资源环境科技发展态势分析平台

Recent glacial periods have included several periods of rapid sea-level drop that are still not well understood. Here we show that rapid sea level drops can occur due to merger of two separate ice sheets without correspondingly rapid climate forcing. Using the Parallel Ice Sheet Model (PISM), we simulate glaciation of the Laurentide Ice Sheet (LIS) by gradually decreasing equilibrium-line altitude (ELA). Merger of the extended Keewatin sector of the Laurentide Ice Sheet with Labrador sector of the Laurentide Ice Sheet south of Hudson Bay causes a positive feedback between increasing surface elevation and increasing surface mass balance in the merger region, leading to fast ice sheet growth. The simulated saddle merger of LIS lowers sea level by 20 m in less than 20 kyr with periods of sea level fall exceeding 2 m/kyr, similar to those observed in paleo-sea level records.