A cosmogenic 10Be chronology for the local last glacial maximum and termination in the Cordillera Oriental, southern Peruvian Andes: Implications for the tropical role in global climate

Abstract

Resolving patterns of tropical climate variability during and since the last glacial maximum (LGM) is fundamental to assessing the role of the tropics in global change, both on ice-age and sub-millennial timescales. Here, we present a 10 Be moraine chronology from the Cordillera Carabaya (14.3°S), a sub-range of the Cordillera Oriental in southern Peru, covering the LGM and the first half of the last glacial termination. Additionally, we recalculate existing 10 Be ages using a new tropical high-altitude production rate in order to put our record into broader spatial context. Our results indicate that glaciers deposited a series of moraines during marine isotope stage 2, broadly synchronous with global glacier maxima, but that maximum glacier extent may have occurred prior to stage 2. Thereafter, atmospheric warming drove widespread deglaciation of the Cordillera Carabaya. A subsequent glacier resurgence culminated at ~16,100 yrs, followed by a second period of glacier recession. Together, the observed deglaciation corresponds to Heinrich Stadial 1 (HS1: ~18,000-14,600 yrs), during which pluvial lakes on the adjacent Peruvian-Bolivian altiplano rose to their highest levels of the late Pleistocene as a consequence of southward displacement of the inter-tropical convergence zone and intensification of the South American summer monsoon. Deglaciation in the Cordillera Carabaya also coincided with the retreat of higher-latitude mountain glaciers in the SouthernHemisphere. Our findings suggest that HS1 was characterised by atmospheric warming and indicate that deglaciation of the southern Peruvian Andes was driven by rising temperatures, despite increased precipitation. Recalculated 10 Be data from other tropical Andean sites support this model. Finally, we suggest that the broadly uniform response during the LGM and termination of the glaciers examined here involved equatorial Pacific sea-surface temperature anomalies and propose a framework for testing the viability of this conceptual model. 1 Introduction As the energetic powerhouse of the globe, the tropics (23°N-23°S) are the principal source of heat energy and water vapour for the climate system andthus represent a fundamental and dynamic component of global climate (Cane, 1998; Pierrehumbert, 1999; Visser et al., 2003). Today, the tropical influence is exemplified by the El Niño

Across the Arid Diagonal: deglaciation of the western Andean Cordillera in southwest Bolivia and northern Chile

“…Zech et al (2008) argues for a ~40 ka advance based on a review of records in Patagonia and south-central Chile. Recent cosmogenic glacial records both from the tropics (e.g., Bromley et al, 2016) and subtropical Argentina (e.g., Moreiras et al, 2016) indicate moraine formation at ca. 40 ka and 25 ka.…”

Prospecting Glacial Ages and Paleoclimatic Reconstructions Northeastward of Nevado Coropuna (16° S, 73° W, 6377 m), Arid Tropical Andes

“…It is possible that NC9 and NC10 are dating 1-2 older advances and NCNE01 a younger advance, which reached the same place and added a new moraine to pre-existing moraines. The younger moraines aggregation on older moraines, could also be the cause of the dispersed ages in many Andean glacial sites, such as Cajamarca [45], Cordillera Blanca [29], Jeulla Raju [105], Huayhuash [106], Junín [28], Quelccaya ice cap [6,107], Carabaya [46], Huayna Potosí, Río Suturi and Huamaní Loma [39]; Coropuna [37,38]; (this work); Hualca Hualca [7], Cerro Tunupa [8], and Uturuncu volcano [9].…”

Timing of past glaciation at the Sierra de Aconquija, northwestern Argentina, and throughout the Central Andes

“…Much of the Central Andes are currently unglaciated due to the relatively warm and dry climate in this region. However, during the past several tens of thousands of years, the Central Andes experienced glacial advances during cooler and wetter episodes associated with orbital cycles and millennial-scale climate events (Smith et al, 2005a,b;Jomelli et al, 2014;Bromley et al, 2016;Martini et al, 2017;Ward et al, 2017). These climate changes have been reconstructed using archives and proxies including lake cores and shorelines (Sylvestre et al, 1999;Baker et al, 2001;Placzek et al, 2006Placzek et al, , 2013Baker and Fritz, 2015), plant fossils and pollen (Chepstow-Lusty et al, 2005;Maldonado et al, 2005;Torres et al, 2016), stable isotopes (Cruz et al, 2005;Wang et al, 2007;Kanner et al, 2012), ice cores (Thompson et al, 1995(Thompson et al, , 1998Ramirez et al, 2003), biomarkers (Fornace et al, 2016), and basin sediments (Nester et al, 2007;Steffen et al, 2009Steffen et al, , 2010Bekaddour et al, 2014;Schildgen et al, 2016;Tofelde et al, 2017).…”