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: 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=633861
• 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.

过去几十年北极迅速变暖导致海冰范围和厚度急剧下降，其速度比气候模型模拟的速度还要快。如果目前的趋势持续下去，预测表明北极夏季海冰可能会在未来几十年内消失。然而，海冰模型的不确定性很大，因为仪器和卫星记录较短，通常不会延续到 20 世纪 70 年代后期之后，人们对长期海冰变化知之甚少。为了准确地模拟并预测北极气候的未来演变，有必要更好地了解过去几个世纪的逐年温度和海冰变化，特别是在人类开始影响气候的工业革命之前以及化石燃料排放造成的海洋化学。这种重建通常是通过使用代理档案来实现的，例如陆地上的树木年轮或冰芯。但直到最近，亚北极和北冰洋还没有这样的代理档案。在一项突破性研究中，我的研究小组现已发现，浅海海底的长寿珊瑚藻堆积物可用于重建过去 650 年来的北极气候和冰层变化。在海冰广泛覆盖的时期，到达海底的光线很少，导致光合藻类的年增长率较低。相反，当海冰覆盖率较低时，藻类的年增长率就会增加。通过逐年测量藻类生长和地球化学成分，可以重建过去的海冰覆盖和温度。珊瑚藻在整个北冰洋广泛分布，它们可以附着在浅海海底生活几个世纪，同时在其方解石骨架中形成年度生长带。