NOAA/WDS Paleoclimatology - 1000 Year Composite Sea Surface Temperature Record from the North Atlantic Ocean

We undertake the first comprehensive effort to integrate North Atlantic marine climate records for the last millennium, highlighting some key components common within this system at a range of temporal and spatial scales. In such an approach, careful consideration needs to be given to the complexities inherent to the marine system. Composites therefore need to be hydrographically constrained and sensitive to both surface water mass variability and three-dimensional ocean dynamics. This study focuses on the northeast (NE) Atlantic, particularly sites influenced by the North Atlantic Current. A composite plus regression approach is used to create an inter-regional NE Atlantic reconstruction of sea surface temperature (SST) for the last 1000 years. We highlight the loss of spatial information associated with large-scale composite reconstructions of the marine environment. Regional reconstructions of SSTs off the Norwegian and Icelandic margins are presented, along with a larger-scale reconstruction spanning the NE North Atlantic. The latter indicates that the ‘Medieval Climate Anomaly’ warming was most pronounced before ad 1200, with a long-term cooling trend apparent after ad 1250. This trend persisted until the early 20th century, while in recent decades temperatures have been similar to those inferred for the ‘Medieval Climate Anomaly’. The reconstructions are consistent with other independent records of sea-surface and surface air temperatures from the region, indicating that they are adequately capturing the climate dynamics of the last millennium. Consequently, this method could potentially be used to develop large-scale reconstructions of SSTs for other hydrographically constrained regions.

本研究首次系统性整合了过去千年的北大西洋海洋气候记录，揭示了该气候系统在不同时间与空间尺度下共有的若干关键特征组分。采用此类整合方法时，需充分考量海洋系统本身固有的复杂性。因此，合成分析需满足水文约束条件，且需同时响应表层水团变化与三维海洋动力学过程。本研究聚焦东北大西洋（NE Atlantic），尤其关注受北大西洋洋流影响的海域。本研究采用合成分析结合回归的方法，构建了过去千年东北大西洋跨区域的海表温度（sea surface temperature, SST）重建序列。本研究同时指出，海洋环境的大尺度合成重建会伴随空间信息的丢失。本研究展示了挪威与冰岛陆缘海域的SST区域重建序列，以及覆盖东北北大西洋的大尺度SST重建序列。后者显示，‘中世纪气候异常期（Medieval Climate Anomaly）’的增温在公元1200年前最为显著，公元1250年后则呈现出长期的降温趋势。该降温趋势持续至20世纪早期，而近数十年的海表温度已与‘中世纪气候异常期’重建得到的温度水平相当。本次重建结果与该区域其他独立的海表及地表气温记录相一致，表明其能够充分捕捉过去千年的气候动力学特征。因此，该方法有望用于构建其他受水文约束区域的大尺度SST重建序列。