Permafrost, wildfire, climate change processes, interactions, and feedbacks: co-development of Earth System Models between China and Norway

Arctic-boreal regions are warming at a much faster rate than the global mean. Arctic-boreal ecosystems combined are the largest reservoirs of terrestrial carbon and have long snow covered seasons. As a result, processes involved in these ecosystems have a high significance for global climate. Projected climate warming is expected to accelerate permafrost thaw and increase wildfire size, severity, and frequencies in Arctic-boreal ecosystems. Recent studies strongly argue that failing to represent some of the key Arctic-boreal ecosystem processes will lead to large uncertainty in future climate projections. Yet, key knowledge gaps remain, mainly because the potential for additional feedbacks and interactions across abrupt permafrost thawing, wildfires, and the climate systems are not commonly assessed. Furthermore, these processes are not typically included in state-of-the-art Earth System Models (ESMs), making it difficult to systematically quantify the interactions and feedbacks within the climate system. Therefore, there is an urgent need to invest in ESM development to better represent Arctic-boreal ecosystem processes and the coupling of these processes to the atmosphere. We aim to advance our understandings of the interactions and the feedback cycles between key Arctic-Boreal ecosystem processes and the climate system. We will investigate the impacts of 1) emissions driven climate feedbacks and 2) physically driven feedbacks from albedo associated with abrupt permafrost thaw and wildfire. We will achieve this goal by collaboratively improving ESMs that are developed and maintained in China and Norway. These regional scale model process developments are often under prioritized from the main model development efforts. When supported, however, these improvements can make great synergies with other main model developments, which will be extremely useful in closing the knowledge gap in the climate system. Within the two years of the project period, the CN-coESM partners have made ample model improvements. The NorESM model improvements made during this project framework includes implementing and accounting for interactive sources of methane and wildfires between the land and the atmosphere. Interactive here means that the respective sources depend spatio-temporally on an evolving climate accounting for land properties. First simulations indicate a stability of the methane levels for pre-industrial conditions, which is important for the understanding of the impact of anthropogenic emissions and any perturbation of the natural sources of methane. The Chinese parts have made improvements in the fire model within the land model of the NorESM. This includes development and implementation of 38 different greenhouse gas species emitted during wildfire occurrences. In addition, the land modeling groups between the Norwegian and Chinese partners have jointly made model improvements to better represent permafrost thaw processes such as excessive ground ice, land surface subsidence, wetland formation, and snow redistribution within the two models used in this project. A recent publication under the CN-coESM demonstrated that climate change can accelerate permafrost degradation, which will have a cascading effect in abrupt changes in the ecosystems where wildfires can occur much easier. Taken together, the model improvements being made in the CN-coESM will greatly advance our understanding in the processes related to how climate warming affects high latitude ecosystems and will increase our predictability under future climate warming.

Arctic-boreal regions are warming at a much faster rate than the global mean. Arctic-boreal ecosystems combined are the largest reservoirs of terrestrial carbon and have long snow covered seasons. As a result, processes involved in these ecosystems have a high significance for global climate. Projected climate warming is expected to accelerate permafrost thaw and increase wildfire size, severity, and frequencies in Arctic-boreal ecosystems. Recent studies strongly argue that failing to represent some of the key Arctic-boreal ecosystem processes will lead to large uncertainty in future climate projections. Yet, key knowledge gaps remain, mainly because the potential for additional feedbacks and interactions across abrupt permafrost thawing, wildfires, and the climate systems are not commonly assessed. Furthermore, these processes are not typically included in state-of-the-art Earth System Models (ESMs), making it difficult to systematically quantify the interactions and feedbacks within the climate system. Therefore, there is an urgent need to invest in ESM development to better represent Arctic-boreal ecosystem processes and the coupling of these processes to the atmosphere. We aim to advance our understandings of the interactions and the feedback cycles between key Arctic-Boreal ecosystem processes and the climate system. We will investigate the impacts of 1) emissions driven climate feedbacks and 2) physically driven feedbacks from albedo associated with abrupt permafrost thaw and wildfire. We will achieve this goal by collaboratively improving ESMs that are developed and maintained in China and Norway. These regional scale model process developments are often under prioritized from the main model development efforts. When supported, however, these improvements can make great synergies with other main model developments, which will be extremely useful in closing the knowledge gap in the climate system.