『Abstract
Glaciers produce cirques by scouring their beds and sapping their
headwalls, but evidence to constrain models of these processes
has been elusive. We report a suite of environmental measurements
from three cirque glacier bergschrunds, including the first temperature
series recorded at depth throughout most of an annual cycle. Compared
to the ambient air, the bergschrunds were colder in summer and
warmer in winter. Freeze-thaw cycles were rare, and relatively
stable subfreezing temperatures persisted from November until
May. Using a model for rock fracturing driven by ice segregation,
we demonstrate that favorable conditions for fracturing occur
not only on the headwall above the glacier, but also within the
bergschrund, where periglacial weathering and glacial transport
can act together to drive cirque headwall retreat. A small (〜3℃)
year-round decrease in temperatures to conditions more typical
of the Pleistocene would likely intensify the weathering process.
Though so far ignored in all glacial landscape evolution models,
the bergschrund likely plays an essential role in the sculpting
of alpine landscapes.』
Introduction
Field instrumentation and temperature measurements
Potential frost damage in and above the bergschrund
Model results and implications
Contribution of freeze-thaw cycles to headwall degradation
Role of the bergschrund in cirque evolution
Acknowledgments
References cited