Comparing the evolution of debris-free and debris-covered glaciers during the end of the Lateglacial and the Holocene in Dudh Koshi basin, Everest region, Nepal

2024

Article référencé dans le Web of Science WOS:001347221400001

Jomelli V., Wagnon Patrick, Charton J., Braucher R., Martin L., Schimmelpfennig I., Swingedouw D., Verfaillie D., Brun Fanny, Gairoard S., Shrestha D., Aster Team

Quaternary Science Reviews, 2024, 344, 108994 [15 p.] ISSN 0277-3791

Debris-covered glaciers are very frequent geomorphological features in Khumbu Himal (Nepal). Rock debris on the glacier surface play a significant role in glacier-climate relationships and glacier dynamics. These effects may cause an asynchronous evolution of debris-covered glaciers compared to debris-free glaciers at a multicentennial to millennial scale. Here, we explore this hypothesis by documenting and comparing the multi-millennial Holocene evolution of a debris-free glacier, Sabai glacier, and two debris-covered glaciers, Dig and Huuku glaciers, from adjacent catchments in Dudh Koshi basin (Everest region, Nepal). To do so, we dated rock samples collected from moraine boulders on both debris-covered and debris-free glaciers using the Be-10 cosmic ray exposure (CRE) dating method. Be-10 CRE ages obtained from 41 moraine boulder samples provide time constraints from similar to 13.5 ka to 0.1 ka. While at Dig (debris-covered) and Sabai (debris-free) glaciers, no moraines from the Lateglacial and the Early Holocene are preserved, debris-covered Huuku glacier evidenced a large glacier extent during the B & oslash;lling-Aller & oslash;d and Early Holocene with two moraines dated respectively to similar to 13.5 ka and 11 ka, synchronously with most debris-free and debris-covered glaciers in this region. These two glacier advances are concomitant with enhanced monsoon precipitation supporting a qualitative relationship. The absence of debris landforms in the main valley question the nature of Huuku glacier during the B & oslash;lling-Aller & oslash;d and Early Holocene, which could have been either debris-free or covered by a thin debris layer only. During the Mid Holocene, significant differences are observed in the evolution of the two glacier types. The two debris-covered glaciers recorded a significant advance at similar to 4.8 ka, synchronous with that observed on other debris-covered glaciers in Khumbu valley. However, such glacier advance during the Mid Holocene was not evidenced on debris-free glaciers in the Dudh Koshi valley. Such a Mid Holocene glacier advance may have a spatial signature with frequent cases reported from both types of glaciers in the western part of High Mountain Asia, which are however infrequent in the arid and semi-arid southern and north-eastern Tibet. During the Late Holocene, both types of glaciers evolved similarly again, with moraines spanning the last two millennia, including the Little Ice Age, concomitant with enhanced monsoon precipitation.

Hydrologie [062] ; Géologie et formations superficielles [064]

NEPAL ; HIMALAYA

Fonds IRD [F B010092019]

fdi:010092019