Mapping the Vulnerability of Boreal Permafrost in Central Alaska in Relation to Thaw Rate, Ground Ice, and Thermokarst Development

IF 3.8 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
M. Torre Jorgenson, Thomas A. Douglas, Yuri L. Shur, Mikhail Z. Kanevskiy
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Abstract

Permafrost roughly affects half of the boreal region in Alaska and varies greatly in its thermo-physical properties and genesis. In boreal ecosystems, permafrost formation and degradation respond to complex interactions among climate, topography, hydrology, soils, vegetation, and disturbance. We synthesized data on soil thermal conditions and permafrost characteristics to assess current permafrost conditions in central Alaska, and classified and mapped soil landscapes vulnerable to future thaw and thermokarst development. Permafrost soil properties at 160 sites ranged from rocky soils in hillslope colluvium and glacial till, to silty loess, to thick peats on abandoned floodplains and bogs, across 64 geomorphic units. Ground-ice contents (% moisture) varied greatly across geomorphic units. Mean annual ground temperatures at ∼1 m depth varied 12.5°C across 77 sites with most permafrost near thawing or actively thawing. To assess the vulnerability of permafrost to climate variability and disturbance, we differentiated permafrost responses in terms of rate of thaw, potential thaw settlement, and thermokarst development. Using a rule-based model that uses geomorphic units for spatial extrapolation at the landscape scale, we mapped 10 vulnerability classes across three areas in central Alaska ranging from high potential settlement/low thaw rate in extremely ice-rich loess to low potential settlement/high thaw rate in rocky hillslope colluvium. Permafrost degradation is expected to result in 10 thermokarst landform types. Vulnerability classes corresponded to thermokarst features that developed in response to past climates. Differing patterns in permafrost vulnerability have large implications for ecosystem trajectories, land use, and infrastructure damage from permafrost thaw.

绘制阿拉斯加中部北方永久冻土带的脆弱性与融化速率、地面冰和热岩溶发育的关系
永久冻土带大约影响了阿拉斯加一半的北方地区,其热物理性质和成因差异很大。在北方生态系统中,多年冻土的形成和退化响应气候、地形、水文、土壤、植被和干扰之间复杂的相互作用。我们综合了土壤热条件和永久冻土特征的数据,以评估阿拉斯加中部目前的永久冻土条件,并对未来易受融化和热岩溶发育影响的土壤景观进行了分类和绘制。160个地点的永久冻土区的土壤特性包括64个地貌单元,从山坡崩积层和冰川垄的岩石土壤,到粉质黄土,再到废弃洪泛平原和沼泽上的厚泥炭。地冰含量(%水分)在不同的地貌单元之间变化很大。77个站点的年平均地表温度在~ 1 m深度变化12.5°C,大多数永久冻土接近融化或正在融化。为了评估多年冻土对气候变率和扰动的脆弱性,我们根据融化速率、潜在融化沉降和热岩溶发育对多年冻土的响应进行了区分。使用基于规则的模型,在景观尺度上使用地貌单元进行空间外推,我们绘制了阿拉斯加中部三个地区的10个脆弱性等级,从极富冰黄土的高潜在沉降/低融化速率到岩石山坡崩积层的低潜在沉降/高融化速率。预计多年冻土退化将导致10种热岩溶地貌类型。脆弱性等级对应于响应过去气候而形成的热岩溶特征。永久冻土脆弱性的不同模式对生态系统轨迹、土地利用和永久冻土融化对基础设施的破坏具有重大影响。
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来源期刊
Journal of Geophysical Research: Earth Surface
Journal of Geophysical Research: Earth Surface Earth and Planetary Sciences-Earth-Surface Processes
CiteScore
6.30
自引率
10.30%
发文量
162
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