Permafrost and seasonally frozen ground comprise a critically important component of the dynamic arctic terrestrial system, constituting a closely tied subsystem interacting with snow cover, vegetation, and the overlying atmosphere. This permafrost subsystem regulates the local exchange of energy, water, and materials (including carbon and nitrogen), and its influence extends beyond the arctic land to the hydrosphere and the extra-tropical climate. Furthermore, the long timescale of permafrost dynamics requires evaluation of the evolution and impacts of the subsystem on the glacial-interglacial time frame. While some recent numerical projections show rapid and widespread degradation of permafrost in response to climate change during this century, global climate system models with physically based snow and permafrost dynamics have not been fully tested, using new observationally-based evidence, for spatial and temporal variability of the subsystem under different climate conditions such as the Holocene optimum or the Last Glacial Maximum (LGM). Evaluation of the climate sensitivity to the permafrost will provide vital insight to future scenarios, especially in the Northern Hemisphere. The focus will be on three late Quaternary eras for which numerical simulations are widely performed by the collaborative efforts of the Paleoclimate Model Intercomparison Project (PMIP: i.e., the preindustrial present (0 ka, where ka = thousand years before present), mid-Holocene (6 ka), and the LGM (21ka). This project will focus on evaluating the structure and function of the permafrost subsystem under different climate conditions.
The primary questions to be addressed are: 1. How well do the permafrost distributions simulated by global climate models agree with reconstructions from the proxy data? 2. How widely did the permafrost distribution change under different climate conditions? Will permafrost change have serious consequences in nature, life, and societies in the Arctic? Correspondingly, by which processes and interactions does the permafrost subsystem impact the climate of the past and present? How important are the vegetation and soil types? 3. What can we learn from the permafrost subsystem simulations under different climatic conditions to mitigate or adapt to future changes?
Intellectual merits: The reconstructed vegetation map currently available for the climate model inputs will be updated by combining recent results from paleobotanic research, providing a basis for our surface boundary conditions. The simulated results (permafrost distribution) from multiple models as well as the forcing data from the PMIP2 outputs (surface temperature, precipitation [or wetness], and surface wind) will be compared and evaluated with other updated proxy-derived maps. A series of organized numerical sensitivity experiments with different levels of complexity in snow-permafrost dynamics will delineate the essential processes within the permafrost subsystem. Hierarchical experiments of coupled and uncoupled simulations with the atmosphere will quantify the interactions between the atmosphere and the subsurface, and the function of the subsystem as a whole in arctic and global climate.
Broader impacts: broader impact activities will focus on delivering information about direct implications for future climate change projection, and for adaptation planning. Improved scientific understanding of the permafrost subsystem will enhance assessments of the risks of climate change to infrastructure and society, especially on life and culture in the Arctic. This project will also contribute to emerging efforts in earth system modeling, which requires realistic subsurface simulations in order to study the biogeochemical processes that are important for surface exchanges of water vapor and other radiatively active gases. Maps of past permafrost distribution, vegetation and other simulated results in Beringia provide materials to the social and anthropogenic sciences, particularly in such topics as the history of human migration into North America, and the early history of Alaska Natives. It will also facilitate outreach to secondary schools, universities, museums and the general public. Underrepresented student populations such as Alaska Natives, those geographically isolated and economically disadvantaged are among the target audiences.