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基于浮游有孔虫Mg/Ca温度重建的末次盛冰期以来北欧海次表层温度的变化
Sub sea surface temperatures in the Nordic Seas during the LGM by planktic foraminiferal Mg/Ca temperature reconstructions
【摘要】 对我国第五次北极科考在北欧海所采集的两根岩芯样品进行了冰筏碎屑(Ice-Rafted Debris, IRD)丰度、AMS 14C测年、有孔虫丰度统计、浮游有孔虫Neogloboquadrina pachyderma(sin.)(Nps)稳定氧碳同位素及其Mg/Ca重建的次表层海水古温度等指标分析,建立了20ka以来的年代框架。结果表明,在末次盛冰期(20.0~17.5kaBP),次表层温度整体较低(~3℃),钙质生产力下降,冰筏碎屑输入增加;在冰消期(17.5~11.7kaBP)的Heinrich Stadial 1(HS1)事件中较轻的δ18O和δ13C指示大量淡水输入,水体分层加剧,向北输送的北大西洋水聚集在次表层,导致次表层水温逐渐升高。从B?lling-Aller?d (B/A)事件开始,次表层水温度达到4.5℃,表明北大西洋水流入增强。早全新世(11.7~8.2kaBP)早期次表层温度达到6.5℃,钙质生产力升高,冰筏碎屑输入降低;在中全新世(8.2~4.2kaBP)早期(8.2~5.6kaBP),钙质生产力逐渐升高反映通风作用增强,导致营养盐供应增加;6.6~5.6kaBP,明显降低的次表层温度(~4℃)反映夏季太阳辐射量降低以及大西洋水流入减弱;5.6~4.2kaBP期间次表层水变暖导致δ18O偏轻,而δ13C轻值反映生产力降低。晚全新世(4.2~0.8kaBP)的新冰期(4.2~3.0kaBP),次表层温度逐渐降低,Nps-δ13C偏轻反映生产力下降,Nps-δ18O偏轻以及IRD增加反映冰融水排放。3.0kaBP以来,生产力上升,次表层水体温度不断上升,可能是向北输送的北大西洋水增强。
【Abstract】 In order to reconstruct the changes in(sub)surface water mass since 20.0 kaBP, multiproxy investigations, including Ice Rafted Debris(IRD) abundance, AMS14C dating, foraminiferal abundance, stable oxygen and carbon isotopes of planktonic foraminifera Neogloboquadrina. pachyderma(sin.)(Nps), and(sub)surface temperature derived from Nps Mg/Ca ratios, have been carried out for two cores collected from the Nordic Seas during the Fifth Chinese National Arctic Expedition. The LGM(20.0~17.5 kaBP) is characterized by low subsurface water temperature(~3℃), poor calcium productivity, and enhanced IRD input. During the deglaciation(17.5~11.7 kaBP). Nps-δ18O and-δ13C depletions suggested a freshwater event during Heinrich Stadial 1(HS1). Stronger water stratification and north Atlantic water gathering in the subsurface layer caused the increase in subsurface temperature. At the onset of B?lling-Aller?d(B/A) event, the subsurface water temperature(4.5℃) indicated an increased advection of Atlantic water. The early Holocene(11.7~8.2 kaBP) was characterized by higher subsurface temperature(6.5℃), bioproductivity, and lower IRD input. During the middle Holocene(8.2~4.2 kaBP), the gradual increase in bioproductivity during 8.2~5.6 kaBP indicated the enhanced ventilation, which led to an increase in nutrient supply. Lower subsurface temperature(~4℃) during the 6.6~5.6 kaBP may suggest the decrease in summer solar radiation and weakening of Atlantic water advection. During 5.6~4.2 kaBP, the depletion of Nps-δ13C and δ18O values indicated poor bioproductivity and subsurface water warming, respectively. During the late Holocene(4.2~0.8 kaBP), the Neoglaciation(4.2~3.0 kaBP), was characterized by low subsurface temperature and poor bioproductivity. The light values of Nps-δ18O and the increase in IRD reflected a meltwater event. Since 3 kaBP, the continuous increasing of subsurface temperature and bioproductivity may be explained by the increased advection of Atlantic water.
【Key words】 paleoceanography; sub SST reconstruction; Last Glacial Maximum(LGM); Nordic Sea;
- 【文献出处】 海洋地质与第四纪地质 ,Marine Geology & Quaternary Geology , 编辑部邮箱 ,2019年03期
- 【分类号】P532;Q958.8
- 【网络出版时间】2019-05-27 11:34
- 【被引频次】3
- 【下载频次】256