ENSO EVENTS, EARTH’S ROTATION AND OCEAN SURFACE CIRCULATION

The El Niño/ENSO events have turned out to represent a very important process in the Earth’s geodynamic system. From a geological point of view, it has been proposed that there also exist similar signals lasting for decades up to a century or so, viz. “super-ENSO” events. The driving forces should be an interchange of angular momentum between the solid Earth and the hydrosphere (in a feedback coupling) recorded in the East–West displacement of equatorial water masses and the related variability (beat) of the Gulf Stream, the Kuroshio Current, the Humboldt Current, etc. and its paleoclimatic-paleoenvironmental effects on the bordering coasts and land masses. Sea level changes in direct anti-correlation are, for example, recorded between Peru and East Africa, and between Europe and Connecticut. The idea has been successfully tested by instrumental records for the last 300 years in Europe. Variations in the Earth’s rotation correlate with the variability of the Gulf Stream system recorded in regional sea level and paleoclimate. During the Spörer, Maunder and Dalton Sunspot Minima, Earth experienced a general speeding-up due to the decreased Solar Wind out-put and its retarding effect on Earth rotation. During these periods, cold Arctic water was pulled down along the European coasts all the way to central Portugal, hence experiencing a drastic cooling or “Little Ice Age” of the bordering land areas. At the same time, the hot Gulf Stream water was concentrated to Gibraltar and northwest African region, which hence experienced a simultaneous warming or “Little Interglacial”. The ocean surface circulation (also a very large heat store) is the first hydrosphere layer to respond to changes in Earth’s rate of rotation. Besides thermo-haline forces, rotation is proposed as a prime factor for driving changes in ocean circulation (e.g. www.pog.su.se/sea; GeoJournal, 37.4, 1995, 419-430).