Guest essay by Samuel I Outcalt
Introduction: Several global climate regime transitions are well documented. These transitions are listed in Table 1.
The Treeflow Records at Lees Ferry, Arizona and Cisco Utah: Treeflow records are constructed using the parameters derived by the regression analysis of modern tree ring and stream discharge data. Lees Ferry is located just downstream from the Glen Canyon Dam, which formed Lake Powell. Dam construction began in 1960. The Treeflow parameters were calculated to allow for the altered flow produced by the dam. The Treeflow record at Lees Ferry is displayed as Figure 1.
Figure 1. The Normalized Treeflow Data at Lees Ferry, Arizona.
In Figure 1 regime transitions are detected by inflections in the integral trace (cumulative deviations from the record mean). Note that all of the regime transitions listed in Table 1 were detected. This method is described in a recent paper (Outcalt et.al.(1997). The latter part of this record is presented as Figure 2.
Figure 2. The Treeflow Record from 1800 to 2002.
Note that all of the modern regime transitions from Table 1 were detected. To validate the transitions detected in Figure 2 the modern discharge record on the Colorado River near Cisco, Utah is displayed as Figure 3.
Figure 3. The modern Treeflow record and integral trace near Cisco, Utah (185 miles North East of Lees Ferry, Arizona).
In Figure 3 all the modern regime transitions from Lees Ferry were detected.
Conclusion: All of the major climate regime transitions from the Onset of the Medieval Warm Period to the End of the Modern Warm Regime are detectable in the Treeflow and Modern Discharge Data for the Upper Colorado Basin using the Hurst ReScaleing technique.
Outcalt,S.I., Hinkel, K.M.,Meyer,E . and Brazel,A.J.(1997) The application of Hurst Rescaling to serial geophysical data. Geographical Analysis 29, 72-87.