[A-OS14] Physical Oceanography (General)

[AOS14-P11] Contribution of deep vertical velocity to deficiency of Sverdrup transport in the low-latitude North Pacific

*Kun Zhang¹ (1.Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China)

Keywords:Ocean, North Pacific Ocean, Ocean circulation

Deep vertical velocity is a key factor causing deficiencies in Sverdrup theory, yet its impact in the low-latitude western Pacific is not well-studied. Through analyses of observational, reanalysis, and simulation data, this study explores the role of deep non-zero vertical velocity in Sverdrup transport inaccuracies in the low-latitude North Pacific. The vertical velocities inducing relatively small non-Sverdrup transport are located within 1500–2500 m, which exhibit similar patterns with opposite values to the south and north of 13°N. The zonally integrated meridional volume transport related to these vertical velocities displays non-negligible dipolar zonal bands west of 150°W. The positive and negative transport bands, centered at 11°N and 17°N, can reach an amplitude of ~8.0 Sv when integrated to the western boundary. On average, such integrated meridional transport makes up roughly half of the prominent Sverdrup transport discrepancies in the central-western Pacific. It is noted that the spatial pattern of these vertical velocities is influenced by ocean topography and deep southward currents. A near-global test further suggests that meridional non-Sverdrup transport related to deep vertical velocity is widespread and undergoes remarkable multidecadal variation. This study reveals the disruptive role of deep vertical velocity in perturbing the Sverdrup balance and emphasizes the consideration of its long-term variation when diagnosing wind-driven circulation changes using Sverdrup theory.