New Publication from the Wooster Tree Ring Lab

The lead author of this work, Fred (Wenshuo) Zhao, photographed in front of the Mendenhall Glacier in Juneau, Alaska. The logs at his feet, recently exposed by the retreating ice, are the subject of his undergraduate thesis and this publication. The College of Wooster Tree Ring Lab has an extensive collection of subfossil wood (trees run over in the past by glaciers) and this wood is often stained by exposure to the elements altering the color of the wood. This alteration inhibits the measurement of tree-ring parameters like blue intensity measurements. Measuring blue intensity (BI) has been shown to improve climate reconstruction and improve general tree-ring dating (Wilson et al, 2017, 2019). Fred, with the great help of Junpeng Fu and Nick Wiesenberg at Wooster, chemically treated the wood showing an improved climate signal in the BI measurements after treatment.  This paper describes the process and evaluation of this chemical method using wood sampled from along the Gulf of Alaska as an example.

Degrees C

One of the clever tests that Fred performed to evaluate the improved climate signal was to compare climate signal of latewood blue intensity measurements before soaking in hydrogen peroxide (graph on the left) and after soaking (right) with temperature data. Since the tree-ring samples date back to 1050-1350 CE, we were not able to compare the tree-ring measurements with actual (observational) climate records of temperature. So Fred used a published tree-ring based temperature reconstruction for the Gulf of Alaska (Wiles et al., 2014) for the comparison. The graphs show an improved climate signal (R=0.56 to 0.66) after the treatment. Several other statistical metrics described in the paper are consistent with this improved climate signal. This work is a significant step towards improving the study of climate and the ability to use tree-rings to date glaciers, mass movements, earthquakes, and volcanic events along the Gulf of Alaska and into the interior of the Northern North American continent.

Fred and Junpeng (Jerry, also a former Wooster student) are now working toward getting their PhDs at the University of Oklahoma – their research focuses on the use various aspects of biochemistry in understanding the worlds oceans and climate.

References:

Wiles, G.C., D’Arrigo, R.D., Barclay, D., Wilson, Jarvis, S. K., Vargo, L., Frank, D., 2014, Surface air temperature variability for the Gulf of Alaska over the past 1200 years: The Holocene, DOI:            10.1177/0959683613516815.

Wilson, R., D’Arrigo, R., Andreu-Hayles, L., Oelkers, R., Wiles, G., Anchukaitis, K and Davi, N., 2017, Blue Intensity based experiments for reconstructing North Pacific temperatures  along the Gulf of Alaska: Clim. Past Discuss., doi:10.5194/cp-2017-26.

Wilson, R., K Anchukaitis, L Andreu-Hayles, E Cook, R D’Arrigo, N Davi, L Haberbauer, P Krusic, B Luckman, D Morimoto, R Oelkers, G Wiles, C Wood, 2019, Improved dendroclimatic calibration using blue intensity in the southern Yukon. The Holocene, 29(11), 1817-1830, https://doi.org/10.1177/0959683619862037.