Synoptic Atmospheric Circulation and Frost Rings in Araucaria Araucana Trees from Northern Patagonia, Argentina.

MÜLLER, GABRIELA V.

Conferencia; Third American Dendrochronology Conference.; 2016

Frost rings (FR) in tree rings have been long associated with frost damages occurring in the cambium during the growing season. In the early wood, they have been associated with early growing season frosts (late-spring and/or early-summer sub-freezing temperatures). FR thus have the potential to provide information on extreme temperature events and FR chronologies as a climate proxy, providing valuable insights when studying climate variability and climate changes. In this study, trees from five Pehuen (Araucaria araucana (Molina) K.Koch) forests were sampled in northern Patagonia, Argentina. Five frost ring chronologies were developed and analyzed in relation to both surface temperature data and synoptic circulation patterns (geopotential height data). Preliminary results using a composite frost-ring chronology indicated a systematic effect of warm September-October temperatures along the atmosphere. Similarly to results reported for the Northern Hemisphere, FR in Northern Patagonia appear to be associated with early spring conditions (warm September and October) and an early onset of the growing season. In Northern Patagonia, the month of October corresponds to the beginning of the radial growth period in A. araucana. Early resumption of growth associated with warm springs may make trees more susceptible to record frost damages by lengthening the period of exposure to sub-freezing temperatures