Thermal and hydrological investigations of degrading permafrost

永久冻土退化的热学和水文研究

• 批准号: RGPIN-2016-06156
• 负责人: Burn, Christopher
• 金额: $ 4.81万
• 依托单位: Carleton University
• 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=754908
• 关键词: Thermal; hydrological; investigations; degrading; permafrost

The long-term objective of our research program is to understand the response of permafrost terrain to changes in factors that control ground temperatures, particularly changes in surface conditions and climate. Permafrost is ground that remains at or below 0C for two or more years. The principal factor governing the presence of permafrost is climate, and recent climate warming has led to increases in permafrost temperature throughout the North. The practical consequences of such warming are greatest when the seasonally thawed active layer penetrates into icy ground at the top of permafrost.We propose to study the relations between climate and permafrost in western Arctic Canada, and deepening of the active layer. We will emphasize four topics.(1) Near Whitehorse, where permafrost is close to 0 C, ground temperatures do not respond sensitively to climate because of energy needed for thawing ice. We intend to compare adjacent sites with and without permafrost, to determine how much more efficiently sites without permafrost present the climate warming signal, despite seasonal freezing and thawing. We have a 25 year record of ground temperatures to draw upon.(2) Near the western Arctic coast, we will examine the effect of slope angle on active-layer thickening. We expect that in flat terrain water liberated from permafrost may remain in place and freeze back, but it may run off from hill slopes. Therefore we expect greater subsidence on hill sides than in flat ground. We expect the association between annual climate and active-layer thickness to vary with slope angle if the top of permafrost changes each year with thawing.(3) In the western Arctic, we observe widespread thawing of the ice wedges that bound tundra polygons. These wedges are almost pure ice, and their melting leads to the greatest possible subsidence. The wedges lie below troughs in which snow accumulates, so subsidence may lead to further warming, as the depth of snow and its insulation effect increase. In lowlands water commonly accumulates in the troughs. We wish to determine the rate of trough deepening, its dependence on water and snow depth, and whether it accelerates in the wedges. We will study freeze-back of the troughs, for only once the active layer has refrozen may underlying permafrost cool. We may be able to forecast critical water and snow depths at which trough constituents do not freeze back and ice wedges melt completely.(4) Finally, we will study the gradient in permafrost and climate from the western Arctic coast through British Mountains to Old Crow Flats to determine how permafrost-climate relations change due to the influence of the mountains. We suspect that the coldest ground is found where winter inversions develop in mountain valley floors. We wish to determine the effects on permafrost temperatures of the mountains as they block coastal weather from moving inland.

我们的研究计划的长期目标是了解永冻土地形对控制地面温度的因素变化的反应，特别是地表条件和气候的变化。永久冻土是指两年或两年以上保持在0摄氏度或以下的地面。决定永久冻土存在的主要因素是气候，最近的气候变暖导致整个北方的永久冻土温度上升。这种变暖的实际后果是最大的季节性解冻的活动层渗透到冰冷的地面在顶部的permafrost. We建议研究气候和加拿大北极地区西部的永久冻土之间的关系，和深化的活动层。我们将重点讨论四个主题。(1)在怀特霍斯附近，永久冻土层接近0 ℃，地面温度对气候的反应并不敏感，因为融化冰需要能量。我们打算比较附近的网站和没有永久冻土，以确定有多少更有效的网站没有永久冻土目前的气候变暖的信号，尽管季节性冻结和解冻。我们有25年的地面温度记录可以利用。(2)在北极西部海岸附近，我们将研究倾斜角对活动层增厚的影响。我们预计，在平坦地带，从永久冻土中释放出来的水可能会留在原地并冻结，但它可能会从山坡上流失。因此，我们预计山坡上的沉降比平地上的大。如果永久冻土顶部每年随着融化而变化，我们预计年度气候和活动层厚度之间的关联会随着坡度角的变化而变化。(3)在北极西部，我们观察到连接苔原多边形的冰楔广泛融化。这些楔形体几乎是纯冰，它们的融化导致了最大可能的下沉。这些楔形物位于积雪的波谷之下，因此随着积雪深度和隔热效果的增加，下沉可能会导致进一步变暖。在低地，水通常积聚在槽中。我们希望确定低压槽加深的速度，它对水和雪深的依赖性，以及它是否在楔形中加速。我们将研究冻结回槽，只有一次活动层已经重新冻结可能下面的永久冻土冷却。我们也许能够预测临界水和雪的深度，在这个深度上，槽的成分不会冻结，冰楔完全融化。(4)最后，我们将研究从北极西部海岸到英国山脉到老乌鸦平原的永久冻土和气候梯度，以确定由于山脉的影响，永久冻土与气候的关系如何变化。我们怀疑最冷的地面是在山谷底部冬季逆温发展的地方。我们希望确定山脉对永久冻土温度的影响，因为它们阻止沿海天气向内陆移动。