Low frequency inverted barometer signals and the sea level record

Author: Rui M. Ponte
December 1, 2005
AGU Fall Meeting, San Francisco

Ponte, R.M., 2005. Low frequency inverted barometer signals and the sea level record, AGU Fall Meeting, San Francisco, December 2005, invited.

A dynamical interpretation of sea level records requires knowledge of the inverted barometer signals (ηib) associated with the ocean response to atmospheric pressure. Variability in ηib is estimated over the global ocean for the period 1958-2000 using monthly sea level pressure fields from two different atmospheric reanalyses. Low frequency ηib signals and linear trends based on the two reanalyses are in good agreement over most regions. Uncertainties in estimates of ηib seem to be largest in the Southern Ocean, where atmospheric pressure values are less well determined. Seasonal and interannual slib ~variability have weak rms amplitudes in equatorial regions <1 cm but can reach values >7 cm at high latitudes. Joint analyses with the global tide gauge dataset reveal the importance of both seasonal and interannual ηib signals as contributors to observed sea level variance in many locations. Correcting the data for ηib effects can lead to changes in variance of 40% or more. Linear trends in ηib are mostly negative at low and mid latitudes and can cause negative biases in tide gauge estimates of global mean sea level rise, which are comparable in magnitude to the effects of post-glacial rebound. Removal of ηib variability can reduce formal trend uncertainties, particularly when analyzing relatively short (decadal) records such as those available from satellite altimetry.