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: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633865
• 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，由于全球变暖和直接的人类影响，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的淡水资源，包括洪水和干旱。我的长期目标是更好地了解多年代际和百年的水变化，并应用这一长期基线来更好地估计洪水、干旱和其他相关极端事件的可能性。这种类型的低频变异性刚好在或超出仪器记录的范围内，但理解它是必不可少的。对于这些基线，我们需要最长的（即百年或更长）和最准确的水记录。在不久的将来，由于全球变暖，加拿大将受到更加极端的洪水和干旱的影响。因此，由于使用过短的基线记录而低估它们的重现概率将证明代价高昂。此外，了解低频变率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，我们必须知道多年代际到百年的自然变率是什么，因为这种低频变率很容易被误认为是全球变暖的影响。自然变率的来源包括大气-海洋气候振荡，如厄尔尼诺-南方涛动和太平洋年代际涛动。在我的长期基线研究中，我使用最长的观察记录，然后再回到它们之外，使用从树木年轮宽度或保存在湖泊沉积物中的花粉中获得的记录，并以高分辨率采样。我的建议的短期目标是：1)检查加拿大中部、北部和沿海的河流记录，以了解气候波动对洪水的影响，因为忽略这些可能会导致对洪水复发间隔和高度的低估；2)利用基于树木年轮的千年河流重建的长基线来更好地估计阿尔伯塔省南部和魁省东南部干旱和潮湿期的概率，这些基线经过精心构建以捕捉低频变异；3)通过湖泊沉积物中保存的花粉和高分辨率采样，研究了青海东南部近1000年来的湿度和温度变化，从而研究了森林组成；4)利用沉积花粉将萨斯喀彻温省中部一千年的火灾记录延长（火灾和干旱密切相关）。这个研究项目是新颖的，因为它在几十年和几百年的尺度上研究水的变化，使用尽可能广泛的数据来源，并关注加拿大干旱和洪水的昂贵影响。在全球变暖的情况下，它将使更有弹性的水资源管理取得重大进展。