Glaciation of alpine valleys: The glacier – debris-covered glacier – rock glacier continuum

Anderson, Robert S.; Anderson, Leif S.; Armstrong, William H.; Rossi, Matthew W.; Crump, Sarah E.

doi:10.1016/j.geomorph.2018.03.015

Cited by 121 publications

(135 citation statements)

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“…Icy seeps are cold like glacier-fed streams (T SUMMER < 2°C), exhibit relatively high SPC (>50 μS/cm) like groundwater-fed streams, and have moderately stable stream channels (PI ~20-25; Figure S4; Table S1). Beyond taxonomic overlap with other ice-fed stream types, icy seeps may be particularly important as climate change proceeds because they often stem from subterranean ice covered by thick layers of inorganic debris (e.g., rock glaciers) and are predicted to be more resistant to warming (Anderson et al, 2018;Fegel et al, 2016;Millar et al, 2013Millar et al, , 2015. Beyond taxonomic overlap with other ice-fed stream types, icy seeps may be particularly important as climate change proceeds because they often stem from subterranean ice covered by thick layers of inorganic debris (e.g., rock glaciers) and are predicted to be more resistant to warming (Anderson et al, 2018;Fegel et al, 2016;Millar et al, 2013Millar et al, , 2015.…”

Section: Discussionmentioning

confidence: 99%

“…Among these, glacier-fed streams are typically the coldest and least physically stable, groundwater-fed springs the warmest and most stable, and snowmelt-fed streams intermediate between the two. Given their inorganic debris cover and/or subterranean nature, rock glaciers and other icy seep sources may be more buffered against warming atmospheric conditions than glaciers and perennial snowfields, making them less susceptible to climate change (Anderson, Anderson, Armstrong, Rossi, & Crump, 2018;Clark, Clark, & Gillespie, 1994;Knight, Harrison, & Jones, 2019). These "icy seeps" generally occur at geological transition zones, are cold like glacier-fed streams, but seasonally stable like groundwater-fed springs, and are most commonly fed by rock glaciers, masses of subterranean ice insulated by thick layers of inorganic debris (Janke, 2007(Janke, , 2013Millar, Westfall, & Delany, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Microbial assemblages reflect environmental heterogeneity in alpine streams

Hotaling

Foley

Zeglin

et al. 2019

Global Change Biology

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Alpine streams are dynamic habitats harboring substantial biodiversity across small spatial extents. The diversity of alpine stream biota is largely reflective of environmental heterogeneity stemming from varying hydrological sources. Globally, alpine stream diversity is under threat as meltwater sources recede and stream conditions become increasingly homogeneous. Much attention has been devoted to macroinvertebrate diversity in alpine headwaters, yet to fully understand the breadth of climate change threats, a more thorough accounting of microbial diversity is needed. We characterized microbial diversity (specifically Bacteria and Archaea) of 13 streams in two disjunct Rocky Mountain subranges through 16S rRNA gene sequencing. Our study encompassed the spectrum of alpine stream sources (glaciers, snowfields, subterranean ice, and groundwater) and three microhabitats (ice, biofilms, and streamwater). We observed no difference in regional (γ) diversity between subranges but substantial differences in diversity among (β) stream types and microhabitats. Within‐stream (α) diversity was highest in groundwater‐fed springs, lowest in glacier‐fed streams, and positively correlated with water temperature for both streamwater and biofilm assemblages. We identified an underappreciated alpine stream type—the icy seep—that are fed by subterranean ice, exhibit cold temperatures (summer mean <2°C), moderate bed stability, and relatively high conductivity. Icy seeps will likely be important for combatting biodiversity losses as they contain similar microbial assemblages to streams fed by surface ice yet may be buffered against climate change by insulating debris cover. Our results show that the patterns of microbial diversity support an ominous trend for alpine stream biodiversity; as meltwater sources decline, stream communities will become more diverse locally, but regional diversity will be lost. Icy seeps, however, represent a source of optimism for the future of biodiversity in these imperiled ecosystems.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microbial assemblages reflect environmental heterogeneity in alpine streams

Hotaling

Foley

Zeglin

et al. 2019

Global Change Biology

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“…However, the size distributions of rock glaciers in the three mountain belts are very similar across all elevation bands ( Figure 5(A), (E)), so that we exclude such size effects in our analysis. Such distinction might also contain valuable information on the fraction and thickness of debris cover and ice content (Barsch, 1996;Berthling, 2011;Janke et al, 2015;Anderson et al, 2018). The choice of a t-distributed prior on the coefficients mitigates the effect of correlated inputs and acts as a Bayesian analogue to regularised regression in frequentist statistics (Gelman et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…Our inventory also contains different types of rock glaciers, including those derived from or mainly nourished by talus, moraines or debris-covered lower parts of glaciers. Such distinction might also contain valuable information on the fraction and thickness of debris cover and ice content (Barsch, 1996;Berthling, 2011;Janke et al, 2015;Anderson et al, 2018). Yet the geographic scope of our study makes representative site assessments of mixed complexes of debris-covered glaciers and rock glaciers impractical.…”

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confidence: 99%

Rock‐glacier dams in High Asia

Blöthe

Rosenwinkel

Hoeser

et al. 2018

Earth Surf Processes Landf

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Rock glaciers in semiarid mountains contain large amounts of ice and might be important water stores aside from glaciers, lakes, and rivers. Yet whether and how rock glaciers interact with river channels in mountain valleys remains largely unresolved. We examine the potential for rock glaciers to block or disrupt river channels, using a new inventory of more than 2000 intact rock glaciers that we mapped from remotely sensed imagery in the Karakoram (KR), Tien Shan (TS), and Altai (ALT) mountains. We find that between 5% and 14% of the rock glaciers partly buried, blocked, diverted or constricted at least 95 km of mountain rivers in the entire study area. We use a Bayesian robust logistic regression with multiple topographic and climatic inputs to discern those rock glaciers disrupting mountain rivers from those with no obvious impacts. We identify elevation and potential incoming solar radiation (PISR), together with the size of feeder basins, as dominant predictors, so that lower‐lying and larger rock glaciers from larger basins are more likely to disrupt river channels. Given that elevation and PISR are key inputs for modelling the regional distribution of mountain permafrost from the positions of rock‐glacier toes, we infer that river‐blocking rock glaciers may be diagnostic of non‐equilibrated permafrost. Principal component analysis adds temperature evenness and wet‐season precipitation to the controls that characterise rock glaciers impacting on rivers. Depending on the choice of predictors, the accuracy of our classification is moderate to good with median posterior area‐under‐the‐curve values of 0.71–0.89. Clarifying whether rapidly advancing rock glaciers can physically impound rivers, or fortify existing dams instead, deserves future field investigation. We suspect that rock‐glacier dams are conspicuous features that have a polygenetic history and encourage more research on the geomorphic coupling between permafrost lobes, river channels, and the sediment cascades of semiarid mountain belts. © 2018 John Wiley & Sons, Ltd.

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“…) or to distinguish a rock glacier from a heavily debris‐covered glacier (e.g. ) because of its mixed ice‐debris nature evolving over a long period of time . Therefore, spatial permafrost models commonly have high uncertainties.…”

Section: Introductionmentioning

confidence: 99%

Long‐term monitoring of sporadic permafrost at the eastern margin of the European Alps (Hochreichart, Seckauer Tauern range, Austria)

Kellerer‐Pirklbauer

2019

Permafrost & Periglacial

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Delineating the spatial extent and the altitudinal lower limit of mountain permafrost is difficult due to complex topo‐climatic and variable ground thermal conditions within short distances. Little information exists regarding sporadic permafrost existence, its thermal characteristics and its long‐term changes at the eastern margin of the European Alps. To reduce this gap, permafrost monitoring was initiated in 2004 in the Seckauer Tauern mountains, Austria. Research was carried out in the summit region of Mt Hochreichart (2416 m a.s.l.) and at several nearby cirques and valleys, all with rock glaciers. Geomorphic mapping, numerical permafrost modeling, measurements of the bottom temperature of the winter snow cover, continuous ground temperature monitoring, electrical resistivity tomography and optical snow cover monitoring were applied. Results indicate sporadic permafrost occurrence in the summit region with mean annual ground temperatures slightly below 0°C at the surface and −1.4°C at 2.5 m depth. Permafrost lenses also exist in the transition zone between the rock glacier and the talus slope behind attributed to coarse‐grained, blocky material causing additional ground cooling. Thanks to long‐term data, statistically significant trends of atmospheric and ground warming were observed in 2000–2018. Permafrost at this site will presumably disappear within the next few decades.

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Glaciation of alpine valleys: The glacier – debris-covered glacier – rock glacier continuum

Cited by 121 publications

References 71 publications

Microbial assemblages reflect environmental heterogeneity in alpine streams

Microbial assemblages reflect environmental heterogeneity in alpine streams

Rock‐glacier dams in High Asia

Long‐term monitoring of sporadic permafrost at the eastern margin of the European Alps (Hochreichart, Seckauer Tauern range, Austria)

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