Mountain glaciers and ice caps (GIC) independent of the Greenland Ice Sheet respond rapidly to climate variations and records of their past extent provide information on the natural envelope of climate variability. Here, we use a multi-proxy approach that combines proglacial lake sediment analysis, cosmogenic nuclide surface-exposure dating (in situ 10Be and 14C), and radiocarbon dating of recently ice-entombed moss to generate a centennial-scale record of Holocene GIC fluctuations in southwestern Greenland. Following local deglaciation ∼10-9 ka, sediments from proglacial Crash Lake record a glacier advance at ∼9 ka that is indistinguishable from nearby ice sheet moraines, implying a synchronous response of GIC and the Greenland Ice Sheet to a centennial-scale climate event. Following this local glacier advance, GIC experienced net recession until ∼4.6 ka. Radiocarbon ages of in situ moss (n = 29) and Crash Lake sediments reveal intervals of glacier expansion at ∼1.8, 1.2 and 0.7 ka that are superimposed on an overall trend of net glacier expansion throughout the late Holocene. In situ 14C concentrations from bedrock adjacent to radiocarbon-dated moss samples further constrain the duration of ice cover through the Holocene in this region. We find that our glacier-size proxy records during the past ∼4 ka are broadly consistent with relatively lower temperatures recorded in GISP2 and occur during, or following, intervals of volcanic perturbations. Thus, we speculate that volcanic activity, although less frequent and intense than in the early Holocene and during the Little Ice Age, may have led to centennial-scale variability imprinted on net glacier expansion due to decreasing summer insolation through the late Holocene.
Bibliographical noteFunding Information:
We would like to thank CH2M Hill Polar Field services for logistical support and the United States 109 th Air Lift Wing Air National Guard. We are grateful to PolarTREC for supporting Christina Ciarametaro for research opportunities on Greenland. We thank A. Lesnek for field assistance, S. Cronauer, S. Clements, and C. Sbarra for contributions to lab work in the University at Buffalo Cosmogenic Isotope Laboratory, and C. Beel and B. Goehring for assistance with lab work at Purdue University and in PRIME Lab. Two anonymous reviewer's comments strengthened this manuscript. This research was supported by National Science Foundation grant ARC-1204005 .
© 2018 Elsevier Ltd
Copyright 2018 Elsevier B.V., All rights reserved.
- Cosmogenic in situ C
- Glacier fluctuations
- Lake sediment
Continental Scientific Drilling Facility tags