Thermal and Hydrological Assessment of the Goethe Rock Glacier, Sierra Nevada, CA

Transcription

1 Thermal and Hydrological Assessment of the Goethe Rock Glacier, Sierra Nevada, CA Thesis Proposal for the Master of Science Degree, Geology Department, Western Washington University, Bellingham, WA Jezra Beaulieu 9/14/11 Committee Members: Dr. Doug Clark, Thesis Committee Chair, Geology Department Dr. Robert Mitchell, Thesis Committee Member, Geology Department Dr. Andy Bunn, Thesis Committee Member, Department of Environmental Sciences

2 INTRODUCTION Rock glaciers may provide critical habitat refuges for nearby alpine communities as they experience accelerated warming predicted by most climate forecasts. The surficial debris on rock glaciers insulates their ice cores allowing them to persist while normal glaciers retreat (e.g., Clark et al., 1994; Clark et al., 1998). Previous work suggests that the thermal and hydrological conditions of these ice reservoirs may be increasingly important to the long term viability of sensitive associated ecosystems (e.g., Millar and Westfall, 2007; Millar and Westfall, 2010). My research will test this concept at an active rock glacier in the central Sierra Nevada by measuring discharge and temperature of the outlet stream, analyzing isotopic components of melt water, and collecting temperature profiles across the rock glacier. I will also collect similar control measurements of adjoining talus in the same cirque in order to compare their thermal regime to that of the rock glacier. This work will help provide a baseline on the thermal and hydrological inputs of rock glaciers to alpine ecosystems in the Sierra Nevada. BACKGROUND Rock glaciers are lobate bodies of flowing ice and rock debris whose surfaces consist of angular boulders often displaying ridge and furrow morphologies similar to viscous lava flows, and usually forming a steep frontal slope at their terminus that is at or greater than the angle of repose (Potter, 1972). They are common in continental mountain ranges at high altitudes, but also occur in the dryer portions of maritime ranges such as the Sierra Nevada and Cascade Mountains (e.g., Clark et al., 1994). Although substantial debate has surrounded the origins of rock glaciers (e.g., Potter, 1972; Clark et al., 1998; Burger et al., 1999) Most workers accept that active rock glaciers preserve a core of mostly ice below an insulating debris mantle (e.g., Clark et al., 1994; Konrad and Clark, 1998; Brenning, 2005). Because of the insulation provided by the surface debris, rock glaciers continue to persist and can even advance during warmer climatic periods while nearby clean glaciers thin and retreat (Clark et al., 1994). Millar and Westfall (2007) first recognized the potential for rock glaciers to support climatically sensitive wetland environments in alpine regions of the Sierra Nevada that might otherwise perish without a persistent ice body nearby. Their mapping indicates that rock glaciers extend 1

3 from 2225 to ~4000 meters in elevation and lie within NNW to NNE facing cirques (Millar et al., 2010; Millar and Westfall, 2007). Similarly, ecosystems near these sites are of particular interest when assessing their sensitivity to local climate. Based on Parameter elevation Regressions on Independent Slopes Model (PRISM) climate data (Daly et al., 1994) the mean annual air temperatures (MAAT) of modern and relict rock glaciers varies from 0.3 C to 2.2 C and the mean annual precipitation varies from 1346 to 1513 millimeters (Millar and Westfall, 2007). Meltwater streams of these rock glaciers flow year round and have mean summer temperatures that vary from 2 C to 2 C, well suited for biota to survive through summer conditions that are otherwise too warm (Millar et al., 2010; Millar and Westfall, 2007). Results from my research will provide detailed hydrological and geomorphological constraints that complement and test these reconnaissance studies. Such focused studies are needed to fully evaluate the modern climatic and hydrologic contributions of rock glaciers to alpine ecosystems in the Sierra Nevada. FIELD AREA Goethe rock glacier resides in a NNW facing cirque and is one of the larger active rock glaciers in the High Sierra, with an area of approximately 1 km 2 (Figure 1). The Goethe cirque is one of many in the Glacier Divide ridge that runs east west relative to the main Sierra Nevada crest, and feeds a series of lakes in the valley below. The rock glacier itself is approximately 1000 meters wide and 650 meters long, ranging in elevation from 3500 at the toe of the rock glacier to 3700 meters at the cirque headwall. It feeds an outlet stream and contains two thermokarst ponds on its surface, indicating that ice is actively melting beneath the surface regolith of the rock glacier (Figure 2). The Goethe cirque also contains other periglacial landforms such as active and relict valley wall rock glaciers and talus that will be monitored in addition to the main rock glacier in order to compare temperature profiles in these comparable but ice free landforms at different elevations and aspects. The main rock glacier consists of two lobes that are separated by a medial longitudinal moraine; each lobe supports at least one thermokarst lake. The active valley wall rock glaciers reside to the east of the main rock glacier (Figure 2). The eastern active rock glacier 2

4 ranges in elevation from meters and is about 100 meters wide and 220 meters long. The western active rock glacier ranges in elevation from meters and is about 150 meters wide and 120 meters long. They have characteristics similar to the main rock glacier such as a steep angle of repose at the terminus, unstable surficial boulders, and ridge andfurrow morphology, hence why they are designated as active rock glaciers. Their surface debris however is more oxidized with intermittent soil and vegetation in areas of fine sediment. The relict valley wall rock glaciers are on the west side of the cirque and are immediately north from the western most lobe of the main rock glacier (Figure 2). One relict rock glacier is directly below the other about 60 meters apart in elevation; the upper relict rock glacier is at 3680 meters in elevation and the lower is at 3620 meters in elevation. Their dimensions are similar, but difficult to determine because their morphology is not as defined as the other features in the cirque. I will also investigate a talus field that is east of the active valley wall rock glaciers and ranges in elevation from meters (Figure 2). Its dimensions are 120 meters wide and 170 meters long. PROPOSED RESEARCH For this project, I will investigate the thermal regime, microclimate, hydrology, and isotopic chemistry of the Goethe rock glacier from August 2011 to September 2012 by collecting temperature profiles across the rock glacier, measuring discharge and temperature of the outlet stream, and analyzing the Tritium components of melt water from the outlet stream. This will test whether the rock glacier provides cool air, cold water, and persistent streamflow throughout the summer months when it is most crucial to sustaining alpine life. I will also collect similar control measurements of adjoining talus and valley wall rock glaciers at various elevations and aspects in the same cirque in order to compare their thermal regime to that of the rock glacier and to each other. I began fieldwork in August 2011, and will return in September of 2012 to collect all instrumentation from the field area. 3

5 METHODS Thermal Regime: The microclimate of alpine valleys is complex, reflecting effects of aspect, elevation, regional and global weather systems, and even rock type (Barsch, 1996). Because macro scale temperature profiles of these alpine valleys are poorly understood, I chose to compare temperature profiles of multiple landforms within one cirque to investigate the signal of a single large rock glacier. Forty small thermistors called ibuttons were placed throughout the landforms at varying elevations and aspects. I chose twenty locations on the landforms that could be easily found, usually near the largest boulders in the area, which also had the deepest crevices to place the thermistors. I also designated locations according to morphology, placing thermistors on ridges, furrows, and frontal slopes, or at the center and sides of the features. These locations are important for interpreting airflow through the debris matrix or the relative thickness of the debris layer at each respective site. Two thermistors were installed at each location, one at the surface of the debris and one at a depth of 1 3 meters, in order to evaluate the range of temperatures within the debris matrix of the feature. The thermistors at depth were placed as far as they could possibly go before meeting an obstacle, though most were within 1 2 meters deep. The thermistors at the surface were secured between boulders to record the temperature of the surface of the debris in the summer, and the base of the snow cover (BTS) in the winter. Temperature will be recorded every four hours over the course of 12 months with an accuracy of ± 1 o C. On the main rock glacier, thermistors were placed on ridges and furrows of the two main lobes at varying elevations, at the top of the steep frontal slope of the lobes, near the thermokarst lakes, and on the medial moraine between the two lobes. On the active valleywall rock glaciers to the east, thermistors were placed on the steep frontal slope and at the spoon shaped depression that occurs between the rock debris and cirque headwall (Figure 3). On the relict valley wall rock glaciers to the west and the talus to the east, thermistors were placed at two different elevations to compare the thermal regime of a non ice cored landform at the same elevation and aspect as the main rock glacier. Though the relict rock glaciers and 4

6 talus are at different aspects and elevations relative to each other, I can compare their lapse rates to that of the rock glacier directly adjacent to each respective landform. Microclimate: To constrain local weather in the cirque, I established an automated Campbell Scientific weather station on a large stable boulder near the middle of the rock glacier along the longitudinal moraine separating the two main lobes at 3650 meters in elevation. The weather station records solar radiation, wind speed and direction, total precipitation, and temperature and humidity at hourly intervals for 12 months (Figure 3). These parameters are important for understanding the response times of alpine landforms to local weather events as well as longterm conditions. With respect to active rock glaciers, it is important to know how much accumulation and ablation is occurring and where it is occurring within the cirque. By combining information of the thermal and hydrological conditions of the rock glacier with data from the weather station, I may be able to assess the rock glacier s equilibrium with the modern climate and assess the longer term significance of the insulating debris mantle. Hydrology: Stream discharge and temperature measurements will test whether the outlet stream from the rock glacier is consistently near freezing and persistently flowing throughout the year. Two surface melt water streams emanate from the rock glacier, and multiple subsurface melt water streams flow beneath the debris layer of the rock glacier. The site I chose for stream flow measurements had simple morphology, with only some boulders in the channel, and was bound by large boulders that constrain the flow. The smaller surficial outlet stream on the east side of the rock glacier was dominated by sheet flow and too shallow to collect stream flow measurements. I have begun to collect flow velocity measurements with a Marsh McBirney Flo Mate in the main outlet stream of the rock glacier at various stages in order to create a rating curve for the stream. Measurements were taken daily at mid morning when water depth was low and late afternoon when water depth was high from the daily snow melt. A stilling well was installed right at the toe of the rock glacier and about 50 meters upstream from the 5

7 delta into Goethe Lake (Figure 3), where water depth and temperature will be continuously recorded with a Solinst Junior Levelogger at intervals of 20 minutes for 12 months. Isotopic Analysis: Water samples were collected throughout the cirque to determine the sources of water in the drainage in relation to the total discharge of the outlet stream. Tritium radiometric analysis of the samples will help constrain the age of the ice, snow and melt water and furthermore the total contribution of melt water from the ice core versus seasonal precipitation to the total discharge from the rock glacier. Tritium is commonly used for dating groundwater, but has been used for dating rock glacier ice (Cecil et al., 1998). It has proven to be a valuable tracer for young water because of the spike of 3 H in atmospheric fallout from bomb testing in the 1950 s (Plummer et al., 2003). The 3 H from precipitation decays to 3 He with a half life of 12.4 years, where precipitation before the 1950s will contain less than 0.1 Tritium units (TU), and precipitation that fell during the decade of will now contain approximately 70 TU (Plummer et al., 2003). Samples were collected from the main outlet stream, the small sidechannel, snow at a range of depths, and ice from the thermokarst lake (to be collected in September). More water samples from the outlet streams will also be collected in late September 2011 to observe the change in Tritium content over the course of the summer. Statistical Analysis: When data from the thermistors, levelogger and weather station are collected in the summer of 2012, I will examine these data and external data from previous studies or nearby weather stations for statistical significance and correlation using bivariate statistics (e.g., Kendal s τ). Although the recording intervals of the sensors may differ, they were programmed to record at the same time of day for their respective intervals. This overlap should allow me to discern correlations between the datasets, both diurnally and seasonally. Ideally, the sensors would all record at the same interval, but power availability and memory storage were not compatible among the sensors because of the various manufacturers of the sensors. 6

8 TIMELINE Establish instrumentation in the field and collect preliminary data Summer 2011 Collect hydrological data and water samples Summer 2011 Fall 2011 Isotopic Analysis of water, snow and ice samples Fall 2011 Winter 2012 Complete background, methods, and preliminary results of thesis Fall 2011 Spring 2012 Revisit field area and dismantle instrumentation Summer 2012 Statistical analysis Fall 2012 Complete results, discussion, and conclusions Fall 2012 Deliverables: The expected outcomes of this project include: Temperature profiles for the Goethe rock glacier, active and relict valley wall rock glaciers, and talus in the Goethe Lake cirque Detailed meteorological data for the Goethe Lake cirque Rating curve relating stage of the outlet stream to total discharge Tritium analyses of the outlet stream and a ratio of melt water contribution from seasonal snow vs. ice core for early and late summer EXPECTED RESULTS Thermal Regime: The thermal profiles of each landform in the cirque will give insight into response times of the debris layer to weather events and seasonal and diurnal variance. They will also document the variability of the temperature with depth and the insulating effect of the debris layer in preserving ice within the rock glacier. Additionally, they will help constrain the thermal variability throughout the cirque at a range of elevations, aspects and morphologies. 7

9 Studies of rock glaciers in the Swiss Alps and Greenland found that conductive and nonconductive processes govern the air circulation through the debris of a rock glacier depending on surface morphology and the extent and thickness of snow cover (Humlum, 1997; Hanson and Hoelzle, 2004). Conductive processes would consist of movement of cool, dense air moving either downslope or vertically downward into the debris matrix, which in turn forces warmer and less dense air to move upslope or vertically upward in the debris. The micro topography on the surface of the rock glacier can play a significant role in creating pockets of cold air that preserves and protects the ice core from warmer temperatures above the debris (Hanson and Hoelzle, 2004). Discontinuous snow cover can also generate funnels through which there is open exchange of cool and warm air with the atmosphere (Hanson and Hoezle, 2004). Nonconductive processes consist of wind pumping and the zero curtain effect, where percolating water from snowmelt refreezes to boulders or the ice core and creates an energy sink (Humlum, 1997; Hanson and Hoelzle, 2004). Warming of the superimposed ice must occur first in order for debris matrix temperatures to rise, thus keeping the matrix temperatures at 0 o C (Hanson and Hoelzle, 2004). Temperatures of the debris matrix will significantly vary depending on the presence of an ice core, and temperatures of the surface of the debris will vary depending on extent of snow cover and changes in air temperature. The presence of an ice body below the regolith in an active rock glacier should reduce the variability of temperature at depth because it should act as a thermal buffer relative to a dry talus. Berger et al. (2004) measured the winter basal temperatures of the snow (BTS) on an active rock glacier in the Austrian Alps and found that they are 3 4 o C lower than on permafrost free ground adjacent to the rock glacier, reportedly because of ventilation of cold air from the ice core (Berger et al., 2004). They also found that summer temperatures on the rock glacier were as high as +15 o C at the surface and +5 o C at a depth of 1.5 meters. Similar findings are described in Millar (2010) for rock glaciers in the Sierra Nevada (Figure 4). I expect to find trends similar to those of previous work for the landforms in the Goethe cirque. In general, the temperature gradient between the debris matrix at a few meters depth and the 8

10 surface of the debris will be steepest in the ice cored landforms and shallowest in the non icecored landforms throughout the year. In the summer, the temperature at the surface of the debris is mainly influenced by direct radiant heating, air temperature and the thermal properties of the debris. Both ice cored and non ice cored landforms will have their steepest gradient in the summer, when daily heating at the surface is greatest but matrix temperatures remain closer to annual mean temperatures. Summer surface temperatures near and downslope of active rock glaciers could potentially be several degrees lower than the ice free landforms because of the outflow of air from the matrix cooled by the ice core. This would mainly occur at the toe or below local slopes on the rock glacier where denser air that is cooled by an ice core moves down slope. Conversely, the temperature gradient of both ice cored and non ice cored landforms should be shallower in the winter when the heavy winter snowpack insulates and buffers the regolith from atmospheric cooling extremes. In the winter, the temperature gradient of the ice cored landforms should be steeper relative to non ice cored landforms because ice is a large thermal mass that moderates the temperature within the matrix. As snow accumulates in the winter, air temperature has a reduced influence on temperatures below the snow and an inverse temperature gradient can develop on the rock glacier, in which temperatures increase with depth from the BTS (Berger et al., 2004). Berger et al. (2004) suggest that the BTS of a rock glacier in winter, when snow cover is continuous, directly reflects the mean annual ground temperature, which varies from 3 to 5 o C, and the matrix temperature at a few meters depth reflects the temperature of trapped air within the debris layer that remains o C higher than the BTS (Berger et al., 2004). With regards to elevation, I expect to see lower temperatures at the surface and in the debris matrix at higher elevations throughout the year. With regards to morphology and aspect, I expect to see warmer temperatures in the relict rock glaciers throughout the year because they have a SE facing aspect, as opposed to a NNW facing aspect like the active rock glaciers and talus. Ridges on the rock glaciers may trap warm air, whereas furrows will preserve cold, denser air. 9

11 Microclimate: The thermal and hydrological conditions of these landforms will highly depend on local weather in the cirque. According to Barsch (1996) rock glaciers develop in regions with a mean annual temperature (MAAT) between 1 and 2 o C. However, Millar and Westfall (2007) found that the MAAT of active and relict rock glaciers in the Sierra Nevada ranged from 0.3 to 2.2 o C, which is further evidence that rock glaciers are not in equilibrium with modern climate, or perhaps that they do not require permafrost conditions to develop. Similar findings were described in Brenning (2005) in the Chilean Andes, where the MAAT of active rock glaciers is between 0.5 and 4 o C, which is normally the MAAT necessary for discontinuous permafrost. Mean annual precipitation for the Sierra Nevada is between 1346 and 1513 mm (Millar and Westfall, 2007), and according to PRISM data, the winter of experienced excess amounts of precipitation with snowpack accumulating to nearly 200% of normal, which will certainly be reflected in the stream flow data for the summer of The abundant summer snow pack in the Goethe cirque will likely be the dominant contribution to stream flow in the outlet streams in place of melt water from the rock glacier core. This will make it difficult to discern ice core meltwater when completing the isotopic analysis of the outlet streams. The Sierra Nevada s Mediterranean climate is usually characterized by peak precipitation in the winter as snowfall and peak stream runoff in the spring that diminishes by late summer. Thus far, the summer of 2011 has stayed true to its roots with minimal precipitation and high temperatures, though response times of stream runoff and vegetation has been delayed at least one month, because of such a high winter 2011 snowpack. Hydrology: Many studies have attempted to model the amount of water that is currently being stored in alpine permafrost and furthermore project the longevity of those reserves (e.g., Barsch, 1996; Azocar and Brenning, 2009; Berger et al., 2004). Though my research is much shorter term than previous research, I will attempt to supply one piece of the hydrological puzzle by assessing lag 10

12 times in stream runoff to weather events as well as seasonal and diurnal variation in runoff of an active rock glacier in the Sierra Nevada. Diurnal variation would consist of low flow in the morning and high flow in the evening after snow and ice have melted during the day. I would expect seasonal variation to consist of peak runoff in late spring that then lessens by autumn, where the stream would completely freeze in the winter months (Figure 5). Berger et al. (2004) measured discharge of an active rock glacier in the Austrian Alps and found that diurnal variations in discharge ceased by late summer, when all snow was melted. They also found that peak runoff occurred during warm weather periods and immediately after thunderstorm events, whereas cold weather periods resulted in a strong decrease in discharge (Berger et al., 2004) Because peak runoff in the Sierra Nevada is snowmelt dominated at high altitudes, I expect a lag time of 4 5 months relative to peak precipitation and peak runoff of lower altitude rivers (Dettinger and Cayan, 1994). Water temperature should stay consistently below 1 o C during the melt season, even after warm rain events (Berger et al., 2004, Millar and Westfall (2010); however Millar (2010) found that some outlet streams may reach up to 4 o C in the summer (Figure 5). This may be a reflection of abundant snowmelt that flows over rock debris as opposed to snow melt that flows over the ice core of the rock glacier. Isotopic Analysis: The goal of the Tritium isotopic analysis is to assess variation in meltwater contribution to total discharge over the course of the summer. Although the absolute age of the Goethe rock glacier ice core is undetermined, it should vary between a few hundred to a thousand years at its oldest, to the most recent snowfall, which will be reflected by varying values of Tritium content. Recent snow, however, should have small amounts of Tritium (<5 TU) that are remnants of the bomb spike in the 1950s. Some post bomb snow and snowmelt may have adhered to the ice core as congelation ice, which could obscure the Tritium signal from the ice core in this study. Cecil et al. (1998) determined that ice from the Galena Creek rock glacier in Wyoming, independently dated to contain ice that is at least 2000 years old, had 3 H values that varied from 1.3±1.3 to 0.2±1.0 TU, indicating that the ice is old enough for Tritium to have almost completely decayed. They found that the outlet stream concentrations were 9.2±0.6 to 11

13 13.2±0.8 TU, equivalent to values of precipitation from the five years prior to their study. They concluded that such a low apparent contribution from melting of old ice in the stream suggests slow melt rates for the ice core, providing further evidence for an insulating debris mantle (Cecil et al., 1998). I originally expected that both outlet streams near the rock glacier would have a large snow signal with higher 3 H content in early summer and lower 3 H content by late summer, indicating a switch from snowmelt dominated flow to ice melt dominated flow. Because of the exceptionally heavy snowfall during the previous winter, however, I now expect to see results similar to those of Cecil et al. (1998), in which most if not all of the discharge in the outlet stream is from snowmelt, even in the late summer. Tritium analysis is a quantitative method with qualitative results. Modern Tritium concentrations in precipitation can be quite variable between regions and even precipitation events, requiring calibration for a specific field site (Plummer et al., 2003). Tritium concentration in precipitation has also decreased at the same rate as Tritium decay over the past 25 years, making it difficult to determine unique ages of a mixed meltwater stream (Plummer et al, 2003). However, the method should still provide constraints on the relative contributions of old ice vs. more recent precipitation in the outlet stream of the rock glacier. SIGNIFICANCE OF STUDY The macro scale thermal and hydrological regimes in alpine valleys are poorly understood due to difficult access and short field seasons, but have become increasingly important in a warming climate. Rock glaciers in particular have proven to be a promising and relatively persistent reservoir of water because of the insulating debris matrix that slows ablation rates of the ice core. They have also been recognized for their ecological importance as sources of cold air and water in arid mountain ranges; rock glaciers are composed of at least 50% ice and are especially abundant in semi arid continental mountain ranges, where they are particularly crucial (Barsch, 1996). Connie Millar and others at the Pacific Southwest Research Station in California have already begun extensive investigations of rock glaciers as refugia for alpine fauna that heavily rely on the source of water and vegetation surrounding these rock glaciers. My study should 12

14 provide new constraints on the potential for the Goethe rock glacier to provide persistent water and cooler air temperatures in the face of continued warming and drying predicted for the region. Understanding the environmental significance of rock glaciers in a warming world could ultimately aid natural resource management and ecosystem conservation efforts that are currently underway in the Sierra Nevada. BIBLIOGRAPHY Azocar, G.F. and Brenning, A. (2009). Hydrological and geomorphological significance of rock Glaciers in the dry Andes, Chile (27 o 33 o S). Permaforst and Periglacial Processes 21: Barsch, D. (1996). Rock Glaciers Indicator for the Present and Former Geoecology in High Mountain Environments. Springer Verlag, Berlin Stuttgart. Berger, J., Krainer, K., Mostler, W. (2004). Dynamics of an active rock glacier: Oztal Alps, Austria. Quaternary Research 62: Burger, K.C., Degenhardt, J. J., Giardino, J.R. (1999). Engineering geomorphology of rock glaciers. Geomorphology 31: Brenning, A. (2005). Geomorphological, hydrological and climatic significance of rock glaciers in the Andes of central Chile (33 35 degrees S). Permafrost and Periglacial Processes, 16: Cecil, L. D., Green, J., Vogt, S., Michel, R. and Cottrell, G. (1998). Isotopic composition of ice cores and meltwater from Upper Fremont Glacier and Galena Creek rock glacier, Wyoming. Geografiska Annaler: Series A, Physical Geography, 80: doi: /j x Clark, D.H., Clark M.M., and Gillespie, A.R. (1994). Debris covered glaciers in the Sierra Nevada, California, and their implications for snowline reconstructions. Quaternary Research, 4: Clark, D.H., Steig, E.J., Potter, N., Gillespie, A.R. (1998). Genetic variability of rock glaciers. Geografiska Annale, 80: Daly, C., Neilson, R.P., Phillips, D.L. (1994). A statistical topographic model for mapping climatological precipitation over mountainous terrain. Journal of Applied Meteorology, 33: Dettinger, M.D. and Cayan, D.R. (1994). Large scale atmospheric forcing of recent trends toward early snowmelt runoff in California. Journal of Climate 6:

15 Dettinger, M.D., Cayan, D.R., Meyer, M.K., and Jeton, A.E. (2004). Simulated hydrological responses to climate variations and change in the Merced, Carson, and American River Basin, Sierra Nevada, CA, Climatic Change 62: Hanson, S., Hoelzle, M. (2004). The thermal regime of the active layer at the Murtel rock glacier based on data from Permafrost and Periglacial Processes, 15: Humlum, O. (1997). Active layer thermal regime at three rock glaciers in Greenland. Permafrost and Periglacial Processes, 8: Konrad, S.K., and Clark, D.H. (1998). Evidence for an Early Neoglacial glacier advance from rock glaciers and lake sediments in the Sierra Nevada, California, U.S.A. Arctic and Alpine Research, 30: Millar, C.I., Westfall, R.D., and Delany, D.L. (2010). Thermal and hydrologic attributes of rock glaciers and related landforms in the Sierra Nevada, CA: five years of ibutton records. Poster to be presented at: Pacific Climate Workshop (PACLIM); 2011 March 6 9; Pacific Grove, CA. Millar, C.I. and Westfall, R.D. (2007). Rock glaciers and related periglacial landforms in the Sierra Nevada, California, U.S.A; inventory, distribution and climatic relationships. Quaternary International, doi: /j.quaint Plummer, L.N., Böhkle, J.K., and Busenberg, Eurybiades (2003). Approaches for ground water dating in Lindsey, B.D., Phillips, S.W., Donnelly, C.A., Speiran, G.K., Plummer, L.N., Böhlke, J.K., Focazio, M.J., Burton, W.C., and Busenberg, Eurybiades, Residence times and nitrate transport in groundwater discharging to streams in the Chesapeake Bay Watershed: U.S. Geological Survey Water Resources Investigations Report : Potter, N. (1972). Ice cored rock glacier, Galena Creek, Northern Absaroka Mountains, Wyoming. Geological Society of America Bulletin, 83:

16 FIGURES Figure 1. Map of the study area in the Inyo National Forest, Fresno County, California. 15

17 Figure 2. Map of landforms in the Goethe Rock Glacier cirque. Red: main rock glacier; purple: active valley wall rock glaciers; brown: talus; green: relict valley wall rock glaciers. 16

18 N (meters) Figure 3. Google Earth image showing approximate locations of monitoring equipment installed in the Goethe Lake cirque. Red dots are temperature loggers, the blue triangle is the stilling well containing the levelogger, and the yellow triangle is the weather station. 17

19 Figure 4. Temperature profile for Mt. Excelsior rock glacier in the Sierra Nevada showing surface temperatures in red and matrix temperatures in blue. Note the reversal of the temperature gradient when the temperatures cross the 0 o C isotherm and the zero curtain plateau (Millar, 2010). 18

20 Outlet streams freeze Snow covers Snow melts 8/06 10/06 12/06 2/07 4/07 6/07 8/07 Time Millar and Westfall, 2010 Figure 5. Example of temperature profiles for air and stream water of a rock glacier in the Sierra Nevada from August 2006 August Diurnal fluctuation can be up to 20 o C in the summer and fall months. In the winter, the stream is frozen and remains a constant 2 o C, but never rises above +4 o C in the summer months (Miller and Westfall, 2010). 19

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