GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 127-4
Presentation Time: 2:25 PM

WHAT MIGHT GROUNDWATER IN THE CRITICAL ZONE TELL US ABOUT CLIMATE CHANGE? DECADAL SHIFT IN THE ONSET OF EVAPOTRANSPIRATION IN A NORTHERN RIPARIAN WOODLAND


DOSS, Paul K., Geology and Physics, University of Southern Indiana, 8600 University Blvd, Evansville, IN 47712

Phenology, studying the timing of seasonal ecosystem behaviors, is clearly relevant for understanding impacts of climate change. Spring leaf-out of deciduous vegetation is a phenological change that is shown to respond to climate change. Quantifying leaf-out is a challenge due to time and labor demands for direct observations, and the need for satellite imagery and data for remote sensing interpretations. “Phenocams,” fixed-location cameras to continuously record canopy character, are also used to document timing of leaf-out. Integrated phenology investigations combine satellite data, webcams, and CO2 sensors to monitor and interpret timing of leaf-out. High resolution groundwater monitoring along a headwater reach of the White River in Manistee National Forest, Michigan, was put in place a decade ago in response to ecosystem threats from bottled water extraction. That monitoring effort has become well-positioned to capture ecosystem changes that may arise from climate change. In this, and other linked upland-aquatic systems, shallow groundwater displays dynamic and pronounced diurnal declines that result from evapotranspiration (ET) by phreatophytic vegetation. Preliminary observations in the riparian corridor along the White River from 2008 – 2017 suggest that ET discharge from groundwater has started approximately 17 days earlier. Coincident with this earlier ET onset, was a measurable increase in May temperatures, the month of leaf-out for this location (43.5 ° N). Maximum, average, and minimum temperatures for the month of May during this decade increased 0.219, 0.230, and 0.240 ° C per year, respectively. The observed onset of diurnal ET fluctuations in groundwater may serve as a proxy for leaf-out of local and regional vegetation communities, as ET onset coincides with the onset of photosynthesis. Preliminary conclusions from this decade of high-resolution hydrogeological monitoring is consistent with other observations of seasonal leaf-out change, observed climate changes, and predicted responses to increased atmospheric CO2 concentrations.