Holocene glacier fluctuations in Patagonia are modulated by summer insolation intensity and paced by Southern Annular Mode-like variability

• Published in: Quaternary science reviews Vol. 220; pp. 178 - 187
• Main Authors: Reynhout, Scott A., Sagredo, Esteban A., Kaplan, Michael R., Aravena, Juan Carlos, Martini, Mateo A., Moreno, Patricio I., Rojas, Maisa, Schwartz, Roseanne, Schaefer, Joerg M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.09.2019
• Subjects: Cosmogenic isotopes; Geomorphology; Glacial; Glaciation; Holocene; Insolation; Paleoclimatology; South America; Southern annular mode; South America; Glaciation; Paleoclimatology; Geomorphology; Glacial; Insolation; Southern annular mode; Holocene; Cosmogenic isotopes
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2019.05.029

Alpine glaciers are sensitive indicators of changes in climate, and their ubiquity in mountainous regions make them valuable proxies for terrestrial climate reconstructions worldwide. However, the timing and extent of glacier change across the South American mid-latitudes through the Holocene are still poorly constrained relative to their counterparts in the Northern Hemisphere. Here we report a new 10Be surface exposure-based chronology of moraines recording a series of progressively less-extensive glacier advances of Glaciar Torre (Argentina, 49.3°S/73.0°W) since the Last Glacial Maximum, with expansions culminating at 17,600 ± 900, 13,500 ± 500, 9700 ± 400, 6900 ± 200, 6100 ± 300, 4500 ± 200, and 530 ± 60 yr BP. The declining magnitude of Holocene glacier expansions parallels a gradual rise in local summer insolation intensity during the Holocene, while individual advances occurred during inferred negative Southern Annular Mode (SAM)-like states at centennial to millennial timescales. These observations suggest that (i) summer insolation intensity modulated antiphased trends in glacier extent in the polar hemispheres during the Holocene, and that (ii) centennial-scale ‘SAM-like’ temperature and precipitation anomalies paced glacier fluctuations throughout Patagonia. Given the persistence of the inferred ’SAM-like’ anomalies throughout the Holocene, the modern measured trend towards positive SAM index conditions could mark the onset of a fundamental shift in the climate of the Southern Hemisphere midlatitudes that warrants consideration in projections of future climate. [Display omitted] •Seven advances of the Torre glacier, Argentina (49°S), are dated using cosmogenic 10Be surface exposure dating.•Progressively less-extensive advances occurred at 17.1 ka, 13.5 ka, 9.7 ka, 6.9 ka, 6.1 ka, 4.5 ka, and 0.5 ka.•Late-glacial advances correspond to the onset of the Last Glacial Termination and the ACR.•Repeated expansions after an early Holocene glacier maximum define a new pattern in Patagonia, reminiscent of New Zealand.•We propose Holocene glaciers in Patagonia were controlled by trends in summer insolation and the Southern Annular Mode.