Sadatzki Henrik, Dokken Trond M, Berben Sarah M P, Muschitiello Francesco, Stein Ruediger, Fahl Kirsten, Menviel Laurie, Timmermann Axel, Jansen Eystein
Department of Earth Science and Bjerknes Centre for Climate Research, University of Bergen, 5007 Bergen, Norway.
NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, 5007 Bergen, Norway.
Sci Adv. 2019 Mar 6;5(3):eaau6174. doi: 10.1126/sciadv.aau6174. eCollection 2019 Mar.
The last glacial period was marked by pronounced millennial-scale variability in ocean circulation and global climate. Shifts in sea ice cover within the Nordic Seas are believed to have amplified the glacial climate variability in northern high latitudes and contributed to abrupt, high-amplitude temperature changes over Greenland. We present unprecedented empirical evidence that resolves the nature, timing, and role of sea ice fluctuations for abrupt ocean and climate change 32 to 40 thousand years ago, using biomarker sea ice reconstructions from the southern Norwegian Sea. Our results document that initial sea ice reductions at the core site preceded the major reinvigoration of convective deep-water formation in the Nordic Seas and abrupt Greenland warming; sea ice expansions preceded the buildup of a deep oceanic heat reservoir. Our findings suggest that the sea ice variability shaped regime shifts between surface stratification and deep convection in the Nordic Seas during abrupt climate changes.
末次冰期的特征是海洋环流和全球气候存在明显的千年尺度变率。北欧海域海冰覆盖范围的变化被认为放大了北半球高纬度地区的冰川气候变率，并导致格陵兰岛出现急剧的、大幅度的温度变化。我们提供了前所未有的实证证据，利用挪威海南部的生物标志物海冰重建数据，确定了3.2万至4万年前海冰波动对海洋和气候变化突变的性质、时间和作用。我们的结果表明，核心站点最初的海冰减少先于北欧海域对流性深水形成的主要复苏以及格陵兰岛的突然变暖；海冰扩张先于深海热储的积累。我们的研究结果表明，在气候突变期间，海冰变率塑造了北欧海域表层分层和深层对流之间的状态转变。
