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Wednesday, June 18, 2008

SST By Latitude

Figure 1 is a busy graph that illustrates SST by 30 degree latitude increments, from January 1854 to May 2008, where the data have been smoothed with an 85-month (7-year+) running average filter. The two curves that caught my eye were the Northern Mid-Latitude (Red) with its multidecadal oscillation and the Southern High-Latitude (Black), which drops so drastically in recent years.

Figure 1

High Latitude SST Anomalies are shown in Figure 2. They do not appear to influence one another. The Northern Hemisphere temperatures (Yellow) peaked in the 1940s, when Arctic ice thickness must have been reduced, allowing the drops in concentration in more recent years. As noted earlier, the recent decrease in Southern Hemisphere (SH) High-Latitude SSTs (Black) does not agree with claims that Antarctic warming is unprecedented, unless a 0.2+ degree C drop is considered an increase.
Figure 2

Northern (Red) and Southern (Green) Hemisphere Mid-Latitude SST anomalies are illustrated in Figure 3. No, that’s not just the Atlantic; the North Pacific, which oscillates nearly as much, is included in the data. The SH data appears similar to global SST anomaly curves. Does it show a delayed reaction to the Northern Hemisphere oscillation?

Figure 3

Figure 4 is an illustration that compares Arctic and Northern Hemisphere (NH) combined land and sea surface temperatures. The NH mid-latitude SST oscillation (Figure 3) is similar to the Arctic combined LST/SST anomaly curve (Figure 4) after 1920.

Figure 4

Low-Latitude data (Figure 5) appear to contain influences of Northern and Southern Mid-Latitudes, or vice versa. With the 7-year smoothing, ENSO events appear as small perturbations.

Figure 5

Looking at the three Southern Hemisphere (SH) latitudinal data sets in Figure 6, the affect of the mid-latitudes on low-latitudes appear obvious, but then the mid-latitudes appear to be influenced by both low and high latitudes. Which drives which? Tough to say, but the SH high latitudes appear to react to something other than the mid-latitudes. Will the SH mid-latitude temperatures continue to drop, being drawn down by the plummeting Southern Ocean?

Figure 6

If the magnitudes of the variations are the key to which latitude drives which, there would be little question that the Northern Hemisphere (NH) mid-latitudes drive both the NH high- and low-latitude SST anomalies. Refer to Figure 7.

Figure 7


Sea Surface Temperature Data is Smith and Reynolds Extended Reconstructed SST (ERSST.v2) available through the NOAA National Operational Model Archive & Distribution System (NOMADS). http://nomads.ncdc.noaa.gov/#climatencdc

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