>Supplement To ENSO Is A Major Component Of Sea Level Rise

>In my post ENSO Is A Major Component Of Sea Level Rise, I illustrated that ENSO is the cause of the pattern of Sea Level Trends illustrated in Figure 1. The IPCC confirms this in their discussion of regional variations in the rate of Sea Level Change.

http://i30.tinypic.com/4jrrr6.png
Figure 1

The following is that IPCC discussion on the rate of sea level change. The illustrations referenced by the IPCC follow the quote. Refer to page 416 of the IPCC AR4, or page 32 of 48 of AR4, Chapter 5.

http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter5.pdf

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“5.5.4 Interpretation of Regional Variations in the Rate of Sea Level Change

“Sea level observations show that whatever the time span considered, rates of sea level change display considerable regional variability (see Sections 5.5.2.2 and 5.5.2.3). A number of processes can cause regional sea level variations.

“5.5.4.1 Steric Sea Level Changes

“Like the sea level trends observed by satellite altimetry (see Section 5.5.2.3), the global distribution of thermosteric sea level trends is not spatially uniform. This is illustrated by Figure 5.15b and Figure 5.16b, which show the geographical distribution of thermosteric sea level trends over two different periods, 1993 to 2003 and 1955 to 2003 respectively (updated from Lombard et al., 2005). Some regions experienced sea level rise while others experienced a fall, often with rates that are several times the global mean. However, the patterns of thermosteric sea level rise over the approximately 50-year period are different from those seen in the 1990s. This occurs because the spatial patterns, like the global average, are also subject to decadal variability. In other words, variability on different time scales may have different characteristic patterns.

“An EOF analysis of gridded thermosteric sea level time series since 1955 (updated from Lombard et al., 2005) displays a spatial pattern that is similar to the spatial distribution of thermosteric sea level trends over the same time span (compare Figure 5.20 with Figure 5.16b). In addition, the first principal component is negatively correlated with the Southern Oscillation Index. Thus, it appears that ENSO-related ocean variability accounts for the largest fraction of variance in spatial patterns of thermosteric sea level. Similarly, decadal thermosteric sea level in the North Pacific and North Atlantic appears strongly influenced by the PDO and NAO respectively.

“For the recent years (1993–2003), the geographic distribution of observed sea level trends (Figure 5.15a) shows correlation with the spatial patterns of thermosteric sea level change (Figure 5.15b). This suggests that at least part of the nonuniform pattern of sea level rise observed in the altimeter data over the past decade can be attributed to changes in the ocean’s thermal structure, which is itself driven by surface heating effects and ocean circulation. Note that the steric changes due to salinity changes have not been included in these figures due to insufficient salinity data in parts of the World Ocean.”

http://i32.tinypic.com/2zow7zm.png
Figure 5.15
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http://i31.tinypic.com/2kn1xl.png
Figure 5.16
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http://i25.tinypic.com/mayl8j.png
Figure 5.20

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Note that the negative correlation between the Southern Oscillation Index (SOI) and the first principal component of thermosteric sea level time series means that the first principal component would correlate directly (not negatively) with NINO3.4 and Cold Tongue Index SST anomalies.

Also, by using the trend maps, the IPCC fails to present the magnitude of the ENSO component in those sea level trends. I plotted the data in ENSO Is A Major Component Of Sea Level Rise. Figures 2 and 3 illustrate the Sea Level variations (total, not just thermosteric) for the Cold Tongue Index area of the eastern tropical Pacific (6S-6N, 180W-90W) and of the Pacific Warm Pool in the western tropical Pacific (10S-20N, 110E-175E).
http://i25.tinypic.com/24oohzo.png

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Figure 2
http://i28.tinypic.com/15yykj5.png
Figure 3