Exploring new climate feedbacks in the Arctic

探索北极新的气候反馈

• 批准号: RGPIN-2018-03941
• 负责人: Domine, Florent
• 金额: $ 5.25万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=748669
• 关键词: Exploring; new; climate; feedbacks; Arctic

The Arctic is warming at over twice the planetary rate because of specific feedbacks such as the snow-albedo feedback. Discovering and quantifying other feedbacks is essential for reliable projections of Arctic and planetary climate. The thawing of permafrost and the resulting atmospheric release of permafrost carbon as CO2 and CH4 has not been included in the latest IPCC climate projections, illustrating our insufficient understanding of Arctic climate feedbacks. I will study feedbacks relevant to the evolution of the permafrost thermal regime and to its carbon budget. Warming favors shrubs growth on tundra, leading to enhanced permafrost warming because of the extra thermal insulation provided by deeper snow in shrubs. This effect must be quantified. We first observed that the snow thermal conductivity was lower in shrubs, enhancing their permafrost warming potential. Alternatively, shrubs, by absorbing solar radiation in the fall, can lead to snow melt and the formation of melt-freeze crusts of high thermal conductivity, possibly reversing the shrub warming effect. These complex snow-shrubs-permafrost interactions will be studied by: (1) observing the correlation between meteorology, shrub properties and snow physical properties; (2) measuring the impact of shrubs on the winter surface energy budget. This requires measuring albedo but also vertical irradiance profiles as solar radiation penetrates >10 cm depth in the snow; (3) performing 3-D radiation transfer simulations using the DART model to understand and predict shrub impact on the 3-D radiation field, energy deposition in the snowpack and on snow metamorphism; (4) quantify soil shading in summer by measuring radiation transfer, therefore gaining a year-round understanding of shrub impact on the radiation budget of the surface and on the permafrost thermal regime; (5) implementing findings in a land surface and snow physics model.Shrub growth also leads to carbon sequestration by enhancing biomass and litter buildup, possibly mitigating the microbial respiration of thawed old carbon. I will study the evolution of carbon stocks of soils near Umiujaq, Nunavik, where lichen tundra is being invaded by dwarf birch shrubs. Soils there contain almost no old carbon, facilitating the quantification of new carbon. Biomass and litter will be quantified, and shrub age obtained by dendrochronology. The structure of the organic matter in litter will be analyzed to understand its degradation kinetics and quantify mid- to long-term storage potential. Lastly, biologists and I will collaborate on the interactions between snow, climate and the population dynamics of lemmings. We will test the hypothesis that rain on snow events in the fall, by leading to a hard basal snow layer, impede the ability of lemmings to feed and reproduce in winter, thus preventing a population irruption.

由于特定的反馈，如雪的反馈，北极正在以超过地球速度两倍的速度变暖。发现和量化其他反馈对于北极和行星气候的可靠预测至关重要。永久冻土的融化以及由此产生的永久冻土碳以CO2和CH 4的形式释放到大气中，并没有包括在IPCC最新的气候预测中，这表明我们对北极气候反馈的理解不足。我将研究反馈相关的永冻土热制度的演变和碳收支。变暖有利于苔原上灌木的生长，由于灌木中较深的积雪提供了额外的隔热作用，导致永久冻土层变暖。这种影响必须量化。我们首先观察到，雪的导热性较低的灌木，提高他们的永久冻土变暖的潜力。另一方面，灌木在秋季吸收太阳辐射，可导致积雪融化，形成高导热性的融冻结皮，从而可能逆转灌木的升温效应。这些复杂的雪-灌木-冻土相互作用将通过以下方式进行研究：（1）观察气象学、灌木特性和雪物理特性之间的相关性;（2）测量灌木对冬季地表能量收支的影响。这需要测量太阳辐射穿透雪中>10厘米深度时的垂直辐照度分布;（3）使用DART模型进行三维辐射传输模拟，以了解和预测灌木对三维辐射场、积雪中的能量沉积和雪变质的影响;（4）通过测量辐射传输来量化夏季土壤遮蔽，从而获得灌木对地表辐射收支和冻土热状况的全年影响;（5）在陆地表面和雪物理模型中实施研究结果。灌木的生长也通过增加生物量和凋落物的积累而导致碳固存，可能减轻解冻的旧碳的微生物呼吸作用。我将研究努纳维克的Umiujaq附近土壤碳储量的演变，那里的地衣苔原正被矮桦树灌木入侵。那里的土壤几乎不含旧碳，这有利于新碳的量化。生物量和凋落物将被量化，灌木年龄通过树木年代学获得。将分析凋落物中有机物的结构，以了解其降解动力学并量化中长期储存潜力。最后，生物学家和我将合作研究雪、气候和旅鼠种群动态之间的相互作用。我们将测试的假设，在秋天的雪事件雨，通过导致一个硬的基底雪层，阻碍旅鼠的能力，以饲料和繁殖在冬季，从而防止人口的入侵。