Response of palaeooceanography evolution of eastern and western Pacific Ocean and marginal sea to the Arctic Icecap formation
Guo Jianqing1, Cheng Xinrong2, Chen Ronghua2,3
1 Earth Resource and Information College，China University of Petroleum（East China)，Dongying 257061，Shandong 2 State Key Laboratory of Marine Geology，Tongji University，Shanghai 200092 3 The Second Institute of Oceanograhy，SOA，Hangzhou 310012，Zhejiang
Abstract：The most important palaeoclimate event in the Pliocene is the formation and expansion of the Arctic Icecap during 3.2-2.5 Ma.We obtained δ18O(oxygen isotopes)，δ13C(carbon isotope)record data of planktonic foraminifera Globigerinoides ruber and Pulleniatina obliquiloculata from the Pliocene-Early Pleistocene interval(4.5-1.6Ma)in ODP807A in the Western Pacific Warm Pool.Based on the formation process of the Arctic Icecap，the above data can be divided into three stages: prior to Icecap formation(4.5-3.2Ma)，during Icecap formation(3.2-2.5Ma)and after Icecap formation(2.5-1.6Ma).The results show that since the Icecap formation，δ18O values in both G.ruber and P.obliquiloculata showed increasing trend，respectively indicating the continuous temperature decrease in the surface and subsurface in the Warm Pool.During the Icecap formation，the δ18O value of G.ruber changed little，but that of P.obliquiloculata was heavier，which indicate that the subsurface was affected more strongly by Icecap formation.The δ18O difference between P.obliquiloculata and G.ruber(or Δδ18O（P-G）） reflects little change in the depth of thermocline，implying a very weak influence from the Icecap formation.According to the Mg/Ca value from ODP806(Wara et al.，2005)and UK′37 value from ODP 847(Herbert and Laura，2010)，both the surface temperature of western Pacific Ocean and the eastern Pacific Ocean decreased since the Arctic Icecap formation，and a greater range of the eastern Pacific.Compared with Δδ18O(P-G) from the western Pacific ODP807A with Δδ18O(T-S) from the eastern Pacific ODP847 at the same period，the eastern Pacific thermocline changed shallowing，suggesting the gradient of the depth of thermocline between the western and eastern Pacific enlarged.Compared δ18O and δ13C value between G.rubber and P.obliquiloculata at Site 1143 and Site 1148, it also indicated that the surface temperature and the productivity level were more evidently affected in the northern(Site 1148)than in the southern South China Sea(Site 1143).
Guo Jianqing,Cheng Xinrong,Chen Ronghua. Response of palaeooceanography evolution of eastern and western Pacific Ocean and marginal sea to the Arctic Icecap formation[J]. JOPC, 2011, 13(3): 334-346.
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