Climate and ocean changes in Arctic-subarctic environments

北极-亚北极环境中的气候和海洋变化

• 批准号: RGPIN-2014-03575
• 负责人: deVernal, Anne
• 金额: $ 5.25万
• 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: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=565953
• 关键词: Climate; ocean; changes; Arctic; subarctic

The research program concerns the variability of climate, ocean and environments at high latitudes of the Northern Hemisphere, and their recording by sedimentary archives. It will address fundamental questions about i) the resilience of Arctic sea ice under "warm" climates of the past, ii) the ocean circulation patterns in response to the opening/closure of the Arctic gateways and iii) the pre-Anthropogenic baseline conditions in the Arctic-subarctic realm. Some focus will be put on the sea ice cover, which is a critical climate parameter through ice-albedo feedback responsible for Arctic amplification. The possible disappearance or resilience of Arctic sea ice and their impact on the biota and global climate are critical issues that need to be urgently examined. Whereas the recent decline of Arctic sea ice led to hypothesize the disappearance of perennial ice within 30 years, the rarity of sea ice data prior to satellite observations prevents assessing its natural variability. Moreover, paradoxical indication for multi-year sea ice in the Arctic during warm episodes of the last millions of years, suggests that Arctic sea ice might be a resilient feature in the Late Cenozoic climate system. Similarly, the ocean response to the ongoing warming is not unequivocal, especially in the subarctic basins as the freshwater budget of the Arctic Ocean and its exchanges with the North Atlantic control heat fluxes, salinity, density and convection, i.e., the North Atlantic thermohaline circulation. As a contribution to international initiatives, I intend to reconstruct climate and ocean conditions in the Arctic-subarctic realm, notably for documenting the Earth’s system response under extreme conditions. Special attention will be given to the early Holocene (~10-6 ka), and warm interglacial stages of the Quaternary marked by high insolation, and to the Pliocene (~5.3-2.5 Ma) when forest extended into the Canadian Arctic and atmospheric carbon dioxide peaked at about 400 ppmv. To meet these objectives, access to marine sedimentary archives from Arctic and subarctic seas are needed. Sediments to analyze include cores from ODP (Ocean Drilling Program) and IODP (Integrated ODP) in addition to cores to be collected within the frame of international expeditions. From a methodological point of view, the reconstruction of climate and ocean parameters will be based on the analysis of organic-walled microfossils, notably dinoflagellate cysts, as tracers of planktonic production and sea-surface conditions, and pollen and spores, as proxies for land-sea correlation and terrestrial climate reconstructions, in addition to complementary sedimentological, isotopic and geochemical analyses. Aside the main stream of research, some attention will be paid to ocean and environmental changes over the last centuries, with the aim to fill the gap between instrumental and sedimentary records and to better calibrate quantitative reconstructions from proxies. This work is needed to determine pre-Anthropocene baseline conditions (i.e., prior to instrumental records) and thus improve estimates of anthropogenic trends. It will also permit to assess life-threatening environmental changes (eutrophication, hypoxia, red tides) in coastal settings and will provide a clue on their natural vs human-driven causes. The research program is tightly linked to national and international initiatives (VITALS, ArcTrain, PMIP, IODP) aiming at the monitoring and forecasting of ocean and climate changes in Arctic-subarctic environments, which is indispensable for sustainable development of high latitude regions. It will contribute to the training of students of all levels to address complex issues related to Arctic-subarctic climate change and/or coastal processes.

该研究项目关注北半球高纬度地区气候、海洋和环境的变化，并通过沉积档案对其进行记录。它将解决以下基本问题：1)北极海冰在过去“温暖”气候下的复原力；2)北极门户打开/关闭时的海洋环流模式；3)北极-亚北极地区的前人类活动基线条件。一些重点将放在海冰覆盖上，这是一个通过冰反照率反馈负责北极放大的关键气候参数。北极海冰可能消失或恢复以及它们对生物群和全球气候的影响是迫切需要研究的关键问题。虽然最近北极海冰的减少导致了30年内常年冰消失的假设，但卫星观测之前海冰数据的稀缺性阻碍了对其自然变率的评估。此外，在过去数百万年的温暖时期，北极多年海冰的矛盾迹象表明，北极海冰可能是晚新生代气候系统中的一个弹性特征。同样，海洋对持续变暖的反应也不是明确的，特别是在亚北极盆地，因为北冰洋的淡水收支及其与北大西洋的交换控制着热通量、盐度、密度和对流，即北大西洋热盐环流。作为对国际倡议的贡献，我打算重建北极-亚北极地区的气候和海洋条件，特别是记录极端条件下地球系统的反应。本文将特别关注全新世早期（~10-6 ka）和第四纪高日照的暖间冰期，以及上新世（~5.3-2.5 Ma），当时森林扩展到加拿大北极，大气二氧化碳峰值约为400 ppmv。为了实现这些目标，需要获得北极和亚北极海域的海洋沉积档案。要分析的沉积物包括ODP（海洋钻探计划）和IODP（综合ODP）的岩心，以及在国际考察框架内收集的岩心。从方法学的角度来看，气候和海洋参数的重建将基于有机物壁微化石的分析，特别是鞭毛藻囊，作为浮游生物生产和海面条件的示踪剂，以及花粉和孢子，作为陆海对比和陆地气候重建的代用物，此外还将进行互补的沉积学、同位素和地球化学分析。除了主流的研究之外，还将对过去几个世纪的海洋和环境变化给予一些关注，目的是填补仪器记录和沉积记录之间的空白，并更好地校准来自代用物的定量重建。需要这项工作来确定前人类世的基线条件（即在仪器记录之前），从而改进对人类活动趋势的估计。它还将允许评估沿海环境中危及生命的环境变化（富营养化、缺氧、赤潮），并将提供关于自然与人为原因的线索。该研究项目与旨在监测和预测北极-亚北极环境海洋和气候变化的国家和国际倡议（VITALS、ArcTrain、PMIP、IODP）密切相关，这对高纬度地区的可持续发展至关重要。它将有助于培训各级学生解决与北极-亚北极气候变化和/或沿海过程有关的复杂问题。