Rock glaciers in Pearse Valley, Antarctica record outlet and alpine glacier advance from MIS 5 through the Holocene

Swanger, Kate M.; Babcock, Esther; Winsor, Kelsey; Valletta, Rachel D.

doi:10.1016/j.geomorph.2019.03.019

Cited by 6 publications

(17 citation statements)

References 36 publications

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“…Based on the GPR data and field investigations, the South Fork rock glacier contains ice-rich sediments (30–50% porosity if ice-filled, with isolated centimetre-scale ice lenses). This talus-derived model of formation distinguishes the rock glacier of South Fork from many of the other rock glaciers and viscous flow lobes in Taylor Valley, which have been shown to contain > 10 m-thick lenses of clean ice of glacial origin overlain by talus and fluvial sediments (Swanger et al 2010, 2019). The demonstrated variation in the ice content and origin for viscous flow features in the McMurdo Dry Valleys provides a compelling analogue for the large viscous flow features on Mars, especially given recent insights into the possibility that some Martian features contain clean ice lenses at depth while others might not (Petersen et al 2018, Brough et al 2019).…”

Section: Discussionmentioning

confidence: 96%

“…Rock glaciers are numerous in this cold, hyper-arid region (Hassinger & Mayewski 1983, Bockheim 2014). Despite regional snowfall precipitation of ~10–100 mm water equivalent per year (Fountain et al 2010), rock glaciers and debris-covered ice are able to form and survive, possibly for timescales of 10 5 –10 6 years (Mackay et al 2014, Swanger et al 2019). The mechanism of rock glacier formation probably varies within the McMurdo Dry Valleys (Bockheim 2014).…”

Section: Introductionmentioning

confidence: 99%

“…When debris is supersaturated with ice, the material deforms and creeps readily, whereas saturated or unsaturated debris experiences much higher internal friction and thus its interstitial ice (or ice cement) experiences reduced deformation. In a second model, rock glaciers form when glacial ice becomes covered by debris, yielding clean ice cores (Haeberli et al 2006, Fukui et al 2008, Swanger et al 2019). Features fitting within this model are often called glacigenic rock glaciers or debris-covered glaciers.…”

Section: Introductionmentioning

confidence: 99%

“…Complicating the characterization of rock glaciers in the McMurdo Dry Valleys is that ice cement is present year-round in the upper ~1 m of many McMurdo Dry Valley rock glaciers, and some (but not all) are cored by clean ice (Hassinger & Mayewski 1983, Marchant & Head 2007, Swanger et al 2010, 2019). The presence of near-surface ice cement and/or clean ice is often evidenced by polygonal ground, which forms via contraction cracking of near-surface ice (Marchant & Head 2007).…”

Section: Introductionmentioning

confidence: 99%

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Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

Winsor

Swanger²,

Babcock³

et al. 2020

Antarctic Science

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The South Fork of Wright Valley contains one of the largest rock glaciers in the McMurdo Dry Valleys, Antarctica, stretching 7 km from the eastern boundary of the Labyrinth and terminating at Don Juan Pond (DJP). Here, we use results from ground-penetrating radar (GPR), qualitative field observations, soil leaching analyses and X-ray diffraction analyses to investigate rock glacier development. The absence of significant clean ice in GPR data, paired with observations of talus and interstitial ice influx from the valley walls, support rock glacier formation via talus accumulation. A quartz-dominated subsurface composition and discontinuous, well-developed desert pavements suggest initial rock glacier formation occurred before the late Quaternary. Major ion data from soil leaching analyses show higher salt concentrations in the rock glacier and talus samples that are close to hypersaline DJP. These observations suggest that DJP acts as a local salt source to the rock glacier, as well as the surrounding talus slopes that host water track systems that deliver solutes back into the lake, suggesting a local feedback system. Finally, the lack of lacustrine sedimentation on the rock glacier is inconsistent with the advance of a glacially dammed lake into South Fork during the Last Glacial Maximum.

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Section: Discussionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

Winsor

Swanger²,

Babcock³

et al. 2020

Antarctic Science

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“…Besides the burial of glacier ice (e.g. Lacelle et al, 2011, Marchant et al, 2002, Swanger et al, 2010, Swanger, 2017, Swanger et al, 2019, different hypotheses have been advanced to explain the emplacement of ground ice in the permafrost of the upper MDV. For example, in places where ground temperatures remain < 0°C, ground ice was likely emplaced by vapour-diffusion, whereas in places where ground surface temperatures rise > 0°C, it was likely emplaced by vapour-diffusion as well as by the freezing of evaporated snowmelt (e.g.…”

Section: Cryostratigraphy Of Mid-miocene Permafrost At Friis Hills Upper Mcmurdo Dry Valleys Of Antarcticamentioning

confidence: 99%

Reconstructing 15 Myr of environmental change in the McMurdo Dry Valleys through permafrost geochemistry

Verret¹

2021

Preprint

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The McMurdo Dry Valleys of Antarctica are the largest ice-free region in Antarctica. Valley downcutting by major outlet glaciers and post-glacial uplift since the mid-Miocene have resulted in predominantly younger surficial sediments in the low elevation, coastal areas and significantly older sediments in high elevation, inland areas. The hyper-arid conditions that prevail in the high elevations (> 1000 m a.s.l.) of the McMurdo Dry Valleys have protected these surfaces from alteration and weathering, and provide important sediment records of paleoenvironments dating back to the early Miocene. The Friis Hills (77°45’S, 161°30’E, 1200–1500 m a.s.l.) are a 12 km-wide inselberg situated at the head of Taylor Valley. This unique location allowed Miocene-age sediments to be preserved and protected from subsequent ice sheet expansions. Permafrost within these sediments is potentially the oldest on Earth. As sediments accumulate in periglacial environments, permafrost aggrades with minimal lag time and potentially preserves sediments, organic material and ground ice. The 2016 Friis Hills Drilling Project retrieved a ∼50 m thick permafrost sequence, which not only consists of an archive of Antarctic environmental changes from approximately 14–15 Ma but also records the paleoenvironmental changes of the Neogene and provides insight on the modern hyper-arid environment. The main objective of this project is to understand the unique geochemical characteristics of these permafrost cores and document 15 Myr of change in the upper elevations of the McMurdo Dry Valleys. Paleoenvironmental reconstructions of interglacial periods suggest a tundra-like environment in the high elevations of continental Antarctica through the mid-Miocene. Plants such as lichens, liverworts, mosses, grasses and sedges, dicots and Nothofagaceae occupied the Friis Hills during the mid-Miocene. The δ13C signal of C3 plants (-25.5 ± 0.7 ‰ VPDB) corresponds to a semi-arid environment with a mean annual precipitation ranging from 300 to 850 mm yr-1. The unusually high δ15N reflects an ecosystem with up to three trophic levels, supported by the presence of insect fragments, feathers barbs (birds) and tardigrades fragments within the sediment. The deep ice lenses and their meteoric signature suggest a near-saturated active layer during the mid-Miocene. Temperature reconstructions based on the corrected δ18O value of the deep ground ice and change in paleogeography imply that the mid-Miocene (11.1–13.9 Ma) was ∼6 to 12°C warmer. These paleoenvironmental conditions are comparable to those found in the modern Arctic, such as in west Greenland. A dominant trend of literature suggests that the high elevations of the McMurdo Dry Valleys have remained under a hyper-arid polar climate since ∼13.8 Ma. However, the presence of 10Bemet in the upper section of the Friis Hills and Table Mountain cores provides evidence for the translocation of clays, which is only possible under a warmer and wetter climate. The 10Bemet concentrations imply that these conditions were present until ∼6.0 Ma at Friis Hills and Table Mountain, consequently challenging the idea that the upper McMurdo Dry Valleys have remained frozen under hyper-arid climate since the mid-Miocene climate transition. Hence, this finding supports the hypothesis that the Miocene has undergone progressive cooling with onset of polar aridity between 7 and 5.4 Ma. The erosion-corrected paleo-active layer depth suggests mean annual air temperatures ranging from -12 to -9°C ∼6.0 Ma. In other words, this thesis shows that the upper McMurdo Dry Valleys have been frozen under hyperarid conditions only since ∼6 Ma and not for 14 Myr as previously thought. The ground ice in the uppermost 1 m originates from the modern freezing of evaporated snowmelt and the presence of high salt content which allows unfrozen water in the near-surface. The conformity of dry permafrost samples to biological ratios suggests that the modern environment is regulated by biochemical processes and the current pool of organic carbon in the dry permafrost appears to be in equilibrium with a modern climate and ecosystem. These findings not only characterize the paleoenvironmental changes of continental Antarctica through the late Miocene but also provide a better understanding of the modern ultraxerous conditions of the McMurdo Dry Valleys.

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Antarctic permafrost processes and antiphase dynamics of cold-based glaciers in the McMurdo Dry Valleys inferred from ¹⁰Be and ²⁶Al cosmogenic nuclides

Anderson,

Fujioka,

Fink

et al. 2023

The Cryosphere

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Abstract. Soil and sediment mixing and associated permafrost processes are not widely studied or understood in the McMurdo Dry Valleys of Antarctica. In this study, we investigate the stability and depositional history of near-surface permafrost sediments to ∼ 3 m depth in the Pearse and lower Wright valleys using measured cosmogenic 10Be and 26Al depth profiles. In Pearse Valley, we estimate a minimum depositional age of ∼ 74 ka for the active layer and paleoactive-layer sediments (< 0.65 m). Combined depth profile modelling of 10Be and 26Al gives a depositional age for near-surface (< 1.65 m) permafrost in Pearse Valley of 180 +20/-40 ka, implying that the deposition of permafrost sediments predates MIS 5 advances of Taylor Glacier. Deeper permafrost sediments (> 2.09 m) in Pearse Valley are thus inferred to have a depositional age of > 180 ka. At a coastal, lower-elevation site in neighbouring lower Wright Valley, 10Be and 26Al depth profiles from a second permafrost core exhibit near-constant concentrations with depth and indicate the sediments are either vertically mixed after deposition or sufficiently young so that post-depositional nuclide production is negligible relative to inheritance. 26Al/10Be concentration ratios for both depth profiles range between 4.0 and 5.2 and are all lower than the nominal surface production rate ratio of 6.75, indicating that prior to deposition, these sediments experienced complex, yet similar, exposure–burial histories. Assuming a single-cycle exposure–burial scenario, the observed 26Al/10Be ratios are equivalent to a total minimum exposure–burial history of ∼ 1.2 Myr. In proximity to the depth profile core site, we measured cosmogenic 10Be and 26Al in three granite cobbles from thin, patchy drift (Taylor 2 Drift) in Pearse Valley to constrain the timing of retreat of Taylor Glacier. Assuming simple continuous exposure, our minimum, zero-erosion exposure ages suggest Taylor Glacier partially retreated from Pearse Valley no later than 65–74 ka. The timing of retreat after 65 ka and until the Last Glacial Maximum (LGM) when Taylor Glacier was at a minimum position remains unresolved. The surface cobble ages and permafrost processes reveal Taylor Glacier advances during MIS 5 were non-erosive or mildly erosive, preserving the underlying permafrost sediments and peppering boulders and cobbles upon an older, relict surface. Our results are consistent with U/Th ages from central Taylor Valley and suggest changes in moisture delivery over Taylor Dome during MIS 5e, 5c, and 5a appear to be associated with the extent of the Ross Ice Shelf and sea ice in the Ross Sea. These data provide further evidence of antiphase behaviour through retreat of a peripheral lobe of Taylor Glacier in Pearse Valley, a region that was glaciated during MIS 5. We suggest a causal relationship of cold-based glacier advance and retreat that is controlled by an increase in moisture availability during retreat of sea ice and perhaps the Ross Ice Shelf, as well as, conversely, a decrease during times of sea ice and Ross Ice Shelf expansion in the Ross Sea.

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Rock glaciers in Pearse Valley, Antarctica record outlet and alpine glacier advance from MIS 5 through the Holocene

Cited by 6 publications

References 36 publications

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

Reconstructing 15 Myr of environmental change in the McMurdo Dry Valleys through permafrost geochemistry

Antarctic permafrost processes and antiphase dynamics of cold-based glaciers in the McMurdo Dry Valleys inferred from ¹⁰Be and ²⁶Al cosmogenic nuclides

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Rock glaciers in Pearse Valley, Antarctica record outlet and alpine glacier advance from MIS 5 through the Holocene

Cited by 6 publications

References 36 publications

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

Reconstructing 15 Myr of environmental change in the McMurdo Dry Valleys through permafrost geochemistry

Antarctic permafrost processes and antiphase dynamics of cold-based glaciers in the McMurdo Dry Valleys inferred from 10Be and 26Al cosmogenic nuclides

Contact Info

Product

Resources

About

Antarctic permafrost processes and antiphase dynamics of cold-based glaciers in the McMurdo Dry Valleys inferred from ¹⁰Be and ²⁶Al cosmogenic nuclides