Modelling climate change effects on the spatial distribution of mountain permafrost at three sites in northwest Canada

Spatial models of present-day mountain permafrost probability were perturbed to examine potential climate change impacts. Mean annual air temperature (MAAT) changes were simulated by adjusting elevation in the models, and cloud cover changes were examined by altering the partitioning of direct beam and diffuse radiation within the calculation for potential incoming solar radiation (PISR). The effects of changes in MAAT on equilibrium permafrost distribution proved to be more important than those due to cloud cover. Under a −2 K scenario (approximating Little Ice Age conditions), permafrost expanded into an additional 22–43% of the study areas as zonal boundaries descended by 155–290 m K − 1. Under warming scenarios, permafrost probabilities progressively declined and zonal boundaries rose in elevation. A MAAT change of +5 K, caused two of the areas to become essentially permafrost-free. The absolute values of these predictions were affected up to ±10% when lapse rates were altered by ±1.5 K km − 1 but patterns and trends were maintained. A higher proportion of diffuse radiation (greater cloud cover) produced increases in permafrost extent of only 2–4% while decreases in the diffuse radiation fraction had an equal but opposite effect. Notwithstanding the small change in overall extent, permafrost probabilities on steep south-facing slopes were significantly impacted by the altered partitioning. Combined temperature and PISR partitioning scenarios produced essentially additive results, but the impact of changes in the latter declined as MAAT increased. The modelling illustrated that mountain permafrost in the discontinuous zone is sensitive spatially to long-term climate change and identified those areas where changes may already be underway following recent atmospheric warming.

[1]  W. Haeberli.  Die Basis-Temperatur der winterlichen Schneedecke als moglicher Indikator fur die Verbreitung von Permafrost in den Alpen , 1973 .

[2]  S. Harris.  Altitude Trends in Permafrost Active Layer Thickness, Kluane Lake, Y.T. , 1987 .

[3]  S. Harris.  Altitude Trends in Permafrost Active Layer Thickness, Kluane Lake, Yukon Territory , 1987 .

[4]  Martin Hoelzle,et al.  Permafrost occurrence from BTS measurements and climatic parameters in the eastern Swiss Alps , 1992 .

[5]  A. Corte,et al.  Interactions and relations between mountain permafrost, glaciers, snow and water , 1992 .

[6]  J. A. Heginbottom,et al.  Permafrost and ground ice conditions of northwestern Canada , 1992 .

[7]  G. Cheng,et al.  Mountain permafrost and climatic change , 1993 .

[8]  C. Burn.  Permafrost, tectonics, and past and future regional climate change, Yukon and adjacent Northwest Territories , 1994 .

[9]  Thian Yew Gan,et al.  Northward migration of permafrost along the Mackenzie highway and climatic warming , 1994 .

[10]  Simulating the effects of mean annual air-temperature changes on permafrost distribution and glacier size: an example from the Upper Engadin, Swiss Alps , 1995 .

[11]  E. S. Melnikov,et al.  Circum-Arctic map of permafrost and ground-ice conditions , 1997 .

[12]  Stephan Gruber,et al.  Statistical modelling of mountain permafrost distribution: local calibration and incorporation of remotely sensed data , 2001 .

[13]  M. Smith,et al.  Climate and the limits of permafrost: a zonal analysis , 2002 .

[14]  A. Lewkowicz,et al.  Probability mapping of mountain permafrost using the BTS method, Wolf Creek, Yukon Territory, Canada , 2004 .

[15]  E. Blake,et al.  Multidisciplinary Investigations of Alpine Ice Patches in Southwest Yukon, Canada: Paleoenvironmental and Paleobiological Investigations , 2004 .

[16]  S. Burns,et al.  Regional atmospheric circulation change in the North Pacific during the Holocene inferred from lacustrine carbonate oxygen isotopes, Yukon Territory, Canada , 2005, Quaternary Research.

[17]  David M. Lawrence,et al.  A projection of severe near‐surface permafrost degradation during the 21st century , 2005 .

[18]  C. Symon,et al.  Arctic climate impact assessment , 2005 .

[19]  Alexander Brenning,et al.  Sampling and statistical analyses of BTS measurements , 2005 .

[20]  J. Janke,et al.  Modeling past and future alpine permafrost distribution in the Colorado Front Range , 2005 .

[21]  F. Nelson,et al.  Comment on “A projection of severe near‐surface permafrost degradation during the 21st century” by David M. Lawrence and Andrew G. Slater , 2006 .

[22]  M. Hoelzle,et al.  Ground surface temperature scenarios in complex high-mountain topography based on regional climate model results , 2007 .

[23]  Mountain permafrost probability mapping using the BTS method in two climatically dissimilar locations, northwest Canada , 2008 .

[24]  D. Froese,et al.  Ancient Permafrost and a Future, Warmer Arctic , 2008, Science.

[25]  D. Colombaroli,et al.  Fire—vegetation interactions during the Mesolithic—Neolithic transition at Lago dell'Accesa, Tuscany, Italy , 2008 .

[26]  David M. Lawrence,et al.  Sensitivity of a model projection of near‐surface permafrost degradation to soil column depth and representation of soil organic matter , 2008 .

[27]  P. Mayewski,et al.  The Mt Logan Holocene—late Wisconsinan isotope record: tropical Pacific—Yukon connections , 2008 .

[28]  B. Luckman,et al.  Maximum June–July temperatures in the southwest Yukon over the last 300 years reconstructed from tree rings , 2008 .

[29]  A. Lewkowicz.  Evaluation of miniature temperature‐loggers to monitor snowpack evolution at mountain permafrost sites, northwestern Canada , 2008 .

[30]  P. Bonnaventure,et al.  Interchangeability of mountain permafrost probability models, northwest Canada , 2008 .