Riccardo Riva (Department of Geoscience and Remote Sensing, Delft University of Technology, Netherlands)

The Tropical Asian Seas (TAS) are an important study area due to the large sea level rise, up to five times the global average, and the subduction of large cities like Manilla, Bangkok and Jakarta due to water extraction. Several studies attempted to explain the hotspot of sea level rise by linking it to multi-decadal signals like the Pacific Decadal Oscillation (PDO) and Southern Oscillation Index (SOI). All of the studies so far, analysed the absolute sea level of altimetry, relative sea level from tide gauges, or a combination of both, but did not do an attempt to separate the steric and the Ocean Bottom Pressure (OBP) signals. In global sea level budgets, the Tropical Asian Seas are often omitted, because barely any Argo data are present and GRACE is cut-off 300 km from the coast to avoid hydrological signal leakage. Von Schuckmann et al. (2014) showed that the omission of the TAS leads to an underestimation of global sea level trends of 0.5 ± 0.2 mm yr −1 between 2005-2011. We attempt to separate the steric and OBP components in the TAS, using altimetry, optimally filtered ITSG-Grace2016 gravity fields and temperature and salinity grids from various ocean reanalyses. By combining the observations from the three sources in a statistically optimal way, we aim to get the best separation of OBP and steric sea level. The sum of the OBP and steric sea level trends is statistically equal to trends computed by Von Schuckmann et al. (2014). This makes it possible to correct global sea level budgets for the omitted TAS area and to study TAS sea level fluctuations in more detail.

Von Schuckmann, K., Sall ́ee, J. B., Chambers, D., Le Traon, P. Y., Cabanes, C., Gaillard, F., ... & Hamon, M. (2014). Consistency of the current global ocean observing systems from an Argo perspective. Ocean Science, 10(3), 923-949.