Advised by: Dr. Wiles
Abstract: Reconstructing and understanding historical lake levels provides information about how climate influences lake level fluctuations, which is important for managing Lake Michigan- Huron’s (MH) coasts. This study reconstructs historical MH lake levels using ten ring-width chronologies from Southeast Alaska, which are significantly correlated at the 0.01 confidence level with January – June average MH lake levels. Tree ring chronologies from Southeast Alaska can be used to create a model of MH because of atmospheric teleconnections, like the Pacific North American Pattern (PNA), which produce similar atmospheric pressure anomalies across both regions. The model explains 33.8% of the variance in MH lake levels (January – June), and the validity of the model was tested through a series of calibration and verification statistics, confirming a well-verified stable relationship through time.
Findings indicate that MH lake level fluctuations are primarily based on large-scale atmospheric climate patterns that may be altered by human activity, volcanic eruptions, or strong climate events. Reconstructed high lake levels are attributed to volcanic activity in the 1690s, 1673, 1755, and 1809 and a strong El Niño event from 1876 to 1878, whereas lows are attributed to droughts, corresponding with the conditions of the 1930s Dust Bowl.
Tag Archives: tree ring
Voices in the Trees: Update on the Alaska Youth Stewards and The College of Wooster Tree-Ring Lab Collaboration at Five Years
Participants: Greg Wiles, Nick Wiesenberg, Ben Gaglioti, Daniel Mann, Gabrielle Sjoberg, Eloise Peabbles, Eric Benedict, Julian Narvaez, Bob Girt, Arianna Lapke, Lilly Hinkley, Amanda Flory, Michail Protopapadakis, Wenshuo Zhao, Tyrell Cooper, Lynnsey Delio, Isabel Held, Dexter Pakula, Landon Vaughan, Lev Sugerman-Brozan, and AYS students.
General: For the past five years faculty, staff, and students from The College of Wooster Tree Ring Lab, University of Alaska, Fairbanks and the Alaska Youth Stewards (AYS) from Kake, Hoonah, Angoon and Klawock in Southeast Alaska (SEAK) have been collaborating to understand environmental change through the collection of tree-ring data. Together, we sampled and processed eight tree-ring chronologies from a previously under-sampled region of SEAK. These data are records of past climate with direct linkages to cultural and land-use histories. The collection includes the first two western redcedar (Thuja plicata) series for Alaska, one from Kake based on the farthest known north stand of redcedar in its natural range and the other from Klawock. The remaining chronologies include three Alaska yellow cedar (Callitropsis nootkatensis) series from Kake, Hoonah and Klawock, a Sitka spruce (Picea sitchensis) series from Angoon, and two mountain hemlock (Tsuga mertensiana) series from Hoonah and Angoon.
Background: The collaboration started remotely in the summer
Dating a Cabin from Pittsburgh
Dr. Mark Abbott and his graduate students Cole and Adeel visited the Wooster Tree Ring Lab with portions of white oak beams from a historic cabin in Pittsburgh. The mission was to tree ring date the outer ring of the samples to determine which calendar year the timber was cut for the structure. Here the Pitt team in the sample prep. lab with the two samples where they polished them for analysis.
Nick Wiesenberg oversaw the dating, which started with a tour in the west wing of the Wooster Tree Ring Lab.
Adeel measured one of the samples – understandably he is amazed with the anatomy of the white oak rings.
Cole measured the other sample measuring ring widths from the screen using CooRecorder. The Pitt group are exports in lake core analysis and both Adeel and Cole are analyzing lake varves, they are also thinking about using this measuring setup for varve analyses (see below).
Nick takes the controls and analyzes the measurement data against our tree-ring database and reveals the date of cutting for the cabin.
The crossdating with our master series shows that the outer ring of the samples were both 1834, at least for the two samples both were cut in the
A New Paper on Deciduous Conifers at Secrest Arboretum
Imagine a world with larch trees in the uplands and dawn redwoods in the flats, and bald cypress trees in the wetlands. This existed in the Eocene (~40 million years ago) when the world was warmer, the treeline was at higher latitudes and altitudes, and carbon dioxide in the atmosphere was more than two times Earth’s preindustrial levels. In fact, in the high Arctic where no trees can survive today, deciduous conifers were as lush in terms of carbon sequestration and bioproductivity as today’s rain forests. Now, imagine a world that is sliding back into the greenhouse after millions of years of relative icehouse conditions.
How can we better understand the role of deciduous conifers in the biosphere and their utility in a warmer world. One “natural” experiment is to use dendroclimatology to infer the response of deciduous conifers to a warmer and wetter world. Secrest Arboretum in Wooster, Ohio has two species of larch trees (Siberian and European) as well as bald cypress and dawn redwood trees. These species are all exotic to Ohio and have been growing in the arboretum in some cases for over 100 years. How do they grow in their new homes? This is the subject
A New Tree Ring Study from the Kashmir Valley, western Himalaya
The global tree-ring community is racking up the papers investigating the utility of the relatively new proxy using blue intensity of annually-dated tree rings. This latest effort is a blue intensity investigation followup of a recent study on ring widths also led by Dr. Santosh Shah of Birbal Sahni Institute of Palaeosciences in Locknow, India. Blue intensity is a proxy that has added a new dimension to thermal histories across the globe including efforts at the The College of Wooster Tree Ring Lab. Shah et al. (2025) used cores extracted from three sites of the Western Himalayan Fir (Abies pindrow) from the Kashmir Valley.
Map from the study showing the location of the three tree-ring sites and the meteorological station (Srinager). The centrally-located Srinager climate station has records of precipitation and temperature spanning 1901-2024, one of the longest in the region.
A figure from the paper showing the beautiful images of earlywood (above) and latewood (below) blue light reflectance for individual rings from the Western Himalayan Fir (Abies pindrow).
The upshot of the work is that time series of blue intensity values from the latewood of A.Pindrow are strongly correlated with monthly average and maximum temperature series from nearby climate station (Srinager). Ring-width are