Measuring heat storage changes in the equatorial Pacific: A comparison between TOPEX altimetry and Tropical Atmosphere‐Ocean buoys

Abstract

Abstract. Heat storage variations in the equatorial Pacific have been studied from December 1992 through February 1997, using sea level data from the TOPEX altimeter and temperatures measured by 42 tethered buoys that are part of the Tropical Ocean-Atmosphere (TAO) array. The TOPEX measurements are converted to heat storage anomalies using a coefficient determined from mean climatological values. For 30-day averages the two measurements agree well over most of the region, except for the southwestern quadrant of the warm pool and a small region of the north-central equatorial Pacific. In the southwestern quadrant the TOPEX measurements indicate a smaller long-term heating rate than the TAO measurements, differing by as much as 30%. After examining conductivity-temperature-depth data in this region, it appears that the difference is due to a change in ocean salinity which is reflected in the TOPEX sea level measurements but not in the TAO heat measurements. The signal in the north-central region is predominately at an annual period, but there is not enough external measurements to determine what the source of the difference is. In the remainder of the equatorial Pacific, the agreement between the data suggests that the TOPEX measurements can be used to measure heat storage variations in the upper layer with reasonable accuracy. Thus TOPEX altimeter data can provide information about the heat budget of the equatorial Pacific in regions where there are few or no direct measurements.

Argo data assimilation into HYCOM with an EnOI method in the Atlantic Ocean

“…The thermal expansion of seawater constitutes a very important component of SSH and then the reduction of the temperature and the heat content in the assimilation experiments contribute strongly to the SSH decrease. For example, the heat content is positively correlated with SSH (Chambers et al, 1998;Willis et al, 2004;Dong et al, 2007). In this work, mean correlation values of 0.802, 0.815 and 0.812 between the HC and SSH are found for the experiments CTL, ASSIM and VL_DPTS, respectively.…”

Global seiching of thermocline waters between the Atlantic and the Indian‐Pacific Ocean Basins

“…Using modern data (directly measured SST anomalies at the TOGA-TAO array and remotely sensed SSH anomaly from the TOPEX altimetric satellite for the last 10 years) we find that a % 0.14°C cm À1 : a positive (negative) displacement in SSH of 2 centimeters as shown in Figure 3 corresponds to a warming (cooling) of 0.3 degrees centigrade. No such relation between SSH and SST exists in the western equatorial Pacific [Chambers et al, 1998]. Thus an increase in the equatorial SSH, induced by the reduction of deep water formation in the North Atlantic, leads to an anomaly in the equatorial east-west temperature gradient that can initiate the weakening (strengthening) of the trade winds that triggers an El Niño (La Niña) event.…”

Observing ocean heat content using satellite gravity and altimetry

“…The thermal expansion of seawater associated with the ocean's time‐varying heat storage is a large component of the time‐varying sea surface height [ Gill and Niiler , 1973; Repert et al , 1985]. Previous studies have made use of this fact to estimate the ocean's time‐varying heat storage from sea surface heights observed with satellite altimetry [ White and Tai , 1995; Hendricks et al , 1996; Wang and Koblinski , 1997; Chambers et al , 1997, 1998; Leuliette and Wahr , 1999; Sato et al , 2000; Polito et al , 2000; Chen et al , 2000; Ferry et al , 2000]. Overall, these studies have found a significant correlation between the estimated heat storage derived from altimetry, and the observed heat storage.…”