The 1470-Year Climate Oscillation of the North Pacific Gyre
Isono, D., Yamamoto, M., Irino, T., Oba, T., Murayama, M., Nakamura, T. and Kawahata, H. 2009. The 1500-year climate oscillation in the midlatitude North Pacific during the Holocene. Geology 37: 591-594.
Working with three sediment cores retrieved off the coast of central Japan in the northwestern Pacific (36°02'N, 141°47'E), Isono et al. generated a multidecadal-resolution record of alkenone-derived sea surface temperature (SST) that covers the full expanse of the Holocene, which they then analyzed in a number of different ways.
The seven scientists report that "the SST record showed centennial and millennial variability with an amplitude of ~1°C throughout the entire Holocene," and that "spectral analysis for SST variation revealed a statistically significant peak with 1470-year periodicity." In addition, they say "the SST variation partly correlated with the variations of ice-rafted hematite-stained grain content in North Atlantic sediments" that Bond et al. had discovered and analyzed.
With respect to the latter end of their record, Isono et al. report that "SST minima centered at ca. 0.3 ka and ca. 1.5 ka are correlated with the Little Ice Age and the Dark Ages Cold Period in Europe, respectively, whereas the SST maximum centered at ca 1.0 ka is correlated with the Medieval Warm Period." In addition, they note that "the periodicity is most stable at warming events, suggesting that the oscillation is paced at warming events."
The Japanese researchers state that "a persistent 1500-year cycle in glacial and interglacial modes suggests that such a regular cycle is a response to a periodic external forcing rather than an internal oscillation in the climate system," but they note that "spectral analysis of solar radiation variation does not show ~1500-year periodicity." However, they say that Braun et al. (2005) have suggested that "a nonlinear response of freshwater input into the North Atlantic Ocean to the solar DeVries-Suess and Gleissberg cycles (210- and 87-year periodicities, respectively) is a candidate mechanism for the 1500-year cycle." But in yet another twist, they state that the "more regular periodicity in the Japan margin SST record than in the North Atlantic hematite-stained grain record [of Bond et al.] suggests that the North Pacific gyre system has been involved in propagating or generating [the] 1500-year oscillation in the earth climate system."
We also add that all of these observations and implications have absolutely nothing to do with atmospheric CO2 concentration being a contributing factor to the 1500-year cycle of warming and cooling that permeates both glacial and interglacial environments alike, and that the Current Warm Period may thus also be largely unrelated to the historical rise in the air's CO2 content.
Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P. deMenocal, P., Priori, P., Cullen, H., Hajdes, I. and Bonani, G. 1997. A pervasive millennial-scale climate cycle in the North Atlantic: The Holocene and late glacial record. Science 278: 1257-1266.
Braun, H., Christl, M., Rahmstorf, S., Ganopolski, A., Mangini, A., Kubatzki, C., Roth, K. and Kromer, B. 2005. Possible solar origin of the 1,470-year glacial climate cycle demonstrated in a coupled model. Nature 438: 208-211.