《Last Century Warming Over the Canadian Atlantic Shelves Linked to Weak Atlantic Meridional Overturning Circulation》

  • 来源专题:物理海洋学知识资源中心
  • 编译者: cancan
  • 发布时间:2018-12-14
  • 摘要:The Atlantic meridional overturning circulation (AMOC) is a key component of the global climate system. Recent studies suggested a twentieth‐century weakening of the AMOC of unprecedented amplitude (~15%) over the last millennium. Here we present a record of δ18O in benthic foraminifera from sediment cores retrieved from the Laurentian Channel and demonstrate that the δ18O trend is linked to the strength of the AMOC. In this 100‐year record, the AMOC signal decreased steadily to reach its minimum value in the late 1970s, where the weakest AMOC signal then remains constant until 2000. We also present a longer δ18O record of 1,500 years and highlight the uniqueness of the last century δ18O trend. Moreover, the Little Ice Age period is characterized by statistically heavier δ18O, suggesting a relatively weak AMOC. Implications for understanding the mechanisms driving the intensity of AMOC under global warming and high‐latitude freshwater input are discussed.

    全文链接:https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080083

  • 原文来源:https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080083
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    • 来源专题:物理海洋学知识资源中心
    • 编译者:cancan
    • 发布时间:2018-11-14
    • Saba V S, Griffies S M, Anderson W G, et al. Enhanced warming of the Northwest Atlantic Ocean under climate change. 来源: Journal of Geophysical Research Oceans, 2012, 121(1) 摘要: The Intergovernmental Panel on Climate Change (IPCC) fifth assessment of projected global and regional ocean temperature change is based on global climate models that have coarse (~100-km) ocean and atmosphere resolutions. In the Northwest Atlantic, the ensemble of global climate models has a warm bias in sea surface temperature due to a misrepresentation of the Gulf Stream position; thus, existing climate change projections are based on unrealistic regional ocean circulation. Here we compare simulations and an atmospheric CO2 doubling response from four global climate models of varying ocean and atmosphere resolution. We find that the highest resolution climate model (~10-km ocean, ~50-km atmosphere) resolves Northwest Atlantic circulation and water mass distribution most accurately. The CO2 doubling response from this model shows that upper-ocean (0-300 m) temperature in the Northwest Atlantic Shelf warms at a rate nearly twice as fast as the coarser models and nearly three times faster than the global average. This enhanced warming is accompanied by an increase in salinity due to a change in water mass distribution that is related to a retreat of the Labrador Current and a northerly shift of the Gulf Stream. Both observations and the climate model demonstrate a robust relationship between a weakening Atlantic Meridional Overturning Circulation (AMOC) and an increase in the proportion of Warm-Temperate Slope Water entering the Northwest Atlantic Shelf. Therefore, prior climate change projections for the Northwest Atlantic may be far too conservative. These results point to the need to improve simulations of basin and regional-scale ocean circulation. 全文网址:https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015JC011346
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    • 来源专题:物理海洋学知识资源中心
    • 编译者:cancan
    • 发布时间:2018-11-28
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