PAGES Chile

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Several Nothofagus pumilio tree-ring chronologies have been developed for northern Patagonia as well as Tierra del Fuego in Argentina and the central Andes in Chile. These studies have demonstrated the relationship between spring-summer climate and Nothofagus pumilio tree growth. The current climate of the west coast of southern Patagonia is dominated by a precipitation and humidity gradient. Precipitation originates mainly from the influence of the westerly winds, which dominate the whole region.

Fig.1 Nothofagus pumilio forest located in Navarino Island in southern extreme Chilean Patagonia (55º S), Cape Horn County, Chile.

The Andean range intercepts these winds, which then raise, leading to an annual rainfall of up to 8000 mm on the windward side. The winds then reach the leeward side, creating drier conditions, with an annual precipitation of 250 mm and less. There is almost no seasonality in the distribution of rainfall, especially on the windward western slopes of the Andes. There is a strong oceanic influence on temperature on the windward area of the Andes, with little seasonal variation in mean monthly temperature.

For example, in Faro Evangelistas, located at 52º24'S, 75º06'W in the western archipelagos, the mean temperature for January is about 8ºC and 4ºC for July. Conversely, in Punta Arenas, which is located leeward (53º00'S, 70º51'W), values range from 10ºC in January to 1ºC or less in July.


Fig.2 Nothofagus pumilio tree-ring based reconstruction of minimum annual temperature for Chilean Southern Patagonia (51º-55ºS) from 1829 to 1996, from Aravena et al. (2002).

The reconstruction shows that during most of the 19th century, minimum annual temperatures remained below-average and increased to values fluctuating around the mean during the 1900-1960 period, followed by a clear trend with above-average values after 1963.


References:

Aravena, J.C., Lara, A., Wolodarsky-Franke, A., Villalba, R. y  Cuq, E. (2002) Tree-ring growth patterns and temperature reconstruction from Nothofagus pumilio (Fagaceae) forests at the upper tree line of southern Chilean Patagonia. Revista Chilena de Historia Natural, 75: 361-376.

Lara, A., Aravena, J. C., Villalba, R., Wolodarsky-Franke, A., Luckman, B. H., andWilson, R. (2001) Dendroclimatology of High-Elevation Nothofagus pumilio Forests at their Northern Distribution Limit in the Central Andes of Chile. Canadian Journal of Forest Research 31, 925–936.

Villalba, R., Lara, A., Boninsegna, J.A., Masiokas, M., Delgado, S., Aravena, J.C., Roig, F.A., Schmelter, A., Wolodarsky, A. y Ripalta, A. (2003) Large-scale temperature changes across the southern Andes: 20th-century variations in the context of the past 400 years. Climatic Change 59: 177–232.