Arctic Landscapes in Transition: Responses to Thawing Permafrost

Abstract

Observations indicate that over the past several decades, geomorphic processes in the Arctic have been changing or intensifying. Coastal erosion, which currently supplies most of the sediment and carbon to the Arctic Ocean [Rachold et al., 2000], may have doubled since 1955 [Mars and Houseknecht, 2007]. Further inland, expansion of channel networks [Toniolo et al., 2009] and increased river bank erosion [Costard et al., 2007] have been attributed to warming. Lakes, ponds, and wetlands appear to be more dynamic, growing in some areas, shrinking in others, and changing distribution across lowland regions [e.g., Smith et al., 2005]. On the Arctic coastal plain, recent degradation of frozen ground previously stable for thousands of years suggests 10–30% of lowland and tundra landscapes may be affected by even modest warming [Jorgenson et al., 2006]. In headwater regions, hillslope soil erosion and landslides are increasing [e.g., Gooseff et al., 2009].

Thermo-erosion gullies boost the transition from wet to mesic tundra vegetation

“…Continuous permafrost zones with well-developed polygonal ice-wedge networks are particularly vulnerable to climate change because ice wedges are usually found near the top of permafrost Jorgenson et al, 2006;Woo et al, 2008;Vonk et al, 2013). In these regions, thawing permafrost can result in ground ice erosion and displacement of sediments, carbon and nutrients by drainage (Rowland et al, 2010;Godin et al, 2014;Harms et al, 2014). This thermo-erosion process has especially been observed across North-America (Grosse et al, 2011), in Siberia (Gün-ther et al, 2013 and in the Antarctic Dry Valleys (Levy et al, 2008).…”

“…Several forms of ground and massive ice can be found within permafrost (Rowland et al, 2010), especially ice wedges in regions where winter temperatures enable thermal contraction cracking (Fortier and Allard, 2005;Kokelj et al, 2014;M. T. Jorgenson et al, 2015;Sarrazin and Allard, 2015).…”

Eos, Transactions, American Geophysical Union Volume 92, Number 9, 1 March 2011

“…Of particular significance are the 2 million square kilometers (or 8.8%) of the total Northern Hemisphere permafrost region (22.8 × 10 6 square kilometers) that have ice-rich permafrost (>20% excess ice content) in the upper 10 meters [Zhang et al, 1999] (see Figure S1a in the online supplement to this Eos issue (http:// www .agu .org/ eos _ elec)). Though all permafrost can be affected by warming and thawing, thawing of ice-rich permafrost causes particularly strong feedbacks to ground surface stability, microtopography, hydrology, ecosystem function, and the carbon cycle [Rowland et al, 2010].…”

Detection and Attribution of Observed Impacts

“…Climate change impacts have been related to permafrost changes, including an increase of flow speed of rock glaciers and debris lobes in the European Alps and Alaska (high confidence), resulting in rockfall, debris flows, and potential hazards to transport and energy systems (Kääb et al, 2007;Delaloye et al, 2010;Daanen et al, 2012), expansion, deepening and higher dynamics of thermokarst lakes and ponds in the Arctic (Rowland et al, 2010), and a doubled erosion rate of Alaska's northern coastline over the past 50 years (high confidence; Section 18.3.3.1, Table 18-8; Mars and Houseknecht, 2007;Karl et al, 2009;Forbes, 2011). Expansion of channel networks (Toniolo et al, 2009), increased river bank erosion (Costard et al, 2007), and an increase in hillslope erosion and landsliding in northern Alaska since the 1980s (Gooseff et al, 2009) have all been related to climate.…”

“…Feedbacks and interactions complicate detection of drivers and effects. For example, drying of land surface due to permafrost degradation may cause an increase in wildfires, in turn resulting in a loss of ground surface insulation and change in surface albedo that accelerates permafrost thawing (Rowland et al, 2010;Forkel et al, 2012).…”