The major pathways of near‐surface Atlantic water in the northern North Atlantic and Nordic Seas are identified as current speeds above 30 cm/s, using 1014 Lagrangian drifters combined with previously published hydrography. The inflow over the Scotland‐Greenland ridge and establishment of the two‐branch Norwegian Atlantic Current (NwAC) are described in light of the circulation in the northern North Atlantic. The western branch of the NwAC appears as a jet in the Polar Front, topographically guided from the Iceland‐Faroe Front, through the Nordic Seas toward Fram Strait. The eastern branch starts as a shelf edge current above the Irish‐Scottish continental shelf, and after passing through the Faroe‐Shetland Channel, it continues northward along the Norwegian shelf edge toward the Arctic, with a branch bifurcating into the Barents Sea. The NwAC appears to maintain its two‐branch structure throughout the Nordic Seas, with the Atlantic water confined to a 200–600 km wide wedge.
Presented here are three mean dynamic topography maps derived with different methodologies. The first method combines sea level observed by the high-accuracy satellite radar altimetry with the geoid model of the Gravity Recovery and Climate Experiment (GRACE), which has recently measured the earth’s gravity with unprecedented spatial resolution and accuracy. The second one synthesizes near-surface velocities from a network of ocean drifters, hydrographic profiles, and ocean winds sorted according to the horizontal scales. In the third method, these global datasets are used in the context of the ocean surface momentum balance. The second and third methods are used to improve accuracy of the dynamic topography on fine space scales poorly resolved in the first method. When they are used to compute a multiyear time-mean global ocean surface circulation on a 0.5° horizontal resolution, both contain very similar, new small-scale midocean current patterns. In particular, extensions of western boundary currents appear narrow and strong despite temporal variability and exhibit persistent meanders and multiple branching. Also, the locations of the velocity concentrations in the Antarctic Circumpolar Current become well defined. Ageostrophic velocities reveal convergent zones in each subtropical basin. These maps present a new context in which to view the continued ocean monitoring with in situ instruments and satellites.
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