This project will develop and apply a regional Arctic System model for enhanced decadal predictions. It builds on successful research by four of the current PIs with support from the DOE Climate Change Prediction Program, which has resulted in the development of a fully coupled Regional Arctic Climate Model (RACM) consisting of atmosphere, land-hydrology, ocean and sea ice components. An expanded RACM, a Regional Arctic System Model (RASM), will include ice sheets, ice caps, mountain glaciers, and dynamic vegetation to allow investigation of coupled physical processes responsible for decadal-scale climate change and variability in the Arctic. RASM will have high spatial resolution (~5-50 times higher than currently practical in global models) to advance modeling of critical processes and determine the need for their explicit representation in Global Earth System Models (GESMs).

The pan-Arctic region is a key indicator of the state of global climate through polar amplification. However, a system-level understanding of critical arctic processes and feedbacks is still lacking. Rapid climate change has occurred in a number of Arctic System components during the past few decades, including retreat of the perennial sea ice cover, increased surface melting of the Greenland ice sheet, acceleration and thinning of outlet glaciers, reduced snow cover, thawing permafrost, and shifts in vegetation. Such changes could have significant ramifications for global sea level, the ocean thermohaline circulation and heat budget, ecosystems, native communities, natural resource exploration, and commercial transportation. The overarching goal of the RASM project is to advance understanding of past and present states of arctic climate and to improve seasonal to decadal predictions. To do this we will focus on variability and long-term change of energy and freshwater flows through the arctic climate system. The three foci of this research are:

• changes in the freshwater flux between arctic climate system components resulting from decadal changes in land and sea ice, seasonal snow, vegetation, and ocean circulation
• changing energetics due to decadal changes in ice mass, vegetation, and air-sea interactions
• the role of small-scale atmospheric and oceanic processes that influence decadal variability.

This research will address modes of natural climate variability as well as extreme and rapid climate change. It will also facilitate studies of climate impacts (e.g., droughts and fires) and of ecosystem adaptations to these impacts.

RASM will explore spatial resolutions not yet achievable in GESMs and will readily allow the addition of other earth system components, such as ecosystem or biochemistry models, thus allowing it to be a foundation for more complete Arctic System models. RASM will address societal needs for improved Arctic decadal climate projections. The educational and outreach efforts will provide interactions with scientists, real-world problems for student-directed research, and teacher training. Innovative educational materials for public dissemination, such as curriculum units, lesson plans, simulations, movies, and images, will be used by students and teachers in high school and university classrooms. This project will also emphasize the recruitment and mentoring of underrepresented groups and will provide undergraduates, graduate students, and postdocs with practical training in coupled climate system modeling and analysis. The PIs will incorporate research findings in their courses and departmental seminars and will contribute model improvements and findings to aid arctic climate-change predictions. Finally, the RASM code will be made freely available to the community. Simulation results will be broadly disseminated through peer-reviewed publications, presentations at conferences and workshops, the project web site, and public lectures.