Clockwise propagation of coastally trapped waves around the Korean peninsula

It is increasingly important to monitor the long- and short-term sea level variability at world coasts in a condition of the global sea level rise. Here, we examine subtidal (periods from 3 to 30 days) sea level oscillations for 21 years (1997-2017) at 7 tide gauge (TG) stations around the Korean peninsula (KP), and apply the coastal-trapped wave (CTW) theory to account for the clockwise propagation of subtidal sea level oscillations around the KP found from the TG observations. A cross-correlation analysis of the TG data demonstrates consistent sea level propagations around the peninsula equatorward along the east coast, westward along the south coast, northward along the west coast with the coastline on the right (clockwise around the KP), and the observed propagating speeds are consistent with theoretical phase speeds of mode 1 CTWs (2.0-9.0 m/s) estimated using the realistic shelf topographies and time-varying stratifications. Both observed and modeled (mode 1 CTWs) propagating speeds of the sea level consistently show significant spatial differences associated with shelf topography, yielding their maximum speeds of 8.0-9.0 m/s along the east coast between Mukho and Pohang during winter, their minimum speeds below 4.5 m/s along the south coast between Busan and Yeosu during winter. Temporal (seasonal and interannual) variations, within 1.5 m/s, of propagating speeds in observed and modeled sea level associated with stratification, are also consistent, yielding slower propagations with the speed less than 4.5 m/s along the east coast, e.g., between Sokcho and Pohang during fall 2006 and between Pohang and Busan during spring 2010 and spring 2014. Our results support clockwise propagation of subtidal sea level oscillations around the KP with speeds varying with shelf topography and stratification.