Hole worked in the ice free part of the Nordic Seas. Here two hydrographic sections obtained by Oden, augmented by tracer and velocity measurements with Lowered Acoustic Doppler Current Profiler (LADCP), are examined. The first section, reaching from the Svalbard shelf across the Yermak Plateau, covers the region north of Svalbard where inflow to the Arctic Ocean takes place. The second, western, section spans the outflow area extending from west of the Yermak Plateau onto the Greenland shelf. Geostrophic and LADCP derived velocities are both used to estimate the exchanges of water masses between the Nordic Seas and the Arctic Ocean. The geostrophic computations indicate a total flow of 3.6 Sv entering the Arctic on the eastern section. The southward flow on the western section is found to be 5.1 Sv. The total inflow to the Arctic Ocean obtained using the LADCP derived velocities is much larger, 13.6 Sv, and the southward transport on the western section is 13.7 Sv, equal to the northward transport north of Svalbard. Sulphur hexafluoride (SF6) originating from a tracer release experiment in the Greenland Sea in 1996 has become a marker for the circulation of AIW. From the geostrophic velocities we obtain 0.5 Sv and from the LADCP derived velocities 2.8 Sv of AIW flowing into the Arctic. The annual transport of SF6 into the Arctic Ocean derived from geostrophy is 5 kg/year, which is of the same magnitude as the observed total annual transport into the North Atlantic, while the LADCP measurements (19 kg/year) imply that it is substantially larger. Little SF6 was found on the western section, confirming the dominance of the Arctic Ocean water masses and indicating that the major recirculation in Fram Strait takes place farther to the south.
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| 13. |
- Messias, M. J, et al.
(författare)
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The Greenland Sea tracer experiment 1996–2002: Horizontal mixing and transport of Greenland Sea Intermediate Water
- 2008
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Ingår i: Progress In Oceanography. - : Elsevier BV. - 0079-6611. ; 78:1, s. 85-105
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Tidskriftsartikel (refereegranskat)abstract
- In summer 1996, a tracer release experiment using sulphur hexafluoride (SF6) was launched in the intermediate-depth waters of the central Greenland Sea (GS), to study the mixing and ventilation processes in the region and its role in the northern limb of the Atlantic overturning circulation. Here we describe the hydrographic context of the experiment, the methods adopted and the results from the monitoring of the horizontal tracer spread for the 1996–2002 period documented by 10 shipboard surveys. The tracer marked “Greenland Sea Arctic Intermediate Water” (GSAIW). This was redistributed in the gyre by variable winter convection penetrating only to mid-depths, reaching at most 1800 m depth during the strongest event observed in 2002. For the first 18 months, the tracer remained mainly in the Greenland Sea. Vigorous horizontal mixing within the Greenland Sea gyre and a tight circulation of the gyre interacting slowly with the other basins under strong topographic influences were identified. We use the tracer distributions to derive the horizontal shear at the scale of the Greenland Sea gyre, and rates of horizontal mixing at 10 and 300 km scales. Mixing rates at small scale are high, several times those observed at comparable depths at lower latitudes. Horizontal stirring at the sub-gyre scale is mediated by numerous and vigorous eddies. Evidence obtained during the tracer release suggests that these play an important role in mixing water masses to form the intermediate waters of the central Greenland Sea. By year two, the tracer had entered the surrounding current systems at intermediate depths and small concentrations were in proximity to the overflows into the North Atlantic. After 3 years, the tracer had spread over the Nordic Seas basins. Finally by year six, an intensive large survey provided an overall synoptic documentation of the spreading of the tagged GSAIW in the Nordic Seas. A circulation scheme of the tagged water originating from the centre of the GS is deduced from the horizontal spread of the tracer. We present this circulation and evaluate the transport budgets of the tracer between the GS and the surroundings basins. The overall residence time for the tagged GSAIW in the Greenland Sea was about 2.5 years. We infer an export of intermediate water of GSAIW from the GS of 1 to 1.85 Sv (1 Sv = 106 m3 s−1) for the period from September 1998 to June 2002 based on the evolution of the amount of tracer leaving the GS gyre. There is strong exchange between the Greenland Sea and Arctic Ocean via Fram Strait, but the contribution of the Greenland Sea to the Denmark Strait and Iceland Scotland overflows is modest, probably not exceeding 6% during the period under study.
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| 14. |
- Olsson, Anders, 1970, et al.
(författare)
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A comparison of anthropogenic carbon during the LOMROG 07 and IAOE 91cruises in the Arctic Ocean
- 2008
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Ingår i: Geophysical Research Abstracts. ; 10
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Konferensbidrag (refereegranskat)abstract
- During summer 2007, the Swedish icebreaker Oden travelled to the Arctic and amongst other investigations repeated a CTD- transect occupied 16 years earlier during the IAOE cruise. Data measured on both cruises were e.g. nutrients, oxygen, alkalinity, total dissolved inorganic carbon (DIC), and chlorofluorocarbons (CFC11, CFC12 and CCl4). Preliminary results of the comparison show a shallowing of the saturation levels of calcite and aragonite with increasing concentrations of DIC, found almost throughout the entire water column. An estimation of the anthropogenic carbon increase is made by using three different methods, multi linear regression (MLR), the C* methods and the TrOCA method. The C* method and the TrOCA approach shows reasonable agreements while the MLR method gives unrealistic results. The increase in anthropogenic carbon through the water column is well matched with the CFC 11 increase.
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| 15. |
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| 16. |
- Olsson, Anders, 1970, et al.
(författare)
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Intermediate water from the Greenland Sea in the Faroe Bank Channel: spreading of released sulphur hexafluoride
- 2005
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Ingår i: Deep-Sea Research Part I: Oceanographic Research Papers. - : Elsevier BV. - 0967-0637. ; 52:2, s. 279-294
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Tidskriftsartikel (refereegranskat)abstract
- The Faroe Bank Channel is the deepest passage for dense water leaving the Nordic Seas into the North Atlantic. The contribution to this part of the Greenland-Scotland Overflow by intermediate water from the Greenland Sea is investigated by the tracer sulphur hexafluoride (SF6) that was released into the central Greenland Sea in summer 1996. Continuous monitoring has since traced it around the Nordic Seas and into the connecting areas. It was observed for the first time close to the Faroe Islands in early 1999, indicating a transport time from the Greenland Sea of around 2.5 years. This study estimates that approximately 16 kg of SF6 had passed the Faroe Bank Channel by the end of 2002, that is 5% of the total amount released. Both the arrival time and the amount of exported SF6 deduced from the observations are consistent with the results from a numerical ocean model simulating the tracer release and spreading.
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| 17. |
- Olsson, Anders, 1970, et al.
(författare)
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Pathway and mixing of Greenland Sea water to the Faroe area and the Iceland Basin
- 2008
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Ingår i: Geophysical Research Abstracts. ; 10
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Konferensbidrag (refereegranskat)abstract
- The spreading of intermediate water from the Greenland Sea through the Norwegian Sea, the Faroese Channels and the Iceland Basin is studied with means of the released tracer sulphur hexafluoride (SF6). The released tracer tagged the intermediate water in the Greenland Sea (GSAIW), which subsequently could be traced as it spread to the adjacent seas. A main flow of GSAIW was through the Jan Mayen Channel into the Norwegian Sea, where it was transported southward in a boundary current at 1000 m. In the southern Norwegian Sea this tracer path meets another path of the tracer, from the Iceland Sea. Part of the tracer entered the Faroese Channels while some recirculated northward along the eastern side of the Norwegian Basin. The transport of the released tracer through the Faroe Bank Channel was estimated to approximately 3 kg yr−1, which is less than reported earlier. An excess of the released tracer could also be detected in the Iceland Basin, south of the Greenland-Scotland Ridge.
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| 18. |
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| 19. |
- Olsson, Anders, 1970, et al.
(författare)
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The East Greenland Current studied with CFCs and released sulphur hexafluoride
- 2005
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963. ; 55:1-2, s. 77-95
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Tidskriftsartikel (refereegranskat)abstract
- The distribution and evolution of water masses along the East Greenland Current (EGC) from south of the Fram Strait to the Denmark Strait were investigated using chlorofluorocarbons (CFCs) and the released tracer sulphur bexafluoride (SF6) together with hydrographic data. Water masses contributing to the Denmark Strait overflow, and to some extent also contributions to the Iceland-Scotland over-flow, are discussed from observations in 1999. Special emphasis is put on the advection and mixing of Greenland Sea Arctic Intermediate Water (GSAIW), which could be effectively traced thanks to the release of sulphur hexafluoride in the Greenland Sea Gyre in 1996. By means of the dispersion of the tracer, Greenland Sea Arctic Intermediate Water was followed down to the Denmark Strait Sill as well as close to the Faroe-Shetland Channel. The results indicate that this water mass can contribute to both overflows within 3 years from leaving the Greenland Sea. The transformation of Greenland Sea Arctic Intermediate Water was dominated by water from the Arctic Ocean, especially by isopycnal mixing with upper Polar Deep Water (uPDW) but, to a less extent, also by Canadian Basin Deep Water. A mixture of Greenland Sea Arctic Intermediate Water and upper Polar Deep Water was lifted 500 m on its way through southwestern Iceland Sea, to a depth shallow enough to let it reach the sill of the Denmark Strait from where it can be incorporated in the densest layer of the overflow. The observations show contributions to the Denmark Strait overflow from both the East Greenland Current and the Iceland Sea. (c) 2004 Elsevier B.V. All rights reserved.
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| 20. |
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| 21. |
- Tanhua, Toste, 1965, et al.
(författare)
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Formation of Denmark Strait overflow water and its hydro-chemical composition
- 2005
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963. ; 57:3-4, s. 264-288
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Tidskriftsartikel (refereegranskat)abstract
- The dense overflow across the Denmark Strait is investigated with hydrographic and hydro-chemical data and the water mass composition of the Denmark Strait Overflow Water (DSOW) is determined by multivariate analysis. Hydrographical properties, the transient tracers CFC-11 and CFC-12, oxygen and nutrients are utilized for the water mass definitions. Distribution and characteristics of water masses north of Denmark Strait are described, the important water masses at the sill and the variability on weekly time-scales are discussed, and the entrainment and mixing of water into the overflow plume in the northern Irminger Basin is calculated. The analysis indicates that water masses both from the Nordic Seas and the Arctic Ocean are important for the formation of DSOW. It is found that water masses transported with the East Greenland Current make up about 75% of the overflow at the sill. The overflow at, and shortly south of, the sill is inhomogeneous with a low-salinity component dominated by Polar Intermediate Water. The high-salinity component of the overflow is mainly of Arctic origin. The water mass composition, and the short-term variability for 7 repeats of sections close to the sill are described, and these illustrate that the overflow is in fact a composite of a number of water masses with different formation and transport histories. This indicate that the overflow is a robust feature, but that it responds to variations in the circulation or atmospheric forcing that influences the formation of intermediate and deep water masses within the Arctic Mediterranean and the North Atlantic. At a section about 400 kin south of the sill the overflow is well mixed and modified by entrainment of, mainly, Iceland-Scotland Overflow Water and Labrador Sea Water, together constituting 30% of the overflow plume. The entrainment of Middle Irminger Water dominates shortly downstream of the sill, before the overflow plume reaches too deep but the entrainment seems to be intermittent in time. (c) 2005 Elsevier B.V. All rights reserved.
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| 22. |
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| 23. |
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| 24. |
- Tanhua, Toste, et al.
(författare)
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Ventilation of the Arctic Ocean: Mean ages and inventories of anthropogenic CO2 and CFC-11
- 2009
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Ingår i: J. Geophys. Res.. ; 114
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic Ocean constitutes a large body of water that is still relatively poorly surveyed because of logistical difficulties, although the importance of the Arctic Ocean for global circulation and climate is widely recognized. For instance, the concentration and inventory of anthropogenic CO2 (C ant) in the Arctic Ocean are not properly known despite its relatively large volume of well-ventilated waters. In this work, we have synthesized available transient tracer measurements (e.g., CFCs and SF6) made during more than two decades by the authors. The tracer data are used to estimate the ventilation of the Arctic Ocean, to infer deep-water pathways, and to estimate the Arctic Ocean inventory of C ant. For these calculations, we used the transit time distribution (TTD) concept that makes tracer measurements collected over several decades comparable with each other. The bottom water in the Arctic Ocean has CFC values close to the detection limit, with somewhat higher values in the Eurasian Basin. The ventilation time for the intermediate water column is shorter in the Eurasian Basin (∼200 years) than in the Canadian Basin (∼300 years). We calculate the Arctic Ocean C ant inventory range to be 2.5 to 3.3 Pg-C, normalized to 2005, i.e., ∼2% of the global ocean C ant inventory despite being composed of only ∼1% of the global ocean volume. In a similar fashion, we use the TTD field to calculate the Arctic Ocean inventory of CFC-11 to be 26.2 ± 2.6 × 106 moles for year 1994, which is ∼5% of the global ocean CFC-11 inventory.
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