Evolution of glacial Lake Ojibway and impact of meltwater discharges on early Holocene abrupt climate changes

奥及布韦冰川湖的演化及融水排放对全新世早期气候突变的影响

• 批准号: 327685-2012
• 负责人: Roy, Martin
• 金额: $ 1.97万
• 依托单位: Université du Québec à Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=595287
• 关键词: Evolution; glacial; Lake; Ojibway; impact; Evolution; glacial; Lake; Ojibway; impact

Paleoclimate research has revealed that the Earth's climate experienced abrupt climate changes involving important reorganizations of the atmosphere and oceans at decadal to millennial timescales. The most compelling mechanism to explain these reorganizations during the Late Quaternary relate to the impact of freshwater discharges on the Atlantic Meridional Overturning Circulation, which plays a fundamental role in redistributing vast amounts of heat in the Northern Hemisphere. Much of the climate variability of the end of the last glacial period and current interglacial (the Holocene) was due to the decay of continental ice sheets, which gave rise to massive releases of glacial meltwaters that accumulated in large ice-dammed lakes. One of the best examples of ice-ocean interaction occurred about 8200 years ago when the decaying ice over Hudson Bay suddenly allowed glacial lakes Agassiz and Ojibway to drain abruptly into the North Atlantic and cause a global-scale cooling. The precise impact of this freshwater perturbation is however questioned by marine sediment records that indicate that the time interval comprising the so-called 8.2-ka cooling event was characterized by multiple outbursts of meltwaters. Yet geological data supporting a multi-step final drainage of Lake Agassiz-Ojibway is limited. This research program focuses on the late-stage history of Lake Ojibway though the study of newly recognized shorelines that reflect abrupt drawdown(s) of Ojibway lake levels and by documenting sedimentary sequences that possibly record drainage episode(s) preceding the final lake drainage in northeastern Ontario and northwestern Quebec. The proposed research projects will result in the advanced training of several graduate students, which will contribute to the research on meltwater volume estimates and on the chronology of the abrupt meltwater discharges. A long-term objective of this research program is to increase our understanding of the role of freshwater discharges in abrupt climate changes and provide boundary conditions to predictive climate models. This represents an important contribution considering the uncertainties related to the response of the cryosphere to the current global warming.

古气候研究表明，地球的气候经历了突然的气候变化，涉及十年中大气和海洋的重要重新组织。在第四纪晚期期间解释这些重组的最引人注目的机制与淡水排放对大西洋子午线倾覆循环的影响有关，这在重新分布北半球的大量热量中起着基本作用。最后一个冰川时期和当前冰川间（全新世）的气候变化的大部分是由于大陆冰盖的衰变引起的，这导致了大量冰川融化物的大量冰川融化，这些冰川融化物积聚在大型冰膜的湖泊中。大约8200年前，哈德逊湾腐烂的冰突然使冰川湖Agassiz和Ojibway突然流入北大西洋并引起全球尺度​​的冷却，这是冰山相互作用的最佳例子之一。但是，这种淡水扰动的确切影响受到海洋沉积物记录的质疑，该记录表明，包括所谓的8.2 ka冷却事件的时间间隔的特征是多次熔体爆发。然而，支持Agassiz-Ojibway湖的多步最终排水的地质数据有限。该研究计划的重点是奥吉布韦湖的后期历史，尽管对新认识的海岸线的研究反映了奥吉布韦湖水平的突然降低，并通过记录了在安大略省东北部和西北Quebec之前最终湖泊排水之前记录排水次数的沉积序列。拟议的研究项目将导致几名研究生进行高级培训，这将有助于对融化量估算的研究以及突然融合出院的年代学的研究。该研究计划的一个长期目标是增加我们对淡水排放在突然的气候变化中的作用的理解，并为预测性气候模型提供边界条件。考虑到与当前全球变暖的反应有关的不确定性，这代表了重要的贡献。