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A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past ∼40 years.

Located in Peru's Cordillera Blanca, the Queshque Glacier (∼9.8° S) has experienced nearly continuous retreat since the mid-20th century. More recently, this trend has accelerated after the glacier transitioned from land to lake terminating. We use observations of glacier surface height change (1962–2008), bed topography, and climatology to evaluate the relative drivers of Queshque's evolution from 1962–2020. Six Open Global Glacier Model ensemble members differing in climatic sensitivity are calibrated to fit the mass balance rate of −442 ± 16 mm w.e. a−1 calculated over the 2008 glacier area between 1962–2008. The models are then used to simulate monthly glacier mass balance over the entire study period and dynamic glacier evolution from 2008 to 2020. The models reproduce a typical outer-tropical glacier mass balance regime, showing continuous ablation throughout the year that increases during the pronounced wet season. Climatological trend analyses along with coupled mass balance and ice flow simulations indicate that temperature has been the predominant driver of mass loss since 2008 and that recent precipitation amounts have caused minor dampening of this trend. The strongest negative correlation between temperature and mass balance occurs during the wet season, while a positive correlation between precipitation and annual mass balance is most pronounced during the dry season. The influence of ENSO over mass balance trends appears to decline throughout the study period except during the wettest months, suggesting that wet season Pacific sea-surface temperatures are strong predictors of outer-tropical glacier mass balance variability. Finally, frontal ablation into the newly formed lake began in 2010. This caused ice acceleration at the glacier front, an average mass loss increase of 4 %, and a significant narrowing of the model ensemble mass loss spread. We conclude that while Queshque's trajectory remained coupled to climatic forcings, the new proglacial lake exacerbated and modified the retreat pattern regardless of the model climate sensitivity.

Six ice cores from Kilimanjaro provide an ~11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: ~8.3, ~5.2, and ~4 thousand years ago (ka). The latter is coincident with the \"First Dark Age,\" the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between ~11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased ~80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020.