Saw‐tooth pattern of North Atlantic current speed during Dansgaard‐Oeschger cycles revealed by the magnetic grain size of Reykjanes Ridge sediments at 59°N
Saw‐tooth pattern of North Atlantic current speed during Dansgaard‐Oeschger cycles revealed by the magnetic grain size of Reykjanes Ridge sediments at 59°N
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北纬 59° 雷克雅内斯海脊沉积物的磁性粒度揭示了 Dansgaard-Oeschger 循环期间北大西洋海流速度的锯齿模式
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
M. Moros
中科院分区：
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作者：
I. Snowball;M. Moros
对从北大西洋雷克雅内斯海脊回收的三个沉积物岩心进行了详细的矿物（岩石）磁性测量，包括高分辨率磁滞回线测量。在物理粒度分析的支持下，钛磁铁矿粒度变化形成了近底电流速度的代表，并揭示了Dansgaard-Oeschger周期8和5之间的周期性“锯齿”模式。磁性粒度数据表明，这些Dansgaard-Oeschger周期的特点是逐渐加强的近底电流速度，而其他古海洋学代理表明冰山流量不断增加和海面温度下降。这些观测结果与经常假设和严格应用的高纬度温暖和北大西洋深水形成之间的正相关关系相反。然而，在时间控制的范围内，似乎冰山流量的峰值和缓慢的近底流速是同步的。磁滞数据还表明，磁浓度参数，如磁化率，不一定提供直接证据的古循环。（减）
Detailed mineral (rock) magnetic measurements, including high-resolution magnetic hysteresis loops, were carried out on three sediment cores recovered from the Reykjanes Ridge in the North Atlantic. Supported by physical grain-size analyses, titanomagnetite grain-size variations form a proxy of the speed of near-bottom currents and reveal a cyclic ""saw-tooth' pattern between Dansgaard-Oeschger cycles 8 and 5. The magnetic grain-size data suggest that these Dansgaard-Oeschger cycles were characterized by gradual intensification of the near-bottom current speed, while other paleoceanographic proxies indicate escalating iceberg discharge and declining sea surface temperatures. These observations are contrary to the frequently assumed and strictly applied positive relationship between high-latitude warmth and North Atlantic Deep Water formation. Within the confines of temporal control, however, it would appear that peaks in iceberg discharge and slow near-bottom current speeds were synchronous. The magnetic hysteresis data also demonstrate that magnetic concentration parameters, such as magnetic susceptibility, do not necessarily provide direct evidence of paleocirculation. (Less)