Rock Glaciers and Periglacial Rock-Ice Features in the Sierra
Classification, distribution, hydrology, and climate relationships;
their significance for the west in a climate-change context
Research Project Summary
Rock glaciers and related periglacial rock-ice features (RIF) are
widespread landforms in arctic and alpine environments with cold
temperatures, low humidities, and abundant shattered rock. Compared
to typical ice glaciers, however, rock glaciers are little understood
and studied. Rock glaciers are especially significant in the context
of a warming world: While ice glaciers have been retreating worldwide,
water contained in the ice of rock glaciers or RIFs is protected
from rising air temperatures by insulating rock mantles. As a result,
thaw of ice in rock glaciers significantly lags behind ice glaciers.
For this reason, rock glaciers are likely to become increasingly
critical alpine water reservoirs as temperatures rise.
Rock glaciers and RIFs are ubiquitous in the high Sierra Nevada
south of the Lake Tahoe region, but no previous information exists
on their classification, rangewide distribution, hydrology, or modern
climate relations. Because these features are rock-covered and often
appear similar superficially to rockfalls, talus, and scree slopes,
their presence and hydrologic significance have been widely overlooked.
A few focused studies on paleoclimate and glacial advances have
been conducted on a subset of glacigenic (debris-covered) rock glaciers
in the southern Sierra Nevada, but beyond this, rock glacier implications
have not been incorporated into studies that estimate regional distribution
and extent of stored ice, assess timing and abundance of mountain
streamflows, model changes in water yields under warming climates,
or define wetland alpine refugia for biodiversity. As elsewhere,
rock glaciers in the Sierra Nevada remain "...landforms whose wide
distribution, occurrence, and significance often go unnoticed".
Our studies seek to fill research gaps and address the distribution
and significance of these alpine features in a climate-change context.
Relative to rock glaciers and RIFs in the Sierra Nevada, our study
goals are to:
Develop a regional classification and nomenclature
Compile a geo-referenced database with type localities and photos
derived from field-mapping
Analyze geographic and climatic relations (modern and historic)
of the mapped features
Formulate and test hypotheses of process and origins
Initiate reconnaissance-level monitoring of rock glaciers and RIF
movement; meltwater, including flow, seasonal persistence, temperature,
water age, and chemistry; lichen and plant cover and ages
APPLICATION OF RESEARCH RESULTS
We expect contributions from the ongoing work to basic science
as well as regional water and resource management and alpine biodiversity
conservation. The role of rock glaciers is of critical importance
in arid mountain ranges as snowpacks decrease and ice glaciers retreat.
Due to their lag with climate and the insulating role of rock mantling,
rock glaciers may soon become the primary sources of persistent
year round groundwater from high mountain regions, in particular
the Sierra Nevada . We anticipate that elucidating the ubiquity,
distribution, role of climate and hydrology in high mountains to
have diverse applications under changing climates. Among the most
important will be to improve input into hydrologic and especially
groundwater models and future simulations, and to document the significance
of rock glaciers as sources of water for alpine wetlands and biodiversity.
High Sierra Nevada, cismontane, but mostly east of the Sierran
crest; extending from the Tahoe Basin to the southern extent of
the alpine Sierra, south of Mt. Whitney. Emphasis is on the central
Sierra north of Bishop to Bridgeport latitudes.
C.I. 1) Westfall,
R.D. 1) Delany,
D.D. 2) Dettinger, M.
3) Clow, D. 4) Lundquist, J. 5) Franklin, R. 6) Finkel, R.
1) USDA Forest Service, PSW Research Station
Sierra Nevada Research Center
800 Buchanan St., Albany, CA 94706 USA
2) USGS, Scripps Institution of Oceanography, UC San Diego, La
3) USGS, Water Resources Division, Denver, CO
4) Dept of Civil Engineering, University of Washington, Seattle,
5) Lab of Tree-Ring Research, University of Arizona, Tucson, AZ
6) Lawrence Livermore National Lab, Livermore, CA
PUBLICATIONS AND REPORTS
PDFs are available at: http://www.fs.fed.us/psw/programs/snrc/staff/millar/