Late Holocene summer temperatures in the central Andes reconstructed from the sediments of high-elevation Laguna Chepical, Chile (32° S)

Abstract

High-resolution reconstructions of climate variability that cover the past millennia are necessary to improve the understanding of natural and anthropogenic climate change across the globe. Although numerous records are available for the mid- and high-latitudes of the Northern Hemisphere, global assessments are still compromised by the scarcity of data from the Southern Hemisphere. This is particularly the case for the tropical and subtropical areas. In addition, high elevation sites in the South American Andes may provide insight into the vertical structure of climate change in the mid-troposphere. This study presents a 3000 yr-long austral summer (November to February) temperature reconstruction derived from the ²¹⁰Pb- and ¹⁴C-dated organic sediments of Laguna Chepical (32°16' S, 70°30' W, 3050 m a.s.l.), a high-elevation glacial lake in the subtropical Andes of central Chile. Scanning reflectance spectroscopy in the visible light range provided the spectral index <i>R</i>₅₇₀/<i>R</i>₆₃₀, which reflects the clay mineral content in lake sediments. For the calibration period (AD 1901–2006), the <i>R</i>₅₇₀/<i>R</i>₆₃₀ data were regressed against monthly meteorological reanalysis data, showing that this proxy was strongly and significantly correlated with mean summer (NDJF) temperatures (<i>R</i>_{3 yr} = &minus;0.63, <i>p</i>_adj = 0.01). This calibration model was used to make a quantitative temperature reconstruction back to 1000 BC. <br><br> The reconstruction (with a model error RMSEP_boot of 0.33 °C) shows that the warmest decades of the past 3000 yr occurred during the calibration period. The 19th century (end of the Little Ice Age (LIA)) was cool. The prominent warmth reconstructed for the 18th century, which was also observed in other records from this area, seems systematic for subtropical and southern South America but remains difficult to explain. Except for this warm period, the LIA was generally characterized by cool summers. Back to AD 1400, the results from this study compare remarkably well to low altitude records from the Chilean Central Valley and southern South America. However, the reconstruction from Laguna Chepical does not show a warm Medieval Climate Anomaly during the 12–13th century, which is consistent with records from tropical South America. The Chepical record also indicates substantial cooling prior to 800 BC. This coincides with well-known regional as well as global glacier advances which have been attributed to a grand solar minimum. This study thus provides insight into the climatic drivers and temperature patterns in a region for which currently very few data are available. It also shows that since ca. AD 1400, long-term temperature patterns were generally similar at low and high altitudes in central Chile

A 700-year record of climate and environmental change from a high Andean lake: Laguna del Maule, central Chile (36°S)

“…Regional records from Central Chile (De Jong et al, 2013;Urrutia et al, 2010;Von Gunten et al, 2009c) show that climate was characterized by relatively colder conditions, particularly cooler summers and relatively wetter conditions since AD 1350, although summer temperatures during the 18th century were significantly higher than the previous interval (De Jong et al, 2013;Figure 7c). A reflectance record from Laguna Aculeo indicates summer temperatures even higher than those at present from AD 1100 to 1350 (Von Gunten et al, 2009c), at the end of the MCA (sensu Graham et al, 2007) and prior to the onset of the LIA.…”

Late Holocene environmental changes reconstructed from stable isotope and geochemical records from a cushion‐plant peatland in the Chilean Central Andes (27°S)

“…According to the austral summer temperature reconstruction for the high Andes of Central Chile by de Jong et al . (; Fig. d), this period seems to be characterized by higher temperatures compared to the period before 470 cal a BP.…”

“…(c) Mn/Fe values of the Cerro Tuzgle peatland (black line: five‐point running average; Schittek et al ., ), presented on an age–depth model recalculated with the SHCal13. (d) Austral summer temperature anomalies as recorded in the Laguna Chepical (de Jong et al ., ). Grey bars indicate the periods with increased humidity in LP.…”

Centennial‐Scale SE Pacific Sea Surface Temperature Variability Over the Past 2,300 Years

“…Although annually resolved, South American tree rings mostly only extend back over a few centuries (Neukom & Gergis, , and references therein), albeit with some exceptions (Lara & Villalba, ), and their interpretation may be complicated by sensitivity to precipitation (Boninsegna et al, , and references therein). Lake sediments have provided high‐resolution (annual‐decadal) and longer records (Boës & Fagel, ; de Jong et al, ; Elbert et al, , ; von Gunten et al, ). Although these temperature records display a similar evolution over the last three centuries, differences in temperature evolution between the sites have been noted further back in time (de Jong et al, ), perhaps highlighting a high degree of spatial heterogeneity of temperature on these timescales, as is also seen over the last few decades (Villalba et al, ).…”