Low-frequency variability in Canadian hydroclimate

加拿大水文气候的低频变化

• 批准号: RGPIN-2017-04795
• 负责人: StJacques, JeannineMarie
• 金额: $ 1.68万
• 依托单位: Concordia University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709304
• 关键词: Low; frequency; variability; Canadian; hydroclimate

Freshwater is our most vital natural resource and it is under severe threat globally due to global warming and direct human impacts. I study Canadian freshwater availability, including floods and droughts, for the last two millennia, present and near future. My long-term objective is to better understand multi-decadal and multi-centennial water variability and apply this long-term baseline to better estimate the probabilities of floods, droughts and other related extreme events. This type of low-frequency variability is just at or beyond the range of instrumental records, yet its comprehension is essential. For these baselines, we need the longest (i.e. centennial or longer) and most accurate water records. In the near future, Canada will be affected by the extremes of floods and droughts becoming even more extreme due to global warming. Hence an initial present-day underestimation of their recurrence probabilities due to using too short baseline records will prove costly. As well, understanding low-frequency variability is needed for the regional detection of global warming. When we attempt to attribute an observed hydrological change to global warming, we have to know what the natural multi-decadal to multi-centennial variability is, because such low-frequency variability can be easily mistaken for the effects of global warming. Sources of natural variability include atmosphere-ocean climate oscillations such as the El Nino-Southern Oscillation and Pacific Decadal Oscillation. In my long-term baseline studies, I use the longest observed records, and then go back beyond them, using records derived from tree-ring widths or pollen preserved in lake sediments and sampled at high resolution. The short-term objectives of my proposal are: 1) to examine central, northern and Maritime Canadian river records for the impacts of the climate oscillations on floods, because leaving these out may cause underestimation of flood return intervals and heights; 2) to better estimate the probabilities of droughts and wet periods in southern Alberta and southeastern Québec, using long baselines from millennial-length river reconstructions based on tree-rings, carefully constructed to capture low-frequency variability; 3) to examine changes in moisture and temperature, and consequently forest composition in southeastern Québec over the last 1000 years via pollen preserved in lake sediments and sampled at high-resolution; and 4) to use sedimentary pollen to extend fire records back for a millennium in central Saskatchewan (fire and drought are closely linked). This research program is novel as it studies water variability at both multi-decadal and multi-centennial scales, using the widest possible range of data sources, and focuses on the costly impacts of both droughts and floods in Canada. It will allow significant progress in more resilient water management in the presence of global warming.

淡水是我们最重要的自然资源，由于全球变暖和人类的直接影响，它在全球范围内受到严重威胁。我研究了过去两千年、现在和不久的将来加拿大淡水的可获得性，包括洪水和干旱。我的长期目标是更好地了解几十年和几百年的水的可变性，并应用这一长期基线来更好地估计发生洪水、干旱和其他相关极端事件的可能性。这种类型的低频变化只是在仪器记录的范围内或超出了仪器记录的范围，但它的理解是必不可少的。对于这些基线，我们需要最长的(即百年或更长的)和最准确的水记录。在不久的将来，由于全球变暖，加拿大将受到极端洪水和干旱的影响，变得更加极端。因此，由于使用太短的基线记录，目前对其复发概率的初步低估将被证明代价高昂。此外，了解低频变化对于全球变暖的区域探测也是必要的。当我们试图将观测到的水文变化归因于全球变暖时，我们必须知道自然的几十年到几百年的变化是什么，因为这种低频变化很容易被误认为是全球变暖的影响。自然变化的来源包括大气-海洋气候振荡，如厄尔尼诺-南方涛动和太平洋年代际振荡。在我的长期基线研究中，我使用最长的观测记录，然后使用来自树木年轮宽度或保存在湖泊沉积物中并以高分辨率采样的花粉的记录。我建议的短期目标是：1)检查气候振荡对洪水的影响的加拿大中部、北部和沿海河流的记录，因为忽略这些记录可能会导致低估洪水发生的间隔和高度；2)更好地估计艾伯塔省南部和魁北克东南部发生干旱和雨季的可能性，使用基于树木年轮的千年长河流重建的长基线，仔细构建以捕捉低频变化；3)通过保存在湖泊沉积物中的花粉并以高分辨率采样，研究过去1000年来魁北克东南部的湿度和温度变化，以及由此产生的森林组成；以及4)使用沉积花粉将萨斯喀彻温省中部的火灾记录追溯到一千年前(火灾和干旱密切相关)。这项研究计划是新颖的，因为它使用尽可能广泛的数据源，研究了数十年和数百年尺度上的水的可变性，并侧重于加拿大干旱和洪水造成的代价高昂的影响。它将使在全球变暖的情况下，在更具弹性的水管理方面取得重大进展。