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Few simulations of typical Tibetan Plateau glacier response to climate warming have been made, despite the glaciers' importance as water supplies in an arid region. Here we apply a three-dimensional thermomechanically coupled full-Stokes ice dynamics model to simulate the evolution of Qingtang No. 1 Glacier, a representative glacier in the central Tibetan Plateau. A degree-day model along with snow temperature and precipitation estimates based on nearby observations are used to estimate surface mass balance (SMB) over the past three decades. The resulting SMB gradients and equilibrium-line altitude (ELA) sensitivity to air temperature are used to parameterize the SMB in the future. We use the ice-flow model to simulate glacier evolution from 2013 to 2050. Simulated within-glacier temperatures and present-day glacier terminus retreat rates are in reasonable agreement with previous observations. Forcing the glacier model with the historical warming trend of 0.035 °C a-1 and a warming projection from the high-resolution regional climate model (RegCM3) under the A1B scenario for the period 2013–2050 leads to substantial retreat and ice loss, and large increases (110%–155%) in annual water runoff. Losses of 11%–18% in area and 19%–30% in volume are predicted over the next four decades, with the warmer RegCM3 scenario giving larger rates of loss. Sensitivity of glacier change to the parameters in SMB profiles are also assessed.
We examine a firn core from a dome in southeast Greenland that exhibits distinct firn densification. The ice was -20.9 °C at 20 m depth, and the core gives an average accumulation rate of 1.0 m w.e. yr-1 in water equivalent. However, the close-off density of 830 kg m-3 occurs at 83.4–86.8 m depth, which is about 20-m shallower than that obtained from two empirical models. Where the density ρ > 750 kg m-3, the densification appears faster than that from the empirical models. As a result, compared to the empirical coefficient, the actual compactive viscosity coefficient is nonlinear and decreases at ρ > 750 kg m-3, indicating that the firn with a higher density is softer than that from the empirical result. We argue here that the high accumulation rate creates a high overburden pressure in a short time. Thus, the relative softness of the firn may arise from (1) there being not enough time to form bonds between grains as strong as those in a lower accumulation-rate area, and similarly, (2) the dislocation density in the firn being relatively high.
We tested the main hypothesis that nutrient accumulation during late stages of postglacial succession would decrease nutrient limitation of diazotrophic activity. We tested this hypothesis by adding carbon (C), phosphorus (P), and molybdenum (Mo) independently or in combination, and nitrogen (N) only to symbiotic, epiphylls on bryophytes, and free-living diazotrophs in three stages of glacier foreland succession in Cordillera Darwin (55°S), southern South America. Experiments were run in spring 2013 and 2014 and in autumn 2015. Diazotrophic activity (DA) was assessed by the acetylene reduction assay. Results showed no effect of C, P, or Mo added either singly or in combination in the spring incubations. During autumn, DA was enhanced by adding a mix of C, P, and Mo to the symbiotic N2-fixing Gunnera magellanica from young successional sites, while in the late successional sites, adding C and Mo alone to the diverse bryophyte carpet on the forest floor enhanced DA. Nitrogen added as ammonium sulfate had a strong negative effect on N2 fixation by free-living diazotrophs in the spring and autumn samples from the late successional site, in the bryophyte carpet from the early successional site (autumn), and in Pseudocyphellaria freycinetii of the midsuccessional site (spring). As in other high-latitude biomes, symbiotic and epiphyllous associations and free-living diazotrophs play a crucial role in the incorporation of new N to postglacial subantarctic forest ecosystems, especially in recently exposed substrates that are strongly limited by nutrient availability in soils. The increasing rates of glacier melting in southern South America is exposing new substrates to microbial colonization, including diazotrophic bacteria. In this environment, largely free of reactive N from atmospheric sources, new ecosystems are rapidly developing on deglaciated surfaces, provided that key elements such as Mo and P and C are present in the substrates.
For the Sami people, place names provide the basis for the transmission of a cultural landscape, through an oral way of mapping built around narratives and the designation of specific landmarks. Based on interviews with members of a mountain-based reindeer herding community in Sweden, we found that their transmission is today ensured through continued oral tradition but also by the increasing use of maps. However, because they follow the western cartographic tradition, official maps are unable to express the continual renewal of Sami place names and the land features that are meaningful to the Sami, and thus fail to convey toponymic knowledge. Inscribing place names on maps transforms them into mere labels: toponymic knowledge has to be transmitted along with its context of emergence, situated at the crossroads of cognitive, perceptive, emotional, and social dimensions. There is an urgent need to conceive new forms of cartography that can guarantee the transmission of toponymic knowledge to future generations, maintaining the relationship that binds the Sami to their environment.
In arid and semiarid ecosystems, subterranean herbivorous rodents play an important role in determining the composition, function, and structure of plant communities. We hypothesized that in a high-altitude cold desert in the southern Puna region of Argentina, Ctenomys mendocinus (mendocino tuco-tuco), a subterranean herbivorous rodent, may increase dominance of the shrub Artemisia mendozana (sagebrush). We performed an observational study to assess factors affecting the abundance and fitness of A. mendozana in southern Puna, on sites co-inhabited and undisturbed by C. mendocinus. Density, biomass, plant height, number of fruits per plant, number of seeds, and seed size of A. mendozana were higher in mendocino tuco-tuco—disturbed areas.
Because the abundance and reproductive ability of sagebrush increase in areas inhabited by mendocino tuco-tucos, C. mendocinus may function as an ecosystem engineer in southern Puna. We suggest further manipulative experimental studies be conducted to clarify the role of this subterranean rodent in this ecosystem.
Mani walls, Buddhist sacred walls constructed of carved blocks, are common in Langtang Valley, Nepal Himalaya. Fieldwork in 2009–2015 documented all 80 mani walls, including all occurrences of the lichen Rhizocarpon geographicum. According to local informants, the mani walls were constructed 400–600 years ago, and the original mani wall was in the village of Ghoratabela. Based on the indirect method, the oldest lichen on a mani wall dated only to 1942, which, within modeling error, was concurrent with the 1934 earthquake, the last major earthquake in Nepal prior to the Gorkha earthquake of 25 April 2015. In November 2015 it was found that 15% of mani walls could not be located and 20% were severely damaged. The original mani wall had apparently been reconstructed 170 m from its previous location. In two severely damaged and three fully intact mani walls, large lichens (12–49 mm) with unhealthy appearance were found that were not previously present. The most likely explanation was that the three intact mani walls had already been reconstructed using previously interior blocks as exterior blocks. This research raises the possibility that many Himalayan religious structures are not the original structures, but are replicates that are reconstructed after natural disasters.
This study uses a three-dimensional groundwater flow model to investigate groundwater dynamics and groundwater—surface water (GW-SW) interactions considering the effects of permafrost distribution for the Tanana Flats Basin in interior Alaska. The Parameter ESTimation (PEST) code is used to calibrate the model with observed stream discharge data. A 36-year MODLFOW-USG regional simulation shows the following. (1) Permafrost impedes groundwater movement in all directions and through taliks provides a major pathway to connect the groundwater and surface water systems. More than 80% of the vertical groundwater flow occurs within the permafrost-free zones. (2) Permafrost holds a significant amount of water that cannot be easily released through groundwater movements; however, water above the permafrost table has much higher renewal rates than deep groundwater. (3) Groundwater upwelling supports the base flow for the Tanana River and its tributaries throughout the year and feeds water to the wetland ecosystems at the Tanana Flats through unfrozen zones. Stream leakage is also highly correlated with stream discharge. Our study suggests that cold regional hydrological cycle studies should consider the effects of permafrost distribution under future warming conditions. This study provides a robust three-dimensional hydrological modeling tool that can be applied for the regions underlain with either continuous or discontinuous permafrost.
Whitebark pine (Pinus albicaulis), an endangered keystone alpine tree species, faces multiple threats across its western North American range. Little is known of whitebark pine in the southern Coast Mountains of British Columbia relative to well-studied Rocky Mountain populations, especially with regard to the effects of climate on annual radial growth. Our results indicate centenarian whitebark pine annual radial growth is negatively influenced by the onset of snowfall in the prior autumn. This unusual growth limitation likely stems from the truncation of the prior year growing season and reduced physiological preparedness for growth in the following year. Autumn snowfall is moderated by temperature and the Pacific Decadal Oscillation (PDO), which controls largescale weather patterns in the study region. Our results are distinct from studies of mature whitebark pine trees in continental populations where growth is typically limited by summer temperature, or occasionally by winter snowfall due to a reliance on snow meltwater during spring/summer. We suggest that predicted warmer and wetter climate and reduced snowpacks in the southern Coast Mountains may benefit the growth of the young population of maritime whitebark pine over the next few decades.
We compile new and previously published lichenometric and cosmogenic 10Be moraine ages to summarize the timing of Holocene glacier expansions in the Brooks Range, Arctic Alaska. Foundational lichenometric studies suggested that glaciers likely grew to their Holocene maxima as early as the middle Holocene, followed by several episodes of moraine building prior to, and throughout, the last millennium. Previously published 10Be ages on Holocene moraine boulders from the north-central Brooks Range constrain the culmination of maximum Holocene glacier advances between 4.6 ka and 2.6 ka. New 10Be ages of moraine boulders from two different valleys in the central Brooks Range published here show that maximum Holocene glacial extents in these valleys were reached by 3.5 ka and ca. 2.6 ka, supporting previous studies showing that Holocene maximum, or near-maximum, glacial extents in the Brooks Range occurred prior to the Little Ice Age. However, in-depth reconciliations between glacier extent and local and regional climate are hampered by uncertainties associated with both lichenometry and 10Be dating.
Glacier coverage and behavior are heterogeneous across Tien Shan and Pamir due to a climate gradient from west to east. Regional glacier mass balance data have previously been calculated using GRACE and hydrological models with differing results. In this study, in situ mass balance data of glaciers in the Tien Shan and Pamir, measured by the glaciological method between 2004 and 2012, are spatially extrapolated to the total glacier area by arithmetic averaging using (1) unfiltered balance data, and (2) a smoothing filter to the data in a way similar to that done for GRACE data. GRACE and the in situ data are the only methods that measure mass variations directly. A comparison of the extrapolated unfiltered and filtered in situ data is made with the difference between GRACE and the total water storage of the hydrological model Water Global Assessment and Prognosis Global Hydrology Model that represents glacier mass balance. The annual comparison between the extrapolated in situ and GRACE-related data does not fit very well, but the comparison of mass change rates shows quite good agreement. In comparison with GRACE-related results from the literature, the extrapolation of the unfiltered in situ glacier mass data performs best, especially in the Tien Shan.
Surge-type glaciers have been observed in several mountain ranges of the world. Though Karakoram and Pamir are the hot spots for the occurrence of surge-type glaciers in High Mountain Asia, few surge-type glaciers also exist in Tien Shan. These have not been studied or reported in detail in the recent literature. We have identified 39 surge-type glaciers and five tributary surges in Tien Shan either from available literature or by visual interpretation using available images from the period 1960 until 2014. Out of the 39 glaciers, 9 are confirmed as surge-type, 13 are very probably surge-type, and the remaining are possibly of surge-type. Most of the surge-type glaciers are located in Ak-Shiirak and Central Tien Shan. Compared with the normal glaciers of Tien Shan, the surge-type glaciers are larger, cover higher ranges of elevations, and have shallower slopes. There is no significant difference in aspect. The largest surge events were observed in Central Tien Shan: North Inylchek Glacier (years 1996/1997) and Samoilowich Glacier (years 1992 until 2006) advanced several kilometers. The surge cycle was around 50 years for both of these glaciers. The advance was less pronounced for all other surge-type glaciers during the period ca. 1960–2014. Some of the tributary glaciers behaved differently than the main glaciers in the sense that they continuously advanced during the entire period of our study, whereas the main glaciers have remained stable or retreated.
Air and ground temperature data collected at Canadian Forces Station Alert, Nunavut, Canada, have been analyzed to investigate the potential role that air temperature inversions play in influencing the spatial variation of permafrost thermal conditions in coastal areas of the High Arctic. Frequent, persistent air temperature inversions have been documented using a series of weather stations deployed along an elevation gradient inland from the coast. During inversion periods, which may last several days, air temperatures in valley bottoms can be up to 10 °C lower than adjacent stations located at elevations 47 to 130 m higher. The occurrence of air temperature inversions during the winter combined with thin snow cover suggest a mechanism explaining the observation of lower winter ground-surface temperatures and colder permafrost conditions in valley bottoms compared to higher elevations.