Because of its large heat capacity and organized circulations, the ocean plays important roles in the Earth′s climate system through the storage and transport of heat. As globally averaged atmospheric temperature rises, it becomes increasingly important to quantify the ocean′s ability to absorb and sequester excess heat, as well as to understand how a heated ocean affects the atmosphere and cryosphere. Describing variability in globally averaged, upper-ocean heat content is therefore an important step toward understanding the ocean′s role in the global heat budget.
A time series of upper-ocean heat content from 1993 to the present is calculated using a combination of in situ temperature profiles and satellite altimetry data. The time series is calculated using a new technique to combine in situ and satellite data (Willis et al., JGR, submitted Dec., 2002) that results in substantially less error than estimates made from either data set alone. The time series shows annual to interannual variability of heat content in the upper 800 m of the water column, averaged over the globe, including inland and marginal seas. Maps of the yearly heat content anomaly will also be presented. The merged TOPEX/Poseidon - ERS product from AVISO was used to provide altimetry data for the estimate. By compiling data from several different sources, approximately 950,000 temperature profiles were found for the time-period from 1992 to the present. This includes a large number of profiles taken by subsurface floats as part of the Argo program. In recent years, subsurface floats have begun to contribute a substantial fraction of the globally available profiles as well as to provide data in historically data-sparse regions such as the Southern and Indian Oceans. In addition to quantifying interannual variability on a global scale, this work also illustrates the importance of maintaining continuously updated monitoring systems that provide global coverage of the world′s oceans. Such ongoing projects, like the TOPEX/Jason satellite altimetry program and the Argo float program provide a critical foundation for characterizing variability on regional, basin, and global scales and quantifying the ocean′s role as part of the climate system. |
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