Rasmussen Tine L, Thomsen Erik, Moros Matthias
CAGE- Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology, UiT Arctic University of Norway, N-9037 Tromsø, Norway.
Department of Geoscience, University of Aarhus, DK-8000 Aarhus C, Denmark.
Sci Rep. 2016 Feb 5;6:20535. doi: 10.1038/srep20535.
The precise reason for the differences and out-of-phase relationship between the abrupt Dansgaard-Oeschger warmings in the Nordic seas and Greenland ice cores and the gradual warmings in the south-central Atlantic and Antarctic ice cores is poorly understood. Termed the bipolar seesaw, the differences are apparently linked to perturbations in the ocean circulation pattern. Here we show that surface and intermediate-depth water south of Iceland warmed gradually synchronously with the Antarctic warming and out of phase with the abrupt warming of the Nordic seas and over Greenland. The hinge line between areas showing abrupt and gradual warming was close to the Greenland-Scotland Ridge and the marine system appears to be a 'push-and-pull' system rather than a seesaw system. 'Pull' during the warm interstadials, when convection in the Nordic seas was active; 'push' during the cold stadials, when convection stopped and warm water from the south-central Atlantic pushed northward gradually warming the North Atlantic and Nordic seas.
北欧海域和格陵兰冰芯中丹斯加德-奥eschger 突然变暖与中南部大西洋和南极冰芯中逐渐变暖之间存在差异和异相关系的确切原因，目前还知之甚少。这种差异被称为双极跷跷板，显然与海洋环流模式的扰动有关。在这里，我们表明，冰岛以南的表层和中深层海水与南极变暖同步逐渐升温，与北欧海域和格陵兰上空的突然变暖不同步。显示突然变暖和逐渐变暖区域之间的枢纽线靠近格陵兰-苏格兰海脊，海洋系统似乎是一个“推挽”系统，而不是跷跷板系统。在温暖的间冰期，北欧海域对流活跃时为“拉”；在寒冷的冰期，对流停止，中南部大西洋的暖水逐渐向北推进，使北大西洋和北欧海域逐渐变暖时为“推”。
