4.1. The Vertically Cumulative Transport
 The vertically cumulative transports of S-sadcp are discussed hereafter (Figure 7). The salinity allows us to identify the water masses that dominate in the water column.
Figure 7. Vertically cumulative transports calculated from the S-sadcp run and plotted on the North Atlantic bathymetry, overlaid with the mean salinity of the water column at the corresponding location (in color). The dots are the stations.
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 In June 2002, the East Greenland Coastal Current (EGCC), flowing southward, carried ice that prevented any measurement over the shelf but highlighted the role of this current for the freshwater balance of the Arctic [Bacon et al., 2002]. At the northern tip of the section, the low salinity indicates the influence of the EGCC. Between stations 7 and 6, the surface salinity decreases from 33.35 to 32.35, which corresponds to the salinity at the eastern edge of the EGCC in 1997 [Bacon et al., 2002]. Since the 215-m-deep western station (6) is just inshore of the shelf break, we suppose that the EGCC was not fully sampled in 2002 due to the ice cover, and according to Wilkinson and Bacon , we expect to miss at most 0.7 Sv flowing southward. This 0.7 Sv is therefore added to the final transport uncertainties in the model solutions.
 Away from the shelf, the whole current system in the Irminger Sea is characterized by a mean salinity between 34.88 and 34.92 with a marked cyclonic circulation. On its southeast edge, the aforementioned anticyclonic circulation around the Reykjanes Ridge (RR) between stations 25 and 31 is in the immediate vicinity of a strong anticyclonic mesoscale feature between stations 31 and 34 (see also Figure 2). Traveling toward the southeast, the next noticeable feature is the already mentioned North Atlantic Current beginning at station 48, and followed by three mesoscale patterns centered on stations 53, 58 and 64, whose transports are more easily quantified in Figure 8. The positive salinity anomaly at station 72 centered around 1000 m depth (Figure 2) is wrapped by a strong anticyclonic circulation of 8 ± 4 Sv, which is consistent with the description of a 100-km-wide meddy, and marks the northern limits of the Iberian Abyssal Plain and of the Mediterranean Water spreading across the Ovide section. The other salinity anomalies are not easily associated with any particular circulation patterns that could lead us to identify them as isolated structures. The last noticeable feature is the 2.1 ± 0.4 Sv eastern boundary current on the Iberian slope and shelf between stations 89 and 96.
Figure 8. Vertically integrated cumulative transport from Greenland (left) to Portugal (right), plotted against distance along the Ovide section, with station numbers labeled at the top of the plot. Positive values indicate northward transport. The geostrophic (dashed grey) and LADCP (dashed black) transports are from data only. The three other lines are from model inversions: light grey with mass conservation as the only constraint (S-geost), thick dark grey with mass conservation and SADCP constraints on each pair (S-sadcp), and black with mass conservation and LADCP constraints by region (S-ladcp). The shaded region indicates the uncertainty in the S-sadcp solution.
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 The same circulation patterns can be observed in Figure 8, where transports have been accumulated from Greenland to Portugal. From this figure, we observe a residue of +12 Sv in the geostrophic measurements and −25 Sv in the LADCP cumulative transports. The most significant bias of the latter is caused by stations 32–33 discussed with Figure 5. However, another similar sampling error occurs in an eddy of the DWBC (stations 15–16) and affects the western current system in the Irminger Sea; this quite barotropic eddy can actually be seen in Figure 3. Note that despite these issues, integrating directly measured current data by region allows us to obtain two similar results for S-sadcp and S-ladcp. By incorporating the current data, we get a more barotropic Irminger Gyre, the magnitude of which is increased from 8 to 20 ± 4 Sv. The circulation around the RR found in most models [Treguier et al., 2005] and in float data [Lavender et al., 2000] is also greatly enhanced, leading to a total transport of 7–13 Sv centered on station 27 (the top of the ridge). Next to it, the anticyclonic circulation magnitude reaches 10 ± 5 Sv. Southeast of RR, the influence of the ADCP data decreases, as would be consistent with a more baroclinic circulation.
 The transports for the upper and lower layers are presented in Figure 9. The limit between the layers was fixed at σ2 = 36.94; this isopycnal is very similar to the usual σ0 = 27.8 limit in the northern half of the section, and it has the advantage of not varying rapidly along track in the southern half, where it lies around 2000 m depth. Note that it is also located in the core of the Labrador Sea Water, as indicated by the relative minimum of salinity and maximum of oxygen in Figure 2c. To better localize large-scale features in Figure 9, the transports were filtered with a 200-km low-pass filter along the section. In order to analyze the transports by region, the upper and lower layers are subdivided in two layers in Figure 10. The four resulting layers are delimited by σ1 = 32.35 (above the LSW and similar to σ2 = 36.874 of the work of Bacon ), σ2 = 36.94, and σ4 = 45.95 (above the Antarctic Bottom Water). All these figures will be used to describe the main circulation patterns in June 2002.
Figure 9. Same as Figure 7 but for layers between the surface and σ2 = 36.94 (top) and between σ2 = 36.94 and bottom (bottom). Transports have been low-pass filtered with a cutoff wavelength of 200 km to enhance large-scale patterns.
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Figure 10. Transports in Sv crossing the Ovide section in 2002 (S-sadcp solution), integrated over boxes. The errors are given by the model after inversion. Layer limits are σ1 = 32.35, σ2 = 36.94, and σ4 = 45.85.
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4.2. Upper Layer Circulation (σ2 < 36.94)
 It is believed that barely 2 Sv of the East Greenland Current (EGC) comes from the Nordic seas fresh boundary current, and a major part of this current at 60°N derives from the Irminger Current circulating from the RR and entraining Irminger Sea Water on its way [Pickart et al., 2005]. That is why, at this latitude, the EGC is also called the East Greenland/Irminger Current (we will keep EGC for simplicity in the following). Property sections definitely show strong salinity gradients within the current that both drive the geostrophic flux and testify to the dual origin of the EGC. This strong current is relatively narrow (165 km width, between stations 6 and 14) and extends from the shelf break and the 2800-m isobath. When calculated above the σ2 = 36.94 isopycnal, its transport is estimated at 22 Sv southward (Table 3). Bacon  estimated 21 Sv for the EGC transport at 60°N (from the surface down to σ2 = 36.944). This value is surprisingly similar considering the known variability of the East Greenland Current at short timescale, but models also show that this variability is minimum in summer, consistent with a weaker wind forcing [Treguier et al., 2006]. Furthermore, Bacon  also uses ADCP data and an inverse model to obtain this value, and the overall mass transport constraint used in both models tends to damp the variability at very short timescale (a few days).
 The cyclonic Irminger gyre is well defined in the circulation schemes derived from surface drifters [Fratantoni, 2001; Reverdin et al., 2003; Flatau et al., 2003]. During Ovide, the signature of this cyclonic circulation was a doming of the isotherms and isopycnals between stations 5 and 26 (Figure 2a), a feature that might favor local convection during severe winters [Bacon et al., 2003; Pickart et al., 2003]. In the same figure, the oxygen section shows a relative maximum down to 800 m depth at station 12, as do CFC data discussed in the paper of Forner , at the offshore edge of the EGC. It could possibly be related to locally convected water but has θ-S characteristics of upper Labrador Sea Water (uLSW, see Figure 11). Another O2 maximum characteristic of the classical Labrador Sea Water (cLSW) lies at about 1500 m. Upper LSW is also seen in an anticyclonic eddy at station 20, embedded in saltier and less oxygenated water influenced by the North Atlantic Central Water.
Figure 11. θ-S diagrams of stations 6 to 42. Properties have been averaged in 10-m layers for each pair of stations. On the left diagram, each point is colored according to its oxygen value. On the right diagram, black (grey) points figure southwestward (northeastward) velocities in the model, respectively, and large dots indicate velocities greater than 0.1 m s−1.
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 A question is to determine how the Irminger cyclonic circulation is embedded into a larger circulation scheme. Connections between the Irminger gyre and the NAC over the Reykjanes Ridge (RR) were suggested by surface drifters [Krauss, 1995; Flatau et al., 2003] and at intermediate depth by floats [Lavender et al., 2000]. On the Ovide section, the θ-S-O2 properties in the east Irminger Sea show a strong mesoscale variability and a significant interleaving. The connection with the NAC is observed but not straight through the RR. Indeed, the subarctic front, which delimits the eastern subpolar gyre at stations 48–53, is also intersected twice in the vicinity of the RR: at stations 23–25 and stations 35–37 (Figure 2). The absolute dynamic topography measured by satellite altimetry (Figure 12) consistently suggests an anticyclonic surface circulation around RR. This anticyclonic circulation encompasses a pool of subpolar mode water that is identified around station 33 by its homogeneity and its salinity greater than 35 (Figure 2). The larger thickness of the mode water is within the already mentioned anticyclonic eddy centered at station 33. The eddy core, found at 500 m depth (Figure 4), has no clear surface expression (Figure 12).
Figure 12. Merged absolute dynamic topography in centimeter calculated for 26 June 2002 (from the AVISO Live Access Server). The Ovide track is superimposed in white.
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 The main branch of the North Atlantic Current is found at 52°N (stations 48–51, Figures 8 and 9a), 50 km south of the latitude of the Charlie Gibbs Fracture Zone (CGFZ), which marks the northernmost limit of this NAC branch [Sy, 1988; Belkin and Levitus, 1996; Schott et al., 1999]. A second branch, less intense, is observed at stations 62–63. Eddies are embedded between these two branches (Figures 9a and 12). We estimate 21 ± 2 Sv for the transport of the NAC between 52°N and 45°30′N (Figure 10, first layer between stations 42 and 66), a value that is weaker than some estimates (about 35 Sv between 40° and 54°N in the work of Cunningham  and Paillet and Mercier ) but consistent with the 19 Sv at 52°N in the study of Bacon .
 South of the 44°N meddy already mentioned in the previous section (station 71), a southward net transport can be identified in Figure 8. This southward circulation in the Iberian basin has been documented by Paillet and Mercier  and amounts to 3 ± 1 Sv in the NAC layer (σ1 < 32.35) in 2002. It is of particular importance for the southward advection and subduction of the eastern North Atlantic Mode Water formed in the deep winter mixed layer to the north of the Ovide section.
 A net warm water transport of 19 Sv across a zonal section at 52°N was found in 1991 by Bacon , and it can be compared to the net 19.6 Sv crossing the Ovide section in June 2002 east of 27°W (stations 42 to 96, Table 3).
4.3. Lower-Layer Circulation (σ2 < 36.94)
 The Iceland-Scotland and Denmark Strait overflows are the two sources of the North Atlantic Deep Water coming from the Nordic seas. The Ovide line intersected the DWBC transporting the Iceland-Scotland Overflow Water (ISOW) on the eastern side of the RR upstream of the Charlie Gibbs Fracture Zone (CGFZ). This branch transports 2.5 Sv southward (Figure 10, Table 3), similar to the mean transport value reported by Saunders  in the CGFZ for σ0 > 27.8. From Figure 9b, two peaks of southward flow can be observed: one on the slope of RR, associated with a maximum of temperature and salinity (Figure 2), and a deeper one, partly associated with a deep cyclonic circulation in Maury Channel [Harvey and Theodorou, 1986]. The properties of both branches can be seen in Figure 11: They constitute the saltier deep water of the θ-S diagram, lying from S = 34.95, θ = 2.76°C for the deeper (eastern) branch, to S = 34.975, θ = 3.25°C for the slope branch, richer in oxygen. In the deeper branch, we also observe a relative maximum in the amount of silicate (greater than 15 μmol kg−1; P. Morin, personal communication). Therefore from the analysis of its hydrological properties and from the deep circulation scheme shown by Schmitz and McCartney  (their Figure 12), we conclude that the water of the deep branch transports ISOW from the Faroe-Bank Channel and undergoes the influence of upwelled AABW circulating cyclonically around the northeast Atlantic. This data set does not bring clues on the origin of the upper branch: According to Harvey and Theodorou  or van Aken and Becker , it could come from the sills west of Faroe Islands as well as from the Faroe-Bank Channel.
 In the eastern half of the Irminger Sea, the deep northward flow found between stations 17 and 27 (Figure 9b) amounts to 3.2 Sv (Figure 10, Table 3). The core of this flow is made of ISOW and classical Labrador Sea Water (cLSW), forming a distinct elbow at θ = 3.1–3.25°C and S = 34.92–34.93 in Figure 11b, with northward (grey) velocities. The deep cyclonic circulation in the Irminger Sea is revealed by the θ-S characteristics of its eastern limb which is influenced by Denmark Strait Overflow Water (DSOW, Figure 11a). Estimating the amount of recirculating DSOW is difficult since the errors on the flows west of RR add up to 1 Sv. Furthermore, we found that 80% of the additional 0.7 Sv flowing northward west of RR (as compared to east of RR in Figure 10) lays between σ2 = 36.94 and σ2 = 36.98, i.e., in the cLSW layer, and we would need a careful tracer analysis to separate the recirculating LSW from the directly imported one (along the path shown in the work of Lavender et al. ).
 The DWBC off Greenland transports 9.2 ± 0.9 Sv (Figure 10, Table 3), and it mainly lies between 1700 and 2900 m, with an intense barotropic flow inshore of the 2000-m isobath and a more moderate and mainly baroclinic flow offshore. Although the position of the current is consistent with observations in 1987–1990 reported by Dickson and Brown , its transport is weaker than the 13 Sv previously estimated at Cape Farewell. One might object that we are dealing with a snapshot in an area of strong variability at a scale of a few days, as underlined by mooring measurements of Dickson and Brown . However, in mooring estimates, part of this variability may be spatial and not temporal, and the integration performed by our geostrophic estimates might smooth out this part. Furthermore, the interannual variability of the DWBC transport was consistently documented by Bacon [1998a] from hydrographic sections. For comparison with this latter work, we split our DWBC transport into a baroclinic contribution (5.2 Sv) and a reference level velocity contribution (4 Sv). The baroclinic contribution to the DWBC observed during Ovide is similar to the values reported by Bacon [1998a] for the late 1990s (4–5 Sv). During the 1980s, the DWBC transport was larger by about 3 Sv.
 The relative contribution of DSOW in the 60°N DWBC can be evaluated in Ovide since no deep sill exists between Iceland and 58°N, where the section crosses the RR: All the ISOW and LSW must cross the section northward west of the ridge (3.2 ± 1.0 Sv, Figure 10) before recirculating in the 9.2-Sv DWBC. So we obtain an estimate of 5–7 Sv for the transport of DSOW, which includes entrainment between Denmark Strait and 60°N.
 The deep circulation in the West European Basin is mainly influenced by the spreading of the Labrador Sea Water [Paillet et al., 1998]. The volume transport integrated between σ1 = 32.35 and σ2 = 36.98 and accumulated from Greenland to Portugal is shown in Figure 13. According to Figure 2, this plot is representative of LSW transport between the RR (station 27) and 45°N (station 67). About 4 Sv of LSW is found to cross the section northward under the main branch of the NAC, between 51°30′ and 52°30′N, while about 2 Sv flows southward above ISOW east of the RR. This implies a net export of 2 ± 1 Sv toward the Iceland Basin, as found in the paper of Bacon . In the eastern Irminger Sea, two additional Sverdrups come from the southwest (the Labrador Sea and the Irminger cyclonic gyre), as discussed earlier, while about 4 Sv of uLSW (or Irminger Sea Water) is exported above the DWBC.
Figure 13. Cumulative transport from Greenland (left) to Portugal (right), vertically integrated between σ1 = 32.35 and σ2 = 36.98 (see Figure 2) and plotted against distance along the Ovide section (as in Figure 8). Station numbers labeled at the top of the plot.
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 We know from the study of Paillet et al.  that due to its orientation, the section may intersect a meander of the southeastward spreading of the LSW, with a weak signature in the transports perpendicular to the section. In the data, the southwestward flow that is supposed to underline the southern limit of the LSW influence is not clearly observed due to the predominance of the mesoscale circulation.
 In the Iberian Abyssal Plain, a net northward flow transports 2.2 Sv of Antarctic Bottom Water and Lower Deep Water (Figure 9b, stations 75 to 89). One third of this deep flow recirculates cyclonically north of the Azores Biscay Rise (stations 54 to 70), while two thirds is upwelled in the Lower Deep Water.