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Tipping Points, Positive Feedback Switches, and the Potential for Rapid Change in Arctic Ecosystems

Tipping Points, Positive Feedback Switches, and the Potential for Rapid Change in Arctic Ecosystems
Type: 
Plenary
Time: 
16 March 2010 - 11:20am
Andrea H Lloyd1
1Department of Biology, Middlebury College, 372 Bicentennial Hall, Middlebury College, Middlebury, VT, 05753, USA, Phone 802-443-3165, Fax 802-443-2072, lloyd [at] middlebury [dot] edu

In this talk, I will review the evidence for widespread ecosystem change in the Arctic, and explore the idea that Arctic ecosystems share a tendency to exhibit abrupt shifts in structure and function as climate warms. Improving our understanding of the causes and dynamics of rapid, nonlinear ecosystem change is an important goal common to both terrestrial and marine ecosystems.

Recent years have seen a rapid accumulation of evidence of pervasive change in Arctic ecosystems, marine and terrestrial. Many of these changes are consistent with ecological expectations that more southerly species will work their way northward as climate warms. On land, boreal tree species began moving northward decades ago in many parts of the arctic (e.g., Lloyd 1997), and the areal extent of tall shrub tundra has expanded since the mid-1900s (e.g., Tape et al. 2006). In the oceans, there is similar evidence that subarctic species such as gray whales, Pollock and pink salmon are moving northward into Arctic waters (e.g., Grebmeier et al. 2006). Although the weight of evidence suggests that ecological transformation is widespread, the temporal trajectory of ecosystem change remains more poorly known.

There is mounting evidence, however, that terrestrial and marine ecosystems in the Arctic share a high probability of exhibiting rapid, nonlinear responses to climate change. On land, for example, data suggest that the advance of tall, woody vegetation into low-stature tundra may initiate positive feedbacks that accelerate the rate of change (e.g., Sturm et al. 2005). Such 'positive-feedback switches' (Wilson and Agnew 1992) may allow initially gradual changes in species distribution or community composition to accelerate once thresholds in species abundance are surpassed. In marine systems, tipping points may occur as thresholds in key physical drivers (including water temperature, ice extent, and aragonite saturation) are crossed (e.g., Carmack et al. 2006, Grebemeier et al. 2006, Fabry et al. 2009). Accurate predictions of the future trajectory of change in Arctic ecosystems will require a better understanding of the processes that may promote abrupt, rapid shifts in ecosystem structure.

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National Science Foundation | Division of Arctic Sciences
National Science Foundation
National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
International Arctic Systems for Observing the Atmosphere
International Arctic Systems for Observing the Atmosphere
Study of Environmental Arctic Change
Study of Environmental Arctic Change
Arctic System Science Program
Arctic System Science Program
US Arctic Research Commission
US Arctic Research Commission
North Slope Science Initiative
North Slope Science Initiative
International Arctic Science Committee
International Arctic Science Committee
Arctic Ocean Sciences Board
Arctic Ocean Sciences Board
Alaska Ocean Observing System
Alaska Ocean Observing System
Department of Energy
Department of Energy
National Aeronautics and Space Administration
National Aeronautics and Space Administration
World Wildlife Fund
WWF
Association of Polar Early Career Scientists
Association of Polar Early Career Scientists
Bureau of Land Management
Bureau of Land Management
International Study of Arctic Change
International Study of Arctic Change
ArcticNet
ArcticNet
DAMOCLES
Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies

This work is supported by the National Science Foundation (NSF) under the ARCUS Cooperative Agreement ARC-0618885. Any opinions, findings, and conclusions or recommendations expressed do not necessarily reflect the views of the NSF.