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Understanding the variations of water cycle on orbital timescale and their response to astronomical parameters, greenhouse gases (GHG) and ice sheets is one of the focuses in paleoclimate study. Sea ice and precipitation, two important components of the water cycle, are paid much attention. A better understanding of their variations on orbital timescale, especially their response to external forcing and related processes and feedbacks, could provide insight on their long-term variations in the future. The latest research results show that, on orbital scale, the Arctic sea ice is more sensitive to insolation, while the Southern Ocean sea ice is more sensitive to GHG. Under the combined influence of insolation and GHG, the last nine interglacials all have much less summer Arctic sea ice, as compared to both the present-day and the future, due to the much higher Northern Hemisphere (NH) summer insolation. As compared to the future, the last nine interglacials all have much more annual and seasonal Southern Ocean sea ice due to their much lower CO2. In terms of the astronomical parameters, the Arctic sea ice is more influenced by precession, whereas obliquity plays a more important role in the Southern Ocean sea ice. The different responses of Arctic and Southern Ocean sea ice to astronomical parameters and CO2 are mainly due to their different geographical locations. The Arctic ocean is relatively closed and it is located in the northern highest latitudes, which make it only receives very little insolation during winter and it is mainly influenced by precession-dominated summer insolation. The summer insolation not only influences the summer Arctic sea ice, but also has an effect on the winter one through the summer remnant effect. In addition, the Arctic sea ice is also affected by the vegetation in the northern mid and high latitudes, which is mainly dominated by precession. As compared to the Arctic, the latitudes of Southern Ocean are lower and it is more open, whi

Various abrupt climate events have been reported during the last glacial period, but their regional expressions and causes remain complex and not fully understood largely due to lack of high-resolution paleoclimate records. In this study, a high-resolution loess sequence is presented from North China which is significantly influenced by the East Asian Summer Monsoon, and its multiple proxies reveal two strong, abrupt cooling-drying events occurring at 48 ka and ∼42 ka. The 48 ka event corresponds to the fifth Heinrich (H5) event that was characterized by catastrophic iceberg discharges into the subpolar North Atlantic Ocean. Our loess and model results suggest that the 48 ka event could result from the unique and extreme orbital configuration at 48 ka, characterized by the smallest latitudinal summer insolation gradient over the last glacial period. This orbital configuration led to a cooling-drying in the low and mid-latitudes but a warming in high latitudes. The ∼42 ka event corresponds to a catastrophic environmental crisis discovered on the Eurasian and Australian continents. It also corresponds to a major reversal of the Earth's magnetic poles, i.e., the Laschamps Excursion. The cosmic ray increase due to this Excursion could affect the pedogenesis and dust deposition of the loess sequence via cloud increase, regional cooling, aerosol increase and local wind strengthening. This study is a clear demonstration that both extreme orbital conditions and the change of the Earth's magnetic field could cause abrupt climate and environmental changes.

The loess-paleosol sequences in the Chinese Loess Plateau (CLP) are an important terrestrial paleoclimate record. However, quantitative understanding of the response of paleosol development to various climate and environmental factors remains poor. Based on simulations with combined soil-climate models (SoilGen2-LOVECLIM1.3), this study investigates the sensitivity of paleosol development to different soil forming factors as well as the influence of ice sheets and astronomical forcing during the interglacials of the past 500 ka. Sensitivity analyses show that precipitation, dust addition and evapotranspiration are the dominant factors controlling the interglacial paleosol formation, but their relative importance varies between intergalcials and for different soil properties such as calcite and clay contents. Our results show that the simulated S1, S2, S3, S5-1 paleosols, which correspond to MIS 5, 7, 9 and 13 respectively, exhibit strong relationship with precession through its control on precipitation, whereas the precession signal is weak in the simulated S4 paleosol, in line with the weak precession variation during MIS 11. The results also show variable length of lags between different soil properties and precession and also in different interglacials. The lag between the simulated calcite and precession is shorter than that of clay. Moreover, clay content also shows strong relation with temperature during MIS 5 and MIS 13. Large ice sheets in the early and late phases of the interglacials have substantial impact on both temperature and precipitation in the CLP and thus on carbonate leaching and clay migration. Therefore, the simulated paleosols result mainly from the joint effect of precession and ice sheets via their control on local climate, and they show qualitative agreement with observations.

In this study, a facile synthesis method was employed to create lignin-castor oil-based oleogels by modifying organic lignin with two silane coupling agents. The resulting oleogels demonstrated outstanding lubricating and antioxidation properties, establishing them as promising green lubricating greases. Compared with the pure castor oil, the oxidation induction time (OIT) value of the synthesized oleogels was significantly increased from 20 s (pure castor oil) to 1959 s (oleogel with 20 wt % lignin), indicating an effective improvement of the oxidation resistance. The steel contacts lubricated by the synthesized oleogel also had lower wear than those lubricated by pure castor oil, signifying the better lubricating properties of oleogels. The oleogel with 20 wt % lignin showed the lowest wear, which was around 64% lower than that of pure castor oil. The exceptional performance and environmentally sustainable composition of these oleogels, with the biomass content exceeding 80%, allow them to be used as green lubricating greases for industrial applications. Overall, this study provides valuable insights into the development of high-performance, eco-friendly lubricants., Validerad;2023;Nivå 2;2023-09-06 (joosat);CC BY 4.0 License