Description: Observations from a four-year current meter mooring at 28°44′N, 13°28′W in the Lanzarote passage are used to describe the transport variability of the Eastern Boundary Current of the North Atlantic Subtropical Gyre. Three different water masses are found in the passage: North Atlantic Central Water in the upper levels (roughly Full-size image (〈1 K)), Antarctic Intermediate Water (roughly Full-size image (〈1 K)) and Mediterranean Water in the layer above the bottom at Full-size image (〈1 K). The mean southward transport of NACW is Full-size image (〈1 K)Full-size image (〈1 K) which is the transport of the easternmost branch of the Canary Current. Fluctuations of NACW transport are large, ranging from Full-size image (〈1 K) southward to Full-size image (〈1 K) northward. Every autumn a consistent northward transport is observed, which may be related with the eastern boundary upwelling dynamics. The mean transports of AAIW and MW are Full-size image (〈1 K) northward and Full-size image (〈1 K) southward, respectively. Fluctuations of transport of AAIW and MW are large, from 1.0 to Full-size image (〈1 K) and from −0.32 to Full-size image (〈1 K), respectively. Thus, the mass transports for each water mass show a high standard deviation of comparable magnitude to the mean. This highlights the importance of the temporal variability of the currents in this passage. A remarkable feature of our observations is that the mean transports of NACW and AAIW during an El Niño event are significantly different.

Description: Two major water masses dominate the deep layers in the Mariana and Caroline Basins: the Lower Circumpolar Water (LCPW), arriving from the Southern Ocean along the slopes north of the Marshall Islands, and the North Pacific Deep Water (NPDW) reaching the region from the northeastern Pacific Ocean. Hydrographic and moored observations and multibeam echosounding were performed in the East Mariana and the East Caroline Basins to detail watermass distributions and flow paths in the area. The LCPW enters the East Mariana Basin from the east. At about 13°N, however, in the southern part of the basin, a part of this water mass arrives in a southward western boundary flow along the Izu–Ogasawara–Mariana Ridge. Both hydrographic observations and moored current measurements lead to the conclusion that this water not only continues westward to the West Mariana Basin as suggested before, but also provides bottom water to the East Caroline Basin. The critical throughflow regions were identified by multibeam echosounding at the Yap Mariana Junction between the East and West Mariana Basins and at the Caroline Ridge between the East Mariana and East Caroline Basins. The throughflow is steady between the East and West Mariana Basins, whereas more variability is found at the Caroline Ridge. At both locations, throughflow fluctuations are correlated with watermass property variations suggesting layer-thickness changes. The total transport to the two neighboring basins is only about 1 Sverdrup (1Sv ≡ 106 m3 s−1) but has considerable impact on the watermass structure in these basins. Estimates are given for the diapycnal mixing that is required to balance the inflow into the East Caroline Basin. Farther above in the water column, the high-silica tongue of NPDW extends from the east to the far southwestern corner of the East Mariana Basin, with transports being mostly southward across the basin.