Periodic Reporting for period 1 - TEMPEST (Global Air TEMPerature ESTimation on high mountain glaciers)
Reporting period: 2021-10-01 to 2023-09-30
The TEMPEST project (‘Global Air TEMPerature ESTimation on High Mountain Glaciers’) aimed at improving process understanding and producing a generalizable parameterization of near-surface cooling above mountain glaciers. This cooling is highly relevant to the accurate calculation of glacier melt and has important impacts upon the current and future estimates of water supply to major mountain river systems. These estimates of near-surface cooling on glaciers is typically ignored or crudely represented through bulk calibration.
The project sought to combine new, detailed on-glacier meteorological observations with a wealth of past, community-derived datasets to enhance our understanding about the main controls of temperature distribution on glaciers and their hydrological relevance at the local/regional level. The project moreover leveraged the research lines of the High Mountain Glaciers and Hydrology group (F. Pellicciotti) at WSL, Switzerland to provide a two-way knowledge transfer regarding glacier air temperature and land-surface modelling in glacierized catchments around the world. Its main objectives were to:
- To test the hypothesis that warming air temperature on glacier termini is caused by exposure to competing warm and cold winds and debris/valley surface heating and reassessment of existing, global datasets.
- To develop a novel, unified model framework to improve on-glacier temperature estimation using a global database of on-glacier air temperature and the global reanalysis data.
- To generate an adaptable, open source code implementation for calculating air temperatures of any mountain glacier and assess the impact of this framework on distributed glacier melt in a novel land surface model at experimental catchments around the world.
The project sought to combine new, detailed on-glacier meteorological observations with a wealth of past, community-derived datasets to enhance our understanding about the main controls of temperature distribution on glaciers and their hydrological relevance at the local/regional level. The project moreover leveraged the research lines of the High Mountain Glaciers and Hydrology group (F. Pellicciotti) at WSL, Switzerland to provide a two-way knowledge transfer regarding glacier air temperature and land-surface modelling in glacierized catchments around the world. Its main objectives were to:
- To test the hypothesis that warming air temperature on glacier termini is caused by exposure to competing warm and cold winds and debris/valley surface heating and reassessment of existing, global datasets.
- To develop a novel, unified model framework to improve on-glacier temperature estimation using a global database of on-glacier air temperature and the global reanalysis data.
- To generate an adaptable, open source code implementation for calculating air temperatures of any mountain glacier and assess the impact of this framework on distributed glacier melt in a novel land surface model at experimental catchments around the world.
During the two-year project period, the fellow (T. Shaw) has conducted several field campaigns in the Swiss Alps using low-cost, yet robust meteorological instrumentation in order to explore ongoing questions regarding the role of the glacier boundary layer in determining near-surface air temperatures. The high-resolution data from several on-glacier weather stations yielded interesting findings related to inter-glacier differences exposed to the same regional conditions but also complimented the wealth of data available to a previously instrumented glacier (Haut Glacier d’Arolla). Regarding the latter, these more recent observations provide new evidence as to the decay of the boundary layer for a small glacier, highlighting the complex and non-linear response of a glacier to current and future climate. These results, published in the open-access journal Geophysical Research Letters (Figure 1), demonstrate that, due to the presence and eventual decay of the glacier boundary layer cooling effect, static parameterizations of air temperature biases over glaciers will over-simplify the future of glacier melt and retreat.
Further work related to three glaciers in the Pennine Alps of Switzerland have highlighted how strong the inter-glacier differences of near-surface cooling can be, especially in the context of the extreme summer heat under which the measurements in 2022 were made. This work, recently submitted to the open-access Journal of Geophysical Research: Atmospheres, demonstrates the strong control of glacier exposure to synoptic and valley winds in determining the near-surface cooling and resultant sensible heat transfer to melt ice (Figure 2). This segment of the project makes steps toward a generalizable parameterization of air temperature on glaciers in that it shows that glacier size alone is not enough to explain the inter-glacier differences in sensitivity to atmospheric temperature changes. The extreme 2022 summer provides an indication of likely future climate and further highlights the issues related to stationarity and appropriateness of single parameters used to model regional and global melt and retreat of glaciers.
These new findings work to support the development of a generalizable parameterization of on-glacier air temperature for melt modelling that is ongoing. During the TEMPEST project the fellow has made progress in compiling a new, global dataset of available on-glacier weather station data into a standardized and quality-controlled format. To date, data from ~190 case studies (>90 individual glaciers for multiple summers) have been processed (> 1.5 million hourly data points) in order to explore some of the previously identified controls for on-glacier temperature variability (Figure 3). First-order controls have been established and ongoing international collaborations are helping to further develop the robustness of work that is planned for publication in a high-impact journal.
Data gathered as part of the TEMPEST project has been made publicly available through open-access repositories on Zenodo and the fellow has additionally made efforts to compile and curate past datasets that he has gathered in order to enhance open data science. The datasets are also described and provided freely on the public webpage for the TEMPEST project (tempestglacier.com).
The fellow has presented work related to global analyses (Figure 3) and temporal changes for glacier boundary layers (Figure 1) at large international conferences specific to mountain environments (IMC, September 2022) and geosciences (EGU, April 2023) and interacted with scientific audiences within both glaciological and atmospheric sub-disciplines. Networking at these events led to the fellow’s contribution in the ongoing boundary layer experiments on the Austrian glacier, Hintereisferner (HEFEX II).
Further work related to three glaciers in the Pennine Alps of Switzerland have highlighted how strong the inter-glacier differences of near-surface cooling can be, especially in the context of the extreme summer heat under which the measurements in 2022 were made. This work, recently submitted to the open-access Journal of Geophysical Research: Atmospheres, demonstrates the strong control of glacier exposure to synoptic and valley winds in determining the near-surface cooling and resultant sensible heat transfer to melt ice (Figure 2). This segment of the project makes steps toward a generalizable parameterization of air temperature on glaciers in that it shows that glacier size alone is not enough to explain the inter-glacier differences in sensitivity to atmospheric temperature changes. The extreme 2022 summer provides an indication of likely future climate and further highlights the issues related to stationarity and appropriateness of single parameters used to model regional and global melt and retreat of glaciers.
These new findings work to support the development of a generalizable parameterization of on-glacier air temperature for melt modelling that is ongoing. During the TEMPEST project the fellow has made progress in compiling a new, global dataset of available on-glacier weather station data into a standardized and quality-controlled format. To date, data from ~190 case studies (>90 individual glaciers for multiple summers) have been processed (> 1.5 million hourly data points) in order to explore some of the previously identified controls for on-glacier temperature variability (Figure 3). First-order controls have been established and ongoing international collaborations are helping to further develop the robustness of work that is planned for publication in a high-impact journal.
Data gathered as part of the TEMPEST project has been made publicly available through open-access repositories on Zenodo and the fellow has additionally made efforts to compile and curate past datasets that he has gathered in order to enhance open data science. The datasets are also described and provided freely on the public webpage for the TEMPEST project (tempestglacier.com).
The fellow has presented work related to global analyses (Figure 3) and temporal changes for glacier boundary layers (Figure 1) at large international conferences specific to mountain environments (IMC, September 2022) and geosciences (EGU, April 2023) and interacted with scientific audiences within both glaciological and atmospheric sub-disciplines. Networking at these events led to the fellow’s contribution in the ongoing boundary layer experiments on the Austrian glacier, Hintereisferner (HEFEX II).
Work within the fellow’s current research group utilizes downscaled atmospheric data for land-surface modelling at glacierized catchments in the Andes and across High Mountain Asia. Ongoing developments for the global parameterization of on-glacier temperature are being actively tested to assess their relevance to glacier mass balance and hydrological impact at sites around the world. Progress in this area will aid the understanding of water balance and glacier energy fluxes in distinct hydro-climatic sub-regions. Future changes in such diverse mountain regions will have crucial implications for future water security.
To date, the findings of the project re-iterate the challenges of accurately estimating glacier energy and mass balance and the relevance of a dynamic parameterization that accounts for local characteristics of the glaciers (e.g. size, orientation) and changes in the glaciers themselves (glacier retreat). At the global scale, there remain many challenges of modelling glacier evolution, though at the local-regional scales, the benefits of representing the complexities of boundary layer processes have become increasingly apparent. The TEMPEST project has highlighted an observable non-linearity of glacier boundary layer response to climate. This has critical implications for the future estimates of glacier melt and streamflow. As such, the final (ongoing) steps of TEMPEST to develop a general approach for temperature estimation are anticipated to have tangible and widespread relevance to the glaciological and hydrological modelling communities.
To date, the findings of the project re-iterate the challenges of accurately estimating glacier energy and mass balance and the relevance of a dynamic parameterization that accounts for local characteristics of the glaciers (e.g. size, orientation) and changes in the glaciers themselves (glacier retreat). At the global scale, there remain many challenges of modelling glacier evolution, though at the local-regional scales, the benefits of representing the complexities of boundary layer processes have become increasingly apparent. The TEMPEST project has highlighted an observable non-linearity of glacier boundary layer response to climate. This has critical implications for the future estimates of glacier melt and streamflow. As such, the final (ongoing) steps of TEMPEST to develop a general approach for temperature estimation are anticipated to have tangible and widespread relevance to the glaciological and hydrological modelling communities.