Research

Hydrologic Reconstruction

The WaDR team has used a suite of new tree ring chronologies together with previously published chronologies to reconstruct stream flow of the upper Bear River (1200 years), the Logan River (400 years; a lower tributary of the Bear River) and Weber River (600 years), major suppliers to agriculture and urban areas. These chronologies show greater wet/dry extremes before the instrumental record, coherence with other reconstructions, and a general pattern of 10-14 year wet/dry oscillations. From these reconstructions, the WaDR team, together with the Utah Climate Center, have from the instrumental record identified a 12-14-year wet/dry oscillation centered over the eastern Great Basin that are unconnected to ENSO, but is linked to mid-Pacific sea surface temperatures. Moreover, the Great Salt Lake reconstructions combined with river flow reconstructions, has open to door to predicting the probability of wet and dry peaks during the 12-14 year oscillation.

Climate Reconstruction

The WaDR team is investigating the larger regional climate picture that encompasses river flow reconstruction. In the eastern Great Basin/Salt Lake City metropolitan signature species typically used in Western U.S. dendrochronological research are either lacking significant populations (Ponderosa pine, pinyon pine) or are so high in elevation that ring increment is often unrelated wet and dry cycles. Instead, the WaDR team has focused research on what was available, Utah and Rocky Mountain juniper, making lemonade (or gin, as the case may be) from what was perceived to be lemon species for dendrochronological research. These juniper species have shown to be very sensitive to growing season climate, opening the door to reconstruction of growing season rainfall and temperature. The WaDR team has also taken advantage of dendro-ecological tree cores systematically collected by grid across the U.S. West as a part of the Forest Inventory Assessment authorized by the U.S. congress. These cores from the signature species Douglas Fir and pinyon pine are not as old as targeted sites, but have proven to be related well correlated to climate, illuminating spatially-gridded patterns of El Nino/La Nina cycles and are being used to reconstruct snowpack.

Historical Reconstruction