Reconstruction of changes in sea-ice, water temperature and Greenland Ice Sheet runoff into Disko Bay, Greenland (RECONNECT)

全球变暖将在未来几年导致北极发生重大变化，气候、生物和社会影响日益严重，并波及北极以外的地区。格陵兰特别容易受到持续的人为气候变化和变暖“热点”的影响。观测数据记录了最近许多格陵兰冰盖冰川的快速质量损失、北极海冰加速减少和海洋的大量淡化趋势。地理信息系统的质量损失是全球海平面上升的主要原因，但未来预测的不确定性很大。因此，从地理信息系统中了解导致北极温度、海冰特征和淡水通量变化的内部过程和海洋-冰-大气相互作用至关重要，以便更好地评估人为因素的影响。高纬度地区现有的观测记录稀少而短暂，因此存在很大的不确定性，使预测变得困难。模型需要过去变化的高分辨率数据，以解决GIS对变暖的反应速度。过去的气候可以从所谓的代理档案中重建出来。然而，在高纬度地区，迄今为止使用的大多数代理时间序列来自间接的陆基档案，而海洋档案通常不超过世纪或十年尺度的分辨率。因此，探索新的高分辨率海洋档案是当务之急。这项建议的重点是钙化珊瑚藻堆积生长附着在海底，最近出现了新的亚年度分辨率气候记录仪。通过针对来自西格陵兰岛迪斯科湾的长寿个体，我解决了这个数据缺口。我的研究地点位于雅各布港冰川附近，雅各布港冰川是格陵兰岛最大的冰川之一，也是过去20年来地理信息系统中最大的质量损失来源。在卫星时代之前，融化变率和冰川径流的估计仍然不确定，长期的十年到几十年的变率和机制还没有得到很好的理解。该项目的主要目标是：（1）通过对长寿藻类骨骼的硬年代学和地球化学分析，开发第一个年度分辨率的多世纪替代重建，以重建过去的海水温度、海冰的季节性持续时间和格陵兰迪斯科湾的淡水通量，（2）建立工业化前自然低频北极气候和海洋变化的基线数据，重建雅格布港冰川径流的十年到多十年尺度的变化，为海洋和大气过程的联系提供一个长期的视角。这些新的长期年度分辨率记录是非常需要的，是改进对未来冰冻圈变化和具有区域和全球影响的基本指导机制的预测的一个重要里程碑。

Global warming will lead to major Arctic changes in years to come, with increasing climatic, biological, and social impacts - also reaching regions outside the Arctic. Greenland is particularly vulnerable to ongoing anthropogenic climate change and a warming "hotspot". Observational data document recent rapid mass loss of many of the Greenland ice sheet (GIS) glaciers, accelerated decline in Arctic sea-ice and substantial oceanic freshening trends. Mass loss of the GIS represents a major contributor to global sea level rise, but uncertainties in future projections are large. Thus, it is crucial to understand internal processes and ocean-ice-atmosphere interactions driving variability in Arctic temperatures, sea-ice characteristics and freshwater flux from the GIS, in order to better assess the influence of anthropogenic contributions. Available observational records from high latitudes are sparse and short, thus large uncertainties remain, making predictions difficult. Models require high-resolution data of past variability to resolve how fast the GIS reacts to warming. Past climate can be reconstructed from so-called proxy archives. In high latitudes, however, most proxy time series utilised to date come from indirect land-based archives, while marine archives generally do not exceed century- or decadal-scale resolution. Hence, the exploration of new high-resolution marine archives is a top priority. This proposal focuses on calcified coralline algal buildups growing attached to the seafloor, that have recently emerged as novel subannual resolution climate recorders. By targeting long-lived individuals from Disko Bay, West-Greenland, I address this data gap. My study sites are located close to Jakobshavn Glacier, one of the largest glaciers in Greenland and the single largest source of mass loss from the GIS over the last 20 years. Estimates of melt variability and glacier runoff remain uncertain before the satellite era and long-term decadal- to multidecadal variability and mechanisms are not well understood. The main goals of this project are: (1) to develop the first annually-resolved multicentury-length proxy reconstructions of past seawater temperature, seasonal duration of sea-ice, and freshwater flux to Disko Bay, Greenland, by means of sclerochronological and geochemical analysis of long-lived algal skeletons, (2) to establish baseline data of pre-industrial natural low-frequency arctic climate and ocean variability, and (3) to reconstruct decadal- to multidecadal-scale variability in Jakobshavn Glacier runoff, providing a long-term perspective on linkages to oceanic and atmospheric processes. These new long-term annual-resolution records are highly needed and represent a major milestone for improving predictions of future cryospheric change and underlying steering mechanisms which have regional and global implications.