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

在过去的几十年里，北极的快速变暖导致了海冰范围和厚度的急剧下降，其速度超过了气候模型模拟的速度。预测显示，如果目前的趋势持续下去，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，因为由于仪器和卫星记录较短，人们对海冰的长期可变性知之甚少，通常不会延续到1970年代末。为了准确地模拟和预测北极气候的未来演变，必须更好地了解过去几个世纪，特别是在工业革命之前，人类开始通过排放化石燃料影响气候和海洋化学的年复一年的温度和海冰变化。这种重建通常是通过使用代理档案实现的，例如陆地上的树轮或冰芯。然而，直到最近，还没有从亚北冰洋和北冰洋获得这样的代理档案。在一项突破性的研究中，我的研究小组现在发现，在浅海海底长时间存活的珊瑚藻类可以用来重建过去650年来北极的气候和冰层变化。在海冰覆盖广泛的时期，很少有光线到达海底，导致光合藻的年生长率很低。相比之下，当海冰覆盖率较低时，藻类的年生长率会增加。通过测量藻类的生长和地球化学组成，可以重建过去一年的海冰复盖和温度。珊瑚藻类的堆积广泛分布在整个北冰洋，在那里它们可以附着在浅海底生活几个世纪，同时在其钙化的骨骼中形成年度生长带。 这项提议的首要目标是建立一个多中心记录过去海水温度、季节性海冰持续时间和珊瑚藻骨架海洋化学的网络，以更好地了解亚北极-北极海洋环境的历史性变化。重建将集中在最近从加拿大北极、格陵兰和斯皮茨卑尔根收集的样本-这些关键地点的特点是强烈的季节性温度和海冰波动。这项研究将为即将到来的变化提供急需的基线数据和历史视角，这些变化将影响航运、基础设施和资源开发，从而影响北方社区。

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.