Causes : regional scale

by octavocb — last modified Nov 22, 2011 06:38 PM

OBSERVATIONS CAUSES:GLOBAL SCALE CAUSES: REGIONAL SCALE DATA AND MAPS

The geographical distribution of thermal expansion trends for 1993-2003 correlates with regional sea level trends observed by Topex/Poseidon (Figure 1). This indicates that while other phenomena contribute to regional variations in sea level (atmospheric pressure variations, wind stress, etc.), the steric effect is dominant and responsible for the spatial patterns detected by satellite altimetry.
Thermal expansion trends calculated on the basis of Ishii et al., 2003, 2006 and Levitus et al. 2005) ocean data for 1950-2000, over successive 10-years periods, present oscillating structures through time (Lombard et al., 2005b).

EOF (Empirical Orthogonal Functions) analyses of the thermal expansion grids over the 1950-2000 period demonstrate that the steric variations in sea level are dominated by interannual/decadal oscillations associated with the main climate perturbations of the ocean-atmosphere coupled system (ENSO, PDO and NAO phenomena) (Figure 2: thermal expansion varies in space and time in response to these climate fluctuations).
The thermal expansion trend map calculated for the 1955-2003 period (Figure 3) turns out to be very different from the map in figure 1 or 1993-2003. The results of these analyses are published in Lombard et al. (2005b, 2005c).

Figure 1: Comparison of sea level trends for 1993-2003, by Topex/Poseidon (right) and thermal expansion according to temperature and salinity data from the CLS Armor database (left)
(Lombard et al., 2005c).

Figure 2 : EOF 1 of thermal expansion for 1950-1998. Upper panel: spatial patterns
Lower panel : temporal curve (in red), SOI- index (in blue)
(Lombard et al., 2005b)

Figure 3 : Geographical distribution of thermal expansion for 1955-2003 - according to Ishii et al. temperature data
(Lombard et al., 2005b)

Contacts : A. Lombard, A. Cazenave, K. Do Minh

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