Periodic Reporting for period 2 - IVORI (New Insights on the Snow Cover: From Snowflakes to Ice Sheets, in Seconds to Centuries.)
Período documentado: 2022-08-01 hasta 2024-01-31
Snow is a pillar of the Earth’s climate system, affecting all its components with critical impacts for Nature and human societies. Moreover, perennial snow evolves to firn and ice, providing unique records of the past climate. Yet today no snow model adequately simulates relevant snow variables worldwide, not to mention their inability to represent firn processes and snow/permafrost interactions. The overarching aim of the IVORI project is to build such a model in view of three scientific objectives :
(1) Understand the role of water vapour transport in snow and its subsequent impacts on the ground thermal regime governing permafrost evolution;
(2) Understand how initial changes in surface snow microstructure are transferred deeper into the firn and affect ice core records;
(3) Determine the contributions of snow-climate feedbacks, triggered by changes in the albedo and insulating capacity of snow to the past and future of snow cover and ground temperature.
The model will provide a reliable assessment of snow-climate feedbacks in a changing climate and a rigorous appraisal of the modelling uncertainties. When completed, this work will pave the way for crucial advances in our understanding of glaciers, ice sheets and past climate through ice core records, with many fallouts for sea ice and permafrost evolution.
(1) Understand the role of water vapour transport in snow and its subsequent impacts on the ground thermal regime governing permafrost evolution;
(2) Understand how initial changes in surface snow microstructure are transferred deeper into the firn and affect ice core records;
(3) Determine the contributions of snow-climate feedbacks, triggered by changes in the albedo and insulating capacity of snow to the past and future of snow cover and ground temperature.
The model will provide a reliable assessment of snow-climate feedbacks in a changing climate and a rigorous appraisal of the modelling uncertainties. When completed, this work will pave the way for crucial advances in our understanding of glaciers, ice sheets and past climate through ice core records, with many fallouts for sea ice and permafrost evolution.
Since the beginning of the project in February 2021, we gathered two winter-long datasets of the detailed evolution of the snow at a few microns resolution in the French Alps. We prepared the expedition to the High Canadian Arctic (69 N) to gather a similar dataset for arctic snow that differs a lot from alpine snow. These datasets will be key in guiding and evaluating the new snow model that we are currently building. To do so, we worked on the numerical implementation of several processes responsible for snow evolution, namely phase changes, water vapour and heat transport in snow and percolation of liquid water. Our work led to numerical implementations that are stable and accurate and do not require extensive computation time. A first prototype of our new snow model is currently being implemented. In parallel, we dedicated our time to improve assimilation methods and satellite products that can be used to guide the model for regional simulations over Europe and the Canadian Arctic. Finally, we made several crucial advances in understanding how sunlight interacts with the snow microstructure and the light absorbing impurities that it may contains, in other words how to accurately model the colour of snow, a key driver of the Earth's climate. Some of these progresses were made thanks to inter-disciplinary collaborations and citizen science. These advances are milestones to obtain accurate regional simulations of the snow evolution.
In summary, we made significant progress beyond the state of the art regarding the numerics and formalism of snow modelling, regarding theoretical snow optics and regarding knowledge on the impact of light absorbing particles such as mineral dust or black carbon on snow evolution. For the second half of the project, we will gather the first winter-long dataset observations of the arctic snow microstructure. We plan to finish the snow model prototype and include firn evolution as well as delivering regional snow cover evolution simulations over Europe and the Canadian Arctic for the past 50 years and to the end of the century. The model and simulations will provide a reliable assessment of snow-climate feedbacks in a changing climate, for instance the impact of the snow cover evolution on ground temperature and permafrost thaw.