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Rock glaciers are common landforms in many alpine permaforst landscapes that play an important role in alpine hydrology and landscape evolution, principally through the release of seasonal meltwater and the downslope transport of coarse material. Here, we use satellite-based interferometric synthetic aperture radar (InSAR) to identify and monitor rock glaciers in the Western USA. We focus on the movement of active and transitional rock glaciers in Utah (Uinta, Wasatch, and La Sal Mountains), and Wyoming (Wind River Mountains) between 2015 and 2022. Using the new framework established by the International Permafrost Association (IPA) Action Group, we identified 255 active and transitional rock glaciers in the ~3500 km2 Uinta Mountains, 45 rock glaciers in the ~200 km2 La Sal Mountains, 55 rock glaciers in the ~135 km2 Wasatch Mountains, and 120 rock glaciers in the ~3000 km2 Wind River Mountains. These rock glaciers currently occur under different climatic regimes based on data from the 30 year (1991-2020) normal Parameter-elevation Relationships on Independent Slopes Model (PRISM). The La Sals and Wasatch are warmer and wetter with a mean annual air temperature (MAAT) of ~3.0± 1.9 ˚C and 2.7 ± 1.1 ˚C and a mean annual precipitation (MAP) of ~92 ± 13 cm and ~130 ± 17 cm, respectively, whereas the Uintas and Wind Rivers are cooler and drier with a MAAT of ~0.24 ± 1.4 ˚C and -0.87 ± 1.4 ˚C and a MAP of ~87 ± 11 cm and ~81 ± 10 cm. The mean line-of-sight (LOS) velocities for individual rock glaciers range from ~1 to 10 cm/yr. We also examined the time-dependent relationship between the motion of the rock glaciers and local climatic drivers such as temperature and precipitation. We found that rock glaciers exhibit seasonal and annual velocity changes, likely driven by liquid water availability (from snowmelt and rainfall), with accelerated motion during summers and during wetter years. Our findings demonstrate the ability to use satellite InSAR to monitor rock glaciers over large areas and provide insight into the environmental factors that control their kinematics.

Water draining from rock glaciers in the Uinta Mountains of Utah (USA) was analyzed and compared with samples of groundwater and water from the primary stream in a representative 5000 ha drainage. Rock glacier water resembles snowmelt in the early summer but evolves to higher values of d-excess and greatly elevated Ca and Mg content as the melt season progresses. This pattern is consistent with models describing a transition from snowmelt to melting of seasonal ice to melting of perennial ice in the rock glacier interior in late summer and fall. Water derived from this internal ice appears to have been the source of ∼25 % of the streamflow in this study area during September of 2021. This result emphasizes the significant role that rock glaciers can play in the hydrology of high-elevation watersheds, particularly in summers following a winter with below-average snowpack.

Rock glaciers are a prominent component of many alpine landscapes and constitute a significant water resource in some arid mountain environments. Here, we employ satellite-based interferometric synthetic aperture radar (InSAR) between 2016 and 2019 to identify and monitor active and transitional rock glaciers in the Uinta Mountains (Utah, USA), an area of ∼3000 km2. We used mean velocity maps to generate an inventory for the Uinta Mountains containing 205 active and transitional rock glaciers. These rock glaciers are 11.9 ha in area on average and located at a mean elevation of 3308 m, where mean annual air temperature is −0.25 ∘C. The mean downslope velocity for the inventory is 1.94 cm yr−1, but individual rock glaciers have velocities ranging from 0.35 to 6.04 cm yr−1. To search for relationships with climatic drivers, we investigated the time-dependent motion of three rock glaciers. We found that rock glacier motion has a significant seasonal component, with rates that are more than 5 times faster during the late summer compared to the rest of the year. Rock glacier velocities also appear to be correlated with the snow water equivalent of the previous winter's snowpack. Our results demonstrate the ability to use satellite InSAR to monitor rock glaciers over large areas and provide insight into the environmental factors that control their kinematics.

Water draining from rock glaciers in the Uinta Mountains of Utah (USA) was analyzed and compared with samples of ground water and water from the master stream in a representative 5000-ha drainage. Rock glacier water resembles snowmelt in the early summer, but transitions to higher values of d-excess and greatly elevated Ca and Mg content as the melt season progresses. This pattern is consistent with models describing a transition from snowmelt, to melting of seasonal ice, to melting of perennial ice in the rock glacier interior in late summer and fall. Water derived from this internal ice appears to have been the source of ~25 % of the streamflow in this study area during September of 2021. This result emphasizes the significant role that rock glaciers can play in the hydrology of high-elevation watersheds, particularly in summers following a winter with below average snowpack.

Sedimentary records were analyzed from three lakes in the Ruby Mountains and East Humboldt Range of northeastern Nevada. Lakes are rare in the arid Great Basin, and these represent the highest-elevation lacustrine records from this region. The three cores cover overlapping time intervals: One, from a lake located just beyond a moraine, is interpreted to represent the Last Glacial Maximum, extending back to 26 cal ka; another extends to deglaciation ca. 14 cal ka; and the third extends to deposition of the Mazama ash, ca. 7.7 cal ka. Multiproxy analysis focused on measurements of bulk density, organic matter content, C:N ratio, biogenic silica abundance, and grain-size distribution. Depth-age models were developed using optically stimulated luminescence (OSL) dating, along with accelerator mass spectrometry (AMS) 14C dating of terrestrial macrofossils (wood and conifer needles), charcoal, and pollen concentrates (for deep sediment in one lake). Collectively, the three lakes record a series of discrete intervals spanning an unusually long stretch of time. These include the local Last Glacial Maximum (26.0–18.5 cal ka), local deglaciation (18.5–13.8 cal ka), the onset of biologic productivity (13.8–11.3 cal ka), early Holocene aridity (11.3–7.8 cal ka), deposition and reworking of the Mazama ash (7.8–5.5 cal ka), a neopluvial interval (5.5–3.8 cal ka), a variable late Holocene climate (3.8–0.25 cal ka), and a latest Holocene productivity spike (250 yr B.P. to the present) that may be anthropogenic. Data from all three lakes are presented, and the collective record of climate and environmental change for the Ruby Mountains and East Humboldt Range is compared with other paleorecords from the Great Basin.

Mineral dust was collected with a network of passive samplers in the Uinta Mountains (Utah, USA) over a 10-year period to evaluate the relation between regional drought and dust deposition. A total of 72 samples from eight collectors were analyzed for flux, grain size distribution, mineralogy, geochemistry, and their Sr and Nd isotopic fingerprint. The dust is primarily very fine silt, with an average median grain size of 11.6 μm. The clay minerals illite and kaolinite are common in the dust, along with quartz, potassium feldspar, and plagioclase. The most abundant elements (after Si) are AlFeKCaMgTi. The trace elements Cd, Sn, Sb, Zn, Cu, As, and Pb are present at abundances greatly in excess of normal levels in upper crustal rocks. Dust fluxes average 14.4 mg/m

The deposition of aeolian dust has profound effects on biogeochemical cycling, soil development, and hydrology in alpine ecosystems. In the western United States, it has been proposed that much of the dust reaching the Rocky Mountains is derived from arid regions located to the west-southwest. Because these areas are vulnerable to drought-related changes in vegetation, grazing impacts, mining, off-road vehicle travel, urban development, and other factors that affect the availability of fine-grained sediment for wind deflation, it is imperative that source areas for this dust be better constrained to guide future management decisions. Here we collect modern dust in the Uinta Mountains (Utah) and compare its 87Sr/86Sr and 143Nd/144Nd “fingerprint” with surficial sediments in possible source areas. Our results confirm that this dust is exotic to the Uinta Mountains, and demonstrate its similarity to numerous dune fields in western Utah, as well as surficial sediments in parts of the Colorado Plateau, southern Basin and Range, and the Mojave Desert. The seasonal sampling we employed also reveals that considerable dust is deposited during the shorter alpine summer. Recognition that specific areas in the southwestern US are sources of dust to the Rocky Mountains, particularly during summer months, should be considered in future land management planning.

Twenty-one sediment cores were obtained from 20 lakes in the Uinta Mountains, Utah, USA. Depth-age models were developed using 14C dating, and sediments were analyzed for loss-on-ignition (LOI), carbon-nitrogen ratio (C:N), and grain size distribution. Although some of these cores have been considered individually in previous studies, here the entire set of cores is evaluated collectively to identify consistent patterns, commonalities, and trends in the post-glacial interval. All lakes accumulated substantially greater amounts of submicron-size clastic material before ca. 9.5 ka BP. This pattern is interpreted as a signal of prolonged landscape instability following deglaciation. Values of LOI and C:N exhibit a strong, positive correlation in nearly all lakes, indicating that organic matter accumulation is controlled by the influx of terrestrial material. In the six lakes exhibiting the strongest correlation, and featuring the most robust inflowing streams, median grain size and the abundance of sand increased between 10 and 6 ka BP, simultaneous with increases in LOI and C:N. This correspondence is interpreted as evidence for frequent high-intensity storms during the early Holocene, likely driven by enhanced monsoonal circulation. The early parts of five of the records contain a sharp increase in LOI. Lakes exhibiting this pattern are typically smaller and shallower, and are located in less rugged watersheds. Finally, all six cores from the western Uinta Mountains contain evidence for an environmental perturbation ca. 4.5 ka BP. Although the nature of this event is unclear, these lakes accumulated notably finer-grained sediment with less organic matter at this time. This analysis illuminates the post-glacial history of this strategically located mountain range, and underscores the value inherent in analyzing cores from multiple lakes when reconstructing paleoclimatic history.

Winter Wonderland Cave contains perennial ice associated with two types of cryogenic cave carbonate (CCC) formed during the freezing of water. CCCfine is characterized by relatively high δ13C values, whereas CCCcoarse exhibits notably low δ18O values indicating precipitation under (semi)closed-system conditions in a pool of residual water beneath an ice lid. Previous work has concluded that CCCcoarse forms during permafrost thaw, making the presence of this precipitate a valuable indicator of past cryospheric change. Available geochronologic evidence indicates that CCC formation in this cave is a Late Holocene or contemporary process, and field observations suggest that the cave thermal regime recently changed in a manner that permits the ingress of liquid water. This is the first documented occurence of CCCcoarse in the Western Hemisphere and one of only a few locations where these minerals have been found in association with ice. Winter Wonderland Cave is a natural laboratory for studying CCC genesis.

The DUST^2 project is a new Critical Zone Thematic Cluster funded by the US National Science Foundation. DUST^2, an abbreviation for Dust across a Desert-Urban-Summit Transect, will study the modern dust system in southwestern North America, from source to sink using a combination of methods. Previous work has demonstrated that arid lands in the southwestern US are significant sources of mineral dust. The amount of dust emitted increased notably following European settlement, and climate models predict future increases in dust emission in response to climate warming. This dust is transported to the north and east by the wind, particularly during the springtime and coincident with the passage of strong frontal systems. The properties of this natural dust are altered as it mixes with anthropogenic aerosols sourced from industry and other activities along the densely populated Wasatch Front in northern Utah. Eventually, this dust is delivered to mountain ranges at the eastern border of the Basin and Range as well as in the Rocky Mountains. There, dust impacts the albedo of snowpack, triggering changes in snowmelt timing and magnitude. Dust also influences the developmental trajectories of mountain soils and alters the nutrient status of mountain ecosystems. The six primary investigators of the DUST^2 project, along with an array of additional staff and students, will study this dust system with field and lab-based methods focused on dust emitting landscapes, dust transport modeling, dust collection in urban and mountain settings, snow monitoring and snowmelt modeling, and investigation of dust-influenced soils coupled with analysis and modeling of the cycling of dust-derived nutrients. A major goal of this project is to incorporate researchers beyond those responsible for establishing the overall project framework. Anyone interested in learning about ways to collaborate or become involved with the DUST^2 effort should contact a member of the project leadership team listed as authors on this abstract.

The concept of “Vineyard Geological Identity” (VGI) was introduced (Ferretti, 2019: Catena) in recognition of the role of geologic setting in contributing to fertility, hydrology, and other important aspects of vineyard soils. This study applied the VGI concept to two vineyards in the Champlain Valley of Vermont, USA where a burgeoning wine-making industry has been catalyzed by the development of French-American hybrid grape variety capable of surviving cold winters and bringing fruit to ripeness in relatively cool summers. The vineyards studied here, “LP” and “SV”, both produce the hybrid grape known as “Marquette”, are at a similar elevation (~100 m), have a similar macroclimate (MAT ~7 °C, MAP ~ 850 mm, ~1400 GDD), and were inundated by proglacial Lake Vermont during deglaciation (~15,000 years ago). Notable differences between the sites are the lithology of the underlying bedrock (Ordovician carbonate at LP, and Cambrian quartzite at SV), and the fact that the SV site was located at the edge of a marine embayment at the Pleistocene/Holocene transition after Lake Vermont drained. The hypothesis tested was the prediction that despite their broadly similar physical settings and geologic histories, the VGI of the two vineyards would vary as a result of differences in their underlying bedrock and the soil parent materials at these settings. Samples were collected at depths of 25, 50, 75, and 100 cm from 10 locations within the Marquette block at in each vineyard. All samples were evaluated for grain size distribution (with the hydrometer method and a laser scattering analyzer), thermogravimetric analysis (from 25 to 1000 °C), pH, nutrient status, base saturation, and cation exchange capacity. The deepest samples were also analyzed for mineralogy (with XRD) and major element chemistry (with XRF). Results confirm the tested hypothesis. Most base cations are significantly more abundant in the samples from the LP site (reflecting the underlying carbonate bedrock), and the LP site is significantly finer grained (reflecting its former deepwater location in Lake Vermont). Conversely, at the SV vineyard Na is significantly more abundant and samples are significantly coarser, consistent with the former location of this site in the nearshore zone of a marine embayment. In future work these results could be used as a physical foundation for evaluating the possible role of terroir in controlling aspects of the flavors expressed in Marquette wines from these two vineyards.

This research has been supported by the Directorate for Geosciences of the National Science Foundation (grant nos. AGS-1602105 and AGS-1903548)., We thank the USGS John Wesley Powell Center for Analysis and Synthesis, which hosted a meeting that led to this synthesis effort. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US government. We thank the original data generators who made their data available for reuse, and we acknowledge the data repositories for safeguarding these assets., Holocene climate reconstructions are useful for understanding the diverse features and spatial heterogeneity of past and future climate change. Here we present a database of western North American Holocene paleoclimate records. The database gathers paleoclimate time series from 184 terrestrial and marine sites, including 381 individual proxy records. The records span at least 4000 of the last 12 000 years (median duration of 10 725 years) and have been screened for resolution, chronologic control, and climate sensitivity. Records were included that reflect temperature, hydroclimate, or circulation features. The database is shared in the machine readable Linked Paleo Data (LiPD) format and includes geochronologic data for generating site-level time-uncertain ensembles. This publicly accessible and curated collection of proxy paleoclimate records will have wide research applications, including, for example, investigations of the primary features of oceanatmospheric circulation along the eastern margin of the North Pacific and the latitudinal response of climate to orbital changes. The database is available for download at https://doi.org/10.6084/m9.figshare.12863843.v1 (Routson and McKay, 2020)., National Science Foundation (NSF) AGS-1602105 AGS-1903548

Winter Wonderland Cave contains perennial ice associated with two types of cryogenic cave carbonate (CCC) formed during the freezing of water. CCCfine is characterized by relatively enriched δ13C values, whereas CCCcoarse exhibits notably depleted δ18O values indicating precipitation under (semi)closed-system conditions in a pool of residual water beneath an ice lid. Previous work has concluded that CCCcoarse forms during permafrost thaw, making the presence of this precipitate a valuable indicator of past cryospheric change. Available geochronologic evidence indicates that CCC formation in this cave is a Late Holocene or contemporary process, and field observations suggest that the cave thermal regime recently changed in a manner that permits the ingress of liquid water. This is the first documented occurence of CCCcoarse in the Western Hemisphere and one of only a few locations where these minerals have been found in association with ice. Winter Wonderland Cave is a natural laboratory for studying CCC genesis.

Rock glaciers are a prominent component of many alpine landscapes and constitute a significant water resource in some arid mountain environments. Here, we employ satellite-based interferometric synthetic aperture radar (InSAR) to identify and monitor active rock glaciers in the Uinta Mountains (Utah, USA), an area of ~10,000 km2. We used mean velocity maps to generate an inventory for the Uinta Mountains containing 255 active rock glaciers. Active rock glaciers are 10.8 ha in area on average, and located at a mean elevation of 3290 m, where mean annual air temperature is 0.12 °C. The mean line-of-sight (LOS) velocity for the inventory is 2.52 cm/yr, but individual rock glaciers have LOS velocities ranging from 0.88 to 5.26 cm/yr. To search for relationships with climatic drivers, we investigate the time-dependent motion of three rock glaciers over the summers of 2016–2019. Time series analysis suggests that rock glacier motion has a significant seasonal component, with motion that is more than 5 times faster during the late summer compared to rest of the year. Rock glacier velocities also appear to be correlated with the snow-water equivalent of the previous winter's snowpack. These results demonstrate the ability to use satellite InSAR to monitor rock glaciers over large areas and provide insight into the environmental factors that control their kinematics.

Winter Wonderland Cave is a solution cave at an elevation of 3140 m above sea level in Carboniferous-age Madison Limestone on the southern slope of the Uinta Mountains (Utah, USA). Temperature data loggers reveal that the mean annual air temperature (MAAT) in the main part of the cave is −0.8 ∘C, whereas the entrance chamber has a MAAT of −2.3 ∘C. In contrast, the MAAT outside the cave entrance was +2.8 ∘C between August 2016 and August 2018. Temperatures in excess of 0 ∘C were not recorded inside the cave during that 2-year interval. About half of the accessible cave, which has a mapped length of 245 m, is floored by perennial ice. Field and laboratory investigations were conducted to determine the age and origin of this ice and its possible paleoclimate significance. Ground-penetrating-radar (GPR) surveys with a 400 MHz antenna reveal that the ice has a maximum thickness of ∼ 3 m. Samples of rodent droppings obtained from an intermediate depth within the ice yielded radiocarbon ages from 40±30 to 285±12 years. These results correspond with median calibrated ages from CE 1560 to 1830, suggesting that at least some of the ice accumulated during the Little Ice Age. Samples collected from a ∼ 2 m high exposure of layered ice were analyzed for stable isotopes and glaciochemistry. Most values of δ18O and δD plot subparallel to the global meteoric waterline with a slope of 7.5 and an intercept of 0.03 ‰. Values from some individual layers depart from the local waterline, suggesting that they formed during closed-system freezing. In general, values of both δ18O and δD are lowest in the deepest ice and highest at the top. This trend is interpreted as a shift in the relative abundance of winter and summer precipitation over time. Calcium has the highest average abundance of cations detectable in the ice (mean of 6050 ppb), followed by Al (2270 ppb), Mg (830 ppb), and K (690 ppb). Most elements are more abundant in the younger ice, possibly reflecting reduced rates of infiltration that prolonged water–rock contact in the epikarst. Abundances of Al and Ni likely reflect eolian dust incorporated in the ice. Liquid water appeared in the cave in August 2018 and August 2019, apparently for the first time in many years. This could be a sign of a recent change in the cave environment.

Rock glaciers are perennially frozen bodies of ice and rock debris that move downslope primarily due to deformation of internal ice. These features play an important role in alpine hydrology and landscape evolution, and constitute a significant water resource in arid regions. In the Uinta Mountains, Utah, nearly 400 rock glaciers have been identified on the basis of morphology, but the presence of ice has been investigated in only two. Here, I use satellite-based interferometric synthetic-aperture radar (InSAR) from the Copernicus Sentinel-1 satellites to identify and monitor active rock glaciers over a 10,000 km2 area. I also compare the time-dependent motion of several individual rock glaciers over the summers of 2016-2019 to search for relationships with climatic drivers such as precipitation and temperature. Sentinel-1 data from the August-October of 2016-2019 are used to create 79 interferograms of the entire Uinta range and are processed with the NASA/JPL/Stanford InSAR Scientific Computing Environment (ISCE) software package. Temporal baselines of intrayear interferograms range from 6-72 days. We use average velocity maps to generate an active rock glacier inventory for the Uinta Mountains containing 196 active rock glaciers. Average rock glacier velocity is 3 cm/yr in the line-of-sight direction, but individual rock glaciers have velocities ranging from 0.3-15 cm/yr. Rock glacier speeds do have a seasonal component, and were fastest in August across all years. One rock glacier reached a speed of 40 cm/yr over a 12 day interval from August 5 to August 17 of 2017. Preliminary results suggest that active rock glaciers are found at altitudes 10 m higher on average than inactive and relic rock glaciers identified in the previous inventory. Rock glacier movement did not accelerate between 2016 and 2019, suggesting that rock glaciers in this part of the Rocky Mountains are not speeding up over time. Our results highlight the ability to use satellite InSAR to monitor rock glaciers over large areas and provide insight into the factors that control their kinematics.

During the last Pleistocene glaciation, dozens of mountain ranges in the Great Basin of the western United States were glaciated and numerous valleys were occupied by pluvial lakes. This unique setting provides an opportunity to reconstruct regional-scale climate change during the last glacial-interglacial transition based on a well-documented record of lacustrine deposits and moraines. Chronologies of water-level changes in pluvial lakes throughout the Great Basin have been developed through decades of effort chiefly involving radiocarbon dating of fossil material recovered from paleoshorelines and sediment cores. Glacial chronologies have been developed more recently through cosmogenic nuclide exposure dating of glacial features in mountains of the northern Great Basin. Here, we resolve the relative timing of mountain glacial maxima and pluvial lake highstands based on an analysis of these chronologies. The moraine record displays evidence of two intervals of near-maximum glacier length, one represented by terminal moraines with cosmogenic nuclide exposure ages 22-19 ka, and another represented by downvalley recessional moraines with exposure ages 18-16 ka. The earlier maximum corresponds to the latter part of the global Last Glacial Maximum, during which lake highstands occurred in the southern Great Basin, whereas many lakes in the northern Great Basin were below their highstand levels. The climate in the northern Great Basin during this interval was apparently cold enough to drive glaciers to their maximum extents but too dry for the expansion of lakes, in contrast to the southern Great Basin where conditions were wetter. The latter glacial maximum was synchronous with lake highstands across much of the Great Basin and to the early part of Heinrich Stadial 1, which featured persistent cooling and shifting precipitation patterns in western North America. Most lake highstands occurred at this time, although some lakes in the extreme northwestern Great Basin reached highstands somewhat later. Widespread lake highstands during the interval 18-16 ka combined with near-maximum glacier lengths suggests a cool and wet climate favoring both glacial and lacustrine maxima, despite rising atmospheric greenhouse gases and summer insolation. Nearly all downvalley moraines in the Great Basin were abandoned by 16 ka, whereas many lakes persisted until 15 ka or later. This pattern suggests a climatic shift at ca. 16 ka to conditions favoring lakes but not glaciers. By the time of the last lake highstands, glaciers had diminished greatly in length and were generally confined to cirques.

The contemporary aeolian system is poorly understood due in part to a scarcity of direct measurements of modern dust deposition. The Uinta Mountains of Northeastern Utah, USA are well-suited to the study of contemporary dust owing to their gently sloping, soil-mantled alpine zones and relatively inert, quartzite-dominated bedrock. Capitalizing on this unique setting, eight marble dust traps, as well as one active dust collector, have been installed throughout the mountain range. Previous study of samples from these collectors has supported the quantification of mineral dust inputs to alpine pedogenesis and identified isotopic fingerprints that link dust to potential source regions. This project focuses on dust emptied from these samplers in Fall 2019, representing two years of continuous dust accumulation. The mean dust flux for these years is 4.1 g/m2/y, which corresponds to historic flux measurements ranging from 2.7 g/m2/y to 4.4 g/m2/y. The relatively large dust mass of these multi-year samples allows for samples from each collector to be split into a coarse and fine fraction prior to further analysis. Before separation, the median grain size of 2019 dust samples is approximately 10 µm. After sample separation, carried out through timed settling following Stoke’s Law, the approximate median particle diameter is 6 µm for the fine fraction, and 20 µm for the coarse fraction. Coarse Uinta dust is more enriched in quartz and feldspar relative to fine dust, which is dominated by clay minerals. The coarse material is therefore more mineralogically similar to local bedrock, supporting the theory that larger particles are endogenous in origin. Clay minerals are less abundant in local bedrock, suggesting that fine mineral dust may have an exogenous source. Analysis of trace and major elemental abundances, as well as Sr and Nd isotopic fingerprinting will support additional interpretations about the nature and origin of modern dust in the Uintas. These results will contribute to ongoing efforts to better understand how specific dust source regions influence the properties of mineral aerosols arriving in remote alpine environments.

Winter Wonderland is an ice cave in the Uinta Mountains of northern Utah, USA. The cave, which has an entrance at 3140 m a.s.l., extends 245 m into a north facing cliff of Mississippi Madison Limestone. The cave was discovered by the U.S. Forest Service in 2014. Winter Wonderland Ice Cave likely originated in the Late Mississippian to Early Pennsylvanian when joints opened up in the vadose zone. The interior of the cave is perennially below freezing with ice covering sections of the floor to a thickness of at least 2 m. Seasonally, meltwater from the epikarst enters the cave, pools on the surface of the older ice and freezes, creating a layered ice mass containing organic matter dating back several centuries. As this water freezes, cryogenic cave carbonates (CCCs) precipitate and are incorporated in the ice. In this study, ice, water, and mineral precipitates in the cave were investigated for the presence of microorganisms adapted to this extreme environment. Samples were collected to investigate the microbial communities that may be present within the Winter Wonderland ice cave, identify what they are, and investigate whether the composition of the microbial community changes spatially within the cave and between sample types. An intact block of ice (18x10x10 cm), liquid water samples (n=8), and 13 CCC samples were collected in August 2019. The ice block was removed from a vertical exposure of ice at the back of the cave using a hand saw, water was collected from a pool on the ice surface, and the CCCs were sampled from the surface of the ice in multiple sections of the cave. The water samples were analyzed for stable isotope composition to better understand water source and freezing history. Crystallographic study of oriented slides cut from the ice revealed that the ice crystallized vertically with some variation in crystal size. All samples were also investigated with fluorescence microscopy, flow cytometry, and DNA sequencing to reveal the abundance and type of microorganisms. Preliminary fluorescence microscopy and SEM imaging reveals the presence of cocci and bacilli type microorganisms within water samples and ~10um wide eukaryotic organisms within the CCCs, suggesting that the CCCs may provide much needed nutrients for the microbes or that the CCCs themselves are products of biomineralization.

Time-lapse photography was employed to monitor a snowbank at 3640 m above sea level in the Uinta Mountains, Utah, USA. The snowbank forms against a 35-m high, east-facing escarpment and is nourished by wind redistribution of snow from an alpine plateau. The snowbank is capped by a large cornice, and its central core persists through the summer in most years. An automated, solar-powered digital camera was deployed between October 2016 and June 2017, and programmed to capture 5 photographs each day between 8:00 and 16:00, local time. Although cold temperatures affected the batteries during the winter, a total of 812 photographs were collected, for an overall average of 3.4 per day. These images were combined in an animation displaying the growth of the snowbank and associated cornice over the course of the winter. The debris fields resulting from nineteen cornice fall avalanches were noted in the sequence of photographs. Data collected at a nearby automated weather station reveal that 12 avalanches (between early December and early April) were preceded by significant increases in snow depth, snow water equivalent, and precipitation, with sustained windspeeds above the winter average. In contrast, six of the last seven events (between late April and early June) occurred in the absence of new snowfall, but were associated with rapid rises in temperature and notable decreases in snow water equivalent. The average interval between recorded avalanches is 10 days, with a maximum of 29 days and a minimum of 2 h. Recurrence intervals were shorter in December/January, in late March/early April, and in late April/early May. Only one avalanche occurred in the 56 days between 27 January and 24 March. Time-lapse photography is a powerful tool for monitoring nival processes.

Holocene loss-on-ignition (LOI) records were developed for radiocarbon-dated sediment cores from 20 lakes in the Uinta Mountains of northeastern Utah, USA. The hydrogeomorphic setting of each lake was characterized, permitting an analysis of connections between LOI values and lake setting. Median LOI values exhibit a significant negative correlation with lake elevation, with the range of elevations and the maximum slope of the watershed, with the extent of ice/snow and exposed rock in the watershed, and with the volume of through-flowing water. In contrast, LOI is positively correlated with the extent of forest cover and wetlands in the watershed. In addition, forward stepwise linear modeling demonstrates that lake area/lake depth ratio is a significant negative predictor for median LOI, that shoreline complexity is a significant positive predictor for maximum LOI, and the standard deviation of LOI values is greater in lakes surrounded by watersheds with more wetlands and surface water. Some LOI time series contain excursions at finer temporal scales that are recorded synchronously in adjacent lakes, however many excursions appear in only a single record. Similarly, step changes in LOI that are clear in some records are not preserved in the sediments of nearby lakes. Over longer timescales, some LOI records are essentially constant during the Holocene. In contrast, some lakes record steadily rising LOI values, and approximately half of the lakes have complicated LOI records with millennial-scale variability. Lakes with large surface area, large area/depth ratios, large watershed area/lake area ratios, rugged watersheds, and extensive ice/snow cover are more likely to record steady LOI values over time. The degree to which LOI records from neighboring lakes vary emphasizes that lacustrine proxy records reflect a strong filtering effect, whereby the signal of an external forcing is recorded to varying degrees depending on the nature of the lake and surrounding watershed.

Mapping at a scale of 1:5000 identified 395 rock glaciers in the Uinta Mountains, Utah. The majority of these have areas1 year, suggests that at least some of these landforms contain buried ice. Late summer water discharge from two rock glaciers exhibits higher pH and significantly elevated concentrations of some ions compared with lake water, consistent with ablation of internal ice after melting of winter snowpack is complete. Although the amount of water discharging from individual rock glaciers may be small, the aggregate discharge from all rock glaciers and talus could constitute a significant component of streamflow in late summer and fall.

This project investigated the origin of clay minerals in regolith present above quartzite bedrock in the alpine zone of the Uinta Mountains, Utah, USA. Geochemical and mineralogical analysis indicates that these clays formed through chemical weathering of two allochthonous parent materials. Smectite-rich clays, with Mg abundance distinctly higher than modern dust or local bedrock, formed through weathering of andesitic ash layers that were deposited during the Oligocene from eruptive centers in the Basin and Range. In contrast, various stages of interstratified kaolinite-illite–smectite clays have formed through weathering of mica and feldspar delivered by eolian processes that continue today. Local bedrock appears to have played only a minor role as a parent material for clay neoformation. These results demonstrate that pedogenic clay can be common even in cold climate soils and regolith overlying weathering resistant bedrock. They also emphasize that the clay inventory in soil and regolith can reflect processes that operated before modern climatic conditions were established, and reinforce the key role played by exogenous mineral inputs in the functioning of the alpine critical zone.

Dunes adjacent to the Snow Water Lake playa in Elko County of northeastern Nevada rise up to ~10 m above the playa surface in seven distinct clusters. The dunes are composed of tan silty loam containing calcite, quartz, plagioclase, and dioctahedral clay. Abundances of trace elements, along with relative proportions of quartz and calcite, are distinct between dunes along the north and south sides of the playa, reflecting proximity to streams draining different lithologies in the neighboring mountains. Luminescence (optically stimulated luminescence and infrared-stimulated luminescence) dating of dune crest samples demonstrates that the last episode of dune accumulation occurred in the mid-eighteenth century. Moisture-sensitive tree ring records from a nearby site indicate that dune accumulation coincided with an interval of below-average precipitation immediately following a very wet decade. This sequence is consistent with models requiring wetter climatic conditions to move coarse sediment onto a playa surface, followed by dune building under drier conditions. Younger luminescence ages from a sand-dominated unit exposed in an arroyo cut through the dunes may reflect a wetter, more erosive climatic regime ca. AD 1800. The Snow Water Lake dunes are currently eroding, signaling a reduction in the amount of sediment reaching the playa.

Twenty lake sediment cores extracted upstream from Last Glacial Maximum terminal moraines constrain the timing of the glacial-interglacial transition in the Uinta Mountains, Utah (USA). The stratigraphy observed in the cores, and accelerator mass spectrometry 14 C dating of inorganic silty clay beneath gyttja, temporally constrain local deglaciation. The majority of basal ages fall within the Bolling-Allerod interval, with strong overlap at ca. 12.7 cal. (calibrated) kyr B.P. This convergence matches regional evidence of rising temperatures, increasing aridity, falling pluvial lake levels, and glacial retreat near the end of the last glacial-interglacial transition. Normalized estimates of glacier terminus retreat and elevation rise in the Uinta Mountains and elsewhere in the Rocky Mountains derived from consideration of cosmogenic ages on terminal moraines consistently average ∼10%/k.y. between ca. 20 and 13 ka, implying a regionally uniform climate forcing during deglaciation. Minor variations between these rates likely reflect hypsometric effects during deglaciation. Seven lakes dammed by cirque-floor moraines have basal ages within, or slightly younger than, the Younger Dryas interval, suggesting advances of favorably located cirque glaciers before the glacial-interglacial transition was complete.

Recent research suggests that organic matter sequestered in lake sediment comprises a larger component of the global carbon cycle than once thought, yet little is known about carbon storage in mountain lakes. Here, we used a set of sediment cores collected from lakes in the Uinta Mountains (Utah, USA) to inform a series of calculations and extrapolations leading to estimates of carbon accumulation rates and total lacustrine carbon storage in this mountain range. Holocene rates of carbon accumulation in Uinta lakes are between 0.1 and 20.5 g/m2/yr, with an average of 5.4 g/m2/yr. These rates are similar to those reported for lakes in Greenland and Finland and are substantially lower than estimates for lakes in Alberta and Minnesota. The carbon content of modern sediments of seven lakes is notably elevated above long-term Holocene values, suggesting recent changes in productivity. The lakes of the Uintas have accumulated from 6 to 10×105 Mt of carbon over the Holocene. This is roughly equivalent to the annual carbon emissions from Salt Lake City, Utah. Based on their long-term Holocene rates, lakes in the Uintas annually sequester an amount of carbon equivalent to the emissions of

Profiles of alpine soils in the Uinta Mountains (Utah, USA) were investigated to determine how long-term dust deposition has influenced soil properties in this environment. Field studies were focused on four above-treeline sites, all of which were apparently beyond the reach of erosive glacial ice during the Pleistocene. Modern dust, soil A and B horizons, and local bedrock were compared in terms of major and trace element geochemistry, along with Sr and Nd isotope compositions. In all cases, soil samples are a mixture of dust and local bedrock end members, with A horizons more closely resembling dust, and B horizons more similar to bedrock. Calculations estimate that these soil profiles contain ~50 to 80% dust, which is effectively mixed downward into the solum by cryoturbation. Because these landscape positions were not glaciated, the total amount of dust contained within soil profiles is large relative to sites at lower elevation within the glacial limit. In addition to altering physical properties of these soil profiles, including horizonation and texture, deposition of dust rich in base cations positively influences soil fertility.

Surface exposure dating with terrestrial cosmogenic nuclides (TCNs) has become the primary method for determining numerical ages of Pleistocene mountain glacial deposits and landforms in the conterminous western United States (U.S.) and in numerous other glaciated settings worldwide. Recent updates to models of TCN production and scaling warrant a reconsideration of published exposure ages of moraines of the last two Pleistocene glaciations and associated paleoclimate inferences. Previously reported TCN exposure ages of moraines are recalculated here using newer production rates and scaling models for nuclides helium-3 (3He), beryllium-10 (10Be), aluminum-26 (26Al), and chlorine-36 (36Cl), in most cases yielding significant differences from originally reported ages. Recalculated TCN exposure ages of moraines of the penultimate glaciation display a high degree of variability for individual landforms, particularly toward the younger end of age distributions, suggesting that exposure history is affected by moraine denudation and that older age modes provide the best estimate of the depositional age of these moraines. Oldest exposure ages of penultimate glaciation moraines are well-aligned among mountain ranges across the western U.S. and yield a mean of 138 ± 13 ka, indicating that mountain glaciation occurred in step with global ice volume maxima during marine oxygen isotope stage 6. On average, terminal moraines of the last glaciation date to 19.5 ± 2.3 ka and correspond to the latter part of the global Last Glacial Maximum (LGM). Down-valley recessional moraines representing prolonged glacial stabilizations or readvances to ≥75% of maximum lengths have a mean exposure age of 17.0 ± 1.8 ka, suggesting that these moraine positions were last occupied during Heinrich Stadial 1. Evidence for multiple glacial culminations during the last glaciation is found in several mountain ranges and likely reflects at least two phases of Late Pleistocene climate: an earlier phase when glaciers attained their maximum length in response to cooling during the LGM, and a later phase when glaciers persisted at or readvanced to near-maximum lengths in response to sustained cold temperatures and/or increased precipitation.

We applied luminescence dating to a suite of shorelines constructed by pluvial Lake Clover in northeastern Nevada, USA during the last glacial cycle. At its maximum extent, the lake covered 740 km2 with a mean depth of 16 m and a water volume of 13 km3. In the north-central sector of the lake basin, 10 obvious beach ridges extend from the highstand to the lowest shoreline over a horizontal distance of ~1.5 km, representing a lake area decrease of 35%. These ridges are primarily composed of sandy gravel and rise ~1.0 m above the alluvial fan surface on which they are superposed. Single grain luminescence dating of K-feldspar using the pIRIR SAR (post-infrared infrared single-aliquot regenerative dose) protocol, corroborated by SAR dating of quartz, indicates that the highstand shoreline was constructed ca. 16&ndash, 17 ka during Heinrich Stadial I (Greenland Stadial 2, GS-2), matching 14C age control for this shoreline elsewhere in the basin. The lake regressed rapidly during the B&oslash, lling/Aller&oslash, d (GI-1), before the rate of regression slowed during the Younger Dryas interval (GS-1). The lowest shoreline was constructed ca. 10 ka. Persistence of Lake Clover into the early Holocene may reflect enhanced monsoonal precipitation driven by the summer insolation maximum.

Atmospheric deposition to urban areas and mountain snowpack often contains a mixture of playa dust and anthropogenic aerosols, yet the relative contribution of trace elements from each source is not well understood. To evaluate dust contributions from regional playas to an urban area, we sampled playa dust sources, urban dust deposition, and snow dust deposition across the Wasatch Front in northern Utah, USA. Dust samples were analyzed for trace and major element chemistry, grain size distribution, and mineralogy. Playa, urban, and snow dust samples contained similar mineralogy, dominated by silicate, carbonate, and evaporite minerals. Grain size distribution between playa, urban, and snow dust samples was also similar, suggesting that playas are a primary dust source for the region. Principal component analysis and enrichment diagrams revealed similar chemistry of playa, urban, and snow dust with some exceptions. Compared with playa dust, urban and snow dust had lower concentrations of Li, Na, Sr, U, Mg, and Ca and higher concentrations of Fe, Al, Be, Sb, Se, Mo, Cr, La, and Cu. The first set of elements are found in evaporite- and carbonate-minerals while the second set of elements are sourced from anthropogenic activities. Mass balance calculations suggest that 90% of the dust mass deposited to the Wasatch Front is from playas, with small additions from local sources that alter the dust chemistry. Sequential leaching of dust samples showed that some elements were readily leached with weak acids, including B, K, Na, Sr, Ca, U, Mo, Cd, and Se, suggesting that they are environmentally available and may serve as important macronutrients or contaminants to ecosystems. This is the first study to directly compare the geochemistry of playa dust sources with dust deposition to urban areas and mountain snowpack in the western US, with implications for understanding how water diversions, land use changes, and population growth may affect the regional dust cycle in the future.

Previous work has explored the contribution of bedrock weathering to soil formation in alpine environments of the northeastern United States. In contrast, the role of surficial sediments as a parent material has received little attention. This study investigated the development of alpine soils in relation to surficial sediments and bedrock in part of the Presidential Range of the White Mountains, New Hampshire, U.S.A. Published mapping of the study area indicates that five contrasting bedrock units are thinly mantled by glacial sediment, providing the opportunity to evaluate the relative importance of these two potential soil parent materials. Samples collected from 25 pedons were analyzed for a variety of physical, chemical, and mineralogical properties. Soil profiles have distinct Oa, A, Bw, and BC horizons. X-ray diffraction analysis reveals the presence of chlorite in soils above all bedrock formations, despite the absence of this mineral in several bedrock types. Trace element concentrations...

Field and laboratory investigations were conducted to determine the origin of a ubiquitous layer of silt that caps soil profiles in the alpine zone of the Uinta Mountains, Utah, USA. Fine sediment isolated from snowbanks was studied to constrain the fraction of this material derived from allochthonous eolian additions. Lake sediments representing deposition over the past few centuries were analyzed to determine whether dust deposition in the Uintas has been a long-term process, and if properties of the modern dust differ from dust which accumulated prior to European settlement. Results indicate that alpine soils have been strongly influenced by long-term eolian deposition. The loess cap in these soil profiles averages 18 cm thick, and physical and chemical properties of soil horizons derived from the eolian parent material are significantly different than those of the subsurface horizons derived from in situ produced congelifractate. Fine sediment observed at the surface of snowbanks in the early summer is a mixture of silty exotic eolian material and sandy locally derived sediment. Snowbanks on ridgecrests and on slopes of blocky scree tend to accumulate the maximum amount of exotic dust with the minimum amount of local material. The grain-size distribution, mineralogy, and geochemistry of lake sediments indicate that dust has been accumulating in the Uintas for at least the last few centuries. Modern lake sediments are significantly enriched in elements indicative of upwind mining and agricultural activity, recording an anthropogenic change in dust composition following settlement of the surrounding lowland basins.