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1. Glacier expansion on Baffin Island during early Holocene cold reversals

   https://doi.org/10.1016/j.quascirev.2020.106419  

   Crump, Sarah E.; Young, Nicolás E.; Miller, Gifford H.; Pendleton, Simon L.; Tulenko, Joseph P.; Anderson, Robert S.; Briner, Jason P. (July 2020, Quaternary Science Reviews)

   The North Atlantic was a key locus for circulation-driven abrupt climate change in the past and could play a similar role in the future. Abrupt cold reversals, including the 8.2 ka event, punctuated the otherwise warm early Holocene in the North Atlantic region and serve as useful paleo examples of rapid climate change. In this work, we assess the cryospheric response to early Holocene climate history on Baffin Island, Arctic Canada, using cosmogenic radionuclide dating of moraines. We present 39 new 10Be ages from four sets of multi-crested early Holocene moraines deposited by cirque glaciers and ice cap outlet glaciers, as well as erratic boulders along adjacent fiords to constrain the timing of regional deglaciation. The age of one moraine is additionally constrained by in situ 14C measurements, which confirm 10Be inheritance in some samples. All four moraines were deposited between ~9.2 and 8.0 ka, and their average ages coincide with abrupt coolings at 9.3 and 8.2 ka that are recorded in Greenland ice cores. Freshwater delivery to the North Atlantic that reduced the flux of warm Atlantic water into Baffin Bay may explain brief intervals of glacier advance, although moraine formation cannot be definitively tied to centennial-scale cold reversals. We thus explore other possible contributing factors, including ice dynamics related to retreat of Laurentide Ice Sheet outlet glaciers. Using a numerical glacier model, we show that the debuttressing effect of trunk valley deglaciation may have contributed to these morainebuilding events. These new age constraints and process insights highlight the complex behavior of the cryosphere during regional deglaciation and suggest that multiple abrupt cold reversalsdas well as deglacial ice dynamicsdlikely played a role in early Holocene moraine formation on Baffin Island. 

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2. Formation and evolution of an extensive blue ice moraine in central Transantarctic Mountains, Antarctica

   https://doi.org/10.1017/jog.2019.83  

   Kassab, Christine M.; Licht, Kathy J.; Petersson, Rickard; Lindbäck, Katrin; Graly, Joseph A.; Kaplan, Michael R. (February 2020, Journal of Glaciology)

   null (Ed.)

   Abstract Mount Achernar moraine is a terrestrial sediment archive that preserves a record of ice-sheet dynamics and climate over multiple glacial cycles. Similar records exist in other blue ice moraines elsewhere on the continent, but an understanding of how these moraines form is limited. We propose a model to explain the formation of extensive, coherent blue ice moraine sequences based on the integration of ground-penetrating radar (GPR) data with ice velocity and surface exposure ages. GPR transects (100 and 25 MHz) both perpendicular and parallel to moraine ridges at Mount Achernar reveal an internal structure defined by alternating relatively clean ice and steeply dipping debris bands extending to depth, and where visible, to the underlying bedrock surface. Sediment is carried to the surface from depth along these debris bands, and sublimates out of the ice, accumulating over time (>300 ka). The internal pattern of dipping reflectors, combined with increasing surface exposure ages, suggest sequential exposure of the sediment where ice and debris accretes laterally to form the moraine. Subsurface structure varies across the moraine and can be linked to changes in basal entrainment conditions. We speculate that higher concentrations of debris may have been entrained in the ice during colder glacial periods or entrained more proximal to the moraine sequence. 

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3. A critical re‐analysis of constraints on the timing and rate of Laurentide Ice Sheet recession in the northeastern United States

   https://doi.org/10.1002/jqs.3563  

   Halsted, Christopher T.; Bierman, Paul R.; Shakun, Jeremy D.; Davis, P. Thompson; Corbett, Lee B.; Drebber, Jason S.; Ridge, John C. (August 2023, Journal of Quaternary Science)

   Abstract We review geochronological data relating to the timing and rate of Laurentide Ice Sheet recession in the northeastern United States and model ice margin movements in a Bayesian framework using compilations of previously published organic¹⁴C (n= 133) andin situcosmogenic¹⁰Be (n= 95) ages. We compare the resulting method‐specific chronologies with glacial varve records that serve as independent constraints on the pace of ice recession to: (1) construct a synthesis of deglacial chronology throughout the region; and (2) assess the accuracy of each chronometer for constraining the timing of deglaciation. Near the Last Glacial Maximum terminal moraine zone,¹⁰Be and organic¹⁴C ages disagree by thousands of years and limit determination of the initial recession to a date range of 24–20 ka. We infer that¹⁰Be inherited from pre‐glacial exposure adds 2–6 kyr to many exposure ages near the terminal moraines, whereas macrofossil¹⁴C ages are typically 4–8 kyr too young due to a substantial lag between ice recession and sufficient organic material accumulation for dating in some basins. Age discrepancies between these chronometers decrease with distance from the terminal moraine, due to less¹⁰Be inherited from prior exposure and a reduced lag between ice recession and organic material deposition.¹⁴C and¹⁰Be ages generally agree at locations more than 200 km distal from the terminal moraines and suggest a mostly continuous history of ice recession throughout the region from 18 to 13 ka with a variable pace best documented by varves. 

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4. Modeling glacier extents and equilibrium line altitudes in the Rwenzori Mountains, Uganda, over the last 31,000 yr

   Doughty AM, Kelly MA (April 2021, Special paper Geological Society of America)

   Waitt RB, Thackray GD (Ed.)

   Mountain glacier moraine sequences and their chronologies allow us to evaluate the timing and climate conditions that underpin changes in the equilibrium line altitudes (ELAs), which can provide valuable information on the paleoclimatology of understudied regions such as tropical East Africa. However, moraine sequences are inherently discontinuous, and the precise climate conditions that they represent can be ambiguous due to the sensitivity of mountain glaciers to temperature, precipitation, and other environmental variables. Here, we used a two-dimensional (2-D) iceflow and mass-balance model to simulate glacier extents and ELAs in the Rwenzori Mountains in East Africa over the past 31,000 yr (31 k.y.), including the Last Glacial Maximum (LGM), late glacial period, and the Holocene Epoch. We drove the glacier model with two independent, continuous temperature reconstructions to simulate possible glacier length changes through time. Model input paleoclimate values came from branched glycerol dialkyl glycerol tetraether (brGDGT) temperature reconstructions from alpine lakes on Mount Kenya for the last ~31 k.y., and precipitation reconstructions for the LGM came from various East African locations. We then compared the simulated fluctuations with the positions and ages (where known) of the Rwenzori moraines. The simulated glacier extents reached within 1.1 km of the dated LGM moraines in one valley (93% of the full LGM extent) when forced by the brGDGT temperature reconstructions (maximum cooling of 6.1 °C) and a decrease in precipitation (-10% than modern amounts). These simulations suggest that the Rwenzori glaciers required a cooling of at least 6.1 °C to reach the dated LGM moraines. Based on the model output, we predict an age of 12–11 ka for moraines located halfway between the LGM and modern glacier extents. We also predict ice-free conditions in the Rwenzori Mountains for most of the early to middle Holocene, followed by a late Holocene glacier readvance within the last 2000 yr. 

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5. A 3He-based Holocene glacial chronology from Villarrica volcano, Chile

   https://doi.org/10.1016/j.quascirev.2025.109707  

   Orellana-Salazar, Yasmeen; Marcott, Shaun A; Tremblay, Marissa M; Romero, Matias; Moreno-Yaeger, Pablo; Mixon, Emily E; Jones, Andrew G; Barth, Aaron M (January 2026, Quaternary Science Reviews)

   Understanding alpine glacier extent during past climate variability is instructive for determining the glacier response to future climate change. Villarrica volcano is a late Pleistocene stratovolcano located in Chile's Southern Volcanic Zone that was covered by the Patagonian Ice Sheet during the last glacial period, and still retains small remnant glaciers today. Moraines preserved several kilometers from the summit on different flanks of the volcano record a history of expanded glacier lengths during the Holocene. However, the precise ages of these moraines are unknown, and the Holocene glacial history of Villarrica remains poorly constrained, limiting our understanding of how glaciers in this region responded to Holocene climate change. To constrain the timing of these moraines, we analyzed cosmogenic 3He in olivine from 25 basaltic andesite moraine boulders for cosmogenic surface exposure dating. Our new chronology reveals multiple late Holocene glacier advances from different flanks of the volcano, with the glaciers culminating and abandoning their moraines during the early Neoglacial period at ∼3355 ± 190 a and ∼1735 ± 215 a, and during the last millennium spanning the Little Ice Age period at ∼720 ± 225 a, ∼370 ± 75 a, and in the last ∼200 years. Our analysis of Holocene climate proxies from south-central Chile indicates that the early Neoglacial advances and subsequent retreat likely reflect increased effective moisture delivered by intensified Southern Westerly Winds and associated shifts in their latitudinal position. In contrast, we interpret the last millennium glacier advances as primarily driven by reduced summer ablation linked to regional cooling, followed by glacier retreat due to increased temperatures. Our chronology and closely spaced moraine positions suggest that glacier retreat on Villarrica, and possibly the broader Southern Volcanic Zone, has been gradual during the late Holocene and interrupted by short-lived advances driven by varying changes in temperature and moisture. 

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