Glacier-dammed lake outburst modelling in Shimshal valley

Recent observations show that the surging tongue of Khurdopin glacier in Shimshal catchment in Northern Pakistan has caused a lake to form in 2017 (Steiner et al. 2018), which might return annually in subsequent years following the melt season. Ongoing monitoring has shown that the lake expanded since November 2017 reaching a constant area of ca 350 000 m2 in March of 2018 and it has remained stable since. As the ice masses from the surge will take many more months to melt the lake is likely to remain or reappear even after drainage events. As the melt season starts the lake may drain and this may cause flooding downstream, in particular close to the village of Shimshal, the adjacent agricultural areas and lake Attabad located further downstream.

Shimshal model area

The mountain hydrology team of Utrecht University is supporting the Aga Khan Foundation for Habitat. The National Disaster Management Authority (NDMA) in Pakistan is coordinating the effort and is dealing with the emerging issue and have put together a team of experts. Our results may support this process.

To assess potential damage from a lake burst an initial BASEMENT hydrodynamic model was constructed for the area using available elevation models , estimated lake water volumes and dam breach scenarios from literature and an initial model simulation assuming a lake volume of 7 million m3 and a short breach period was conducted. The movie below shows the maximum inundation depth as the wave travels through the valley.

Subsequent work will focus on the following:

  • Improve the cross profiles using field data or high resolution DEMs (e.g. ALOS-PRISM)
  • Extend the model run until Attabad lake and assess the potential flood wave there.
  • Include multiple volume and lake growth scenarios
  • Include multiple breach scenarios ranging from a catastrophic, near instantaneous breach to a more gradual scenario
  • Include more detailed exposure data such as infrastructure, houses, agricultural areas

For more information please contact Jakob Steiner or Walter Immerzeel.

Increasing irrigation may lead to growing glaciers

It has been a mystery for years: while glaciers are shrinking all over the world, there is an area in the Asian high mountains where the glaciers are actually growing. New research from our group shows that humans might be responsible for this. The increasing agricultural activity in the region is resulting in more snow and less sunlight in the mountains, precisely in the areas where the glaciers are growing.

The vast majority of glaciers in the high mountains of Asia are partially melting away due to global warming. But there’s an area to the northwest of the Tibetan Plateau where the glaciers are actually growing. ‘Because the region is difficult to access, little has been known about these glaciers for quite some time’, says first author Remco de Kok, a physical geographer at Utrecht University. ‘But with the help of weather models we have shown that these glaciers can expand because local land use has changed. The fact that human activity can have such an immediate impact on the growth of glaciers is new information, and extremely important to know for the many people who depend on the meltwater from glaciers.’ The results of the study are published in the journal Geophysical Research Letters.

More snow, less sunlight
The increasing irrigation in the region is the cause of this remarkable glacier growth. Research leader Walter Immerzeel explains: ‘In the lowlands of China, Pakistan and India, river and groundwater are increasingly being used to irrigate agricultural areas. Much of the irrigation water is eventually “sweated out” by the plants and absorbed into the atmosphere. Using a special weather model, we have shown that the increasing water vapour later comes down as additional snow – precisely in the places where the growing glaciers are found. The additional clouds also allow less sunlight to pass through, causing the glaciers underneath to melt at a slower rate.’

The ice supply in the Asian high mountains is crucial to the many millions of people who depend on the meltwater. The results of this study are primarily good news, although the research group, which also consists of Pleun Bonekamp and ObbeTuinenberg, warns against too much optimism. ‘Due to the limited amount of river and groundwater, the question is to what extent agriculture in Asia can continue to grow in the future. If irrigation decreases, the effect will be undone and it is likely that – in combination with the further warming of the earth – the glaciers will retreat at an accelerated pace.’

 

 

Mountain Hydrology Team at AGU 2017

The AGU Fall Meeting 2017 is coming up at a fast pace and we are excited to present some of our scientific work we have been busy with during the last year.

We are also exited and proud to be chairing a session on the High Mountain Hydrosphere with posters Wednesday afternoon (session) and an interesting oral session on Thursday morning (session). The session features talks from all over the globe aimed at improving our understanding of high mountain hydrology using a wide range of techniques.

 

We have something to present to you on every single day of the week!

Monday

  • In the morning Pleun will show results from her WRF modelling of high-altitude precipitation (abstract), looking at the impact of different resolutions on model outcomes.
  • In the afternoon Emmy will present her estimation of the fraction of high-altitude solid precipitation that returns back to the atmosphere through sublimation (abstract).

Clouds forming over Ganja-La in Langtang Valley.

Gamma ray sensor near Yala glacier used to measure snow water equivalent and derive sublimation. Captured by one of our time-lapse cameras.

Tuesday

  • In the morning Jakob will present his poster on the recent Khurdopin Glacier surge, which we documented using Planet satellite imagery (abstract). To learn more about this study, have a look at our brief communication in The Cryosphere.

Wednesday

  • Walter will give a presentation early morning about the drivers of the future water gap in the Ganges-Indus-Brahmaputra basins (abstract).
  • Maxime will present his recent findings on the differences in turbulent fluxes over debris-covered and debris-free glaciers (abstract) during our poster session in the afternoon.
  • In the same session, Pascal will present his efforts in modelling supraglacial ice cliffs on debris-covered glaciers and estimating their contribution to the glacier mass balance (abstract).

Walter crossing Langtang Khola.

Max admiring the beauty of Langtang Glacier.

Thursday

  • As part of our own session, Remco will present his findings on the influences of cropland irrigation on high-altitude precipitation (abstract).
  • Later in the morning Philip will present his recent paper on the consequences of climate warming on the glaciers in High Mountain Asia (abstract).

Friday

  • Evan will talk about seasonal deformation of Khumbu Glacier as measured from remote sensing and field observations in the morning (abstract).
  • Jakob will talk about turbulent fluxes on a debris-covered glacier just after lunch (abstract).
  • Jakob will also present some recent investigations into the terrestrial ice margin in Greenland in the afternoon (abstract).
  • On Friday afternoon, Joseph and Philip will present their work on the multi-temporal UAV monitoring of a mountain snow pack in the Canadian Rockies using optical and thermal sensors (abstract).

A curious visitor at our time-lapse camera monitoring the debris-covered Shalbachum Glacier.

Joseph pounding in markers for the UAV surveys on Fortress Ridge.

Follow us on a trip into the world of mountain hydrology and visit one of our talks or posters!

Future projections of glacier mass loss

In our new study published in Nature last week, we show that even if the planet only warms up by 1.5 degrees Celsius 36% of all Asian glacier ice will have melted by the end of the century. More extreme temperature scenarios, for example the ones projected by IPCC’s RCP8.5, will result in mass losses of up to 64%.

Glaciers in the high mountains of Asia play a substantial role in regional water resource and they have been losing mass over the last decades (e.g. Brun et al, 2017), a trend that is most likely to persist under future temperature rise. At the 2015 UN Climate Change Conference in Paris, 195 nations signed the “Paris Agreement” and agreed on efforts to limit the global temperature rise to 1.5 °C. It was unknown, however, how much of Asia’s ice mass would be lost under such a scenario, or under more extreme temperature scenarios.

To determine this, we have developed a glacier model for all individual Asian glaciers larger than 0.4 km2. We have forced the glacier model transiently up to 2100 by the full CMIP5 ensemble of 110 climate models, and have taken into account present-day climate, the imbalance of the glaciers, and the effect of debris cover.

Our results show that only a handful of the climate models project a global temperature rise of 1.5 °C and that the glaciers in the region warm consistently more than the global mean because of elevation dependent warming. By the end of the current century the 1.5 °C scenario results in a loss of over one third of the present-day ice mass in the region, while mass losses projected under more extreme temperature projections go up to almost two third.

We have also found that there are large regional differences in projected mass loss, which are caused primarily by regional differences in debris cover, ice mass, present-day glacier imbalance, and glacier sensitivity to climate perturbations.

 

Mass loss projections for the current century aggregated by sub-region of the Randolph Glacier Inventory v5.0. The bar charts indicate the regional prevalence of debris-covered glaciers.

 

To learn more about our study refer to the paper below, or have a look at our visual story line.

 

Impact of a global temperature rise of 1.5 degrees Celsius on Asia’s glaciers
Kraaijenbrink, P. D. A., Bierkens, M. F. P., Lutz, A. F., & Immerzeel, W. W. (2017)
Nature, 549(7671), 257-260. DOI: 10.1038/nature23878

 

New estimates of HMA glacier change

Fanny, Patrick, Etienne Berthier and colleagues from Oslo University (Andreas Kääb and Désirée Treichler) have just published the study “A spatially resolved estimate of High Mountain Asia glacier mass balances from 2000 to 2016” in Nature Geoscience. They used more than 50,000 ASTER satellite images to derive digital elevation models and to track glacier thickness changes over High Mountain Asia. They provide the first consistent estimate of volume change for ~90 000 km2 of glaciers.
 
Their study confirms the existence of the so called “Karakoram anomaly” and, following a 2015 study by Andreas Kääb et al. refines its location: glaciers located in the West Kunlun, Karakoram and Eastern Pamir have balanced or slightly positive mass changes. The most negative mass changes are found in the Eastern Himalaya, where glaciers loose mass at rates similar to the ones in the European Alps (up to 0.62 ± 0.23 m w.e. yr-1).
 

Rate of glacier elevation change (in m/yr) for the period 2000-2016. Red dots represent area where glaciers are thinning and blue dots area where glaciers are thickening.

Rate of glacier elevation change (in m/yr) for the period 2000-2016. Red dots represent area where glaciers are thinning and blue dots area where glaciers are thickening.

 

 
These data will help to constrain glacio-hydrological models and to better understand the contribution of glaciers to stream flow and sea level rise. Nevertheless, they provide only mass balance values averaged over 16 years and therefore do not give access to the processes responsible for these changes. More field data are needed to investigate these.

 

naturegeocmyk

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