(Table 1) Helium isotope ratios of sediment core TT013_114

We present a helium isotope record for core TT013-114PC from the central equatorial Pacific (140°W, 4°N, 4432 m water depth) spanning a period of 1 million years. We focus on the time interval from 560 to 800 kyr, largely coinciding with the mid-Pleistocene climate transition (MPT) when the dominant period of the Earth's climate variability shifted from 41 kyr to 100 kyr. The terrigenous 4He concentrations from our study correlate very well with published titanium concentrations in this core strongly supporting the use of terrigenous 4He as a monitor of continental dust. Normalizing titanium and terrigenous 4He concentrations to 3He suggests that the dust supply during the MPT was approximately 30% lower compared to the subsequent period (560-100 kyr). The 3He-normalized barium, aluminum and phosphorus concentrations, trace elements with a predominantly biogenic source in these sediments, are relatively constant. This is in contrast to previous studies that reported an apparent rise of titanium-normalized productivity proxies. Rather than a significant increase in productivity during the MPT, we conclude that the dust flux to the central equatorial Pacific was reduced and that the export productivity was approximately constant during this period of climate reorganization.

本研究提供了取自中赤道太平洋（西经140°，北纬4°，水深4432米）的TT013-114PC岩芯的氦同位素记录，时间跨度达100万年。本研究聚焦于56万至80万年的时间区间，该区间大体对应中更新世气候转型期（mid-Pleistocene Climate Transition, MPT）——在此期间，地球气候变率的主导周期从4.1万年转变为10万年。本研究测得的陆源氦-4（terrigenous ⁴He）浓度与该岩芯已发表的钛元素浓度具有极强的相关性，有力证明了陆源氦-4可作为大陆粉尘的示踪指标。将钛元素浓度与陆源氦-4浓度以氦-3（³He）标准化后可知，中更新世气候转型期的粉尘供给量较后续时期（56万至10万年）降低了约30%。以氦-3标准化后的钡、铝、磷浓度——这些在沉积物中主要为生物源的微量元素——相对稳定。这与此前研究中报道的、以钛标准化的生产力代用指标显著升高的结论相悖。本研究认为，中更新世气候转型期的粉尘向中赤道太平洋的输送通量有所降低，且在此气候重组阶段的输出生产力大体保持稳定，而非生产力出现显著提升。