Arctic-boreal climate feedbacks: Synthesis of information from integrated research programs

Two workshops were held at NCEAS in April 1997 to examine the major high-latitude climate feedbacks due to trace-gas fluxes, water and energy exchange, and the changes in vegetation and disturbance regimes that modify these climate feedbacks. The results of this synthesis are being prepared for publication in a special issue of Global Change Biology. The objectives of the workshops were to (1) integrate the synthesis of arctic and boreal North American research that addresses the role of climate vs. of vegetation-mediated processes in high-latitude feedbacks to global climate, (2) integrate research findings across a latitudinal gradient spanning tundra and boreal forest to understand the roles of the large climatic and vegetation gradients in controlling ecosystem feedbacks to climate, and (3) identify research gaps and promote modeling of the transient changes in vegetation and climatic feedbacks that occur over time scales of decades to centuries. These workshops integrate the research of four major high-latitude research programs (BOREAS, the Arctic Flux study, and the arctic and boreal LTER programs) and serve to synthesize and model processes along the two IGBP North American high latitude transects (the BOREAS transect and the Alaska transect).

Major integrating synthesis papers are being prepared for each of these topic areas that builds on information from individual studies and integrates it by comparative analysis and/or modeling. In addition, many participants are synthesizing (singly or in groups) the results of individual programatic efforts. These programmatic syntheses were a necessary first step for the broader arctic-boreal synthesis. The papers that are being written as a result of the workshop are listed below. These papers represent a comprehensive synthesis of information on high-latitude climate feedbacks. Global Change Biology has agreed to publish the synthesis.

The broad synthetic papers (sections on integration and circumpolar extrapolation) build on the background (programmatic syntheses) and have a parallel structure. These papers summarize the patterns and controls over a particular process (e.g., energy exchange or CO2 flux), often using models as a framework for synthesis, then extrapolate these results to the two Siberian IGBP transects (East and West Siberia. The purpose here is two-fold: first to provide parallel structure for the synthesis papers and secondly to provide an initial set of predictions about rates and controls over processes that might be observed in the two Siberian transects. The results of these extrapolations will provide a useful starting point for the Siberian research.

The workshop included both established experts in the fields necessary to address the topics of the workshops, as well as several (9) graduate students and postdocs that had actively investigated topics critical to the topics of the workshop. These individuals participated actively in the synthesis, and hopefully this will enhance their involvement in future high-latitude research, because they now know as much as any of the rest of us about the current state of knowledge and the outstanding unresolved issues.

The workshops are important in several regards. They provide the first integration of arctic and boreal research on the role of high-latitude ecosystems in feedbacks to climatic change. The workshops contribute to international coordination of high-latitude research and to the planning for a major research initiative along tundra-boreal transects in Siberia. These workshops will be a major contribution to IGBP synthesis efforts. They explicitly include both climate and land-use change in discussions of terrestrial feedbacks to climate, whereas most past synthesis efforts have separated climatic and land-use effects.

Papers being written as a result of the arctic-boreal synthesis workshops

Ia. Vegetation composition and distribution (Background syntheses)
1. W. Steffen and T. Kittell. Arctic-boreal vegetation distribution and change estimated from dynamic global vegetation models.
2. D. Walker. Interactions of climate and landscape evolution as controls over distribution of arctic vegetation
3. B. Stocks. Current patterns and trends in boreal fire regime
4. K. Raffa and C. Malmstrom. Climate-insect-pathogen interactions as controls over boreal vegetation dynamics.
5. M. Apps. Interaction of environment and disturbance as constrols over boreal vegetation dynamics and carbon stocks
6. M. Fleming, F.S. Chapin, et al. Circumpolar vegetation map of for extrapolation of land-atmosphere exchange at high latitudes

Ib. Integration and circumpolar extrapolation
M. Apps, F.S. Chapin, III, T. Kittell, C. Malmstrom, K. Raffa, W. Steffen, B. Stocks, D.A. Walker, E. Vaganov, Circumpolar extrapolation of patterns and sensitivity to change in arctic-boreal vegetation

IIa. Energy balance feedbacks to climate (Background syntheses)
1. J. McFadden, W. Eugster, and F.S. Chapin. Vegetation and climatic controls over tundra energy budgets
2. W. Rouse. Vegetation and climatic controls over energy budgets of northern wetlands
3. D. Baldocchi et al. Vegetation and climatic controls over boreal energy budgets

IIb. Integration and circumpolar extrapolation
W. Eugster, W. Rouse, R. Pielke, J. McFadden, D. Baldocchi, Y. Vaganov, T. Kittell. and F.S. Chapin, III. Circumpolar extrapolation of water and energy exchange in arctic-boreal ecosystems

IIIa. Trace-gas feedbacks to climate (Background syntheses)
1. J. Randerson, S.A. Zimov, and F.S. Chapin, III. Potential roles of increased productivity and disturbances as causes of high-latitude amplification of atmospheric CO2
2. D. McGuire, W. Parton, J. Randerson, and S. Running. Transect estimates of high-latitude carbon exchange from generic global models.
3. E. Rastetter and M. Williams. Estimates of high-latitude carbon exchange from canopy models
4. N. Roulet. Uncertainty in large-scale estimates of CO2 and CH4 exchange due to landscape heterogeneity
5. G. Livingston. Challenges in identification of wetlands by remote sensing.
6. M. Goulden et al. Boreal carbon exchange: A comparison eddy correlation measurements.
7. G. Vourlitis and W.C. Oechel: Temporal and spatial scaling of Alaskan carbon fluxes.
8. T. Gower et al. Carbon budgets of Canadian boreal forests.
9. J. Yarie, K. Van Cleve and R. Ruess. Carbon budgets of Alaskan boreal forests
10. J. Schimel. Role of winter processes in high-latitude carbon exchange.

IIIb. Integration and circumpolar extrapolation
1. T. Gower, M. Goulden, D. Hooper, E. Rastetter, R. Ruess, S. Running, G. Vourlitis, M. Williams, J. Yarie, S. Zimov, and F.S. Chapin. Physiological approaches to estimates of high-latitude carbon exchange.
2. S. Trumbore, M. Apps, S. Hobbie, D. McGuire, W. Parton, and J. Randerson. A process-based approach to estimates of high-latitude decomposition.
3. P. Crill, N. Roulet, W.S. Reeburgh, and G. Livingston. Circumpolar extrapolation of arctic and boreal methane fluxes.

IV. S. Running et al. High-latitude warming: fact or fiction? An analysis of recent climatic and ecological time series. V. F.S. Chapin, III and M. Apps,. Summary