Open ocean convection drives enhanced eastern pathway of the glacial Atlantic Meridional Overturning Circulation

• 成果类型: Article
• 署名作者: Gu, Sifan; Liu, Zhengyu; Ng, Hong Chin; Lynch-Stieglitz, Jean; Mcmanus, Jerry F.; Spall, Michael; Jahn, Alexandra; He, Chengfei; Li, Lingwei; Yan, Mi; Wu, Lixin
• 署名单位: Shanghai Jiao Tong University; Shanghai Jiao Tong University; Shanghai Jiao Tong University; Shanghai Jiao Tong University; University System of Ohio; Ohio State University; Nanjing Normal University; University of Bristol; University System of Georgia; Georgia Institute of Technology; Columbia University; Woods Hole Oceanographic Institution; University of Colorado System; University of Colorado Boulder; University of Colorado System; University of Colorado Boulder; University of Miami; Ocean University of China
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-14370
• DOI: 10.1073/pnas.2405051121
• 发表日期: 2024-11-05
• 关键词: labrador sea-water; north-atlantic; global climatology; interior pathways; MODEL; surface; earth; maximum; reconstruction; foraminifera

摘要

Abundant proxy records suggest a profound reorganization of the Atlantic Meridional Overturning Circulation (AMOC) during the Last Glacial Maximum (LGM, similar to 21,000 y ago), with the North Atlantic Deep Water (NADW) shoaling significantly relative to the present-day (PD) and forming Glacial North Atlantic Intermediate Water (GNAIW). However, almost all previous observational and modeling studies have focused on the zonal mean two-dimensional AMOC feature, while recent progress in the understanding of modern AMOC reveals a more complicated three-dimensional structure, with NADW penetrating from the subpolar North Atlantic to lower latitude through different pathways. Here, combining Pa-231/Th-230 reconstructions and model simulations, we uncover a significant change in the three-dimensional structure of the glacial AMOC. Specifically, the mid-latitude eastern pathway (EP), located east of the Mid-Atlantic Ridge and transporting about half of the PD NADW from the subpolar gyre to the subtropical gyre, experienced substantial intensification during the LGM. A greater portion of the GNAIW was transported in the eastern basin during the LGM compared to NADW at the PD, resulting in opposite Pa-231/Th-230 changes between eastern and western basins during the LGM. Furthermore, in contrast to the wind-steering mechanism of EP at PD, the intensified LGM EP was caused primarily by the rim current forced by the basin-scale open-ocean convection over the subpolar North Atlantic. Our results underscore the importance of accounting for three-dimensional oceanographic changes to achieve more accurate reconstructions of past AMOC.