Dynamics and Consequences of Increasing Ice-wedge Degradation

冰楔退化加剧的动力学和后果

• 批准号: 1023623
• 负责人: Yuri Shur
• 金额: $ 76.6万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-12-15 至 2015-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1023623&HistoricalAwards=false
• 关键词: Dynamics; Consequences; Increasing; Ice; wedge

This research will quantify the nature and extent of ice-wedge degradation, evaluate the feedbacks controlling the dynamics of degradation and stabilization, and assess the consequences of the degradation to arctic ecosystems. Massive ice in the form of ice wedges occupies 10?70% of near- surface permafrost and fundamentally influences the dynamics and vulnerability of arctic ecosystems to climate change. Arctic permafrost has been considered stable because ground temperatures remain low, but recent observations in northern Alaska of an abrupt increase in degradation of ice-wedges, indicate that even permafrost in the Arctic is susceptible to degradation from climate change because of the massive ice that has formed just below the active layer. High-resolution satellite images of Alaska and Russia reveal that ice-wedge degradation is more extensive in the Arctic than in the subarctic because of this near-surface ice. The dynamics of ice-wedge degradation has been shown to be affected by the positive feedback of impounded surface water and negative feedbacks from rapid vegetation and peat accumulation that are able to stabilize degrading ice wedges, yet there has been no quantification of the physical mechanisms controlling the processes. This degradation of ice wedges greatly affects arctic ecosystems by altering surface topography, modifying drainage networks, enhancing peat accumulation and methane production under anaerobic conditions, and radically shifting vegetation composition, but these consequences are poorly understood. Given that ice-wedge degradation directly or indirectly affects most arctic terrain it is critical to quantify the dynamics and consequences of ice-wedge degradation.This project addresses these uncertainties through a comprehensive assessment of the nature and extent of ice-wedge degradation, the feedbacks controlling ice-wedge dynamics, and the consequences of degradation on ecosystem patterns and processes. The research brings together an interdisciplinary team with expertise in permafrost and soil, biogeochemisty and trace gas emissions, vegetation, and remote sensing to address hypotheses through field surveys, remote sensing, and modeling. The extent and rate of ice-wedge degradation across landscapes and climates will be assessed by comparing the ice-wedge volume by terrain units, describing stages of degradation and stabilization; quantifying degradation across the circumarctic; developing image processing algorithms for mapping thermokarst; and quantifying degradation rates through aerial photo analysis. How the dynamics of ice- wedge degradation and stabilization are controlled by positive and negative feedbacks will be assessed by identifying structural properties of surface soils that protect ice wedges; quantifying differences in net radiation and soil heat flux among degradation stages; and identifying thresholds for thermokarst through numerical modeling. The consequences of ice-wedge degradation will be documented by quantifying micro-topographic changes caused by ice-wedge degradation; changes in surface water storage and drainage patterns; soil-organic carbon stocks through degradation sequence; differences in methane emissions among degradation stages; and quantifying shifts in vegetation composition through degradation sequence. The research is essential for understanding of the effects of climate changes on permafrost and arctic ecosystems because ice wedges are especially sensitive component of terrestrial arctic ecosystems. Knowledge of the nature and extent of ice wedges will improve land management, impact assessment, and facility design in ice-rich permafrost terrain. Information on the dynamics and feedbacks involved in ice-wedge degradation is needed to minimize effects of disturbance and to improve global climate change models that currently lack critical feedbacks. Documentation of the consequences of degradation is needed to better assess the role of fragmenting drainage networks in assessments of circumarctic hydrology, help resolve whether arctic soils will gain or lose carbon in the future, contribute information for assessing methane emissions across dynamically changing ecosystems, and provide data on the rates of vegetation change which can affect satellite measurement of vegetation productivity during assessments of vegetation greening in the Arctic.

本研究将量化冰楔退化的性质和程度，评估控制退化和稳定动态的反馈，并评估退化对北极生态系统的影响。以冰楔形式存在的巨大冰块占据了10？近地表永久冻土的70%，从根本上影响着北极生态系统对气候变化的动态和脆弱性。北极永久冻土一直被认为是稳定的，因为地面温度一直很低，但最近在阿拉斯加北部观测到冰楔退化的突然增加，这表明即使是北极的永久冻土也容易受到气候变化的影响，因为在活跃层下方形成了大量的冰。阿拉斯加和俄罗斯的高分辨率卫星图像显示，由于近地表的冰，北极地区的冰楔退化比亚北极地区更为广泛。冰楔退化的动力学已被证明受到地表水蓄积的正反馈和植被和泥炭快速积累的负反馈的影响，而植被和泥炭的快速积累能够稳定退化的冰楔，但控制这一过程的物理机制尚未量化。冰楔的退化通过改变地表地形、改变排水网络、增加厌氧条件下泥炭的积累和甲烷的产生，以及从根本上改变植被组成，极大地影响了北极生态系统，但人们对这些后果知之甚少。鉴于冰楔退化直接或间接地影响大部分北极地形，量化冰楔退化的动态和后果至关重要。本项目通过全面评估冰楔退化的性质和程度、控制冰楔动力学的反馈以及退化对生态系统模式和过程的影响来解决这些不确定性。该研究汇集了一个跨学科团队，他们在永久冻土和土壤、生物地球化学和微量气体排放、植被和遥感方面具有专业知识，通过实地调查、遥感和建模来解决假设。通过比较不同地形单元的冰楔体积，描述退化和稳定的阶段，将评估不同景观和气候条件下冰楔退化的程度和速度；环北极地区退化的量化；开发热岩溶制图图像处理算法；并通过航空照片分析量化降解率。通过确定保护冰楔的表层土壤的结构特性，评估冰楔退化和稳定的动力学是如何由正反馈和负反馈控制的；土壤净辐射和土壤热通量在不同退化阶段的量化差异并通过数值模拟确定热岩溶的阈值。冰楔退化的后果将通过量化由冰楔退化引起的微地形变化来记录；地表水储存和排水模式的变化；土壤有机碳储量的降解序列；不同降解阶段甲烷排放差异；并通过退化序列量化植被组成的变化。这项研究对于了解气候变化对永久冻土和北极生态系统的影响至关重要，因为冰楔是北极陆地生态系统中特别敏感的组成部分。了解冰楔的性质和范围将有助于改善冻土地区的土地管理、影响评估和设施设计。为了最大限度地减少干扰的影响和改进目前缺乏关键反馈的全球气候变化模式，需要有关冰楔退化的动力学和反馈的信息。需要记录退化的后果，以便更好地评估支离破碎的排水网络在评估环北极水文中的作用，帮助解决北极土壤未来是否会增加或减少碳，为评估动态变化的生态系统中的甲烷排放提供信息。并提供在北极植被绿化评估期间可能影响植被生产力卫星测量的植被变化率的数据。

项目成果

Ice Wedge Degradation and Stabilization Impact Water Budgets and Nutrient Cycling in Arctic Trough Ponds

冰楔退化和稳定影响北极槽池的水预算和养分循环

• DOI: 10.1029/2018jg004528
• 发表时间: 2018
• 期刊: Journal of Geophysical Research: Biogeosciences
• 作者: Koch, J. C.;Jorgenson, M. T.;Wickland, K. P.;Kanevskiy, M.;Striegl, R.
• 通讯作者: Striegl, R.

Middle to late Wisconsinan climate and ecological changes in northern Alaska: Evidences from the Itkillik River Yedoma

威斯康星州中晚期的气候和阿拉斯加北部的生态变化：来自伊特基利克河耶多马的证据

• DOI: 10.1016/j.palaeo.2017.08.006
• 发表时间: 2017
• 期刊: Palaeoecology
• 作者: Lapointe E., Lyna;Talbot, Julie;Fortier, Daniel;Fréchette, Bianca;Strauss, Jens;Kanevskiy, Mikhail;Shur, Yuri
• 通讯作者: Shur, Yuri

Degradation and stabilization of ice wedges: Implications for assessing risk of thermokarst in northern Alaska

冰楔的退化和稳定：对评估阿拉斯加北部热喀斯特风险的影响

• DOI: 10.1016/j.geomorph.2017.09.001
• 发表时间: 2017
• 期刊: Geomorphology
• 影响因子: 3.9
• 作者: Kanevskiy, Mikhail;Shur, Yuri;Jorgenson, Torre;Brown, Dana R.N.;Moskalenko, Nataliya;Brown, Jerry;Walker, Donald A.;Raynolds, Martha K.;Buchhorn, Marcel
• 通讯作者: Buchhorn, Marcel

Ice-wedge thermokarst: Past, present, and future

冰楔热喀斯特：过去、现在和未来

• 发表时间: 2018
• 期刊: France
• 作者: Kanevskiy, M.;Shur, Y.;Jorgenson, T.
• 通讯作者: Jorgenson, T.

Patterns and rates of riverbank erosion involving ice-rich permafrost (yedoma) in northern Alaska

• DOI: 10.1016/j.geomorph.2015.10.023
• 发表时间: 2016-01-15
• 期刊: GEOMORPHOLOGY
• 影响因子: 3.9
• 作者: Kanevskiy, Mikhail;Shur, Yuri;Vasiliev, Alexander
• 通讯作者: Vasiliev, Alexander