The Antarctic Circumpolar Current is an important component of the global climate system connecting the major ocean basins as it flows eastward around Antarctica, yet due to the paucity of data, it remains unclear how much water is transported by the current. Between 2007 and 2011 flow through Drake Passage was continuously monitored with a line of moored instrumentation with unprecedented horizontal and temporal resolution. Annual mean near‐bottom currents are remarkably stable from year to year. The mean depth‐independent or barotropic transport, determined from the near‐bottom current meter records, was 45.6 sverdrup (Sv) with an uncertainty of 8.9 Sv. Summing the mean barotropic transport with the mean baroclinic transport relative to zero at the seafloor of 127.7 Sv gives a total transport through Drake Passage of 173.3 Sv. This new measurement is 30% larger than the canonical value often used as the benchmark for global circulation and climate models.

Abstract.A new method is presented for combining historical hydrography with the acoustic travel time measurements from an inverted echo sounder (IES)to obtain time series of full water column profiles of temperature T and specific volume anomaly 5. Hydrography is used to demonstrate that profiles constructed Eddy.

An analysis of the structure and transport of the Gulf Stream is undertaken using direct current meter observations from a 13-mooring array deployed near 68øW from June 1988 to August 1990. The analysis is based on a "stream-coordinate" approach, in which velocities are rotated into a local, downstream coordinate frame and averaged according to their relative cross-stream location within the current. The picture so obtained represents the average synoptic structure of the Gulf Stream, rather than the Eulerian-averaged structure in which the current is weakened and broadened by lateral meandering of the current and adjacent recirculations. Many familiar features of the Gulf Stream are reproduced in the analysis, including an asymmetric velocity profile with larger shear on the cyclonic (shoreward) side of the current, an offshore displacement of the velocity core with depth, and a subsurface velocity maximum on the offshore side of the current. Westward recirculations are also seen on both sides of the Gulf Stream. Maximum downstream speeds at the axis of the Gulf Stream reach approximately 2.0 m/s at the surface and 0.7 m/s at 1000 m, roughly twice the corresponding Eulerian-averaged values. The analysis also reveals a deep extension of the Gulf Stream at 3500 rn depth with a width of 130 km and average speeds of 3-4 cm/s. The transport of the Gulf Stream in the stream-coordinate frame is 113 ---8 Sv, approximately 30% larger than the Eulerian-averaged transport of 88 Sv. On the basis of these results and other recent studies the downstream transport increase of the Gulf Stream and the inflow structure to the Gulf Stream are reconsidered. It is concluded that approximately 30 Sv, or over half of the transport increase between Cape Hatteras and 68øW, is fed by inflow from the northern side of the Gulf Stream and that this inflow is concentrated near Cape Hatteras and 68øW, where the Gulf Stream flows steeply across isobaths converging from the north. [Worthington, 1976; Halkin and Rossby, 1985; Hogg, 1983]. Knauss [1969] showed that in the first 1000 km downstream of Cape Hatteras the Gulf Stream transport increases from 65 Sv (1 Sv = 10 6 m3/s) to approximately 150 Sv (at 65øW), an average rate of increase of 8 Sv per 100 km. This large transport, of order 150 Sv, is apparently maintained at least as far as 55øW [Hendry, 1982; Hogg, 1992]. Despite this large increase in transport, hydrographic sections show that the Gulf Stream has a very similar baroclinic structure over this domain, in terms of its horizontal and vertical scales and total density contrast across the current. The evolution of the Gulf Stream downstream of 55øW is not well understood at this time, but near the Grand Banks, there appears to be a distinct change in the character of the Gulf Stream, from a single meandering front to multiple, branching fronts feeding into the Azores and North Atlantic Currents [Krauss, 1986]. The region east of 55øW is also thought to be where most of the detrainment from the Gulf Stream to the bordering recirculati...

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The Kuroshio Extension System Study (KESS) aimed to quantify processes governing the variability of and the interaction between the Kuroshio Extension and the recirculation gyre. To meet this goal, a suite of instrumentation, including 43 inverted echo sounders equipped with bottom pressure gauges and current meters [current and pressure recording inverted echo sounders (CPIES)], was deployed. The array was centered on the first quasi-stationary meander crest and trough east of Japan, which is also the region of highest eddy kinetic energy. KESS was the first experiment to deploy a large quantity of these new CPIES instruments, and it was unique in that the instruments were deployed in water depths (5300-6400 m) close to their limit of operation. A comprehensive narrative of the methodology to produce mesoscale-resolving fourdimensional circulation fields of temperature, specific volume anomaly, and velocity from the KESS CPIES array is provided. In addition, an improved technique for removing pressure drift is introduced. Methodology and error estimates were verified with several independent datasets. Temperature error was lowest on the equatorward side of the Kuroshio Extension core and decreased with depth (1.58C at 300 m, 0.38C at 600 m, and ,0.18C below 1200 m). Velocity errors were highest in regions of strong eddy kinetic energy, within and south of the jet core. Near the surface, the error in geostrophic velocity between adjacent CPIES was typically 10 cm s 21 , decreasing downward to 6 cm s 21 at 500-m depth and 5 cm s 21 below 800 m. The rms differences from pointwise current measurements are nearly twice as large as the geostrophic errors, because the pointwise velocities include submesoscale and ageostrophic contributions.

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Abstract. Historical hydrographic data from the Southern Ocean are projected into a baroclinic stream function space, generating a three-dimensional gravest empirical mode (GEM) parameterized by pressure, geopotential height, and longitude. The low-dimensional GEM projection is intrinsically steady, vertically coherent, and equiwlent barotropic. The GEM fields capture more than 97% of the total density and temperature variance in the Antarctic Circumpolar Current region.

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