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<p>Observations indicate that the western boundary current region in the tropical Pacific Ocean exhibits significant multiscale variability, particularly on intra-seasonal time scale. However, the cross-scale interactions between intra-seasonal and low-frequency scales remain unclear. Here we investigate this issue from the perspective of energy transfer using a combination of the multiscale window transform, canonical transfer, and localized multiscale energy analysis framework. The spatiotemporal characteristics of energy transfer between intra-seasonal variability (ISV) and seasonal-biennial variability/background flow are examined. We find that the cross-scale kinetic energy transfer plays a crucial role in the ISV energy input, with substantial differences between the upper and sub-thermocline layers in terms of the contributions from different scales. In the upper layer, intense cross-scale cascades associated with background flow occur in the origin of Kuroshio Current and south of Mindanao Current, while those in the New Guinea Coastal Current are linked to seasonal-biennial scale. In the sub-thermocline layer, forward cascades of kinetic energy from two low-frequency scales contribute over 90% of eddy kinetic energy input in the origin of Kuroshio Current and New Guinea Coastal Current. Nonlocal processes play a major role in sustaining the ISV energy in the North Equatorial Countercurrent region. In the north of Mindanao Current region where sub-thermocline eddies are active, the intra-seasonal available potential energy serves as the important source of subsurface ISV kinetic energy.</p>

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Energy transfers and multiscale interactions between intra-seasonal and low-frequency variability in western boundary currents of the tropical Pacific

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Xinying Guo,
  • Shijian Hu,
  • Yang Yang

摘要

Observations indicate that the western boundary current region in the tropical Pacific Ocean exhibits significant multiscale variability, particularly on intra-seasonal time scale. However, the cross-scale interactions between intra-seasonal and low-frequency scales remain unclear. Here we investigate this issue from the perspective of energy transfer using a combination of the multiscale window transform, canonical transfer, and localized multiscale energy analysis framework. The spatiotemporal characteristics of energy transfer between intra-seasonal variability (ISV) and seasonal-biennial variability/background flow are examined. We find that the cross-scale kinetic energy transfer plays a crucial role in the ISV energy input, with substantial differences between the upper and sub-thermocline layers in terms of the contributions from different scales. In the upper layer, intense cross-scale cascades associated with background flow occur in the origin of Kuroshio Current and south of Mindanao Current, while those in the New Guinea Coastal Current are linked to seasonal-biennial scale. In the sub-thermocline layer, forward cascades of kinetic energy from two low-frequency scales contribute over 90% of eddy kinetic energy input in the origin of Kuroshio Current and New Guinea Coastal Current. Nonlocal processes play a major role in sustaining the ISV energy in the North Equatorial Countercurrent region. In the north of Mindanao Current region where sub-thermocline eddies are active, the intra-seasonal available potential energy serves as the important source of subsurface ISV kinetic energy.