Investigating the future evolution of Norwegian glaciers and hydrological impacts: an integrated modelling approach

The EvoGlac project (Investigating the future evolution of Norwegian glaciers and hydrological impacts: an integrated modelling approach)(2016-2019) aimed to develop a fully-coupled atmosphere-glacier-hydrology model based on existing and new data from Hardangerjøkulen, an ice cap located in central, South Norway. This glacier was selected because it is easily accessible from Finse and well-monitored with the existence of long, continuous time series of surface glacier mass balance and glacier-front variations. The motivating hypothesis was that missing feedbacks, two-way interactions, and resolution-dependent processes in current approaches result in an underestimation of rates of glacier change and related hydrological impacts. The project was a co-operation between 20 researchers from Uni Research Climate AS (now NORCE Climate), University of Bergen, Norwegian Water Resources and Energy Directorate (NVE), University of Oslo, University of Leeds, England, and University Cooperation for Atmospheric Research (UCAR), Boulder, USA. EvoGlac represented a major interdisciplinary effort with meteorologists, hydrologists, climate researchers, modellers, glaciologists and Quaternary geologists designed to create a novel, fully coupled atmosphere-glacier-hydrological modelling system that allowed researchers and decision makers to gain deeper understanding of the future evolution of glaciers and meltwater runoff in glacier catchments. In order to meet the objectives of the project, existing data from Hardangerjøkulen were collected and a diverse team of scientists conducted field campaigns at Hardangerjøkulen to carry out radar measurements of the snow distribution. In addition, the coupled atmosphere-glacier-hydrological modelling system was developed, tested, and subsequently applied over Hardangerjøkulen. The main part of the project consisted of developing a multi-scale, high-resolution, fully coupled, transient simulation for the entire 21st century, which has been used to investigate our main hypotheses and compare against existing approaches to model glacier and hydroclimatic responses to projected atmospheric warming and changes in precipitation in the study area. In EvoGlac, the detailed, physically based snow model 'Crocus' was implemented into the WRF-Hydro modelling system to act as a glacier model (WRF-HydroGlac). It allowed for a direct estimation of glacier surface mass balance and improved the simulation of melting of ice, which have large impacts on the melting of snow and glacier ice, and subsequent meltwater discharge from Hardangerjøkulen. By the mid and late 21st century, both winter precipitation and summer temperature, the two main controlling factors for glacier mass balance, are projected to increase over Hardangerjøkulen. Besides, it is projected to be more days with precipitation as rain and highly intensive precipitation events over Hardangerjøkulen. The simulations show that despite a projected 15% increase in winter precipitation, an estimated temperature increase in the summer season of 3.5 degrees Celsius will cause negative annual mass balance. With the projected summer temperature and winter precipitation values, there may be around 2 m (water equivalents) of negative annual (net) mass balance on Hardangerjøkulen by the end of the 21st century compared to the modern mean values, whereas the future changes in runoff may be more complex in the river catchments surrounding Hardangerjøkulen. Due to the uneven and undulating terrain underneath Hardangerjøkulen, a future retreat of the margin of Hardangerjøkulen will most likely cause formation of new lakes and rerouting of glacier meltwater to other catchments. With the most likely climate scenarios, most of, or the entire Hardangerjøkulen ice cap, may have melted away by the end of the 21st century. The model developed through the EvoGlac project has increased the understanding of the future development of Hardangerjøkulen and the consequences for the meltwater drainage and river runoff in the surrounding river catchments. The model tool that was developed based on data from the Hardangerjøkulen ice cap can be transferred to other glaciers and glacier catchments in Norway and the rest of the world. The results of the project are being published in international, scientific journals. In addition, the EvoGlac project has communicated the results to national, regional and local institutions and policy makers, as well as to school children in the Bergen area.

The EvoGlac project represented a major interdisciplinary effort to create a coupled atmosphere-glacier-hydrological modelling system. It allowed researchers and decision makers to gain deeper understanding of the future evolution of glaciers and glaciated catchments. EvoGlac has interacted with regional public and private stakeholders to increase awareness, educate, and in the long term, enhance adaptation efforts. Three project meetings/workshops were held in Norway during the past three and a half years that brought national and international experts on atmosphere and hydro-cryosphere working and discussing issues around regional climate and hydrological impacts under warming climate and glacier retreat. Three field campaigns to Finse and Hardangerjøkulen and outreach activities were organised by the EvoGlac project during the project period 2016-2019. In 2020, Atle Nesje participated in the NRK TV program SNOWHOW, where he presented some of the measurements at Midtdalsbreen.

Glaciers provide natural storage and regulation of water supply to rivers, which, in turn, contribute to water supply for domestic and industrial consumption, irrigation and hydropower. There is a critical and pressing need to better understand the effects of climate change on glaciers, and the local-to-regional hydrological impacts these changes induce, in a holistic manner. However, the regional processes, mass balance and/or other glacial processes, are still poorly understood. Further, the impacts these changes have on water resources are typically investigated via a one-way chain of discrete models, which often have significant assumptions, missing feedbacks and mismatches in temporal and spatial resolution. EvoGlac represents a major interdisciplinary effort designed to create a novel fully-coupled atmosphere-glacier-hydrological modelling system, which will allow researchers and decision makers to gain deeper understanding of the future evolution of glaciers and glaciated watersheds. In order to meet the primary and secondary objectives described in the grant application form we propose to conduct field campaigns (WP1) and build (WP2), test (WP2), and then apply (WP3), a fully coupled atmosphere-glacier-hydrological modelling system over a well-monitored glacier complex in Norway (Hardangerjøkulen). The centerpiece of the project will be a multi-scale, very high-resolution, fully coupled, transient simulation for the entire 21st century, which will be used to investigate our central hypotheses and compare against existing model-chain and statistical approaches to modelling glacier and hydroclimate responses to warming. Additionally, EvoGlac will actively engage with regional public and private stakeholders to increase awareness, educate and, in the long term, enhance adaptation efforts and improve understanding of how future changes in glacier mass balance may alter streamflow and regional water resources in Norway.