GC41A-0087
Evolution Of Quaternary Stream Fan Deposits At The Confluences Of Turung Khola And Bembung Khola Of Middle Teesta Basin In Sikkim-Darjeeling Himalaya,India: A Tectonic – Climate Response
Tributary fan deposits are well preserved on either side of the Teesta river in the non-glaciated middle part of the Himalayan valley lying in a tectonic region bounded by the MCT and MBT. The lithofacies characteristics and assemblage patterns of these deposits bear testimony to the effects of tectonic and climatic activities on the sedimentation process in the basin. Two tributary streams, with small catchments namely Turung Khola and Bembung Khola are important in this context. Three major fan lobes (F2, F1, and F0) are preserved at Turung Khola. In contrast, two fan lobes (F1,F0) are preserved at the confluence of the Bembung Khola. Terraces, floodplains, channel bars, chute bars are associated geomorphic features in this part of the Teesta basin. Landslides cover an area of 7% and 15% in the catchment of Turung Khola and Bembung Khola, respectively. Dense forest covers 24% and 12%; open forest covers 30% and 29 %; and scrubby vegetation covers 39% and 49% of the Turung Khola and Bembung Khola, respectively. The landslides mainly occur along the margins of the dense forest where they are active in every rainy season. Tributary longitudinal profiles and Hack profiles indicate a relationship between the knick points and high SL-Index values, where fault /thrust intersections are present. Active landslides and scarps are close to the major fault/thrust planes. Sediment characteristics of these fan deposits suggest that four types of depositional flows viz. debris flows, hyperconcentrated flows, sheet flows and channel flows laid down these sequences. The channel flow deposits are dominant (32%-54 %) in the fan sequence of the Turung Khola followed by sheet flow deposits (28.5%), hyperconcentrated flow deposits (26%) and debris flow deposits (12%), respectively. Hyperconcentrated flow deposits are dominant (44%) in the F1 sequence, whereas the active channel fanlobe is dominant (80%) in the channel flow deposits. The rest of the active channel sequence is composed of sheet flow deposits (20%). On the other hand, the major part (52%) of the F1 fanlobe of Bembung Khola is built up of debris flow deposits and F0 fanlobe is composed of channel flow deposits and flood sediment. From the above analysis, an evolutionary model of the deposition and incision at the tributary stream fan confluence is proposed. The insetting of the younger fan lobes into older fan lobe surfaces is an evidence of tectonic uplift in the region. The landform and their depositional pattern are a responds to link tectonic- climatic process systems; some depositional lithofacies assemblages are responses to climatic events. http://www.cismhe.org
GC41A-0088
Integration of Classification Tree Analyses and Spatial Metrics to Assess Changes in Supraglacial Lakes in the Karakoram Himalaya
Alpine glacier responses to climate chnage reveal increases in retreat with corresponding increases in production of glacier melt water and development of supraglacial lakes. The rate of occurrence and spatial extent of lakes in the Himalaya are difficult to determine because current spectral-based image analysis of glacier surfaces are limited through anisotropic reflectance and lack of high quality digital elevation models. Additionally, the limitations of multivariate classification algorithms to adequately segregate glacier features in satellite imagery have led to an increased interest in non-parametric methods, such as classification and regression trees. Our objectives are to demonstrate the utility of a semi-automated approach that integrates classification- tree-based image segmentation and object-oriented analysis to differentiate supraglacial lakes from glacier debris, ice cliffs, lateral and medial moraines. The classification-tree process involves a binary, recursive, partitioning non-parametric method that can account for non-linear relationships. We used 2002 and 2004 ASTER VNIR and SWIR imagery to assess the Baltoro Glacier in the Karakoram Himalaya. Other input variables include the normalized difference water index (NDWI), ratio images, Moran's I image, and fractal dimension. The classification tree was used to generate initial image segments and it was particularly effective in differentiating glacier features. The object-oriented analysis included the use of shape and spatial metrics to refine the classification-tree output. Classification-tree results show that NDWI is the most important single variable for characterizing the glacier-surface features, followed by NIR/IR ratio, IR band, and IR/Red ratio variables. Lake features extracted from both images show there were 142 lakes in 2002 as compared to 188 lakes in 2004. In general, there was a significant increase in planimetric area from 2002 to 2004, and we documented the formation of 46 new lakes. It appears that lake-size increments occur mostly in the lower part of the ablation zone, whereas most of the new lakes are formed in the upper part of the ablation zone. The classification-tree outputs are intuitive and the data-derived thresholds eliminate commonly subjective visual determination of threshold values. Semi-automated methods thus have the potential of eliminating laborious visual multi-temporal analysis of glacier-surface change, thereby producing consistent and replicable results needed to assess the trends of alpine-glacier response to climate change in the Himalaya.
GC41A-0089
Satellite Observations of Glacier Advances and Retreat in the Western Karakoram
Debris-covered alpine glaciers around the world have been retreating and downwasting. This suggests glacier response to atmospheric warming. Recent studies in the eastern Himalaya have shown systematic retreat for many glaciers. In the western Himalaya, however, systematic and quantitative data are not yet available to determine glacier sensitivity and mass balance trend. Given the paucity of bench-mark glaciers in the Himalaya, remote-sensing-based studies are required to obtain baseline information and produce estimates of advance and retreat rates. Consequently, our objectives were to assess glacier fluctuations in the western Karakoram of Pakistan as a part of the Global Land Ice Measurements from Space (GLIMS) project. Specifically, we used multi- temporal satellite data (ASTER 09/13/2004, Landsat TM 10/15/1992, and Landsat MSS 07/15/1992) to quantitatively assess terminus fluctuations. Results indicate that more than 50 percent of the sampled large and large-medium sized glaciers are advancing, and/or exhibit similar terminus positions to past positions. For example, Bualtar Glacier is advancing at the rate of 11 m/yr. On the other hand, most of the small-medium to small glaciers, such as Mani Glacier are retreating (15 m/yr). Some of these glaciers have also shown strong downwasting characteristics in the form of increased frequency and size of supraglacial lakes. Collectively, our results indicate that these glaciers may be responding differently to the current climatic conditions than in the eastern Himalaya (east of the Karakoram) and Wakhan Pamir region (northwest of the Karakoram). These quantitative results from remote-sensing studies also indicate that glacier fluctuations in this region are spatially and temporally complex. These complexities may be governed by multi-scaled topographic effects, as well as by variations in winter precipitation and decreases in summer temperature from increased cloudiness, as suggested by others.
GC41A-0090
Space-Based Observations of Batura Glacier Fluctuations, Western Karakoram Himalaya
Monitoring glacier variations by our GLIMS (Global Land Ice Measurements from Space) Regional Center for Southwest Asia (Afghanistan and Pakistan) shows unusual fluctuations over a 40 year period for Batura Glacier. We use multiple field measurements (1984, 1991, 1992, 1993), maps and the work of others (1966, 1974, 1975, 1978, 1980), and satellite imagery (KH-9 Lower Resolution Mapping Camera 4/Aug/1973; Landsat MSS 15/Jul/1979; SPOT 20/Jun/1990; Landsat 5 TM 15/Oct/1992; Landsat 7 ETM 29/Oct/2000 & 30/Sep/2001; ASTER 29/Oct/2003 & 13/Sep/2004). The terminus was at the Hunza River in late 19th and first half of 20th century and then retreated rapidly ~800 m by 1966, leaving behind prominent end moraines on the north terminus. Declassified KH-9 imagery of 1973 shows Batura Glacier width, due south of Shanoz midway between the Chinese cross sections VI and VII, was only ~1523 m wide, whereas after Chinese mapping of 1974-75, and in all imagery thereafter, width there increased to >2 km. Batura does not surge and kinematic waves have not been detected. An ice cliff had formed at the terminus in 1966, advanced forward 100 m and thickened by 15 m by 1975, and advanced another 33 m by 1978, perhaps from this heretofore undetected, probable kinematic wave. Then instead of advancing as predicted by Chinese scientists, by 1984 the frontal ice cliff had retreated 50-100 m, declined in slope angle, and was covered with debris and vegetation, which makes the slope still visible on recent imagery. Our orthorectified imagery shows that from 1973 – 2004 the front of the white ice stream from the first ice fall on the right (south) side underwent retreat of ~2846 m, (retreat rate of 92m yr-1), mainly through down- wasting increase of debris cover and new melt-water lakes. Similarly the terminus underwent ~392 m of retreat from 1973 – 1990 (~23 m yr-1 annual retreat rate), ~36 m retreat from 1990-1992, (~18 m yr-1 annual retreat rate), and a ~37 m advance (~3 m yr-1 annual advance rate) from 1992-2004. High-resolution imagery on Google Earth™ acquired in 2005 or thereafter shows an exposed-ice terminus that has advanced ~50 m from 2004 on. A large new ice cliff has emerged on the southeast side ~ 275 m behind the present ice terminus, even while the parent south white-ice-stream source continued to retreat up-ice. The Chinese Batura Glacier Investigation Group used mass balance and tree-ring data in the 1970s to predict glacier advance from the 1970s, cessation in 1991 – 1997, and retreat for 20 – 30 years thereafter. Global cooling was hypothesized with advances again by 2060, but the actual situations have been otherwise.
GC41A-0091
Glacial Velocity Changes of Batura Glacier, Western Karakoram Himalaya
Glacier fluctuations represent direct and indirect indicators of climate change. Many glaciers around the world are retreating and downwasting, thereby increasing glacial meltwater, as well as debris cover. These variations can cause variations in glacier-flow dynamics including changes in ice velocity and surging. Our objective was to evaluate ice-flow velocity variations on the Batura Glacier in the western Karakoram Himalaya by combining historical data and diagrams from the Chinese Batura Investigation Group of the early 1970s with information gathered from satellite image analysis (ASTER 29/Oct/2003, 13/Sep/2004). Modern ice-flow velocity estimates were generated utilizing ortho-rectified satellite imagery and feature tracking to produce ice-flow velocity fields. Feature tracking was accomplished using original spectral bands and texture images. We generated an average velocity gradient for the Chinese data (12m/yr/100m) and satellite-derived data (23m/yr/100m) using regression analysis. The Chinese mapping of Batura Glacier delineated the end of the lowermost (south-side) white ice stream at ~3.2 km from the Karakoram Highway in 1975. Due to down wasting and increasing supraglacial debris cover the white ice stream has retreated up-ice to ~5.9 km as of 2004. Comparison with historical data shows a possible increase in the annual-velocity gradient yet a decrease in the overall-velocity magnitude. Changes in meltwater at the base from warmer temperatures, or increased mass flux from increased precipitation at altitude, could both change the velocity gradient but not decrease the overall velocities. Downwasting and thinning ice could explain overall decrease in velocities and increased debris loads although attendant frictional increases on sides and base might have some influence.
GC41A-0092
Comparison of Surface Mountain Climate With Equivalent Free Air Parameters Extracted From NCEP/NCAR Reanalysis: Kilimanjaro, Tanzania.
It is difficult to predict future climate changes in areas of complex relief, since mountains generate their own climates distinct from the free atmosphere. Thus trends in climate at the mountain surface are different from those in the free air. We compare surface climate (temperature and vapour pressure) measured at seven elevations on the south-western slope of Kilimanjaro, the tallest free standing mountain in Africa, with equivalent observations in the free atmosphere from NCEP/NCAR reanalysis data for September 2004 to January 2006. Correlations between daily surface and free air temperature anomalies are greatest at low elevations below 2500 metres, meaning that synoptic (inter-diurnal) variability is the major control here. However, temperatures and moisture on the higher slopes above the treeline (3000 m) are decoupled from the free atmosphere, showing intense heating/cooling by day/night and import of moisture from lower elevations during the day. The lower forested slopes thus act as a moisture source, with large vapour pressure excesses reported in comparison with the free atmosphere (>5 hPa) which move upslope during daylight and subside downslope at night. Strong seasonal contrasts are shown in the vigour of the montane thermal circulation, but interactions with free air circulation (as represented by flow indices developed from reanalysis wind components) are complex. Upper air flow strength and direction (at 500 mb) have limited influence on surface heating and upslope moisture advection, which are dominated by the diurnal cycle rather than inter-diurnal synoptic controls. Thus local changes in surface characteristics (e.g. deforestation) could have a direct influence on the mountain climate of Kilimanjaro, making the upper slopes somewhat divorced from larger scale advective changes associated with global warming.
GC41A-0093
Glacier Change in the Rwenzori Mountains, East Africa
In East Africa glaciers currently exist on Mt. Kilimanjaro and Mt. Kenya, and in the Rwenzori Mountains. While the Mt. Kilimanjaro and Mt. Kenya glaciers have been the subject of many recent studies, the glaciers in the Rwenzori Range are less thoroughly studied. This study reexamines the satellite record of retreat of these glaciers, as well as the climatic factors most responsible for the change. A recent study of the retreat of the Rwenzori glaciers using Landsat images acquired between 1987 and 2003 has been questioned. Using visual mapping and the Normalized Difference Snow Index (NDSI) to analyze Landsat, ASTER and SPOT images, we have re-evaluated the ice areas for the period 1987 to 2006. After identifying sources for possible error, our mapping indicates that the glaciers in the Rwenzori have shrunk from an area of 2.55 km2 in 1987 to 1.31 km2 in 2006. Glacier retreat in the Rwenzori from 1906 to 1990 showed a strong spatial correlation with potential increase in shortwave radiation due to decreased cloud cover as a consequence of a shift to drier conditions in the region. Whether or not recent glacier retreat shows a similar spatial correlation is under investigation.
GC41A-0094
The Relation Between Climate Variability and Glacier Morphometry: A Space-for-Time Substitution Analysis for Glaciers in British Columbia, Canada
We explore the relation between spatial climate variability and glacier morphometry for British Columbia using gridded temperature and precipitation normal data and a comprehensive glacier inventory obtained from aerial photography. The altitudinal range of over 10,000 glaciers, distributed across 10° of latitude (49 to 60°N) and 23° of longitude (115 to 139°W), was related to principal components of local climate and extracted morphometric variables. Derived climatic indices represent maritime-continental, latitudinal, and seasonal variability gradients, whereas the morphometric parameters represent measures of glacier slope, aspect, shape, and flow network order. For glaciers exceeding 6 km2 in area (n=561), over 70% of the altitude range variability can be explained using optimized regression models that incorporate both climatic and morphometric predictor variables. We use the multivariate models to quantify the degree to which spatial patterns of climate can be inferred from glacier altitude data and investigate the degree to which morphometric controls moderate these relations. Applications of the developed models include the reconstruction of past climate patterns from historical glacier extents and the prediction of future altitudinal limits for glaciers given projected climate change scenarios.
GC41A-0095
Neoglacial fluctuations of Deming Glacier, Mt. Baker, Washington USA.
Deming Glacier flows from the upper west slopes of Mt. Baker, a stratovolcano in the Cascade Range of Washington, USA. The north and south lateral moraines of Deming Glacier are composed of at least four tills separated by layers of detrital wood and sheared stumps in growth position. The stratigraphy records fluctuations of the glacier during the Holocene. The outer ten rings of an in situ stump from the middle wood layer, which is about 40 m below the north lateral moraine crest and 1.2 km downvalley from the present glacier terminus, yielded an age of 1750 ± 50~~ 14C yr BP [1810-1550 cal yr BP]. The stump revealed at least 300 rings and thus records a period of landscape stability and relatively restricted glaciation for several hundred years prior to ca. 1750 14C yr BP . Samples from the lowest wood layer also have been submitted for radiocarbon dating. Outer rings of detrital wood samples collected from two wood mats exposed in the south lateral moraine, 2.3 km downvalley of the glacier terminus, returned radiocarbon ages of 1600 ± 30~~ 14C yr BP [1550- 1410 cal yr BP] and 430 ± 30~~ 14C yr BP [AD 1420-1620]. These data indicate that Deming Glacier advanced over a vegetated moraine sometime after 1810 cal yr BP to a position less extensive that it achieved at the peak of the Little Ice Age. The glacier then receded before it began its final and most extensive Holocene advance after AD 1420. The older advance is correlative with the 'First Millennium AD' advance, recently recognized throughout western North America. The younger advance coincides with an advance of Mt. Baker's Easton Glacier [AD 1430-1630], and advances of many alpine glaciers elsewhere in western North America. Our data suggest that glaciers on Mt. Baker fluctuated in a similar manner to alpine glaciers in the Coast Mountains of British Columbia and in other mountain ranges of northwest North America during Neoglaciation.
GC41A-0096
New stratigraphic constraints on Holocene glacier advances at Mt. Baker, Washington
New data from a lake sediment core and moraine exposures at Mt. Baker, WA, indicate that a purported early Holocene glacier advance occurred earlier, likely at the end of the Pleistocene. Previous workers used 14C ages associated with small cirque moraines on the SW flank of Mt. Baker, along with the apparent absence of a distinctive scoria (set SC; 8850 14C yr BP, ~9900 cal yr BP) from other moraines on Mt. Baker, as evidence for an advance at ~8400 14C yr BP (~9450 cal yr BP). Such an advance is important to test because it would contrast with glacial records throughout most of the rest of western North America. A 1.2-m sediment core collected from Pocket Lake, which is dammed by one of the previously dated cirque moraines, contains three tephras: Baker set BA (~5800 14C yr BP; 6600 cal yr BP), Mazama ash (6800 14C yr BP; 7600 cal yr BP), and a basal set of ash beds that are tentatively identified as Baker set SC. The lowest macrofossil in the core, ~2 cm above the top of the basal ash beds, yielded an age of 7640 ± 50 14C yr BP (~8400 cal yr BP), consistent with the tephra being SC. Initial geochemical analyses of the tephra also support this identification. These findings indicate that the previous age on the cirque moraine, from organics near the surface of the till, provides a minimum rather than a direct age for the advance that formed the moraine. A 14C age of 11,400 ± 110 14C yr BP (~13,300 cal yr BP) on bulk sediments below the basal ash is likely contaminated and therefore too old. Tephra overlying other ridges at Mt. Baker that were previously identified as post-SC, early-Holocene moraines has been identified as set SC. The ridges thus are actually pre-SC rather than post-SC in age; they may not be moraines in any event. Meanwhile, abundant 14C ages on tills below Deming Glacier indicate both Younger Dryas and Neoglacial advances, but no early Holocene advances. Together, these observations indicate that glaciers in the Mt. Baker area advanced during the YD, were of minimal extent during the early Holocene, and readvanced during the Neoglacial. The similarity of glacier fluctuations here to those in British Columbia and elsewhere in the North Cascades suggests a coherent history of Holocene climate change over a broad area of the northern Cordillera. http://mbvo.wwu.edu/index.shtml
GC41A-0097
Late-Quaternary Environmental Change in the Sierra Nevada: A 19,000-Year Sedimentary Organic Matter Record From Swamp Lake, Yosemite National Park, California
Paleoclimate and environmental change in California over the last several millennia have received intensive study, in part because future climate warming in this drought-vulnerable region is likely to be expressed most acutely through rearrangements in the hydrological cycle (e.g., changes in the amount and timing of precipitation, snowmelt, and runoff). The 19,000-year sedimentary record from Swamp Lake, a small mid-elevation (1554 m) lake in the central Sierra Nevada, provides a rare opportunity to examine the relationships among climate variability, drought, and ecosystem response over a longer timeframe, spanning deglaciation and the Holocene, including several periods in which the Sierra Nevada is thought to have been warmer and drier than the present. Lake sedimentary organic matter (SOM) preserves paleoenvironmental information in a variety of elemental, isotopic, molecular, and microfossil indicators. In this study we utilize carbon and nitrogen elemental abundances and isotopic compositions (δ13C, δ15N) of bulk organic matter, along with measurements of biogenic silica (BSi), diatom and pollen assemblages, and magnetic susceptibility to reconstruct changes in lake productivity, organic matter sources, and plant and algal community composition in relation to climatic variables. We will also present preliminary measurements of the hydrogen isotope ratios (δD) of specific biomarker compounds extracted from the sediment, providing more direct information about the hydrologic status of the lake and watershed. In addition to tracing the post-glacial recovery and Holocene evolution of Sierra Nevada ecosystems, the Swamp Lake SOM record contains significant millennial- and century-scale variability that may correspond to periods of enhanced/suppressed ENSO activity.
GC41A-0098
Sierra Nevada Rock Glaciers: Biodiversity Refugia in a Warming World?
Rock glaciers and related periglacial rock-ice features (RIFs) are common landforms in high, dry mountain ranges, and widely distributed throughout canyons of the Sierra Nevada, California, USA (Millar & Westfall, in press). Due to insulating rock carapaces, active rock glaciers (ice-cored) have been documented to maintain ice longer, and thus contribute to more enduring hydrologic output, under past warming climates than typical ice glaciers. This function has been suggested for the coming century. We propose a broader hydrologic and ecologic role for RIFs as temperatures rise in the future. For the Sierra Nevada, we suggest that canyons with either active or relict RIFs (Holocene and Pleistocene) maintain water longer and distribute water more broadly than canyons that were scoured by ice glaciers and are defined by primary river and lake systems. RIFs provide persistent, distributed water for extensive wetland habitat, rare in these otherwise barren, high, and dry locations. We mapped and assessed the area of wetlands surrounding active and relict RIFs from the central eastern Sierra Nevada; from these we delineated wetland vegetation community types and recorded plant species found in RIF-supported wetlands. Mid-elevation RIFs, likely inactive or with transient ice, develop soil patches on their rock matrix. At the Barney Rock Glacier (Duck Pass, Mammoth Crest), we inventoried plant species on all soil patches, and measured cover for each species per patch and total plant cover for the rock glacier. RIF landforms also appear to support high-elevation mammals. We show that American beaver (Castor canadensis) is associated with canyons dominated by active or relict RIFs and propose that the articulating, persistent, and distributed nature of streams makes dam-building easier than other canyons. Beavers further contribute to maintaining water and creating wetland habitat in upper watersheds by engineering ponds and marshes, and contributing to riparian extent. We also mapped 125 discrete locations of American pika (Ochotona princeps) and found a strong association of pika presence with active and relict RIFs, in particular cirque rock glaciers, valley rock glaciers, and boulder streams. Using the PRISM climate model and a small network of temperature dataloggers from RIF habitats, we present a climate envelope for the pika habitats we surveyed. We propose that the large area of RIFs in the Sierra Nevada over a range of elevations could provide extensive habitat for pika in the warming future. RIFs in general are a group of landforms little studied in high mountains of western North America but of potential increasing importance to hydrologic and ecologic function as climate warms in the future. Millar, C.I. and R.D. Westfall. In press. Rock glaciers and periglacial rock-ice features in the Sierra Nevada; Classification, distribution, and climate relationships. Quaternary International.
GC41A-0099
Hydrology and Biogeochemistry of Three Alpine Proglacial Environments Resulting From Recent Glacier Retreat
Proglacial environments, formed by glacier retreat, exhibit distinct characteristics in discharge, water temperature, water residence time, and ion, carbon, and suspended sediment fluxes. The unnamed alpine glacier at the headwaters of the Wheaton River, Yukon, Canada, provides a unique setting to compare deglaciation processes that result in three different proglacial environments. The glacier has evolved from occupying one large catchment (4 km2) to two smaller catchments (each 2 km2) via glacier thinning and net mass loss, forming two lobes separated by a medial moraine. Climate and bedrock geology are similar for the subcatchments, providing a natural laboratory to compare deglaciation processes. This study compares the biogeochemistry and hydrology of three outlet streams from this glacier; one stream drains a proglacial lake which is fed by the lower west lobe, a second stream drains the upper west lobe, and a third stream is the major drainage outlet for the east lobe. Hydrological monitoring over the 2006 melt season (June-August) and analyses of water samples for ion content and carbon chemistry indicate certain discrete characteristics for each stream and thus aid in the understanding of climate-induced glacier retreat on hydrochemistry, hydrology, and carbon dynamics in remote high elevation environments.
GC41A-0100
High-altitude varve records of abrupt environmental changes and mining activity over the last 4000 years in the Western French Alps (Lake Bramant, Grandes Rousses Massif)
Two twin short gravity cores and a long piston core recovered from the deepest part of proglacial Lake Bramant (Grandes Rousses Massif, French Alps), under and overlying a large slump identified by high-resolution seismic profile, allow the investigation of Holocene natural hazards and interactions between human activity and climatic changes at high-altitude. Annual sedimentation throughout the cores (glacial varves) is identified on photographs, ITRAX (high-resolution continuous microfluorescence-X) and CAT-Scan (computerized axial tomography) analyses and is supported by (1) the number of dark and light laminations between dates obtained by radionuclide measurements (137Cs, 241Am), (2) the correlation of a slump triggered by the nearby AD 1881 Allemond earthquake (MSK intensity VII) and of a turbidite triggered by the AD 1822 Chautagne regional earthquake (MSK intensity VIII), (3) the number of laminations between two acceleratory mass spectrometry (AMS) 14C dates, and (4) archaeological data. In Lake Bramant, dark layers are coarser, contain less detrital elements, but more neoformed elements and organic matter content. These darker laminations result from calm background sedimentation, whereas the lighter layers are finer and rich in detrital elements and reflect the summer snowmelt. Traces of mining activity during the Roman civilization apogee (AD 115-330) and during the Early Bronze Age (3770-3870 cal BP) are recorded by lead and copper content in the sediments and probably result from regional and local mining activity in the NW Alps. Warmer climate during the Bronze Age in this part of the Alps is suggested by (1) two organic deposits (4160-3600 cal BP and 3300-2850 cal BP) likely reflecting a lower lake level and smaller glaciers and (2) evidence of a different vegetation cover around 2500 m a.s.l. The onset of clastic proglacial sedimentation between 3600-3300 cal BP and since 2850 cal BP is synchronous with periods of glacier advances documented in the Alps and high \m lake levels in west-central Europe. This major change in proglacial sedimentation highlights the development of a larger St. Sorlin glacier in the catchment area of Lake Bramant.
GC41A-0101
Influence of NRCS snowcourse measurement date on data accuracy and climatic trends
The Natural Resources Conservation Service measures high elevation snowpack manually at snowcourses across the western US. The date of the measurement is nominally the first and fifteenth of the month although in recent years it averages approximately two days earlier to support timely operational water supply forecasts whose production begins on the first. This study found that the primary factors influencing measurement dates are, 1) the epoch of the measurement, 2) the day of the week of the nominal measurement date, 3) the presence or absence of snow at the site and 4) if the measurement is for the first or the fifteenth of the month. Specifically, the measurement date is less variable if snow is absent from the site. Mid-month data are collected closer to the nominal measurement date and first of month data have a bias towards being several days early. Since 1957, there has been a stronger aversion to collecting data on Fridays and weekends whereas before 1957 snow surveyors mostly avoided measuring on Sunday. Further, measurements are taken today, on average, 1.34 days earlier than before. These factors were modeled and the effect on climate trends was found to be small, on the order of less than 5% although in individual circumstances the effect can be significant.
GC41A-0102
Modeling the effects of topographic shading on snow-fed runoff with warmer temperatures
Discharge in small, tributary streams affects water table heights, riparian vegetation, and habitat in subalpine meadows. Because of this, meadows are very sensitive to the dates when the ephemeral streams go dry. The Distributed Hydrology Soil Vegetation Model (DHSVM) is used in conjunction with a high density hydroclimate monitoring network in the Tuolumne River basin of Yosemite National Park, California to investigate how high elevation sub-basins with different aspects and elevations respond to warmer temperatures. Specifically, this project investigates how topographic shading affects the advance of snowmelt onset and the date snow disappears as temperatures warm. Observations show that in years where the temperature warms earlier in the season, south-facing sub-basins start melting over a week earlier than north-facing basins. Thus, meadow areas fed by sub-basins with southern aspects are expected to be much more sensitive to warming temperatures than areas fed by sub-basins with northern aspects. Traditionally, most future hydrologic simulations are run for large basins and these effects would not be captured. DHSVM is used to test if high- resolution (150 m) modeling with a complete topographic shading component can represent these observed differences and be used to simulate how warmer temperatures will differentially affect various sub-basins and meadow regions.
GC41A-0103
The Hydrological Response of Snowmelt Dominated Catchments to Climate Change
Hydrological systems dominated by snowmelt discharge contribute greater than half the freshwater resource available to the western United States. Globally, the contribution of mountain discharge to total runoff is twice the expected for their geographical coverage. Therefore, snowmelt dominated mountain catchments have proportionally a more prominent role than other systems to our freshwater resource. A changing climate, or even a more variable climate, could have a significant impact on these systems, and consequently on our freshwater resource. Ergo, a better understanding of how changes and variations in climate will influence mountain catchments is a necessity for improving future water management under predicted/proposed climate change. The research presented here is a first order analysis to improve our understanding of these systems by monitoring and analyzing high mountain catchments along the entirety of the Mission Mountain Front, Montana USA. The Mission Mountain Range is an ideal location for conducting this research as it runs directly north to south with elevations progressively increasing from 7600 feet in the northern section, to over 9700 feet at the southern end. The lower elevation catchments will be used as surrogates for variable climate change, while the high elevation catchments will be used as surrogates for a more stable, cooler, climate regime. We use a combination of USGS and Tribal stream gauges, as well as stage gauge loggers in the headwaters of the catchments, SNOTEL datasets, and weather station datasets. This information is used to determine if, how, and why the snowmelt hydrographs vary between catchments, within the catchments between the upper and lower segments, and the dominant driver or drivers of the hydrograph form in relation to changing climatic variables such as temperature and precipitation. This research will improve current comprehension of how mountain catchments respond to climatic variables, and additionally will expand upon the current understanding of general catchment hydrology.
GC41A-0104
Snow depth and snow water equivalent distribution in a high alpine basin: quantifying the length scales and magnitude of variation in Senator Beck Basin, Colorado
Estimating the distribution of seasonal snow is important for water resource management, as one-sixth of the world's population depends on snowmelt for their water supply. In addition, snow water equivalent (SWE) estimates are important for flood and hydropower forecasting, and are critical for understanding surface and groundwater systems. Because the snow cover has such a large effect on the global energy balance, accurate SWE estimates over large areas are necessary for evaluating future climate change scenarios. To adequately describe the correlation length scales of snow depth and SWE at the basin scale, however, measurements at 10 m resolution or less are required, which is impractical using traditional methods. Using an accurately calibrated, portable FMCW radar, coupled with a survey-grade kinematic GPS system, more than 700,000 independent radar measurements were made throughout Senator Beck Basin over a 3 day period in March 2007. These radar measurements are used to estimate snow depth and SWE, covering scales from 10 cm to several km. Due to the large number of estimates, the variogram of snow depth can be accurately calculated, and used to help interpolate between measurements. The length scales and magnitude of variation both above and below tree line are quantified, and uncertainties in the degree of variation are described. Due to the differences in environmental controls, optimum sampling and interpolation schemes vary with location in the basin.
GC41A-0105
1935-2006 Duration of Snowcover and Growing Degree Trends from the Summit and Base of Mount Washington, NH
Start and end dates of continuous snowcover, growing degree days and thawing degree days were calculated using the 71-year climate record from the summit of Mount Washington (1914m ASL), NH. Preliminary results show the start of continuous snowcover (defined as ≥ 2.54cm of snow on ground) on the summit of Mount Washington occurs later in the autumn by 2.1 days decade -1 and ends slightly later in the spring by 0.3 days decade -1, a net decrease in continuous snowcover of 1.8 days decade -1. The trend of a shorter snow season is more pronounced for the date of first and last observed snow on the ground; the first snow occurring 6.7 days decade -1 later in the autumn and last snow 3.3 days decade -1 earlier in the spring. Similarly, using hourly values, cumulative thawing degree days (>0° C) and growing degree days (>5° C) exhibit spring warming; for example the date at which the cumulative thawing degree days = 50 is occurring earlier by 1.1 days decade -1. There is a slight discrepancy between the later continuous snowcover persistence in the spring and the other metrics that we are examining. The above metrics will also be presented from for the eastern base of the mountain, Pinkham Notch, New Hampshire (619m ASL), and compared with these summit data. These results provide insight into how the remnant islands of Arctic flora surviving on the Northeast's higher peaks are now and will be challenged in the future.
GC41A-0106
Stream Water Temperature and Climate Variability along Two Elevational Gradients in the Sierra Nevada Mountains, California, U.S.A.
Water temperature plays an important role in life cycles and species interactions of aquatic biota in alpine streams. Climatic variability and global change affect the landscape characteristics, flow regime and air-surface water energy balance that collectively determine stream water temperature. Our high frequency measurements of stream temperatures over space and time along two elevational gradients in the Sierra Nevada mountains give insight into the effects of climate variability and change on water temperatures of snowmelt dominated upland streams. ‘Cumulative degree days' is an ecologically relevant metric that integrates the effects of differences in precipitation, snowmelt timing, and air temperature. We present our initial analyses of stream temperature data collected from two study sites in the Sierra Nevada: Sagehen Creek and the Kings River Experimental Watershed. These range in elevation from 1800-2600 m and represent a range of runoff regimes.
GC41A-0107
The Influence of Climate Change on Headwater Stream Discharge in the Southern Sierra Nevada (1957-2007)
The Sierra Nevada Mountains are of critical importance to water availability for the State of California. Historically, the winter snowpack has acted as a natural reservoir of fresh water throughout the winter months when a majority of the precipitation falls in the state. With the onset of spring snow melt, the water in the snowpack is released and made available to the remainder of California over the dry summer months. As a result of global climate change, warmer temperatures on the order of 2-5 °C are predicted for California over the next century. This will lead to diminished winter snow cover and the onset of an earlier release of the snowpack making significantly less water available during the summer period. We use the long-term historical discharge and precipitation records (1957-2007) from the Teakettle Experimental Forest (Teakettle) to evaluate whether the hydrological effects of climate change are already evident on small, headwater systems in the southern Sierra Nevada. Additionally, the long-term pattern from Teakettle is compared to the past five-year record from 10 recently instrumented headwater systems in the Kings River Experimental Watershed (KREW). Teakettle is an unmanaged old-growth forest while the other watersheds are actively managed. At an elevation of 2050 m to 2450 m, winter precipitation on Teakettle is snow dominated. However, winter rain events at this elevation do occur in the southern Sierra Nevada. The KREW watersheds, including Teakettle, extend across the rain-snow interface boundary (1485 m to 2500 m) where winter precipitation may fall as either rain or snow. This provides a good opportunity to observe whether the number of winter rain events on the Teakettle watershed is increasing and what role this may play in the distribution of annual runoff. The historical record also allows us to evaluate any potential changes in the timing of spring snow melt and the effects climate change may have on annual discharge totals.
GC41A-0108
Observing Seasonal and Diurnal Hydrometeorological Variability Within a Tropical Alpine Valley: Implications for Evapotranspiration
Conditions of glacier recession in the seasonally dry tropical Peruvian Andes motivate research to better constrain the hydrological balance in alpine valleys. There is an outstanding need to better understand the impact of the pronounced tropical hygric seasonality on energy and water budgets within pro-glacial valleys that channel glacier runoff to stream flow. This paper presents a novel embedded network installed in the glacierized Llanganuco valley of the Cordillera Blanca (9°S) comprising eight low-cost, discrete temperature and humidity microloggers ranging from 3470 to 4740 masl and an automatic weather station at 3850 masl. Data are aggregated into distinct dry and wet periods sampled from two full annual cycles (2004-2006) to explore patterns of diurnal and seasonal variability. The magnitude of diurnal solar radiation varies little within the valley between the dry and wet periods, while wet season near-surface air temperatures are cooler. Seasonally characteristic diurnal fluctuations in lapse rate partially regulate convection and humidity. Steep lapse rates during the wet season afternoon promote up-slope convection of warm, moist air and nocturnal rainfall events. Standardized grass reference evapotranspiration (ET0) was estimated using the FAO-56 algorithm of the United Nations Food and Agriculture Organization and compared with estimates of actual ET from the process-based BROOK90 model that incorporates more realistic vegetation parameters. Comparisons of composite diurnal cycles of ET for the wet and dry periods suggest about twice the daily ET0 during the dry period, attributed primarily to the 500% higher vapor pressure deficit and 20% higher daily total solar irradiance. Conversely, the near absence of rainfall during the dry season diminishes actual ET below that of the wet season by two orders of magnitude. Nearly cloud-free daylight conditions are critical for ET during the wet season. We found significant variability of ET with elevation up through the valley. Humidity and temperature measurements were analyzed to show significant effects of elevation and proximity to melt-water lakes on vapor pressure deficit.
GC41A-0109
An Investigation of the Impacts of Climate and Environmental Change on Alpine Lakes in the Uinta Mountains, Utah
Aquatic systems in alpine and sub-alpine areas of the western United States are potentially impacted by atmospheric pollution and climate change. Because these mountainous regions are an important water resource for the western United States, it is critical to monitor and protect these systems. The Uinta Mountains are an east- west trending mountain range located on the border between Utah, Wyoming and Colorado and downwind of the Wasatch Front, Utah, which is characterized by a rapidly expanding population, as well as mining and industry. This alpine area provides water to many areas in Utah, and contributes approximately nine percent of the water supply to the Upper Colorado River. Our research is focused on determining the impacts of climate change and pollution on alpine lakes in the Uinta Mountains. The results presented here are based on limnological measurements made at 64 Uinta Mountain lakes spanning a longitude gradient of one degree and an elevation gradient of 3000 feet. At each lake maximum depth, conductivity, salinity, pH, Secchi depth, temperature, alkalinity, and concentrations of major anions, cations and trace metals were measured. Principal Components Analysis (PCA) was performed to determine relationships between these variables and to examine the variability of the values of these variables. Our results indicate that steep climate gradients related to elevation and longitude result in clear differences in limnological properties of the study sites, with high elevation lakes characterized by greater amounts of nitrate and nitrite compared to low elevation sites. As well, diatoms in these lakes indicate that many high elevation sites are mesotrophic to eutrophic, which is unexpected for such remote aquatic ecosystems. We hypothesize that elevated nitrate and nitrite levels at high elevation sites are related to atmospherically derived nitrogen, but are being exacerbated relative to lower elevation sites by greater snow cover and reduced plant cover. Paleolimnological analyses of well dated sediments from selected lakes indicate that some of these high elevation sites have undergone rapid and dramatic change beginning in the late 1800s to early 1900s. Many of these lakes have become more productive as indicated by loss-on-ignition and diatom analyses. Although the exact mechanism of these changes is uncertain, the timing closely follows recent increases in air and chironomid-inferred surface water temperatures, and increased fossil fuel burning in the region. Regardless of the exact mechanism, our results clearly indicate dramatic changes at these high elevation sites, which threaten critical water resources.
GC41A-0110
Assessment of 21st Century Climate Change Projections in the Tropical Andes
The tropical Andes are one of the regions of the globe where climate change has been most evident. This is consistent with the notion that tropical high-elevation mountains extending into the mid-troposphere will be more affected by warming. One of the main impacts of this warming is the rapid retreat of glaciers; a process that could have severe consequences, affecting the availability of water for human consumption, irrigation, mining, and hydroelectric power production. This study presents some results related to the most important changes in climate that might be expected in the tropical Andes, at the end of the 21st century. Results are provided by the comparison of two Regional Climate Model (RCM) simulations based on the Hadley Center Regional Climate Modeling System, PRECIS. A medium-high CO2 emission scenario simulation for the period 2071-2100 (Intergovernmental Panel on Climate Change, IPCC-SRES scenario A2) is compared to a base-line mean climate state simulation for the 1961-1990 period. In addition, some results using a low-medium CO2 emission scenario (IPCC-SRES scenario B2) are also presented for comparison. Preliminary results show a generalized warming over the region with values reaching up to approximately 7° C in some places in the Andes in the A2 scenario. Precipitation presents a mixed pattern of increases and decreases across the region, and a decrease in relative humidity is expected for most of the highlands at the end of the century. Both scenarios (B2 and A2) show an increased warming of the free troposphere at higher altitudes (up to 200 hPa). The obtained results reveal that anthropogenic climate change, as predicted with the A2 scenario, may constitute a serious threat to the survival of tropical glaciers along the Andes Cordillera.
GC41A-0111
Alpine Treeline Changes in the Central Rocky Mountains: A Progress Report
Changes in the elevation, composition, and structure of alpine treeline can reflect climate variability and change, as well as patterns of disturbance which themselves may be mediated by climate variability. Information about past treelines may provide insight into the likely character of future changes. We have recently begun a new project to investigate changes in past treeline and determine the status of the current treeline in the central Rocky Mountains of Colorado, documenting the past and present treeline and their relationships to climate and fire using dendrochronological techniques. In summer 2007, we sampled three sites near Monarch Pass, Cottonwood Pass, and on Sheep Mountain, west of Fairplay, CO. The Monarch site shows evidence of a relict treeline of mixed Pinus flexilis and Pinus aristata above the current treeline, while the current treeline composition is predominantly Picea engelmannii. Dating, when completed, will reveal whether this relict treeline is evidence of a Medieval-era warm period in Colorado or an older period of warmth. At Sheep Mountain, remnant material above a stand of living Pinus flexilis and Pinus aristata trees of 800 years old or more was sampled. The remnant collections include samples with up to 700-1000 rings, and if they overlap in time with the living trees, will provide an extended chronology of climate variability, as well as information on the timing of tree establishment. At both of these sites, the presence of seedlings above the current tree line may be evidence of a rising treeline and warming temperatures, although this study may not be sufficient to confirm this. Evidence of fire at two of the three study sites may also shed light on the role of fire in shaping treeline in this region.
GC41A-0112
A biophysical gradient analysis of climate for understanding conifer establishment in mountain ecosystems of the western U.S.
Establishment of conifer trees at upper treeline is controlled by both physical and ecological phenomena. The physical limitations on tree establishment and growth as well as the ecological and edaphic factors moderating climate vary significantly across western mountain ranges, from the more maritime Cascades through the basin- and-range to the heavily continental central Rockies. In order to understand the factors limiting tree establishment and estimate rates of ecosystem change under future climate change, it is critical to understand the climatic factors limiting tree establishment. We use a multiscale approach to identify climatic patterns associated with upper treeline in nine mountain ranges: the north Cascades, central Cascades, Eagle Cap, Beaverhead, Teton, Beartooth, Wind River, Snowy, and Zirkel mountain ranges. We examined NCDC divisional, SNOTEL, snowcourse, and DAYMET seasonal averages/totals for temperature and precipitation variables to compare the climates at treeline sites identified for conifer establishment research. Divisional data from 1948-2004 indicate a strong geographical gradient in winter precipitation/PDO correlations, but according to SNOTEL data from all mountain ranges, these differences are much weaker in the more recent past. Snow water equivalent at all the sites near the PDO dipole evident in the 1948-2004 correlations appears negatively correlated with PDO. We present DAYMET, SNOTEL, and snowcourse normals for the mountain environments near the treeline sites and relate them to species composition and the nature of recent establishment.
GC41A-0113
Hydrological and Ecological Sensitivities to Climate Change for Four Western U.S. Mountain Ecosystems.
National Parks in Western U.S. mountain ecosystems are rapidly changing as a result of the direct and indirect effects of climate change. With warming temperatures, these systems are expected to experience earlier melt and reductions in snow accumulation. The impact of these changes on other hydrologic patterns, such as summer streamflow, and ecosystem structure and function maybe significant, but is likely to vary across the Western U.S. Park managers need quantitative estimates of these potential changes for development of long- term management strategies. A systematic approach can be used to define where and why these mountain ecosystems are affected by climate, focusing on net ecosystem exchange, net primary production, evapotranspiration, and streamflow trends. We used RHESSys, a spatially distributed, dynamic process model of water, carbon, and nitrogen fluxes, to examine the interplay between ecological and hydrological sensitivities to climate in four National Parks across the Western U.S., including watersheds in the North Cascades (WA), Glacier (MT), Rocky Mountain (CO), and Yosemite (CA) National Park. Analyses show while some systems are more hydrologically sensitive to climate variations, others are more ecologically sensitive. For example, with warm temperatures, the greatest reduction of summer streamflow is likely to occur in Glacier, while greatest sensitivities of vegetation responses, e.g. transpiration, net primary productivity, are predicted for the Cascades. Understanding the degree to which these watersheds are sensitive to climate variability and change will help to predict site specific vulnerabilities and allow park managers to tailor climate change management plans to individual locations.
GC41A-0114
Elevation and Temperature Effects on Carbon Balance Near Alpine-treeline: Comparison of a Treeline and Non-treeline Tree Species
Changes in carbon balance of trees may help explain temperature and range limits of conifers near alpine- treeline and the climate sensitivity of forest boundaries. Our objective was to determine which component of carbon balance most limit tree seedling growth at high elevation, and how growth processes vary in their response to temperature. We assessed relationships of temperature, carbon flux, and growth in whole seedlings of a treeline and non-treeline species (Abies lasiocarpa and Pseudotsuga menziesii, respectively) at two elevations near alpine-treeline in the Teton Range of Wyoming, USA. Seedlings were outplanted as they germinated in potting soil substrate in sites having sparse overhead canopy cover at 2450 m (high forest) and 3000 m (near treeline) elevations. Gas exchange and growth measurements were performed every 2-3 weeks when treeline was snow-free, in 2005 and 2006. Growth was less at the higher elevation in both species, and was associated with less needle area, root mass, and photosynthetic carbon assimilation (A) and respiratory efflux (R). However, R decreased more than A with cooling and at the higher elevation, causing an increase in A:R with elevation. The primary difference between species was greater growth, A, and R in the treeline species. Reductions in A per unit leaf area were expected at the higher elevation from previous studies, but were not observed. Notable differences in our experiment were the elimination of tree canopy (i.e. shading) differences that normally occur among elevations and are known to affect seedlings. Additionally, we did not detect any frost during our study periods, which resulted in part from local topography and snow pack patterns that distinguish the climate regime of the subject treeline. Moreover, microclimate measured beyond our study periods indicates that seedlings experience more frost at the lower compared to upper sites we evaluated, with the frosts typically occurring when the upper elevation site is snow-covered. The results of this study, along with consideration of differences in climate among treeline studies, have important implications for transferability of tree-climate information among treelines, and thus monitoring or predicting treeline change.
GC41A-0115
Climate Influence on Shifts in the Deep Canyon Ecocline, 1977 - 2007
The Deep Canyon Transect in the Santa Rosa Mountains of Southern California spans 2560 m in elevation and four major plant communities: desert scrub, Sonoran pinyon-juniper woodland, montane chaparral, and mixed conifer forest. The plant species distributions of the Deep Canyon Transect were compared from 1977 to 2007 and the causes of change were examined. We hypothesized plant species distributions to move upwards in elevation in response to climate warming and increasing climate variability. In 1977, Jan Zabriskie surveyed plant species coverage along a 400 m isocontour every 122 m in elevation along the transect. Following Zabriskie, I resurveyed these sites in 2006 -– 2007 and compared species coverage. The set of the ten most widespread species spans all elevations, plant communities, and functional types of Deep Canyon. The mean elevation increase for these ten species is 64.7 m, within a two-tailed 95% CI of 30.9 –- 98.5 m. From 1977 -– 2006, the Deep Canyon Transect experienced a significant increase in mean annual temperature of 0.5 –- 0.8° C. Variability in annual precipitation has also doubled over that time. Climate warming and increasing climate variability has been the primary driver of upward plant species shifts in Deep Canyon.
GC41A-0116
A dynamic species modeling approach to assess climate change impacts on California tree species
Global climate change during the 21st century is anticipated to have consequences on potential niche viability for woody plant species. Previous research on modeling bioclimatic envelopes has allowed us to predict where to find species assemblages under future climate scenarios and hence predict loss or gain of specific habitats. However, species may not identically respond to climate change. This could result in species disassembling and disagreement between predicted potential niches and realized niches. Therefore, it is critical to examine potential niche shifts at the species level. We used a spatially explicit demographic model to predict shifts in tree species of the northern Sierra Nevada mountains in the context of competition with neighboring plant functional types as well as disturbance (i.e. fire) under various climate change scenarios. Additionally, we incorporated a dispersal model to account for intermediary dispersal strategies. In particular, we were interested in modeling Pinus species found in the "checkerboard" region of the northern Sierra Nevada. These populations are of novel interest due to their disparate management strategies (private vs. public landownership). Our findings have important implications for the assessment of the impact of climate change on these high elevation Montane species.
GC41A-0117
Providing more informative projections of climate change impact on plant distribution in a mountain environment
Due to their conic shape and the reduction of area with increasing elevation, mountain ecosystems were early identified as potentially very sensitive to global warming. Moreover, mountain systems may experience unprecedented rates of warming during the next century, two or three times higher than that records of the 20th century. In this context, species distribution models (SDM) have become important tools for rapid assessment of the impact of accelerated land use and climate change on the distribution plant species. In this study, we developed and tested new predictor variables for species distribution models (SDM), specific to current and future geographic projections of plant species in a mountain system, using the Western Swiss Alps as model region. Since meso- and micro-topography are relevant to explain geographic patterns of plant species in mountain environments, we assessed the effect of scale on predictor variables and geographic projections of SDM. We also developed a methodological framework of space-for-time evaluation to test the robustness of SDM when projected in a future changing climate. Finally, we used a cellular automaton to run dynamic simulations of plant migration under climate change in a mountain landscape, including realistic distance of seed dispersal. Results of future projections for the 21st century were also discussed in perspective of vegetation changes monitored during the 20th century. Overall, we showed in this study that, based on the most severe A1 climate change scenario and realistic dispersal simulations of plant dispersal, species extinctions in the Western Swiss Alps could affect nearly one third (28.5%) of the 284 species modeled by 2100. With the less severe B1 scenario, only 4.6% of species are predicted to become extinct. However, even with B1, 54% (153 species) may still loose more than 80% of their initial surface. Results of monitoring of past vegetation changes suggested that plant species can react quickly to the warmer conditions as far as competition is low However, in subalpine grasslands, competition of already present species is probably important and limit establishment of newly arrived species. Results from future simulations also showed that heavy extinctions of alpine plants may start already in 2040, but the latest in 2080. Our study also highlighted the importance of fine scale and regional assessments of climate change impact on mountain vegetation, using more direct predictor variables. Indeed, predictions at the continental scale may fail to predict local refugees or local extinctions, as well as loss of connectivity between local populations. On the other hand, migrations of low-elevation species to higher altitude may be difficult to predict at the local scale.
GC41A-0118
Alpine Meadows Vegetation Monitoring
East Shield (3658 m) and Barcroft Gate (3697 m) Meadows in the White Mountains of California on the Inyo National Forest were selected for a pilot study to provide quantitative descriptions of vegetation associations as a baseline for monitoring vegetation change over time. The study is part of the Global Observation Research Initiative in Alpine Environments Project (GLORIA) hosted by the University of California White Mountain Research Station. Separating the effect of climate change from anthropogenic disturbance is an integral step towards quantifying vegetation change in alpine meadows under current scenarios of future increases in global temperature and atmospheric carbon dioxide. In this study we compare the vegetation of East Shield Meadow, which is undisturbed, and Barcroft Gate Meadow, which is disturbed. Both are sedge-rush-grass wet meadows which are sustained by surface water in the form of streams and springs. The objective is to monitor fluctuations in vegetation, especially changes in species diversity and composition over five year time increments, along with tracking annual variations in precipitation. A comprehensive plant list was compiled and the dense vegetation of each meadow was sampled with a point intercept method along north-south and east-west randomly placed transects. The occurrence of all species at predetermined one-meter interval sample points along the transect were recorded, and percent occurrence was calculated. Twenty seven species of plants in Barcroft Gate Meadow and twenty four in East Shield Meadow were recorded, and sixteen species in Barcroft Gate Meadow and eight in East Shield Meadow were sampled. The 2007 IPCC report estimates that a doubling of atmospheric CO2 will increase global temperature within a possible range from 2.0 °C to 4.5 °C, with a best estimate of 3.0 °C. Assuming that the present general lapse rate of -6.32 °C per kilometer for the White Mountains will persist, a 3.0 °C increase may result in an equivalent elevation of about +475 m. Plots of elevation ranges of recorded species indicate that it is not likely that the projected temperature increase will affect the present distribution of the meadow plants. Species composition may change to an unknown degree, however, due to the possible increase in the abundance of those plants now at their upper elevation range limits in the meadows and to the upslope migration of plants whose upper ranges are now at lower elevations. Uncertainties in this projection include the behavior of meadow plants, adequate sampling of their species ranges, and future distribution of precipitation. Monitoring will reduce the uncertainties and confirm or correct the expected consequences of temperature change.
GC41A-0119
Global Research Initiative in Alpine Environments: A New GLORIA Site in Southwestern Montana
Global climate change is expected to have pronounced effects on the alpine environments and thus the alpine plants of western North America. Predicted responses include an upward migration of treelines, altered species compositions, changes in the percentage of land covered by vegetation, and a change in the phenology of alpine plants. To determine the effects of climate change on the alpine flora of southwestern Montana, we are installing a GLORIA (Global Research Initiative in Alpine Environments) site in order to monitor temperature, species composition, and percent cover of vascular plants, lichens, and mosses along an ascending altitudinal gradient. We are including lichens and mosses because of their importance as ecological indicator species. The abundance and spatial distribution of lichens and mosses provides essential baseline data for long-term monitoring of local and global impacts on the environment. Mt. Fleecer (9250 ft.), which is west of the continental divide and semi-isolated from other peaks in the Anaconda-Pintlar Range, is currently the most likely location for the southwestern Montana GLORIA site. Mt. Fleecer is accessible because it does not have the steep and hazardous glaciated talus cirques that characterize many of the neighboring, higher peaks. However, if an accessible and suitable higher summit is found, then it will be included as the highest summit in the GLORIA site. Interesting species at Mt. Fleecer include the whitebark pine, Pinus albicaulis, which is a keystone species in high mountain ecosystems of the western United States and Canada, the green gentian, Frasera speciosa, and the shooting star, Dodecatheon pulchellum. Data from this site will become part of a global network of GLORIA sites with which we will assess changes in alpine flora. Information gained from this GLORIA site can also be used as a link between studies of alpine climate change and related investigations on the timing of snowmelt and its influence on riparian ecosystems in western Montana.
GC41A-0120
Alpine Plant Monitoring for Global Climate Change; Analysis of the Four California GLORIA Target Regions
The Global Observation Research Initiative in Alpine Environments (GLORIA) is an international research project with the goal to assess climate-change impacts on vegetation in alpine environments worldwide. Standardized protocols direct selection of each node in the network, called a Target Region (TR), which consists of a set of four geographically proximal mountain summits at elevations extending from treeline to the nival zone. For each summit, GLORIA specifies a rigorous mapping and sampling design for data collection, with re-measurement intervals of five years. Whereas TRs have been installed in six continents, prior to 2004 none was completed in North America. In cooperation with the Consortium for Integrated Climate Research in Western Mountains (CIRMOUNT), California Native Plant Society, and the White Mountain Research Station, four TRs have been installed in California: two in the Sierra Nevada and two in the White Mountains. We present comparative results from analyses of baseline data across these four TRs. The number of species occurring in the northern Sierra (Tahoe) TR was 35 (16 not found in other TRs); in the central Sierra (Dunderberg) TR 65 species were found. In the White Mountains, 54 species were found on the granitic/volcanic soils TR and 46 (19 not found in other TRs) on the dolomitic soils TR. In all, we observed 83 species in the Sierra Nevada range TRs and 75 in the White Mountain TRs. Using a mixed model ANOVA of percent cover from summit-area-sections and quadrat data, we found primary differences to be among mountain ranges. Major soil differences (dolomite versus non-dolomite) also contribute to floristic differentiation. Aspect did not seem to contribute significantly to diversity either among or within target regions. Summit floras in each target region comprised groups of two distinct types of species: those with notably broad elevational ranges and those with narrow elevational ranges. The former we propose to be species that retain importance in vegetation structure across elevation and the latter to be more sensitive to climate change. In general, we find common species in the Sierra Nevada to be rare in the White Mountains, that the northern Sierra Nevada TR (Tahoe area) to be distinct in many vegetation features, and that distinct substrate differences in the White Mountains delineate significant species diversities. With four target regions, we document patterns of species composition, distribution, and diversity with respect to elevation, aspect, and geographic distance. This provides new information about summit floras in the White Mountains and Sierra Nevada, and documents baseline conditions against which we will measure response to climate change.