Relations between sea level, thermocline depth, heat content, and dynamic height in the tropical Pacific Ocean

Abstract

The use of combined information from expendable bathythermograph and sea level observations for ocean monitoring requires the establishment of relations between sea level, thermocline depth, heat content, and dynamic height. Sea level fluctuations are a good measure of thermocline depth fluctuations in the tropical Pacific between about 15°N and 15°S and allow the determination of changes of upper‐layer volume. Sea level is also a good measure of heat content, and useful correlations extend to higher latitudes. Dynamic height and sea level fluctuations agree only in those areas where the thermal structure resembles a two‐layer system very well, and good correlations are restricted to a narrower area. The combination of bathythermograph and sea level observations will allow a better mapping of the changes of thermocline topography, heat content, and dynamic height for the monitoring of climatic changes in the tropical Pacific.

The role of the southward wind shift in both, the seasonal synchronization and duration of ENSO events

“…This is a crucial consequence as it allows us to quantify the upper-ocean heat content (e.g. Rebert et al 1985), i.e., the warm-water volume (Meinen and McPhaden 2000), and provide an estimate of equatorial SSTA (e.g., Kleeman 1993; Zelle et al 2004).…”

Dynamics of the equatorial undercurrent and its termination

“…Because of the large intensity of the currents above and in the thermocline, located around 150 m in the central Pacific, around 75 m in the central Atlantic, dynamic topography relative to a deeper level (typically chosen between 500 db and 1000 db) is likely to represent pressure adequately, as long as one is not concerned with the deep circulation. Rebert et al (1985) compared sea level gauge measurements to hydrographic data at several locations within the tropical Pacific Ocean. They checked that, between 15 Q N and 15~S, a good correlation exists between directly measured sea levels and the dynamic topography of the sea surface relative to 400 m. When referenced to a deep level, pressure indeed decreases from west to east in the western and central equatorial Atlantic and Pacific.…”

Constraining Wind Stress Products with Sea Surface Height Observations and Implications for Pacific Ocean Sea Level Trend Attribution*

“…In these regions fluctuations in sea surface height anomalies (SSHAs) tend to mirror those of thermocline depth (Rebert et al 1985;Wyrtki 1985). Furthermore, wind stress curl anomalies, which alter near-surface Ekman transport, Ekman pumping, and the resulting oceanic Rossby waves, are predominantly responsible for changes in the thermocline depth.…”