Velocidad de transferencia del módulo WiLink8

Analysis of the kinetic and potential energy of the ocean is used to help clarify the complex process of wave propagation and energy exchanges occurring in the Pacific. Volume averaged values of barotropic and baroclinic kinetic energy, available potential energy and potential energy anomaly are calculated throughout the domain.

All energy fields show strong signals in the source region of the anomaly, starting immediately. Within 14 days the barotropic kinetic energy has propagated around Antarctica, extending away from the Southern Ocean along topographic ridge features such as the Crozet and Kerguelen archipelagos and the Mid- Atlantic Ridge. The signal strengthens over time, and is well defined after 50 days (Figure 5.18). Although the perturbation is only active for 30 days the peak

Fig. 5.19: Baroclinic kinetic energy (kg m−1 _s−2_{) 50 days after the introduction of the}

positive salinity anomaly to the Weddel Gyre in the FORTE model.

Fig. 5.20: Amplitude of the JEBAR term (kg m−1 _s−3_{) 50 days after the introduction of}

Fig. 5.21: Potential energy (kg m−1 _s−2_{) 180 days after the introduction of the positive}

salinity anomaly to the Weddel Gyre in the FORTE model.

Fig. 5.22: Amplitude of the buoyancy term (kg m−1 s−3) 180 days after the introduction of the positive salinity anomaly to the Weddel Gyre in the FORTE model.

in the barotropic energy at the source of the anomaly is at 50 days. Energy is transferred from the baroclinic to the barotropic mode of propagation within the source region. After the 50 day peak energy levels decline rapidly over the next 50 days as energy disperses from the source region.

Baroclinic kinetic energy shows a similar evolution to the barotropic in the Southern Ocean, although high values along ridge features and changes in topography are much better defined due to the much smaller Rossby radius associated with internal wave propagation (Figure 5.19). The JEBAR term shows a similar spatial pattern to the kinetic energy terms (Figure 5.20). Potential energy anomalies are slower to develop, but their spatial extent is similar to that of the barotropic kinetic energy. Interestingly, there is a positive (east) and negative (west) response extending equatorward along the Mid-Atlantic Ridge (Figure 5.21), very similar to the response of the idealised MOMA basin with the temperature anomaly above the ridge (Figure 6.16). The buoyancy term is dominated by a pulsing along the equator. This is attributed to w, the vertical velocity. Anomalies along the equator appear after around 30 days and persist throughout the remainder of the integration (Figure 5.21). Along the equator the period of the signal is predominantly 5 days. Off the equator (+/- 10 – 15◦₎

there is a strong 20 day period that is easily observed in an animation. The

∆T2 _{plots show the same period. It is not obvious what gives rise to these}

periods. They are the same for all ocean basins. All fields show that the majority of the energy remains in the Southern Ocean throughout the integration, and propagates around the coast of Antarctica as barotropic, and later baroclinic, Kelvin waves. Eastward advection of energy from the anomaly can be seen in the kinetic and potential energy fields (Figure 5.21).

In some high latitude NH locations in the Atlantic and Pacific basins, around Iceland for example, signals appear within 7 – 14 days. These are probably a response to the atmospheric anomalies. After 20 days increases in barotropic kinetic energy can be seen to form here also. The NH Atlantic signal arrives 2 days before the Pacific signal. These NH signals continue to grow in barotropic kinetic energy and propagate equatorward (south) along the western boundaries in both basins. Potential energy anomalies only occur in the North Atlantic around Iceland.

Propagation of barotropic Rossby waves can be seen between the East Pacific Rise and the western Pacific boundary. Barotropic kinetic energy in the Southern Ocean remains strong throughout the 360 day integration. Baroclinic kinetic energy along the equator and around Indonesia is relatively strong, and remains so throughout the integration. Some barotropic kinetic energy can be seen along the equator, mostly westward propagating or close to land boundaries, but amplitudes are considerably smaller than in the Southern Ocean or at NH

Fig. 5.23: Available potential energy (kg m−1_s−2_{) in the tropical Pacific after 165 days.}

high latitudes. Energy in the NH is less persistent in both the barotropic and baroclinic modes. Rapid activity along the equatorial waveguide can be seen in the potential energy, although values are small. Available potential energy, which appears very similar spatially to the potential energy anomaly globally, shows a Rossby wave structure extending away from the eastern boundary in the tropical Pacific (Figure 5.23). This signal is distinguishable from around 100 days into the integration, which correlates with the arrival of the first strong baroclinic Kelvin wave at the eastern boundary (Figure 5.12), onwards.

The JEBAR term does not highlight any clear exchange of energy along the western Pacific boundary. Exchange of energy between the barotropic Kelvin and Rossby waves arriving at the boundary and the baroclinic mode of propagation may be smaller than suggested by Ivchenko et al. (2004), and in fact the main mechanism for forcing a strong equatorial response could be more like the one described by Reznik and Zeitlin (2006). In their experiment, the energy which causes an exponentially growing baroclinic response along the equator comes directly from the barotropic mode. Alternatively, the barotropic signal could excite the release of potential energy into the baroclinic mode, which would explain why the buoyancy term shows such a strong response along the equator in the FORTE model.