How well is the upper ocean sampled?

The world ocean is a repository for the bulk of the Earth's heat and water. Variations of global ocean heat and fresh water content are important components of the Earth's climate variability. However, the statistical significance of observed fluctuations is not always clear. By using sea surface height anomaly maps produced from satellite altimeter data by Aviso as a surrogate for ocean heat content anomalies, we estimate sampling errors for annual in situ estimates of globally averaged heat content anomalies over the upper 750 m of the ice- free world ocean. Temporally, there are two major reductions in the sampling error; one in 1967 that coincides with the wide spread use of the XBT's and another in 2002 that coincides with introduction of the Argo profiling floats. Our estimates of sampling error show that both the recent downturn in ocean heat content from 2003- 2005 and an earlier downturn from 1980-1983 are significant. We will update global ocean heat content estimates through most of 2006, to ascertain whether or not the 2003-2005 cooling trend persists for another year. We will also take an initial look at recent upper ocean fresh water content estimated from Argo profiling float data and compare it to historical estimates produced from the World Ocean Data Base climatology.