Response of the southwestern Japan/East Sea to atmospheric pressure

The response of the southwestern Japan/East Sea (JES) to atmospheric pressure (Patm) and wind-stress (τ⇒) forcing is investigated by analyzing 2-year bottom pressure (Pbot) data and coastal tide-gauge records. Coherence analyses between Pbot data reveal that the response of the southwestern JES is nearly uniform at frequencies lower than 0.6 cycles per day (cpd). The Ulleung Basin (UB) average Pbot(P¯bot) departs significantly from inverted-barometer (IB) response to the basin average Patm(P¯atm) at frequency bands from 0.2 to 0.7 cpd. The coherence between P¯atm and P¯bot has maximum value at 0.2 cpd. Multiple coherence analysis, applied with P¯atm and UB average τ⇒(τ⇒¯) as inputs and P¯bot as output, reveals that P¯atm is the most significant forcing, with a peak at frequencies between 0.2 and 0.3 cpd. A simple model [Garrett, 1983. Variable sea level and strait flows in the Mediterranean: a theoretical study of the response to meteorological forcing. Oceanologica Acta 6, 79-87; Lyu et al., 2002. Atmospheric pressure-forced subinertial variations in the transport through the Korea Strait. Geophysical Research Letters 29, 10.1029/2001GL014366] is used to investigate the limiting role of the three straits on the JES response to Patm. Coastal sea-level (η) data inside the JES as well as outside the straits demonstrate that the JES responds with a damped Helmholtz-like resonance. The resonance frequency predicted by this simple model is near the frequency of maximum coherence between P¯atm and η¯d, estimated from P¯bot by the hydrostatic approximation. Phase relations and response function gain between these variables confirm the applicability of this simple model to the JES for low-frequency bands below the Helmholtz-like resonance frequency. At higher frequencies, the response relaxes back toward IB, which suggests the mass field adjusts internally within the JES.