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Calcium carbonate pump during Quaternary glacial cycles in the South china Sea

Chinese Science Bulletin 2003年第17期48卷 1862-1869页

作者： liu zhifei, xu jian, tian jun & wang pinxian laboratory of marine geology, tongji university, Shanghai 200092,{4. laboratory of marine geology Tongji University

The preservation and dissolution of calcium carbonate (namely calcium carbonate pump) controls the pH of seawater in global oceans by its buffer effect, and in turn plays a significant role in global changes in atmospheric CO2 concentration. The results from measured carbonate con-tents over the past 2 Ma at ODP Site 114. in the South china Sea provide high-resolution records to explore the process of the calcium carbonate pump during Quaternary glacial cy-cles. The results indicate statistically that the highest car-bonate accumulation rate leads the lightest d 18O by about 3.6 ka at transitions from glacials to interglacials, and that the strongest carbonate dissolution lags the lightest d 18O by about 5.6 ka at transitions from interglacials to glacials. The calcium carbonate pump releases CO2 to the atmosphere at the glacial-interglacial transitions, but transports atmos-pheric CO2 to deep sea at the interglacial-glacial transitions. The adjustable function of the calcium carbonate pump for the deep-sea 23CO- concentration directly controls parts of global changes in atmospheric CO2, and contributes the global carbon cycle system during the Quaternary.

关键词：中国南海碳酸钙第四纪冰川旋回海洋钻探图古气候

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Exploring cyclic changes of the ocean carbon reservoir

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Chinese Science Bulletin 2003年第23期48卷 2536-2548页

作者： wang pinxian, tian jun, CHENG Xinrong, {4. Quanlian & xu jian Key {4. of marine geology, Ministry of Education, tongji Uni-versity, Shanghai 200092, china Key laboratory of marine geology Ministry of Education Tongji University

A 5-Ma record from ODP Site 114. has re-vealed the long-term cycles of 4.0—500 ka in the carbon isotope variations. The periodicity is correlatable all over the global ocean and hence indicative of low-frequency changes in the ocean carbon reservoir. As the same periodicity is also found in carbonate and eolian dust records in the tropical ocean, it may have been caused by such low-latitude proc-esses like monsoon. According to the Quaternary records from Site 114. and elsewhere, major ice-sheet expansion and major transition in glacial cyclicity (such as the Mid-Brunhes Event and the Mid-Pleistocene Revolution ) were all pre-ceded by reorganization in the ocean carbon reservoir ex-pressed as an episode of carbon isotope maximum (d 13Cmax), implying the role of carbon cycling in modulating the glacial periodicity. The Quaternary glacial cycles, therefore, should no more be ascribed to the physical response to insolation changes at the Northern Hemisphere high latitudes alone; rather, they have been driven by the 揹ouble forcing? a combination of processes at both high and low latitudes, and of processes in both physical (ice-sheet) and biogeochemical (carbon cycling) realms. As the Earth is now passing through a new carbon isotope maximum, it is of vital impor-tance to understand the cyclic variations in the ocean carbon reservoir and its climate impact. The Pre-Quaternary varia-tions in carbon and oxygen isotopes are characterized by their co-variations at the 4.0-ka eccentricity band, but the response of d 13C and d 18O to orbital forcing in the Quater-nary became diverged with the growth of the Arctic ice-sheet. The present paper is the second summary report of ODP Leg 184.to the South china Sea.

关键词：海洋 ODP 海洋钻探工程碳循环南中国海地层学

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Long-term cycles in the carbon reservoir of the Quaternary ocean: a perspective from the South china Sea

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National Science Review 2014年第1期1卷 119-143页

作者： pinxian wang QianYu Li jun tian ZhiMin {4. ChuanLian liu Li Li WenTao Ma State Key laboratory of marine geology Tongji University

In recent years,long-term,high-resolution records from the deep sea and ice-cores have ofered new research opportunities for Quaternary *** studies are no longer restricted to individual glacial cycles,but extend to long-term(≥105 yr)processes across those *** Drilling Program Leg 184.of the South china Sea in 1999 uncovered well-preserved sediment sections,in which three long-term cycles in Pleistocene carbon isotope(δ13C)sequence have been found and demonstrated to be common in the global *** discoveries conirm the existence of long-term processes of 105yr in both the hydrologic(ice-sheet changes)and carbon(biogeochemical changes)cycles,posing the question whether the two processes are *** present review shows that the long-eccentricity cycles prevail throughout theδ13C and other biogeochemical records in geologic history,and 4.0-kyr cycles in the oceanicδ13C sequence before the Quaternary can be hypothetically explained by changes in ratio between particulate and dissolved organic carbon(POC/DOC)in the ocean,depending on the monsoon-controlled nutrient *** is a‘DOC hypothesis’.However,ocean restructuring at 1.6 Ma marked by the isolation of a sluggish abyss under the Southern Ocean has obscured the long-eccentricity 4.0-kyr signal in oceanicδ*** last million-year period has experienced two major changes in the climate regime,namely the mid-Pleistocene transition(MPT)centered at 0.9 Ma and the mid-Brunhes event(MBE)around 0.4.*** MPT and MBE were preluded byδ13C maxima-III(δ13Cmax-III)～1.0 Ma andδ13Cmax-II～0.5 Ma,*** with similar hydroclimatic phenomena over corresponding glacial cycles,the two groups of hydrologic and biogeochemical events appear to have been driven largely by oceanographic changes in the Southern ***,we interpret that the long-term biogeochemical processes originating from the Southern Ocean must have played a crucial role in Quaternary ice-sheet waxing and wa

关键词： carbon cycle long-eccentricity South china Sea Quaternary long-term processes

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