Periodic Reporting for period 4 - RAVEN (Rapid mass loss of debris covered glaciers in High Mountain Asia)
Reporting period: 2022-11-01 to 2024-01-31
RAVEN seeked to elucidate the role of debris-covered glaciers in the water cycle of High Mountain Asia and establish how HMA glacier and runoff will evolve in the future. The project investigated the role that debris-covered glaciers play in the water cycle of HMA. It integrated scales (from the point scale of single ponds and cliffs to the scale of an entire glacier or catchment) and methodological approaches (numerical modelling and observational strategies) to understand which processes are necessary to adequately represent these glaciers in catchment, regional and global glacier models.
Our overall aim was met by four specific outcomes:
1. We characterised the occurrence of cliffs and ponds on debris-covered glaciers using satellite imagery and field measurements to understand their distribution, persistence and characteristics across a range of climates and glacial geomorphologies.
2. We advanced the physical understanding of cliff and pond ablation and quantified their ablation using energy balance models driven by field data and remote sensing observations.
3. We calculate the mass balance of debris-covered and debris-free glaciers by including cliff and pond ablation and evolution into an advanced glacier mass balance model, and developed a new method to infer altitudinal glacier mass balance from satellite imagery.
4. We quantified the future changes in glacier mass-balance and runoff of several catchments representing the climatic diversity of HMA.
Our overall aim was met by four specific outcomes:
1. We characterised the occurrence of cliffs and ponds on debris-covered glaciers using satellite imagery and field measurements to understand their distribution, persistence and characteristics across a range of climates and glacial geomorphologies.
2. We advanced the physical understanding of cliff and pond ablation and quantified their ablation using energy balance models driven by field data and remote sensing observations.
3. We calculate the mass balance of debris-covered and debris-free glaciers by including cliff and pond ablation and evolution into an advanced glacier mass balance model, and developed a new method to infer altitudinal glacier mass balance from satellite imagery.
4. We quantified the future changes in glacier mass-balance and runoff of several catchments representing the climatic diversity of HMA.
The project has reached all its objectives, despite the difficulties related to Covid, and was concluded very successfully. We have made great advances in understanding debris-covered glaciers in High Mountain Asia, their role in the water cycle of the region and how this may change in the future. This is evidenced by two successful PhD theses, numerous publications and outreach activities and open access datasets with meteorological, glaciological and hydrological observations. RAVEN has triggered a tremendous amount of novel, additional research closely linked to it, and in its lifetime I have been granted projects for about 5 million Euros.
Field expeditions to the Himalayas, Pamir and Tibetan Plateau were organized and key datasets of glacier properties, snow, hydrology and meteorology were collected successfully. Important scientific advances have been made, which we elaborate here grouped by each work package (corresponding to the four specific objectives above). RAVEN also resulted in synergistic activities (I was made the chair of a IACS working group on debris-covered glaciers), new collaborations, large new projects and many outreach activities (two art-science exhibitions, photographic documentation, many interviews and cover stories).
Field expeditions to the Himalayas, Pamir and Tibetan Plateau were organized and key datasets of glacier properties, snow, hydrology and meteorology were collected successfully. Important scientific advances have been made, which we elaborate here grouped by each work package (corresponding to the four specific objectives above). RAVEN also resulted in synergistic activities (I was made the chair of a IACS working group on debris-covered glaciers), new collaborations, large new projects and many outreach activities (two art-science exhibitions, photographic documentation, many interviews and cover stories).
RAVEN has resulted in a number of fundamental advances beyond the current state of the art and several groundbreaking insights in High Mountain Asia, in particular regarding the stage of development of supraglacial debris cover in the region, as well as an unprecedented examination of the current health and long-term sustainability of the region’s glaciers.
Our development of a new, transferable method for automated mapping of ice cliffs on debris-covered glaciers opens the door to systematic, robust mapping of both ice cliffs and supraglacial ponds across High Mountain Asia. We have completed analyses of seasonal and interannual ice cliff and supraglacial pond dynamics at four study glaciers and a large-scale assessment (86 glaciers across HMA) of supraglacial ice cliff and pond extent and their topographic and glaciological controls.
We generated a global assessment of glacier debris cover stage of development, which developed a very novel understanding of the stage of evolution of supraglacial debris over all glaciers worldwide. It demonstrated that debris-covered glaciers in High Mountain Asia are at an advanced state of decay, and allowed understanding the conditions over which ice cliffs and ponds can form and develop, thereby giving an unprecedented understanding of the surface topography and melt patterns of debris-covered glaciers and their evolution.
We developed and performed a new systematic analysis of glacier surface mass balance across High Mountain Asia in the first large-scale application of the continuity equation, revealing the poor glacier health in the region in unprecedented detail. Large-scale results stemming from this major advance include an analysis of supraglacial debris thickness and implied debris supply rates across High Mountain Asia and an examination of the importance of sub-debris melt into rivers across High Mountain Asia.
We quantified the melt contribution of ice cliffs and supraglacial ponds at the catchment scale. We completed a global comparison of the energy balance of ice cliffs, supraglacial ponds, and debris-covered ice, extending understanding of associated melt rates beyond High Mountain Asia. A new stochastic population dynamics model of ice cliff and supraglacial pond variations was used for the first time to disentangle these features’ internal dynamics from the influence of external drivers (glacier dynamics and climatic conditions). New datasets collected from time-lapse camera arrays have provided insight into the subseasonal processes and dynamics of ice cliffs, supraglacial hydrology, and debris mobilization rates. We developed time-lapse photogrammetry techniques to derive the evolution of individual cliffs at the weekly scale, and to validate our model. These individual advances were drawn together into a conceptual model of the surface characteristics of debris-covered glaciers at their different stages of evolution.
We led the first debris-covered glacier melt model intercomparison. We performed the first multi-site investigation of the relative influence of the monsoon, debris thickness, and elevation on the energy balance of debris-covered and clean ice glaciers in HMA. We advanced a hyper-resolution land surface model that represents the mountain cryosphere, hydrosphere and biosphere in a much more advanced and substantially distinct manner from traditional glacio-hydrological models. We have quantified the importance of debris-covered glaciers for catchment water balance at the four study sites and provided a first analysis of blue-green water interactions in high-mountain Asian catchments.
We have produced novel long term projections of glacier and streamflow change at four catchments in High Mountain Asia that for the first time: i) describe all components of the cryosphere and hydrosphere using physics-based equations, and do not reply on empirical simplifications; ii) in particular, include the key role of debris in modulating glacier response at short and long time scales, with the potential of importantly altering the trajectory of cryospheric response; and iii) describe the complex interrelationship between cryosphere, hydrosphere and biosphere, and allow for feedback between processes to modulate the catchment response to a warming climate. Using the hyper-resolution land surface model, we have quantified the importance of debris, ice cliffs and supraglacial ponds to future glacier mass balance and change across High Mountain Asia, as well as the changing roles of vegetation phenology and glacier seasonal melt in controlling high-mountain catchment water budgets.
Our development of a new, transferable method for automated mapping of ice cliffs on debris-covered glaciers opens the door to systematic, robust mapping of both ice cliffs and supraglacial ponds across High Mountain Asia. We have completed analyses of seasonal and interannual ice cliff and supraglacial pond dynamics at four study glaciers and a large-scale assessment (86 glaciers across HMA) of supraglacial ice cliff and pond extent and their topographic and glaciological controls.
We generated a global assessment of glacier debris cover stage of development, which developed a very novel understanding of the stage of evolution of supraglacial debris over all glaciers worldwide. It demonstrated that debris-covered glaciers in High Mountain Asia are at an advanced state of decay, and allowed understanding the conditions over which ice cliffs and ponds can form and develop, thereby giving an unprecedented understanding of the surface topography and melt patterns of debris-covered glaciers and their evolution.
We developed and performed a new systematic analysis of glacier surface mass balance across High Mountain Asia in the first large-scale application of the continuity equation, revealing the poor glacier health in the region in unprecedented detail. Large-scale results stemming from this major advance include an analysis of supraglacial debris thickness and implied debris supply rates across High Mountain Asia and an examination of the importance of sub-debris melt into rivers across High Mountain Asia.
We quantified the melt contribution of ice cliffs and supraglacial ponds at the catchment scale. We completed a global comparison of the energy balance of ice cliffs, supraglacial ponds, and debris-covered ice, extending understanding of associated melt rates beyond High Mountain Asia. A new stochastic population dynamics model of ice cliff and supraglacial pond variations was used for the first time to disentangle these features’ internal dynamics from the influence of external drivers (glacier dynamics and climatic conditions). New datasets collected from time-lapse camera arrays have provided insight into the subseasonal processes and dynamics of ice cliffs, supraglacial hydrology, and debris mobilization rates. We developed time-lapse photogrammetry techniques to derive the evolution of individual cliffs at the weekly scale, and to validate our model. These individual advances were drawn together into a conceptual model of the surface characteristics of debris-covered glaciers at their different stages of evolution.
We led the first debris-covered glacier melt model intercomparison. We performed the first multi-site investigation of the relative influence of the monsoon, debris thickness, and elevation on the energy balance of debris-covered and clean ice glaciers in HMA. We advanced a hyper-resolution land surface model that represents the mountain cryosphere, hydrosphere and biosphere in a much more advanced and substantially distinct manner from traditional glacio-hydrological models. We have quantified the importance of debris-covered glaciers for catchment water balance at the four study sites and provided a first analysis of blue-green water interactions in high-mountain Asian catchments.
We have produced novel long term projections of glacier and streamflow change at four catchments in High Mountain Asia that for the first time: i) describe all components of the cryosphere and hydrosphere using physics-based equations, and do not reply on empirical simplifications; ii) in particular, include the key role of debris in modulating glacier response at short and long time scales, with the potential of importantly altering the trajectory of cryospheric response; and iii) describe the complex interrelationship between cryosphere, hydrosphere and biosphere, and allow for feedback between processes to modulate the catchment response to a warming climate. Using the hyper-resolution land surface model, we have quantified the importance of debris, ice cliffs and supraglacial ponds to future glacier mass balance and change across High Mountain Asia, as well as the changing roles of vegetation phenology and glacier seasonal melt in controlling high-mountain catchment water budgets.