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Conference proceedings ; Online: Automatic detection of snowline altitude using high-resolution satellite imageries over the Himalayas

Sasaki, O. / Miles, E. / Pellicciotti, F. / Sakai, A. / Fujita, K.

XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

2023

Abstract: Snow and glacier meltwater are crucial regulators of freshwater resources in High Mountain Asia (HMA). In spite of its importance, the detailed distribution and variation of snow cover are not well known. With anticipated global warming, it is ... ...

Abstract	Snow and glacier meltwater are crucial regulators of freshwater resources in High Mountain Asia (HMA). In spite of its importance, the detailed distribution and variation of snow cover are not well known. With anticipated global warming, it is increasingly imperative to estimate the temporal and spatial distribution of snow cover. Despite various studies presenting detailed changes in snow cover in individual catchments, most large-scale assessments have been focused on annual values without seasonal variations, or have utilized moderate-resolution sensors (>250 m, such as MODIS). Moreover, global snow cover distribution products suffer from cloud cover and topographic shadows, both of which are common in high mountain areas and cause biases. To overcome this limitation, we have developed an automatic detection algorithm for snowline altitude (SLA) using high-resolution multispectral satellite imageries. SLA is a valuable variable to examine snow cover variation in HMA since it is less biased by cloud cover than snow cover extent. The proposed tool was applied to five glacierized watersheds across the Himalayas to quantify variations in seasonal and annual snow cover distribution over the past two decades, and to analyze the meteorological drivers of SLA. Our findings reveal remarkable differences in SLA among the sites in terms of decadal trends, seasonal patterns, and meteorological drivers. The application of the algorithm to a wider geographical area can offer essential insights into the spatio-temporal variability of snow cover and its drivers, which could lead to a better understanding of the future state of snow cover and high mountain hydrology.
Subject code	910 ; 551
Language	English
Publishing date	2023-07-11
Publishing country	de
Document type	Conference proceedings ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Conference proceedings ; Online: Himalayan periglacial environment may be currently preserved from global warming by glacier feedback

Guyennon, N. / Colombo, N. / Romano, E. / Pellicciotti, F. / Godone, D. / Salerno, F.

XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

2023

Abstract: During the last three decades, the glacierised areas of the Himalaya have shown cooling and drying conditions, caused by higher ablation rates of glaciers in response to global warming ( Salerno et al., 2023. Glacier feedback on Himalayan climate under ... ...

Abstract	During the last three decades, the glacierised areas of the Himalaya have shown cooling and drying conditions, caused by higher ablation rates of glaciers in response to global warming ( Salerno et al., 2023. Glacier feedback on Himalayan climate under global warming - this conference ). While this local negative feedback does not preserve glaciers from melting, it could protect the periglacial environment, extending between the mean elevation of glaciers (~5400 m a.s.l.) and downslope areas (even below 4500 m a.s.l.). Across this elevation band, areas of permafrost are likely to exist. Here, we analyse the world’s longest time-series of soil temperature data (from 2003 to 2022) measured at a high-elevation station located close to the glacier masses (Pyramid, Mt Everest, 5035 m a.s.l.), together with climate observations, reanalysis (ERA5-Land), and remote sensing data (MODIS). We show that a diurnal cooling of soil temperature at 5-cm depth occurred in the last twenty years during summer in response to the air temperature decrease. Therefore, the glacier negative feedback has potentially slowed down or even preserved permafrost from thawing, thus potentially depicting a different picture from what is generally postulated for these Himalayan areas. However, in the region, there is a lack of long-term observations to confirm this hypothesis, thus the real implications of this process are currently unknown. Our analysis goes further in evaluating the potential impacts on snow cover and vegetation greening and more generally on how the glacier negative feedback has been able to protect the Himalayan periglacial environment.
Subject code	550
Language	English
Publishing country	de
Document type	Conference proceedings ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Conference proceedings ; Online: DebDab

Groeneveld, L. / Miles, E. / McCarthy, M. / Shaw, T. / Melo Velasco, V. / Pellicciotti, F.

XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

A database of supraglacial debris thickness and physical properties

2023

Abstract: Debris cover significantly influences glacier melt rates, but our knowledge of debris physical properties, their variability and their effects on ablation is limited. In-situ measurements on debris-covered glaciers are relatively sparse and therefore ... ...

Abstract	Debris cover significantly influences glacier melt rates, but our knowledge of debris physical properties, their variability and their effects on ablation is limited. In-situ measurements on debris-covered glaciers are relatively sparse and therefore literature values are often used in modelling studies. To address this issue, we have compiled DebDab, a database of debris cover properties that includes debris thickness, bulk thermal conductivity, surface roughness, albedo, emissivity, porosity and measured subseasonal melt rates from published literature and datasets. The first version contains debris thickness measurements for 73 glaciers, over 7000 individual debris thickness measurements and more than 1700 melt rate measurements. The other properties have more than 400 entries of which only 45% are actual measurements. DebDab is openly available as a community resource and will continue to develop in the coming years, and we welcome community contributions of their measurements of debris thickness and properties. We hope that it will be useful for physical parameter probability distributions, model uncertainty assessments, and as validation data for debris thickness estimation and melt modelling. To demonstrate its utility, we used DebDab to explore the sensitivity of point scale melt simulations to debris properties variability, and in particular to investigate (1) the effect of changing debris thickness on each debris property; (2) the relationship between debris properties; and (3) whether these relationships are the same for different climatic regions worldwide.
Subject code	690
Language	English
Publishing date	2023-07-11
Publishing country	de
Document type	Conference proceedings ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Conference proceedings ; Online: The importance of local debris properties to model the energy balance and ablation of a debris-covered glacier

Melo Velasco, V. / Miles, E. / McCarthy, M. / Shaw, T. / Groeneveld, L. / Pellicciotti, F.

XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)

Pirámide Glacier, Chile

2023

Abstract: Debris, ranging from surface dust to medial moraines and thick, continuous layers covering ablation zones, partially covers glaciers all around the world. This supraglacial layer fundamentally modifies the energy transfer from the atmosphere to the ice, ... ...

Abstract	Debris, ranging from surface dust to medial moraines and thick, continuous layers covering ablation zones, partially covers glaciers all around the world. This supraglacial layer fundamentally modifies the energy transfer from the atmosphere to the ice, thus directly controlling sub-debris melt rates. Debris physical properties such as albedo, surface roughness, and thermal conductivity have only been measured directly or derived from local measurements at a few sites, so studies have relied on literature values. As we now understand, debris properties are highly heterogeneous, potentially implying high uncertainty in melt rates and debris thicknesses derived from literature debris properties.To meet this data gap and evaluate its impact on modeled melt, we undertook an observational campaign to investigate supraglacial debris properties at Pirámide Glacier, in Chile, in a climate distinct from previous studies. First, we derived aerodynamic surface roughness from wind-temperature tower data in three glacier locations and thermal conductivity from thermistor strings in the debris layer colocated with the wind-temperature towers; we measured ablation with stakes adjacent to the towers for validation; and sampled debris thickness across the glacier surface.We then conducted point-scale energy-balance modeling using both locally-derived debris properties and typical literature values to investigate the impact of using literature values when modeling glacier melt. While deriving local debris properties from measurements is challenging, we show that they can differ significantly from literature values; thus, their use in melt models can result in considerable differences in estimates of sub-debris ice ablation.
Subject code	690
Language	English
Publishing date	2023-07-11
Publishing country	de
Document type	Conference proceedings ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Reply to Yang et al.: Global warming and black carbon simultaneously lead to glacier mass decline over the southeastern Tibetan Plateau.

Jouberton, Achille / Miles, Evan S / Shaw, Thomas E / McCarthy, Michael / Fugger, Stefan / Pellicciotti, Francesca

Proceedings of the National Academy of Sciences of the United States of America

2023 Volume 120, Issue 12, Page(s) e2301467120

Language	English
Publishing date	2023-03-13
Publishing country	United States
Document type	Journal Article
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.2301467120
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Aspect controls the survival of ice cliffs on debris-covered glaciers.

Buri, Pascal / Pellicciotti, Francesca

Proceedings of the National Academy of Sciences of the United States of America

2018 Volume 115, Issue 17, Page(s) 4369–4374

Abstract: Supraglacial ice cliffs exist on debris-covered glaciers worldwide, but despite their importance as melt hot spots, their life cycle is little understood. Early field observations had advanced a hypothesis of survival of north-facing and disappearance of ...

Abstract	Supraglacial ice cliffs exist on debris-covered glaciers worldwide, but despite their importance as melt hot spots, their life cycle is little understood. Early field observations had advanced a hypothesis of survival of north-facing and disappearance of south-facing cliffs, which is central for predicting the contribution of cliffs to total glacier mass losses. Their role as windows of energy transfer suggests they may explain the anomalously high mass losses of debris-covered glaciers in High Mountain Asia (HMA) despite the insulating debris, currently at the center of a debated controversy. We use a 3D model of cliff evolution coupled to very high-resolution topographic data to demonstrate that ice cliffs facing south (in the Northern Hemisphere) disappear within a few months due to enhanced solar radiation receipts and that aspect is the key control on cliffs evolution. We reproduce continuous flattening of south-facing cliffs, a result of their vertical gradient of incoming solar radiation and sky view factor. Our results establish that only north-facing cliffs are recurrent features and thus stable contributors to the melting of debris-covered glaciers. Satellite observations and mass balance modeling confirms that few south-facing cliffs of small size exist on the glaciers of Langtang, and their contribution to the glacier volume losses is very small ([Formula: see text]1%). This has major implications for the mass balance of HMA debris-covered glaciers as it provides the basis for new parameterizations of cliff evolution and distribution to constrain volume losses in a region where glaciers are highly relevant as water sources for millions of people.
Language	English
Publishing date	2018-04-09
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.1713892115
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Article: Interannual Dynamics of Ice Cliff Populations on Debris-Covered Glaciers From Remote Sensing Observations and Stochastic Modeling.

Kneib, M / Miles, E S / Buri, P / Molnar, P / McCarthy, M / Fugger, S / Pellicciotti, F

Journal of geophysical research. Earth surface

2021 Volume 126, Issue 10, Page(s) e2021JF006179

Abstract: Ice cliffs are common on debris-covered glaciers and have relatively high melt rates due to their direct exposure to incoming radiation. Previous studies have shown that their number and relative area can change considerably from year to year, but this ... ...

Abstract	Ice cliffs are common on debris-covered glaciers and have relatively high melt rates due to their direct exposure to incoming radiation. Previous studies have shown that their number and relative area can change considerably from year to year, but this variability has not been explored, in part because available cliff observations are irregular. Here, we systematically mapped and tracked ice cliffs across four debris-covered glaciers in High Mountain Asia for every late ablation season from 2009 to 2019 using high-resolution multi-spectral satellite imagery. We then quantified the processes occurring at the feature scale to train a stochastic birth-death model to represent the cliff population dynamics. Our results show that while the cliff relative area can change by up to 20% from year to year, the natural long-term variability is constrained, thus defining a glacier-specific cliff carrying capacity. In a subsequent step, the inclusion of external drivers related to climate, glacier dynamics, and hydrology highlights the influence of these variables on the cliff population dynamics, which is usually not a direct one due to the complexity and interdependence of the processes taking place at the glacier surface. In some extreme cases (here, a glacier surge), these external drivers may lead to a reorganization of the cliffs at the glacier surface and a change in the natural variability. These results have implications for the melt of debris-covered glaciers, in addition to showing the high rate of changes at their surface and highlighting some of the links between cliff population and glacier state.
Language	English
Publishing date	2021-10-13
Publishing country	United States
Document type	Journal Article
ZDB-ID	2130824-X
ISSN	2169-9011 ; 2169-9003
ISSN (online)	2169-9011
ISSN	2169-9003
DOI	10.1029/2021JF006179
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Article: Snow Depth Structure, Fractal Behavior, and Interannual Consistency Over Haut Glacier d'Arolla, Switzerland

Clemenzi, I. / Pellicciotti, F. / Burlando, P.

Water resources research

2018 Volume 54, Issue 10, Page(s) 7929

Language	English
Document type	Article
ZDB-ID	5564-5
ISSN	0043-1397
DOI	10.1029/2017WR021606
Database	Current Contents Nutrition, Environment, Agriculture

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Z 4285: Show issues

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Article ; Online: Changes in glaciers in the Swiss Alps and impact on basin hydrology: current state of the art and future research.

Pellicciotti, F / Carenzo, M / Bordoy, R / Stoffel, M

The Science of the total environment

2014 Volume 493, Page(s) 1152–1170

Abstract: Switzerland is one of the countries with some of the longest and best glaciological data sets. Its glaciers and their changes in response to climate have been extensively investigated, and the number and quality of related studies are notable. However, a ...

Abstract	Switzerland is one of the countries with some of the longest and best glaciological data sets. Its glaciers and their changes in response to climate have been extensively investigated, and the number and quality of related studies are notable. However, a comprehensive review of glacier changes and their impact on the hydrology of glacierised catchments for Switzerland is missing and we use the opportunity provided by the EU-FP7 ACQWA project to review the current state of knowledge about past changes and future projections. We examine the type of models that have been applied to infer glacier evolution and identify knowledge gaps that should be addressed in future research in addition to those indicated in previous publications. Common characteristics in long-term series of projected future glacier runoff are an initial peak followed by a decline, associated with shifts in seasonality, earlier melt onset and reduced summer runoff. However, the quantitative predictions are difficult to compare, as studies differ in terms of model structure, calibration strategies, input data, temporal and spatial resolution as well as future scenarios used for impact studies. We identify two sources of uncertainties among those emerging from recent research, and use simulations over four glaciers to: i) quantify the importance of the correct extrapolation of air temperature, and ii) point at the key role played by debris cover in modulating glacier response.
Language	English
Publishing date	2014-09-15
Publishing country	Netherlands
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	121506-1
ISSN	1879-1026 ; 0048-9697
ISSN (online)	1879-1026
ISSN	0048-9697
DOI	10.1016/j.scitotenv.2014.04.022
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Zs.A 949: Show issues

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Article ; Online: Health and sustainability of glaciers in High Mountain Asia.

Miles, Evan / McCarthy, Michael / Dehecq, Amaury / Kneib, Marin / Fugger, Stefan / Pellicciotti, Francesca

Nature communications

2021 Volume 12, Issue 1, Page(s) 2868

Abstract: Glaciers in High Mountain Asia generate meltwater that supports the water needs of 250 million people, but current knowledge of annual accumulation and ablation is limited to sparse field measurements biased in location and glacier size. Here, we present ...

Abstract	Glaciers in High Mountain Asia generate meltwater that supports the water needs of 250 million people, but current knowledge of annual accumulation and ablation is limited to sparse field measurements biased in location and glacier size. Here, we present altitudinally-resolved specific mass balances (surface, internal, and basal combined) for 5527 glaciers in High Mountain Asia for 2000-2016, derived by correcting observed glacier thinning patterns for mass redistribution due to ice flow. We find that 41% of glaciers accumulated mass over less than 20% of their area, and only 60% ± 10% of regional annual ablation was compensated by accumulation. Even without 21
Language	English
Publishing date	2021-05-17
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2553671-0
ISSN	2041-1723 ; 2041-1723
ISSN (online)	2041-1723
ISSN	2041-1723
DOI	10.1038/s41467-021-23073-4
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