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1. The impacts of warming on rapidly retreating high-altitude, low-latitude glaciers and ice core-derived climate records

   https://doi.org/https://doi.org/10.1016/j.gloplacha.2021.103538  

   Thompson, L. G. ; Davis, M. E. ; Mosley-Thompson, E. ; Porter, S. E. ; Corrales, G. V. ; Shuman, C. A. ; Tucker, C. J. ( January 2021 , Global and planetary change)

   null (Ed.)

   Alpine glaciers in the low- and mid-latitudes respond more quickly than large polar ice sheets to changes in temperature, precipitation, cloudiness, humidity, and radiation. Many high-altitude glaciers are monitored by ground observations, aerial photography, and satellite-borne sensors. Regardless of latitude and elevation, nearly all nonpolar glaciers and ice caps are undergoing mass loss, which compromises the records of past climate preserved within them. Almost without exception, the retreat of these ice fields is persistent, and a very important driver is the recent warming of the tropical troposphere and oceans. Here we present data on the decrease in the surface area of four glaciers from low- to mid-latitude mountainous regions: the Andes of Peru and northern Bolivia, equatorial east Africa, equatorial Papua, Indonesia, and the western Tibetan Plateau. Climate records based on oxygen isotopic ratios (δ18O) measured in ice cores drilled from several glaciers in these regions reveal that the records from elevations below ~6000 m above sea level have been substantially modified by seasonal melting and the movement of meltwater through porous upper firn layers. Fortunately, δ18O records recovered from higher altitude sites still contain well-preserved seasonal variations to the surface; however, the projected increase in the rate of atmospheric warming implies that climate records from higher elevation glaciers will eventually also be degraded. A long-term ice core collection program on the Quelccaya ice cap in Peru, Earth’s largest tropical ice cap, illustrates that the deterioration of its climate record is concomitant with the increase in mid-troposphere temperatures. The melting ice and resulting growth of proglacial lakes presents an imminent hazard to nearby communities. The accelerating melting of glaciers, if sustained, ensures the eventual loss of unique and irreplaceable climate histories, as well as profound economic, agricultural, and cultural impacts on local communities. 

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2. Monitoring tropical debris-covered glacier dynamics from high-resolution unmanned aerial vehicle photogrammetry, Cordillera Blanca, Peru

   https://doi.org/10.5194/tc-11-2463-2017  

   Wigmore, Oliver ; Mark, Bryan ( January 2017 , The Cryosphere)

   The glaciers of the Cordillera Blanca, Peru, are rapidly retreating and thinning as a result of climate change, altering the timing, quantity and quality of water available to downstream users. Furthermore, increases in the number and size of proglacial lakes associated with these melting glaciers is increasing potential exposure to glacier lake outburst floods (GLOFs). Understanding how these glaciers are changing and their connection to proglacial lake systems is thus of critical importance. Most satellite data are too coarse for studying small mountain glaciers and are often affected by cloud cover, while traditional airborne photogrammetry and lidar are costly. Recent developments have made unmanned aerial vehicles (UAVs) a viable and potentially transformative method for studying glacier change at high spatial resolution, on demand and at relatively low cost.
   
   Using a custom designed hexacopter built for high-altitude (4000–6000 m a. s. l. ) operation, we completed repeat aerial surveys (2014 and 2015) of the debris-covered Llaca Glacier tongue and proglacial lake system. High-resolution orthomosaics (5 cm) and digital elevation models (DEMs) (10 cm) were produced and their accuracy assessed. Analysis of these datasets reveals highly heterogeneous patterns of glacier change. The most rapid areas of ice loss were associated with exposed ice cliffs and meltwater ponds on the glacier surface. Considerable subsidence and low surface velocities were also measured on the sediments within the pro-glacial lake, indicating the presence of extensive regions of buried ice and continued connection to the glacier tongue. Only limited horizontal retreat of the glacier tongue was observed, indicating that measurements of changes in aerial extent alone are inadequate for monitoring changes in glacier ice quantity. 

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3. Disappearance of the last tropical glaciers in the Western Pacific Warm Pool (Papua, Indonesia) appears imminent

   https://doi.org/10.1073/pnas.1822037116  

   Permana, Donaldi S. ; Thompson, Lonnie G. ; Mosley-Thompson, Ellen ; Davis, Mary E. ; Lin, Ping-Nan ; Nicolas, Julien P. ; Bolzan, John F. ; Bird, Broxton W. ; Mikhalenko, Vladimir N. ; Gabrielli, Paolo ; et al ( December 2019 , Proceedings of the National Academy of Sciences)

   The glaciers near Puncak Jaya in Papua, Indonesia, the highest peak between the Himalayas and the Andes, are the last remaining tropical glaciers in the West Pacific Warm Pool (WPWP). Here, we report the recent, rapid retreat of the glaciers near Puncak Jaya by quantifying the loss of ice coverage and reduction of ice thickness over the last 8 y. Photographs and measurements of a 30-m accumulation stake anchored to bedrock on the summit of one of these glaciers document a rapid pace in the loss of ice cover and a ∼5.4-fold increase in the thinning rate, which was augmented by the strong 2015–2016 El Niño. At the current rate of ice loss, these glaciers will likely disappear within the next decade. To further understand the mechanisms driving the observed retreat of these glaciers, 2 ∼32-m-long ice cores to bedrock recovered in mid-2010 are used to reconstruct the tropical Pacific climate variability over approximately the past half-century on a quasi-interannual timescale. The ice core oxygen isotopic ratios show a significant positive linear trend since 1964 CE (0.018 ± 0.008‰ per year;P< 0.03) and also suggest that the glaciers’ retreat is augmented by El Niño–Southern Oscillation processes, such as convection and warming of the atmosphere and sea surface. These Papua glaciers provide the only tropical records of ice core-derived climate variability for the WPWP.

    

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4. Climate-warming-driven changes in the cryosphere and their impact on groundwater–surface-water interactions in the Heihe River basin

   https://doi.org/10.5194/hess-27-2763-2023  

   Triplett, Amanda ; Condon, Laura E. ( January 2023 , Hydrology and Earth System Sciences)

   Abstract. The Heihe River basin in northwest China depends heavilyon both anthropogenic and natural storage (e.g., surface reservoirs, rivers andgroundwater) to support economic and environmental functions. The QilianMountain cryosphere in the upper basin is integral to recharging thesestorage supplies. It is well established that climate warming is drivingmajor shifts in high-elevation water storage through loss of glaciers andpermafrost. However, the impacts on groundwater–surface-water interactionsand water supply in corresponding lower reaches are less clear. We built anintegrated hydrologic model of the middle basin, where most water usageoccurs, in order to explore the hydrologic response to the changingcryosphere. We simulate the watershed response to loss of glaciers (glacier scenario),advanced permafrost degradation (permafrost scenario), both of these changes simultaneously (combined scenario) andprojected temperature increases in the middle basin (warming scenario) by alteringstreamflow inputs to the model to represent cryosphere-melting processes, aswell as by increasing the temperature of the climate forcing data. Netlosses to groundwater storage in the glacier scenario and net gains in the permafrost and combined scenarios showthe potential of groundwater exchanges to mediate streamflow shifts. Theresult of the combined scenario also shows that permafrost degradation has more of animpact on the system than glacial loss. Seasonal differences ingroundwater–surface-water partitioning are also evident. The glacier scenario hasthe highest fraction of groundwater in terms of streamflow in early spring. Thepermafrost and combined scenarios meanwhile have the highest fraction of streamflowinfiltration in late spring and summer. The warming scenario raises the temperatureof the combined scenario by 2 ∘C. This results in net groundwater storageloss, a reversal from the combined scenario. Large seasonal changes inevapotranspiration and stream network connectivity relative to the combined scenario show thepotential for warming to overpower changes resulting from streamflow. Ourresults demonstrate the importance of understanding the entire system ofgroundwater–surface-water exchanges to assess water resources underchanging climatic conditions. Ultimately, this analysis can be used toexamine the cascading impact of climate change in the cryosphere on theresilience of water resources in arid basins downstream of mountain rangesglobally. 

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5. A Carboniferous apex for the late Paleozoic icehouse

   https://doi.org/10.1144/sp535-2022-256  

   Griffis, N. ; Mundil, R. ; Montañez, I. ; Le Heron, D. ; Dietrich, P. ; Iannuzzi, R. ( October 2022 , Geological Society, London, Special Publications)

   Icehouse climate systems occur across an abbreviated portion of Earth history, constitutingc.25% of the Phanerozoic record. The Late Paleozoic Ice Age (LPIA) was the most extreme and longest lasting glaciation of the Phanerozoic and is characterized by periods of acute continental-scale glaciation, separated by periods of ice minima or ice-free conditions on the order of <10⁶years. The late Paleozoic glaciogenic record of the Paraná and Kalahari basins of southern Gondwana form one of the largest, best-preserved and well-calibrated records of this glaciation. In the Carboniferous, the eastern and southern margins of the Paraná Basin and the Kalahari Basin were characterized by subglacial conditions, with evidence for continental and upland glaciers. In the latest Carboniferous, these basins transitioned from subglacial reservoirs to ice-free or ‘ice distal‘ conditions evidenced by the widespread deposition of marine deposits juxtaposed on subglacial bedforms. High-precision U–Pb zircon chemical abrasion thermal ionization mass spectrometry geochronological constraints from volcanic ash deposits in the deglacial marine black shales of the Kalahari Basin and from fluvial and coal successions, which overlie marine deposits in the Paraná Basin, indicate subglacial evidence in these regions is constrained to the Carboniferous. The loss of ice in these regions is congruent with a late Carboniferous peak inpCO₂and widespread marine anoxia in the late Carboniferous. The permeant retreat of glaciers in basinal settings, despite an early PermianpCO₂nadir, highlights the influence of short-term perturbations on the longer-term CO₂record and suggests an ice threshold had been crossed in the latest Carboniferous. A definitive driver for greenhouse gases in the LPIA, such as abundant and sustained volcanic activity or an increased biological pump driven by ocean fertilization, is unresolved for this period. Lastly, the proposed Carboniferous apex for the high-latitude LPIA record is incongruent with observations from the low-latitude tropics where an early Permian peak is proposed.

    

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