NOAA/WDS Paleoclimatology - GRIP Ice Core 133KYr Mineralogy of Atmospheric Micro-Particles

The mineralogical composition of atmospheric dust particles changes along the Greenland Ice Core Project (GRIP) ice core in phase with other paleoatmospheric records, showing that climatic changes affect the location, the relative extent, and the surface characteristics of the dust source areas. Fifty GRIP ice samples from the Eemian to the last glacial maximum were analyzed using a scanning electron microscope coupled with X ray energy dispersive system microprobe. More than 20 mineral types or groups were identified and their relative abundance was evaluated. A different mineralogical composition was systematically observed in cold and warm time periods. Quartz, illite, chlorite, micas, and feldspars prevail in the mineral assemblage associated with cold stages or phases (marine isotope stage (MIS) 4, MIS 2, cold part of MIS 3 fast variations), while kaolinite and Fe (hydr)oxides dominate in warm episodes (MIS 5e5, warm parts of fast variations). The first dust mineral assemblage is related mainly to the mechanical weathering prevailing in arid and cold mid-high-latitude areas, while the second dust mineral assemblage is related mainly to deep chemical weathering in warm and humid low-latitude areas. K/C and O/Q ratios may be assumed as indicative of the relative importance of low-latitude versus arid and mid-high-latitude source areas. It is worthwhile to mention that the first warmer part of Eemian (5e5) differs in dust mineralogy from the second part (5e4-5e1) and that also the fast variations are accompanied by clear mineralogical changes of the dust microparticles. The changes of the atmospheric dust mineral background are possibly related to changes of the atmosphere dynamics (meridian pressure gradient, polar front shift, storm track changes, etc.) and or to changes in the relative extent of the deflation source areas.

格陵兰冰芯计划（Greenland Ice Core Project, GRIP）冰芯中大气尘埃颗粒的矿物组成与其他古大气记录同步变化，表明气候变化会影响尘埃源区的位置、相对范围及地表特征。本研究对取自埃姆间冰期（Eemian）至末次冰盛期的50个GRIP冰芯样品开展分析，采用扫描电子显微镜（scanning electron microscope）耦合X射线能量色散系统微探针完成测试。研究共识别出20余种矿物类型或矿物群组，并对其相对丰度进行了评估。冷、暖时段的矿物组成呈现系统性差异：寒冷阶段（海洋同位素阶段（Marine Isotope Stage, MIS）4、MIS 2以及MIS 3快速变化的冷期段）的矿物组合以石英、伊利石、绿泥石、云母类及长石为主；而暖期事件（MIS 5e5、快速变化的暖期段）则以高岭石及铁的（氢）氧化物占主导。前者的尘埃矿物组合主要对应干旱寒冷的中高纬度地区盛行的机械风化作用，后者则主要与温暖湿润的低纬度地区的深度化学风化作用相关。K/C与O/Q比值可用于指示低纬度源区与干旱、中高纬度源区的相对重要性。值得一提的是，埃姆间冰期的首个暖期段（5e5）与后续暖期段（5e4-5e1）的尘埃矿物组成存在差异，且快速气候波动过程中亦伴随尘埃微粒矿物组成的显著变化。大气尘埃矿物本底的变化可能与大气动力过程（经向气压梯度、极锋迁移、风暴路径变化等）或/和风蚀源区相对范围的改变有关。