Ice Core Records of Climate and Environmental Variability in the Tropical Andes of Peru: Past, Present and Future Registros en Núcleos de Hielo de la Variabilidad Climática y Ambiental en los Andes Tropicales del Perú: Pasado, Presente y Futuro Lonnie G. Thompson1,2, Ellen Mosley-Thompson1,3, Mary E. Davis1 and Stacy E. Porter1 1Byrd Polar and Climate Research Center, The Ohio State University, Columbus, Ohio 43210, USA 2School of Earth Science, The Ohio State University, Columbus, Ohio 43210, USA 3Department of Geography, The Ohio State University, Columbus, Ohio 43210, USA https://doi.org/10.36580/rgem.i3.25-40 Abstract Keywords: Peruvian glaciers, climate, El Niño, warming, In the Peruvian Andes mid-tropospheric warming, glacier retreat enhanced by recent strong El Niños, is destroying Resumen the climate signals preserved in the ice fields and accelerating glacier retreat. Nowhere is the loss En los Andes peruanos, el calentamiento de la of tropical glaciers better documented and more troposfera media, potenciado por el reciente fuerte important than in the Andes of Peru. The longest El Niño, está destruyendo las señales climáticas record of glacier retreat comes from a 44-year study preservadas en los campos de hielo y acelerando la conducted on the Quelccaya ice cap in southern retirada de los glaciares. En ninguna parte está mejor Andes, which substantiates the loss of a very important documentada la pérdida de los glaciares tropicales climate archive as well as the accelerating loss of a y es más importante que en los Andes del Perú. El water resource that feeds the Amazon River and Lake registro más largo de retirada de glaciares proviene Titicaca. In the Cordillera Blanca the glaciers below de un estudio de 44 años realizado en el casquete de 5400 masl are undergoing both seasonal melting hielo Quelccaya en el sur de los Andes, que prueba and the movement of melt water through the porous la pérdida de un archivo climático muy importante upper layers. Because of its high elevation Nevado y la pérdida acelerada de un recurso hídrico que Huascarán is one of a few tropical sites where a alimenta el río Amazonas y el lago Titicaca. En la largely unaltered climate history, which extends back Cordillera Blanca, los glaciares por debajo de los to the Last Glacial Stage, is still being preserved. 5400 msnm sufren tanto un deshielo estacional However all the Cordillera Blanca glaciers are como el movimiento del agua de deshielo a través documented by INAIGEM (in press) to be retreating. de las capas superiores porosas. Debido a su gran Given the current rates of warming throughout the altitud, el nevado Huascarán es uno de los pocos tropical Andes, it is only a matter of time before sitios tropicales donde aún se conserva una historia climate records from Huascarán ice will also be climática prácticamente inalterada, que se extiende lost. The glacier retreat throughout the Peruvian hasta la última etapa glacial. Sin embargo, todos los Andes is contributing to emerging water resource glaciares de Cordillera Blanca documentados por crises and environmental hazards for both urban and INAIGEM (en prensa) estar en retroceso. Dadas rural populations. Although currently the dry season las tasas actuales de calentamiento en los Andes discharge is increasing, it will not be sustained in the tropicales, solo es cuestión de tiempo para que los longer term. Most of Peru’s population lives in the registros climáticos del hielo del Huascarán también west coast desert, which relies on glacier fed streams se pierdan. El retroceso de los glaciares a lo largo de for agriculture and livelihoods. Melting glaciers los Andes peruanos está contribuyendo a las crisis also exacerbate geohazards in this earthquake-prone emergentes de los recursos hídricos y los peligros region by forming ice and moraine-dammed glacial ambientales tanto para las poblaciones urbanas lakes, which can result in lake outbursts and flooding como rurales. Aunque actualmente la descarga de la and debris flows. Understanding the impact of this estación seca está aumentando, no se mantendrá así a acceleration of glacier loss on future water resources largo plazo. La mayoría de la población del Perú vive requires information about past changes in high en el desierto de la costa oeste, que depende de los elevation glacier mass balance. ríos alimentados por los glaciares para la agricultura y los medios de subsistencia. El derretimiento de los glaciares también agrava los peligros geológicos en Revista de Glaciares y Ecosistemas de Montaña 3 (2017): 25-40 25 L. Thompson, E. Mosley-Thompson, M. Davis and S. Porter esta región propensa a terremotos, formando lagunas area and volume measurements, will undoubtedly glaciares con represas de hielo o morrenas, lo que have meaningful social and economic implications puede dar como resultado estallidos de lagunas e for understanding climate change and the potential inundaciones y flujos de escombros. Comprender el impacts on water resources. It is of paramount impacto de esta aceleración de la pérdida de glaciares importance to attain a better grasp of the climatic en los recursos hídricos futuros requiere información factors that control the recent low-latitude glacier sobre los cambios del pasado en el balance de masas responses. Moreover, the continued loss of glaciers de los glaciares de alta elevación. and ice caps will increasingly compromise and eventually obliterate most of the non-polar, ice core- Palabras clave: Glaciares peruanos, clima, El Niño, derived climate histories. This is a particular concern calentamiento, retiro de glaciares in the Peruvian Andes, where mid-tropospheric warming, enhanced by recent strong El Niños, is now Introduction destroying the climate signals preserved in the ice Scientific evidence of variations in the atmosphere- fields and accelerating glacier retreat. ocean-climate system verifies that Earth’s globally averaged surface temperature is increasing, and a recent international assessment (Vaughan et al., 2013) indicates that human activities are contributing to these observed changes in the Earth system. Low- latitude paleoclimate histories are critical for the acquisition of a global array of ice cores that provide high-resolution climatic and environmental histories essential for understanding the complex interactions within Earth’s coupled climate system. Improved predictive capability requires better quantification of the system’s physical and chemical linkages along with the complex feedbacks that may dampen or accelerate the initial forcings. Ice core records from Africa, Alaska, Alps, Antarctica, Bolivia, China, Greenland, Peru, Papua (Indonesia) and Russia have made it possible to study processes linking the Polar Regions to the lower latitudes where human activities are most concentrated. The diverse and frequently detailed information obtained from ice cores contributes prominently to Earth’s paleoclimate record, the ultimate yardstick against which the Figure 1. Map of Peru and northwest Bolivia showing significance of present and projected anthropogenic locations of high elevation ice fields mentioned in text from which ice cores have been recovered. Inset: Google Earth effects will be assessed. image of Cordillera Blanca (corresponding to black box in map) showing locations of the mountains from which shallow It is imperative to understand Earth’s climate and deep ice cores have been recovered. HS is emphasized by regime, both past and present. Fifty percent of the yellow triangle. Earth’s surface lies between 30oN and 30oS, where Nevado Huascarán (HS, 9.1oS; 77.6oW; 6757 70% of the world’s inhabitants live and conduct their masl at the highest point, the South Peak summit; activities. Temperate and tropical ice cores offer INAIGEM, 2017) in the Cordillera Blanca of central long-term perspectives of variability in precipitation, Peru is located ~200 km from the western edge of temperature, aridity and atmospheric circulation that the Amazon Basin (Figure 1). Two ice cores that are unavailable from other proxy sources. Ice core were drilled in the col by the Byrd Polar and Climate data allow detailed reconstruction of both climate Research Center at The Ohio State University (OSU- variability and climate forcings (e.g., volcanic and BPCRC) in 1993 provided a paleoclimatic history solar activity) as well as the timing of the most recent extending well into the Last Glacial Stage (LGS), glaciation at different latitudes and altitudes. The which includes evidence of the Younger Dryas cool results from these analyses, as well as from glacier phase in the Tropics (Thompson et al., 1995). 26 Revista de Glaciares y Ecosistemas de Montaña 3 (2017): 25-40 Ice Core Records of Climate and Environmental Variability in the Tropical Andes of Peru: Past, Present and Future Figure 2. Top 100 years of HS record from the 1993 Core 2 showing the seasonal variations in δ18O and concentrations of dust and nitrate (NO3-). El Niño events (Quinn, 1983) are noted by white (M=moderate, M+=moderate plus) and black (S=strong, S+= strong plus, VS=very strong) boxes (from Thompson, 2000). Results of Past Research on Huascarán Ice resolution was limited to the top 270 years. The Cores timescale was originally based on a combination of 18 HS receives abundant snow accumulation (~2 to 3 ice flow modeling and δ Oice matching with a North meters/year) and contains distinct seasonal variability Atlantic marine core (Bard et al., 1987). A strong in δ18O and concentrations of dust and certain ions warming has dominated the last two centuries at the (Figure 2). The majority of the precipitation in the HS site. Peruvian Andes falls during the austral summer (December to February, DJF) (Garreaud et al., 2003; Since the initial publication the Holocene timescale Mantas et al., 2015) in association with the South has been fine-tuned using δ18O measurements of air American summer monsoon (SASM). Although from bubbles in the ice (Thompson, 2000; Davis 70% of Earth’s tropical glaciers are located in Peru, and Thompson, 2006).