On the decadal trend of global mean sea level and its implication on ocean heat content change
Event: 2015 Ocean Surface Topography Science Team Meeting
Session: Science I: Mean sea level monitoring: how to reconcile altimetry, tide gauges, land motion and other in situ observations?
Presentation type: Type Oral
Contribution: PDF file
The variability of the trend of global mean sea level on decadal scales is of great importance to determining its long-term evolution. Trend determination is affected by the temporally correlated processes in the record. The problem is treated as one of optimal estimation weighted by the auto-covariance of the time series, which takes into account the various time scales affecting trend estimation. On decadal scales, the estimated standard error of the trend determined from the global mean sea level record from radar altimetry is about 0.3 mm/yr. The uncertainty does not include the systematic errors (~0.4 mm/yr) in the altimeter bias calibration. The time scale of the systematic errors is assumed to be much longer than decadal. The approach is also applied to determining steric sea level from the difference between altimeter-measured sea level and ocean mass estimated from the GRACE observations of the change of Earth’s gravity. The uncertainty of the estimated trend of steric sea level, 0.12 mm/yr, suggests that the change of the global ocean heat content over decadal scales can be estimated from space observations to an accuracy on the order of 0.1 W/m2. The difference between of the steric sea level estimated from Argo and that from altimeter and GRACE, 0.08 +/- 0.23 mm/yr, provides an estimate of the upper bound of the systematic errors of altimetry and GRACE.