Internal Lee Wave Generation from Geostrophic Flow in the Northwestern Pacific Ocean

• Published in: Journal of Physical Oceanography
• Main Authors: Li, Ji, Xu, Zhenhua, Hao, Zhanjiu, You, Jia, Zhang, Peiwen, Yin, Baoshu
• Format: Report
• Language: English
• Published: AMER METEOROLOGICAL SOC 2023
• Subjects: Eddies; Internal waves; Mountain waves; Small scale processes; Topographic effects; Oceanography; SMALL-SCALE TOPOGRAPHY; STRATIFIED FLOW; GLOBAL BATHYMETRY; DISSIPATION; CIRCULATION; ENERGY; TIDE; IMPACT; RIDGE; MORPHOLOGY; Southern Ocean; Pacific
• Online Access: http://ir.qdio.ac.cn/handle/337002/183948; http://ir.qdio.ac.cn/handle/337002/183949; https://doi.org/10.1175/JPO-D-23-0035.1

Among the global mapping of lee wave generation, a missing piece exists in the northwestern Pacific Ocean (NPO), which features complex topographies and energetic circulations. This study applies Bell's theory to estimate and map internal lee waves generated by geostrophic flows in the NPO using Mercator Ocean reanalysis data and the full topo-graphic spectra obtained from the latest synthetic bathymetry product. Unlike the dominant contributions from abyssal hills in the Southern Ocean, multiple topographies, including ridges, rises, and continental margins, result in an inhomoge-neous lee wave generation with multiple hotspots in the NPO. The generation rate is generally higher in the Philippine basin and lower in the central Pacific seamounts. Over ridges, the rough topography creates a high potential for triggering lee waves. Over rises and continental margins, the stronger currents at the shallow depths are favorable for lee wave gener-ation. In the Kuroshio extension region, the rough topography and strong currents cause the strongest lee wave generation, with an energy flux reaching 100 mW m22. By mean-eddy decomposition, it is found that the lee wave hotspots contrib-uted by mean flow are concentrated in specific regions, while those by geostrophic eddies are widely distributed. Geo-strophic eddies are the primary contributor to lee wave generation, which account for 74.6% of the total energy transferred from geostrophic flow to lee waves. This study also reveals that tides suppress the lee wave generation by 14%, and geo-strophic flow can cause an asymmetric generation of internal tides.