Reconstructing centuries of Arctic climate and sea ice conditions using annually-banded coralline algae

利用每年带状的珊瑚藻重建几个世纪的北极气候和海冰条件

• 批准号: RGPIN-2017-06074
• 负责人: Halfar, Jochen
• 金额: $ 2.33万
• 依托单位: University of Toronto
• 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=712035
• 关键词: Reconstructing; centuries; Arctic; climate; sea

Rapid Arctic warming during the past decades has contributed to a dramatic decline of sea-ice extent and thickness at a pace greater than simulated by climate models. If current trends persist, projections suggest that Arctic summer sea-ice may disappear within the next decades. However, the uncertainties in sea-ice modelling are large as long-term sea-ice variability is poorly understood due to short instrumental and satellite records, generally not extending beyond the late 1970s. In order to accurately model and therefore project future evolution of Arctic climate, it is essential to have a better understanding of year-to-year temperature and sea-ice variability during the past centuries, particularly prior to the industrial revolution when humans started impacting climate and ocean chemistry by the emission of fossil fuels. Such reconstructions are typically achieved by using proxy archives, such as tree rings or ice cores on land. Until recently though, no such proxy archive was known from the Subarctic and Arctic Ocean. In a breakthrough study my research group has now discovered that long-lived coralline algal buildups on the shallow sea floor can be used to reconstruct Arctic climate and ice variability during the past 650 years. During times of extensive sea ice cover little light reaches the seafloor resulting in low annual growth rates of the photosynthetic algae. In contrast, when sea ice cover is low annual algal growth rates increase. By measuring algal growth and geochemical composition year-by-year into the past sea ice cover and temperatures can be reconstructed. Coralline algal buildups are widespread throughout the entire Arctic Ocean where they can live for centuries attached to the shallow seafloor while forming annual growth bands in their calcitic skeletons. The overarching goal of this proposal is to develop a network of multicentury records of past seawater temperature, seasonal duration of sea-ice, and ocean chemistry from the skeletons of coralline algae to better understand historic changes in subarctic-arctic marine environments. Reconstructions will focus on recently collected samples from the Canadian Arctic, Greenland, and Spitsbergen - key sites that are characterised by strong seasonal temperature and sea-ice fluctuations. This research will provide much needed baseline data and a historic perspective for upcoming changes that will impact shipping, infrastructure and resource development and therefore Northern communities.

在过去的几十年中，北极的快速变暖导致海冰范围和厚度的急剧下降，而气候模型的模拟大于模拟。如果目前的趋势持续存在，则预测表明，北极夏季海冰可能会在未来几十年内消失。但是，海冰建模中的不确定性很大，因为由于短期的仪器和卫星记录，长期的海冰可变性尚不清楚，通常不会在1970年代后期延伸。为了准确建模并因此预测了北极气候的未来演变，必须更好地了解过去几个世纪的年度温度和海冰可变性，尤其是在工业革命之前人类开始影响气候之前和海洋化学化石燃料的化学。这种重建通常是通过使用代理档案（例如陆地上的树环或冰芯）来实现的。直到最近，还没有从亚北极和北极海洋中知道这样的代理档案。在一项突破性的研究中，我的研究小组现在发现，浅海地板上的长寿命珊瑚藻堆积可用于重建过去650年的北极气候和冰的可变性。在广泛的海冰覆盖时，很少的光线到达海底，导致光合藻类的年增长率低。相反，当海冰覆盖率为低年度藻类生长速率时。通过测量藻类的生长和地球化学成分，可以重建过去的海冰覆盖和温度。 Coralline藻类的积累在整个北极海洋中都广泛存在，在那里他们可以在浅海地板上生活了几个世纪，同时在其钙质骨骼中形成了年度生长带。 该提案的总体目标是建立一个跨越过去海水温度，海冰季节性持续时间以及从珊瑚藻类骨骼的海洋化学的跨国记录网络，以更好地了解亚北极北极海洋环境的历史变化。重建将集中于最近收集的加拿大北极，格陵兰和Spitsbergen的样品，这些样品以强烈的季节性温度和海冰波动为特征。这项研究将为即将发生的变化提供急需的基线数据和历史观点，这些变化将影响运输，基础设施和资源开发以及北部社区。