Guocheng Dong

10Be dating of boulders on moraines from the last glacial period in the Nyainqentanglha mountains, Tibet

Chronologies of glacial advances during the last glacial period in the Nyainqentanglha mountain range may provide constraints on the past climate in a transition zone of the Asian monsoon. We present 15 new 10Be exposure ages from two moraines in the Payuwang valley, on the north slope of the range. The inner moraine has exposure ages ranging from 18.0±1.7 to 30.6±2.8 ka (n=10), with a mean age of 23.8±4.0 ka, corresponding to the global Last Glacial Maximum (LGM). The outer moraine yields exposure ages ranging from 18.0±1.6 to 39.9±3.7 ka (n=5). Evidence for weathering leads us to view the oldest age as a minimum age, placing moraine formation during MIS3. Chronologies from the last glacial period from south slope of the Nyainqentanglha support this interpretation. Thus, there appears to have been a local LGM (LLGM) during MIS3 and a more limited glacial advance during the global LGM. Glacial advances during MIS3 in the Nyainqentanglha may correlate with millennial-scale climate change (Heinrich events).

Cosmogenic 10Be surface exposure dating of ‘Little Ice Age’ glacial events in the Mount Jaggang area, central Tibet:

The timing and extent of ‘Little Ice Age’ (LIA) glacial advances on the Tibetan Plateau (TP) are critical for understanding climate during the past millennium. However, the lack of LIA chronologies in central Tibet makes it difficult to fully understand the nature of LIA throughout the TP. In this study, two presumed LIA moraines in the east of Mount Jaggang, Xainza range, the central TP, were examined and dated using 10Be surface exposure dating. Eight boulders from the two moraines yielded apparent 10Be exposure-ages ranging from 41 ± 31 to 529 ± 130 years. These 10Be exposure-ages indicate that glaciers advanced at least once in the Mount Jaggang area during the LIA. A relatively extensive glacial advance occurred around 267 ± 36 years, a relatively humid period as indicated by proxy data from lake sediments in the central TP. A glacial standstill might have occurred around 151 ± 36 years. The two LIA glacial events are comparable with those across the TP. However, much more efforts should be made on dating of LIA moraines in the Mount Jaggang area to elucidate the relationships between glacial advances and climate changes during the LIA.

Late Glacial glacier-climate modeling in two valleys on the eastern slope of Samdainkangsang Peak, Nyaiqentanggulha Mountains

Well-preserved Late Glacial moraines in the Barenduo and Yuqiongqu valleys on the eastern slope of the Samdainkangsang Peak present an opportunity to reconstruct glacier extents and examine the character of the climate during the Late Glacial stage in the Nyaiqentanggulha Mountains. This study employs a coupled mass-balance and ice-flow model to reconstruct the glacier extents in the two valleys and assess the magnitudes of temperature and precipitation change during the Late Glacial period. Model results indicate that during the Late Glacial, the Barenduo valley contained an ice volume of 1.67×108 m3, with the equilibrium-line altitude (ELA) being ~5500 m asl; and the Yuqiongqu valley had an ice volume of 5.56×108 m3, with the ELA being ~5470 m asl. A climate scenario, temperature depression of 2.6–2.8°C and 60–70%, percent of modern (1981–2010) precipitation, can sustain both of the Late Glacial glacier extents in the two valleys. A 50% increase or decrease from modern precipitation would have been coupled with the respective Late Glacial temperature depressions of 1.6 and 3.0°C in the Barenduo valley, and 2.1 and 2.8°C in the Yuqiongqu valley.