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

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，地球气候经历了突然的气候变化，涉及十年到千年时间尺度上大气和海洋的重要重组。解释晚第四纪这些重组的最引人注目的机制与淡水排放对大西洋经向翻转环流的影响有关，该环流在北半球重新分配大量热量方面发挥着根本作用。上一个冰期末期和当前的间冰期（全新世）的气候变化很大程度上是由于大陆冰盖的腐烂造成的，导致冰川融水大量释放，并积聚在大型冰坝湖泊中。冰与海洋相互作用的最好例子之一发生在大约 8200 年前，当时哈得逊湾上空的冰逐渐腐烂，导致阿加西湖和奥吉布韦冰湖突然流入北大西洋，导致全球范围的变冷。然而，海洋沉积物记录对这种淡水扰动的确切影响提出了质疑，这些记录表明，所谓的 8.2-ka 冷却事件的时间间隔以多次融水爆发为特征。然而，支持阿加西-奥吉布韦湖多步骤最终排水的地质数据有限。该研究计划通过研究新认识的反映奥及布韦湖水位突然下降的海岸线，并记录可能记录最终湖泊排水之前的排水事件的沉积序列，重点关注奥及布韦湖的后期历史。安大略省东北部和魁北克省西北部。拟议的研究项目将对数名研究生进行高级培训，这将有助于融水量估计和融水突然排放的时间顺序的研究。该研究计划的长期目标是加深我们对淡水排放在气候突变中的作用的了解，并为预测气候模型提供边界条件。考虑到冰冻圈对当前全球变暖的响应的不确定性，这是一个重要的贡献。