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Saturday, March 21, 2009

Oceanic Volcanism and Sea Surface Temperature

I’ve moved to WordPress.  This post can now be found at Oceanic Volcanism and Sea Surface Temperature
Many times when Sea Surface Temperature (SST) anomalies are discussed on blogs, someone mentions ocean volcanoes, stating their belief that the subsurface volcanism causes large areas of positive SST anomalies. When an oceanic volcano becomes active or erupts, bloggers find maps of SST anomalies and latch onto hotspots, believing the new-found volcanism is responsible for the anomalous warmth. They rarely if ever research the hotspot areas to determine if the anomalies are parts of patterns or if they are simply weather noise.

Many things impact regional or local SST anomalies: from changes in cloud cover, to variations in precipitation, to changes in wind speed. SST anomalies in certain areas of the oceans vary inversely to the SST anomalies of the eastern equatorial Pacific during ENSO events. They warm during La Ninas or cool during El Ninos. These patterns are reflected as the Pacific Decadal Oscillation (PDO), the 1st EOF of North Pacific SST anomalies north of 20N; or the Interdecadal Pacific Oscillation (IPO), the 3rd EOF of global SST anomalies; or the North Pacific Gyre Oscillation (NPGO), the 2nd EOF of North Pacific Sea Surface Height (SSH). Many times these warm SST areas form along the South Pacific Convergence Zone (SPCZ). Refer to Figure 1 for the location of the SPCZ. The illustration is courtesy of the NASA Global Tropical Experiment webpage:
Figure 1

Figure 2 is the OI.v2 Global SST anomaly map for the February 2009. Note the line of warm SST anomalies along the SPCZ. The warm anomalies extend from the Pacific Warm Pool past South America to the South Atlantic.
Figure 2

Yet there are those who wrongly attribute the warm spots along the SPCZ to the recent volcanism off the South Pacific island of Tonga.

The following is a Global SSH video from JPL (tpglobal.mpeg) from October 1992 to August 2002 that I’ve placed on YouTube. The video is available in .mpg format through:
Another listing of videos:

As you will note in the video, Sea Surface Height and Sea Surface Temperature anomalies vary greatly over the course of days, weeks, months, years, and decades. These continuous perturbations are not likely caused by an infrequent awakenings of oceanic volcanoes. They’re caused by coupled ocean-atmosphere interactions.

A link to the corresponding YouTube webpage:

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