INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
Unusual Southern Hemisphere tree growth patterns induced by changes in the Southern Annular Mode
VILLALBA, R.; LARA, A.; MASIOKAS, M.H.; URRUTIA, R.; LUCKMAN, B.H.; MARSHALL, G.J.; MUNDO, I.A.; CHRISTIE, D.A.; COOK, E.; NEUKOM, R.; ALLEN, K.; FENWICK, P.; BONINSEGNA, J.A.; SRUR, A.M.; MORALES, M.; ARANEO, D.; PALMER, J.; CUQ, E.; ARAVENA, J.C.; HOLZ, A.; LE QUESNE, C.
NATURE PUBLISHING GROUP
Lugar: Londres; Año: 2012 vol. 5 p. 793 - 798
Recent changes in the summer climate of the Southern Hemisphere extra-tropics are primarily related to the dominance of the positive phase of the Southern Annular Mode1,2. This shift in the behaviour of the Southern Annular Modeessentially a measure of the pressure gradient between Southern Hemisphere mid and high latitudeshas been predominantly induced by polar stratospheric ozone depletion24. The concomitant southward expansion of the dry subtropical belts5,6 could have consequences for forest growth. Here, we use tree-ring records from over 3,000 trees in South America, Tasmania and New Zealand to identify dominant patterns of tree growth in recent centuries.We showthat the foremost patterns of growth between 1950 and 2000 differed significantly from those in the previous 250 years. Specifically, growth was higher than the long-term average in the subalpine forests of Tasmania and New Zealand, but lower in the dry-mesic forests of Patagonia. We further demonstrate that variations in the Southern Annular Mode can explain 1248% of the tree growth anomalies in the latter half of the twentieth century. Tree-ring-based reconstructions of summer Southern Annular Mode indices suggest that the high frequency of the positive phase since the 1950s is unprecedented in the past 600 years.We propose that changes in the Southern Annular Mode have significantly altered tree growth patterns in the Southern Hemisphere.