Tree growth and the Westerlies in the Southern Hemisphere

VILLALBA R.; LARA A.; MASIOKAS M.H.; URRUTIA R.; LUCKMAN B.H.; MARSHALL G.J.; MUNDO I.A.; CHRISTIE D.A.; COOK E.R.; NEUKOM R.; ALLEN K.; FENWICK P.; BONINSEGNA J.A.; SRUR A.M.; MORALES M.S.; ARANEO D. C.; PALMER J.G.; CUQ E.; ARAVENA J.C.; HOLZ A.; LEQUESNE C.

Uspallata

Encuentro; IAI CRN 2047 Science Meeting: Documenting, understanding and projecting changes in the hydrological cycle in the American Cordillera.; 2013

IAI

Climatic variations modulate the growth of forests at large temporal and spatial scales. Based on the most up-to-date network of tree-ring records in the Southern Hemisphere (SH), we identified the dominant patterns of tree growth at sub-continental scales in southern South America, Tasmania and New Zealand. Temporal patterns of radial growth from mid-latitude temperate forests reveal persistent anomalies during the last decades of the 20th century. Positive departures in tree growth at subalpine forests in Tasmania and New Zealand contrast with persistently negative anomalies in dry-mesic forests in Patagonia. Variations in the Southern Annular Mode (SAM), an index of the atmospheric mass exchange between mid and high latitudes in the SH, explain 12 to 48% of the tree-growth anomalies in the SH temperate forests. During the second half of the 20th century, tree-growth variations reflect precipitation and temperature changes induced by a persistent SAM positive phase. A tree-ring based reconstruction of SAM in summer shows that changes in atmospheric circulation recorded since the 1950s are unprecedented in the past 600 years.