- Email: [email protected]
Methods for making point estimates of eddy heat flux as applied to the Antarctic Circumpolar Current
OLR(1985)32 (9)
A. PhysicalOceanography
marginally coherent with longshore wind at a 6-day period. Gulf Stream and local wind forcing accounted for most of the fluctuations in the upper layer over the shelf break for time scales > 5 days and at --,2 days. A low multiple coherence window at 2.8-5 days was probably due to Gulf Stream frontal eddies. In the lower layer current fluctuations had a character intermediate between upper layer currents (Gulf Stream dominated) and mid-shelf currents (wind dominated). Third Inst. of Oceanogr., Natl. Bur. of Oceanogr., Xiamen, People's Republic of China.
85:4930 Middleton, J.F., 1985. Drifter spectra and dlffusivities. J. mar. Res., 43(1):37-55. The relationships between Eulerian and Lagrangian (or drifter) diffusivities and spectra are explored in detail using the Lagrangian correlation predictor of Corrsin (1959). An important dimensionless parameter in the Euler-Lagrange transformations is the ratio of the Eulerian integral to advective time scales. Diffusivity may be approximated to within 10%; the result is insensitive to the shape of the Eulerian spectra. A (wavenumber) -3 energy spectrum may be identified in Lagrangian frequency space by a corresponding (frequency) -3 spectrum. Relationships between drifter and fixed current meter spectra and time-scales are also explored. Dept. of Oceanogr., Dalhousie Univ., Halifax, NS B3H 4Jl, Canada.
85:4931 Monahan, E.C., M.C. SpiUane and E.M. Murphy, 1984. Surface currents off the northwest coast of Ireland. Rapp. P.-v. Rerun. Cons.perm. int. Explor. Met, 185:67-77. The temporal stability of the current patterns between the NW coast of Ireland and Rockall Bank (Tulloch and Tait 1959) is reconsidered in light of the long-term mean dynamic topography determined from hydrographic data in the international data centre files. The stationarity of these flow features, and of those described by Ellett and Martin (1973), were tested by comparing the drift-bottle recovery patterns of the University College, Galway, largecluster drift-bottle releases with the projected landfalls for these clusters calculated from the relevant run-of-the-wind. The non-wind-driven component of the surface circulation N and W of Ireland is markedly non-stationary, possibly due to transient eddies. A major feature of the offshore surface flow is an intermittent strong current running toward the south; the immediate inshore current is predominantly coastwise. Dept. of Oceanogr., Univ. Coll., Galway, Ireland.
725
85:4932 Nowlin, W.D. Jr., S.J. Worley and T. Whitworth III, 1985. Methods for making point estlmtes of eddy heat flux as applied to the Antarctic Circumpolar Current. J. geophys. Res., 90(C2):3305-3324. A careful examination of the characteristics of eddy heat flux and its distribution in the Drake Passage shows that estimates from long-term current and temperature measurements are significantly affected by the nature of both the mooring and eddy variability. A 20% overestimate may result if corrections are not made for the spurious correlation between temperature and current seen when the mooring is blown over in very fast currents. Here, heat flux is defined for a relatively narrow band of mesoscale variability. Removal of the very low frequency variations associated with sporadic shifts of fronts within the Antarctic Circumpolar Current and the use of a coordinate system oriented with the current render the resulting heat fluxes much more homogeneous. Large interannual variability of the estimates are also observed. Dept. of Oceanogr., Texas A&M Univ., College Station, TX 77843, USA. (wbo)
85:4933 Richardson, P.L., 1985. Average velocity and transport of the Gulf Stream near 55°W. J. mar. Res., 43(1):83-111. Long-term current measurements from surface drifters, SOFAR floats at 700 m and 2000 m, and moored current meters at 4000 m have been combined to produce a vertical section of average absolute zonal currents in and adjacent to the Gulf Stream. Three vertically coherent jets, an eastward flowing Gulf Stream flanked by two westward flowing countercurrents, can be consistently identified from the data sets. About 900 km wide at the surface, the Gulf Stream at depth is only ~,200 km wide. Mean Gulf Stream transport of 93 x 106 m3/s, about a third of which is depth-independent, constitutes ~60% of the synoptic transports in the region. Probable subtropical circulation patterns are discussed. WHOI, Woods Hole, MA 02543, USA. (wbo)
85:4934 Saelen, O.H., 1984. On the so-called Jacolmen's formula. Rept geophys. Inst. Div. phys. Oceanogr. Univ. Bergen, 61:5pp. In 1927 Jacobsen published a formula for calculating eddy diffusivity from the change in T-S curves with time. Unfortunately, while the formula is widely used, it is almost never used under conditions fulfilling the numerous assumptions specified. Here a derivation similar to Okada's (1936) is presented
A. PhysicalOceanography
marginally coherent with longshore wind at a 6-day period. Gulf Stream and local wind forcing accounted for most of the fluctuations in the upper layer over the shelf break for time scales > 5 days and at --,2 days. A low multiple coherence window at 2.8-5 days was probably due to Gulf Stream frontal eddies. In the lower layer current fluctuations had a character intermediate between upper layer currents (Gulf Stream dominated) and mid-shelf currents (wind dominated). Third Inst. of Oceanogr., Natl. Bur. of Oceanogr., Xiamen, People's Republic of China.
85:4930 Middleton, J.F., 1985. Drifter spectra and dlffusivities. J. mar. Res., 43(1):37-55. The relationships between Eulerian and Lagrangian (or drifter) diffusivities and spectra are explored in detail using the Lagrangian correlation predictor of Corrsin (1959). An important dimensionless parameter in the Euler-Lagrange transformations is the ratio of the Eulerian integral to advective time scales. Diffusivity may be approximated to within 10%; the result is insensitive to the shape of the Eulerian spectra. A (wavenumber) -3 energy spectrum may be identified in Lagrangian frequency space by a corresponding (frequency) -3 spectrum. Relationships between drifter and fixed current meter spectra and time-scales are also explored. Dept. of Oceanogr., Dalhousie Univ., Halifax, NS B3H 4Jl, Canada.
85:4931 Monahan, E.C., M.C. SpiUane and E.M. Murphy, 1984. Surface currents off the northwest coast of Ireland. Rapp. P.-v. Rerun. Cons.perm. int. Explor. Met, 185:67-77. The temporal stability of the current patterns between the NW coast of Ireland and Rockall Bank (Tulloch and Tait 1959) is reconsidered in light of the long-term mean dynamic topography determined from hydrographic data in the international data centre files. The stationarity of these flow features, and of those described by Ellett and Martin (1973), were tested by comparing the drift-bottle recovery patterns of the University College, Galway, largecluster drift-bottle releases with the projected landfalls for these clusters calculated from the relevant run-of-the-wind. The non-wind-driven component of the surface circulation N and W of Ireland is markedly non-stationary, possibly due to transient eddies. A major feature of the offshore surface flow is an intermittent strong current running toward the south; the immediate inshore current is predominantly coastwise. Dept. of Oceanogr., Univ. Coll., Galway, Ireland.
725
85:4932 Nowlin, W.D. Jr., S.J. Worley and T. Whitworth III, 1985. Methods for making point estlmtes of eddy heat flux as applied to the Antarctic Circumpolar Current. J. geophys. Res., 90(C2):3305-3324. A careful examination of the characteristics of eddy heat flux and its distribution in the Drake Passage shows that estimates from long-term current and temperature measurements are significantly affected by the nature of both the mooring and eddy variability. A 20% overestimate may result if corrections are not made for the spurious correlation between temperature and current seen when the mooring is blown over in very fast currents. Here, heat flux is defined for a relatively narrow band of mesoscale variability. Removal of the very low frequency variations associated with sporadic shifts of fronts within the Antarctic Circumpolar Current and the use of a coordinate system oriented with the current render the resulting heat fluxes much more homogeneous. Large interannual variability of the estimates are also observed. Dept. of Oceanogr., Texas A&M Univ., College Station, TX 77843, USA. (wbo)
85:4933 Richardson, P.L., 1985. Average velocity and transport of the Gulf Stream near 55°W. J. mar. Res., 43(1):83-111. Long-term current measurements from surface drifters, SOFAR floats at 700 m and 2000 m, and moored current meters at 4000 m have been combined to produce a vertical section of average absolute zonal currents in and adjacent to the Gulf Stream. Three vertically coherent jets, an eastward flowing Gulf Stream flanked by two westward flowing countercurrents, can be consistently identified from the data sets. About 900 km wide at the surface, the Gulf Stream at depth is only ~,200 km wide. Mean Gulf Stream transport of 93 x 106 m3/s, about a third of which is depth-independent, constitutes ~60% of the synoptic transports in the region. Probable subtropical circulation patterns are discussed. WHOI, Woods Hole, MA 02543, USA. (wbo)
85:4934 Saelen, O.H., 1984. On the so-called Jacolmen's formula. Rept geophys. Inst. Div. phys. Oceanogr. Univ. Bergen, 61:5pp. In 1927 Jacobsen published a formula for calculating eddy diffusivity from the change in T-S curves with time. Unfortunately, while the formula is widely used, it is almost never used under conditions fulfilling the numerous assumptions specified. Here a derivation similar to Okada's (1936) is presented