Kinetic Energy transfer in the topographically-rich western tropical Pacific

Wednesday 17 October 2018 - 14:00 to 15:00
NOC Liverpool - Nicholson Lecture Theatre (University of Liverpool).
Dr Sarah Zedler (NOC)

The western Tropical Pacific (WTP) is characterized by its complex dynamics and importance to the climate. The way that energy is transferred across length scales is thought to be distinguished from the mid-latitudes. To understand this energy cascade and the influence of both climatic dynamics and topography, we use a high-resolution (2.5km) model nested within a coarser (8km) state estimate model over 2014–2017, a time period that includes the development and realization of the 2014–2015 El Ni ̃no phase as well as an return to normal conditions (2016–2017). During the El Ni ̃no period, the energy cascade is similar to those in the extra-tropics, with simultaneous dual inverse and forward cascades of kinetic energy to larger and smaller scales in the WTP, with the strongest source of energy around the local baroclinic Rossby radius. The mean, eddy kinetic, and potential energy reservoirs, as well as the kinetic energy cascades are stronger in the 2.5km than in the 8km model, suggesting that the high resolution is necessary to capture the effects of the submesoscale. We find the role of topography is to enhance the strength of the mean cascades in both forward and inverse directions; however, the temporal variability of the spectral energy flux is high, and highest during the El Ni ̃no relaxation period, when the topography modified the energy transfer dramatically. These results suggest that topography dramatically alters the energy transfer in the WTP on both the long timescales important for determining the mean distribution of kinetic energy across length scales and the short timescales relevant for dynamical prediction.


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