The concept of lunar forcing of climate appears to be gaining momentum in climate change discussions. According to one recent study, the tidal force exerted by the moon is hypothesized to be an important external mechanism responsible for regulating sea surface temperatures tied to ENSO events. Cerveny and Shaffer (2001), for example, report finding a statistically significant correlation between maximum lunar declination (MLD) and both equatorial Pacific sea surface temperature and South Pacific atmospheric pressure (the Southern Oscillation Index) over the period 1854-1999. Under high MLD, circulation in the Pacific gyre is enhanced by tidal forces, inducing cold-water advection into the equatorial region that is characteristic of La Niña conditions. Under low MLD, on the other hand, tidal forcing is weakened, cold water advection is reduced, and warmer sea surface conditions characteristic of El Niño prevail.
Tidal forcing has also been suggested as a major player in driving the world’s great thermohaline circulation (Munk and Wunsch, 1998; Wunsch, 2000); and Egbert and Ray (2000) have used Topex/Poseidon satellite altimeter data to empirically quantify the spatial distribution of deep-sea tidal energy dissipation, verifying predictions of Munk and Wunsch related to this subject (see our Journal Review Lunar Tides and Climate Change). All of these studies serve to illustrate just how complex earth’s climate system is, and that lunar, as well as solar, phenomena may be as important as anything else in determining the climatic state of the earth.
References
Cerveny, R.S. and Shaffer, J.A. 2001. The moon and El Niño. Geophysical Research Letters 28: 25-28.
Egbert, G.D. and Ray, R.D. 2000. Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data. Nature 405: 775-778.
Munk, W.H. and Wunsch, C. 1998. Abyssal recipes II: Energetics of tidal and wind mixing. Deep-Sea Research 45: 1977-2010.
Wunsch, C. 2000. Moon, tides and climate. Nature 405: 743-744.