Inferring dynamic height variations from acoustic travel time in the Pacific Ocean

Abstract

Using climatological atlas data and historical hydrographic data, the relationship between dynamic height anomaly ΔD and acoustic round-trip travel time τ in the Pacific Ocean is investigated. A tight, linear relation is found in a region centered on the Kuroshio and Kuroshio Extension. In this region, the slopem of the relation is approximately −50 dyn m s⁻¹, about equal to the value expected for first-baroclinicmode response and twice as large as the value form in the Gulf Stream region of the Atlantic Ocean. The value ofm in the Pacific generally increases in magnitude towards the south and with increasing depth to which the integrals for ΔD and τ are carried. It is changed only slightly by correcting for the temperature and salinity march of the seasons in the surface layer. The Kuroshio region is established as one in which the record of τ from an inverted echo sounder can be interpreted reliably in terms of ΔD. An inverted echo sounder can also be used in this way in a number of other regions of the Pacific, although the available hydrographic data sets are too sparse to establish their boundaries clearly.