Abstract

The main goal of this study is to determine how well temperature, salinity, upper ocean heat content (UOHC) and surface mixed layer fields and their variability can be reconstructed from the Argo observing system. Our approach is to sample and reconstruct these oceanic fields from a coarse-resolution ocean general circulation model (OGCM), quantify the errors in the reconstructed fields and analyze the factors controlling these errors. In particular, we analyze the effects of float movements, which act to increase the spatial sampling coverage, but distort the temporal variability.

Overall performance of the simulated Argo array is good, and the reconstructed climatological means of such key quantities as the temperature, salinity, UOHC and mixed-layer depth is very close to the actual OGCM-simulated values in most of the global ocean. However, the differences between the reconstructed and actual fields (“reconstruction errors”) are more significant in several regions with high gradients and strong currents, such as the Antarctic Circumpolar Current (ACC). Our results suggest that the detection of the year-to-year changes in UOHC in ACC and high-latitude North Atlantic can be particularly problematic. As illustrated by sensitivity experiments, the main effect of float movements is to increase reconstruction errors, particularly in the regions of high gradients. This adverse effect of float movements is the main cause of large errors in the UOHC interannual difference in ACC. Very fast redistribution of floats is, however, demonstrated to be able to noticeably improve the reconstruction accuracy, by increasing the overall spatial sampling coverage of the Argo system.