Helium isotope record, CaCO3 concentration and accumulation rate of ODP Site 138-849 (Table 2)

The cause of the 100 kyr glacial–interglacial cycles during the past 800 kyr is one of the fundamental puzzles in paleoclimatology. The widely accepted Milankovitch theory, relating earth's climate cycles to variations in insolation caused by periodic changes in orbital parameters, has difficulties to explain the predominant 100 kyr rhythm. Although earth's eccentricity varies with a period of 100 kyr, the resulting change in insolation is too small to produce the corresponding climate cycle by direct forcing (Imbrie et al., 1993; doi:10.1029/93PA02751. In order to solve the '100 kyr problem', Muller and MacDonald (1995, doi:10.1038/377107b0; 1997, doi:10.1126/science.277.5323.215; Proc. Nat. Acad. Sci. USA 94 (1997b) 8329) proposed an alternative orbital but non-Milankovitch mechanism attributing the glacial cycles to regular variations in the accretion of interplanetary dust particles (IDP) caused by 100 kyr cycles in the orbital inclination of the earth. To test this controversial hypothesis, we study the IDP accumulation in deep-sea sediments from a period in the early Pleistocene. We find apparent 41 kyr cycles but no 100 kyr periodicity in the IDP accumulation rate. As there is no known mechanism to produce 41 kyr cycles in IDP supply from space, we conclude that the 41 kyr cycles are caused by the dynamics of sediment accumulation, and that changes in the IDP flux do not drive the Pleistocene glacial cycles.

过去80万年以来的10万年尺度冰期-间冰期旋回成因，是古气候学领域的核心未解难题之一。广为接受的米兰科维奇理论（Milankovitch theory）将地球气候旋回与轨道参数周期性变化引发的太阳辐射通量变化相关联，但难以解释占主导的10万年尺度节律。尽管地球偏心率以10万年为周期变化，由此产生的太阳辐射通量变化幅度过小，无法通过直接辐射强迫催生对应的气候旋回（Imbrie等，1993；doi:10.1029/93PA02751）。为解决这一“10万年难题”，Muller与MacDonald（1995，doi:10.1038/377107b0；1997，doi:10.1126/science.277.5323.215；《美国国家科学院院刊》94卷(1997b) 第8329页）提出了另一种轨道相关但非米兰科维奇的机制，将冰期旋回归因于地球轨道倾角10万年周期变化引发的行星际尘埃颗粒（interplanetary dust particles, IDP）吸积规律波动。为验证这一颇具争议的假说，我们研究了早更新世时期深海沉积物中的行星际尘埃颗粒堆积记录。结果显示，行星际尘埃颗粒堆积速率呈现显著的4万年尺度旋回，但未发现10万年周期信号。由于目前尚无已知机制可催生空间来源行星际尘埃颗粒补给的4万年尺度旋回，我们据此推断：该4万年尺度旋回由沉积物堆积动力学过程所致，而行星际尘埃颗粒通量变化并未驱动更新世冰期旋回。