The Vertical Partition of Oceanic Horizontal Kinetic Energy

Abstract

To produce an interpretation of the surface kinetic energy as measured by altimeters, a survey is made of the vertical structure of kinetic energy profiles in a large number of globally distributed long current meter records. Although the data are geographically confined primarily to a latitude band in the North Pacific, to the North Atlantic, and to a few moorings in the South Atlantic, the results show, generally speaking, that most regions are dominated by the barotropic and first baroclinic modes. Because of the near-surface intensification of baroclinic modes altimeters primarily reflect the first baroclinic mode, and thus the motion of the main thermocline. There is good quantitative agreement, with a few exceptions, with estimates of the surface kinetic energy obtained from the TOPEX/POSEIDON altimeter and from vertical extrapolations to the surface of the mooring profiles. These results are consistent with previous suggestions that barotropic models have little skill in depicting variability as seen in the altimeter data. An EOF analysis is shown to produce fictitious mode coupling unless the dynamical modes have very different energy levels.

Global observations of quasi‐zonal bands in microwave sea surface temperature

“…Lastly, the depth-integrated temperature contour in both zonal and meridional cross sections has shape nearly identical to SSH. This agreement between Argo-derived and primarily altimeter-derived anomalies supports the notion that altimeter measurements are largely reflective of first-mode baroclinic and surface-trapped processes [Wunsch, 1997;Lapeyre, 2009]. The above relationship between SST, SSH, and subsurface temperature anomaly can be understood by examining the nearly 2-D geostrophic flow associated with the anomalies (D. Chelton, personal communication, 2010).…”

Energy pathways and structures of oceanic eddies from the ECCO2 state estimate and simplified models

“…Also, this idealized model only has one equivalent barotropic mode, in which the lower layer is quiescent, but striations have both barotropic and baroclinic components. The analysis of the ECCO2 model output and the mooring data suggests that both the first baroclinic mode and the barotropic mode contain significant amount of energy and these two modes are coupled (Wunsch, 1997;Wortham, 2012). Furthermore, baroclinic instability process and eddies' feedback on the gyre flow are not included.…”

Length Scales of Eddy Generation and Nonlinear Evolution of the Seasonally Modulated South Pacific Subtropical Countercurrent

“…On a spherical planet the (meridional) planetary potential vorticity gradient ␤ may dominate, which tends to redirect the barotropic inverse cascade more into larger-scale zonally oriented flow at the expense of meridionally oriented flow (Rhines 1977;Vallis and Maltrud 1993;Galperin et al 2004;. It is important to emphasize that the classic inverse cascade, because it is for the barotropic mode only, will likely not be apparent in the altimeter data because the surface dynamics largely reflects the first-baroclinic-mode motions (Wunsch 1997).…”