HR: 1340h
AN: G33B-1238    [Abstracts]
TI: Decadal Changes in the 50-Year GECCO Ocean Synthesis
AU: * Stammer, D
EM: detlef.stammer@zmaw.de
AF: University of Hamburg, Inst. fuer Meereskunde, Bundesstr. 53, Hamburg, 20146, Germany
AU: Koehl, A
AF: University of Hamburg, Inst. fuer Meereskunde, Bundesstr. 53, Hamburg, 20146, Germany
AB: The German partner of the Estimating the Circulation and Climate of the Ocean (GECCO) consortium provided a dynamically consistent estimate of the time-varying ocean circulation over the 50-year period 1952-2001. The estimate results from a synthesis of most of the ocean data sets available during this 50-year period with the ECCO/MIT ocean circulation model. This GECCO estimate is analysed here with respect to decadal and longer term changes in in sea level and meridional overturning. The variability of the meridional overturning is decomposed into contributions from different processes. In agreement with other modeling results, changes in the models MOC strengths are strongly influenced by the southward communication of density anomalies along the western boundary originating from the subpolar North Atlantic which are mainly caused by changes in the Denmark Strait overflow and only marginally influenced by watermass formation in the Labrador Sea. The propagation of density anomalies along the southern edge of the subtropical gyre by baroclinically unstable Rossby waves is found to be at least equally important. Wind driven processes such as local Ekman transport explain a smaller fraction of the variability on those long time scales. Regional changes in sea level are predominantly associated with an intensification of the subtropical gyre circulation and a corresponding redistribution of heat. The horizontal advection of heat due to an increase in wind stress curl is found to explain a major fraction of the estimated regional sea level trends over the last 40 years. Estimated over the top 750 m depth, the increase in thermosteric sea level rise amounts to 1.3 mm/yr on average over the period 1992 through 2001. This corresponds to an increase in upper ocean heat content of 1.5x1022 J/yr and is in agreement with estimates of Willis et al. (2004). However, over the period 1962 through 2001 the global net thermosteric sea level rise is estimated as 0.92 mm/yr from top to bottom, which is three times the recent estimate from Antonov et al. (2005) (0.33 mm/yr). For the last decade, the corresponding global heat flux into the ocean of 1.5 W/m is twice as large as the recent estimate by Willis et al. (2004) due to the heat content change in deeper layers.
UR: http://www.ecco-group.org
DE: 1218 Mass balance (0762, 1223, 1631, 1836, 1843, 3010, 3322, 4532)
DE: 1222 Ocean monitoring with geodetic techniques (1225, 1641, 3010, 4532, 4556, 4560, 6959)
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 3225 Numerical approximations and analysis (4260)
SC: Geodesy [G]
MN: 2007 Fall Meeting