Seasonal global mean sea level change from satellite altimeter, GRACE, and geophysical models

J L Chen,B D Tapley,J S Famiglietti,Matt Rodell,C R Wilson

doi:10.1007/s00190-005-0005-9

Abstract

We estimate seasonal global mean sea level changes using different data resources, including sea level anomalies from satellite radar altimetry, ocean temperature and salinity from the World Ocean Atlas 2001, time-variable gravity observations from the Gravity Recovery and Climate Experiment (GRACE) mission, and terrestrial water storage and atmospheric water vapor changes from the NASA global land data assimilation system and National Centers for Environmental Prediction reanalysis atmospheric model. The results from all estimates are consistent in amplitude and phase at the annual period, in some cases with remarkably good agreement. The results provide a good measure of average annual variation of water stored within atmospheric, land, and ocean reservoirs. We examine how varied treatments of degree-2 and degree-1 spherical harmonics from GRACE, laser ranging, and Earth rotation variations affect GRACE mean sea level change estimates. We also show that correcting the standard equilibrium ocean pole tide correction for mass conservation is needed when using satellite altimeter data in global mean sea level studies. These encouraging results indicate that is reasonable to consider estimating longer-term time series of water storage in these reservoirs, as a way of tracking climate change.

Highlights

IntroductionPrevious studies (e.g., Chen et al 1998, 2002a,b; Minster et al 1999; Cazenave et al 2000) suggested that T/P seasonal changes can largely be accounted for by adding together separate effects of steric (temperature and salinity) and non-steric water mass exchange between the oceans and land
We examine T/P and Jason-1 time series during the Gravity Recovery and Climate Experiment (GRACE) observation period (April 2002 through July 2004), instead of mean seasonal sea level changes used in earlier studies
The opposite phases of altimeter observed global mean seasonal sea level change and estimated steric contribution can be explained as the observed sea seasonal signal being basically the sum of two seasonal signals with opposite phases

Summary

Introduction

Previous studies (e.g., Chen et al 1998, 2002a,b; Minster et al 1999; Cazenave et al 2000) suggested that T/P seasonal changes can largely be accounted for by adding together separate effects of steric (temperature and salinity) and non-steric water mass exchange between the oceans and land.

Objectives

Results

Conclusion