>The time-series graph of the ERSST.v3b SST anomaly data for the Southern Ocean, Figure 1, is unique. It clearly shows that Southern Ocean SST anomalies were higher in the late 1800s than they were at their late 20th century peak. Note also how Southern Ocean SST anomalies have been dropping since the early 1990s.
But where does the unique shape come from?
SOUTHERN OCEAN SST ANOMALIES SOUTH OF THE ATLANTIC, PACIFIC, AND INDIAN OCEANS
Figure 2 is a comparative graph of the Southern Ocean SST anomalies, where the data has been divided by the approximate southernmost longitudes of the three major oceans: Atlantic (90S-60S, 70W-20E), Pacific (90S-60S, 145E-70W), and Indian (90S-60S, 20E-145E). It’s clear that the major variations originate south of the South Pacific.
Figure 3 illustrates the Southern Ocean SST anomalies south of the South Pacific without the distraction of the other datasets.
Dividing the data of the Southern Ocean south of the Pacific, Figure 4, illustrates that the majority of the variability lies in the East Central (90S-60S, 145W-110W) and East (90S-60S, 110W-70W) segments.
If those two sections of the Southern Ocean south of the Southeast Pacific are combined (90S-60S, 145W-70W) and compared to remainder of the data for the Southern Ocean (90S-60S, 70W-145W), Figure 5, two things stand out. First, the remainder of the Southern Ocean made a slow dip (from the late 1870s to the early 1930s) and rebound (from the early 1930s to the late 1970s). And since the 1970s, the SST anomalies for that major portion of the Southern Ocean have been dropping. Is the dip and rebound and recent decline part of a ~100-year oscillation? Second, something adds to the apparent natural oscillation in the Southern Ocean south of the Southeast Pacific, which represents about 21% (75 deg longitude/360 deg longitude) of the Southern Ocean, to create the additional variability.
And the logical contributor to the variability of the Southern Ocean south of the Southeast Pacific would be ENSO. Figure 6 compares scaled NINO3.4 SST anomalies to those of the Southern Ocean south of the Southeast Pacific. The timing of the perturbations agree for the most part. At other times, that portion of the Southern Ocean appears to respond to some other forcing.
Figure 7 illustrates the SST anomalies of the Southern Ocean south of the South Atlantic and Indian Oceans. Note how the two datasets appear to modulate out of sync at times. Is this evidence of Antarctic Circumpolar Waves? Refer to:
Refer back to Figure 2. After 1910, note how two of the three datasets appear to vary in unison, while the third opposes them. There are occasions when all three vary in sync, but they occur less often.
As an additional reference, Figures 8 and 9 are the individual SST anomaly graphs for the Southern Ocean south of the South Atlantic and Indian Oceans.
ONE MORE GRAPH TO CLOSE THIS POST
We often hear that global warming is causing the Wilkins Ice Shelf to break free of Antarctica. Refer to Figure 10. Many times the article will note that the local Southern Ocean SST anomalies have risen for the past 50 years. What they fail to mention are:
-SST anomalies for that location show a negative trend over the past 150+ years,
-SST anomalies in that area were higher in the late 1800s than they were in the late 1900s, and
-SST anomalies have dropped significantly since the late 1990s.
ERSST.v3b SST anomaly data is available through the KNMI Climate Explorer website:http://climexp.knmi.nl/selectfield_obs.cgi?someone@somewhere