Developing a 'Little Ice Age' glacial chronology in the southern Peruvian Andes using lichenometry and cosmogenic beryllium-10 surface exposure dating

• Main Author: Taggart, Jean R
• Format: Text
• Language: unknown
• Published: University of New Hampshire Scholars' Repository 2009
• Subjects: Geology; Paleoclimate Science; Patagonia; New Zealand; Ela; Fuller; New Glacier; glacier; glaciers; Alaska
• Online Access: https://scholars.unh.edu/thesis/498; https://scholars.unh.edu/cgi/viewcontent.cgi?article=1497&context=thesis

The timing and causes of tropical climate changes during the Holocene are important and unresolved issues in paleoclimatology. Glacier chronologies are crucial for discerning the role of the tropics in global climate change, but past glacier activity in this region remains poorly documented. In this study, mapping has identified two prominent glacier advances in three valleys in the Cordillera Vilcabamba (13°20'S). 10Be dating reveals that the most recent glacier culminations occurred during the late AD 1700's to early 1800's, which corresponds to the late 'Little Ice Age' period (LIA; AD 1350--1860). Lichenometric dating suggests near-coeval LIA moraine stabilization in all mapped valleys. The late LIA culmination in the Cordillera Vilcabamba is broadly correlative with glacier chronologies in Europe, North America, and northern Patagonia. However, the timing of events in southern Peru differs from culminations in Alaska and southern Patagonia and from patterns of glaciation in New Zealand. Reconstructed equilibrium line altitudes (ELAs) of glaciers in the Vilcabamba reveal an ELA rise of ∼165--200 m since the LIA, suggesting that temperatures ∼1.1--1.3°C cooler could have sustained glaciers at their LIA position. The difference between ELAs of early Holocene and LIA glaciers is small relative to the ELA rise since the LIA, which highlights the magnitude of the LIA climate oscillation in the tropics. The favored climate hypothesis responsible for sustaining more advanced Vilcabamba glaciers includes a southward displacement of the Intertropical Convergence Zone during the LIA which may have enhanced moisture delivery. The new glacier chronologies developed here augment other high-resolution Holocene tropical records, thereby allowing a fuller understanding of inter-hemispheric climate processes and linkages.