Quantitative reconstruction of Holocene precipitation changes in southern Patagonia

Abstract

Holocene variations in annual precipitation (Pann) were reconstructed from pollen data from southern Argentinian Patagonia using a transfer function developed based on a weighted-averaging partial least squares (WA-PLS) regression. The pollen–climate calibration model consisted of 112 surface soil samples and 59 pollen types from the main vegetation units, and modern precipitation values obtained from a global climate database. The performance (r2 = 0.517; RMSEP = 126 mm) of the model was comparable or slightly lower than in other comparable pollen–climate models. Fossil pollen data were obtained from a sediment core from Cerro Frias site (50°24'S, 72°42'W) located at the forest-steppe ecotone. Reconstructed Pann values of about 200 mm suggest dry conditions during the Pleistocene–Holocene transition (12,500–10,500 cal yr BP). Pann values were about 300–350 mm from 10,500 to 8000 cal yr BP and increased to 400–500 mm between 8000 and 1000 cal yr BP. An abrupt decrease in Pann at about 1000 cal yr BP was associated with a Nothofagus decline. The reconstructed Pann suggests a weakening and southward shift of the westerlies during the early Holocene and intensification, with no major latitudinal shifts, during the mid-Holocene at high latitudes in southern Patagonia.

Strengths and Weaknesses of Quantitative Climate Reconstructions Based on Late-Quaternary Biological Proxies

“…lakes) (Bjune et al 2010) and hence have comparable taphonomies (cf. Minckley & Whitlock 2000;Whitmore et al 2005;Gonzales et al 2009a;Tonello et al 2009;Fletcher et al 2010;Goring et al 2010).…”

Climate variability of the mid- and high-latitudes of the Southern Hemisphere in ensemble simulations from 1500 to 2000 AD

“…The annual precipitation reconstructions by Tonello et al (2009) also indicate that precipitation in southern South America was highly variable during the past centuries. This strong variability, however, is not apparent in the modeled temperature records.…”

“…Nevertheless, the few available records point towards significant fluctuations in both temperature and precipitation occurring during this time period (Jones and Mann, 2004;Masiokas et al, 2009;Tonello et al, 2009). On this time scale orbital boundary conditions only changed slightly and thus internal variability, solar and volcanic forcing played a dominant role before the influence of humans became noticeable (Jones and Mann, 2004).…”

Corredores Naturales, Fuente De Obsidiana Y Estacionalidad: El Caso De La Circulación Humana Entre Pali Aike Y Sierra Baguales (Patagonia Meridional)

“…También la reconstrucción de las variaciones anuales de precipitación (Tonello et al 2009), vegetación (Huber y Markgraf 2003;Mancini et al 2011;Sottile et al 2012; Villa-Martínez y Moreno 2007) y episodios de incendios en Patagonia Meridional (Huber y Markgraf 2003;Huber et al 2004;Sottile et al 2012) permiten estimar la existencia de paisajes vinculados con períodos más y menos favorables para la circulación humana hacia Baguales (Figura 2). La transición PleistocenoHoloceno está marcada por condiciones poco húmedas, gran ocurrencia de incendios y ambientes abiertos en sectores cordilleranos (Mancini et al 2011;Tonello et al 2009;Villa-Martínez y Moreno 2007).…”