有孔虫Mg/Ca温度计是古海洋学研究中恢复古温度的重要手段之一。然而, 越来越多的研究表明, Mg/Ca温度计的准确性受多种因素的影响, 特别是盐度的控制十分重要。文章实测并搜集整理了印-太暖池地区全新世(大约11kaB.P.以来) 1000余个浮游有孔虫Mg/Ca比值数据, 分别利用包含和不包含盐度信息的两个常用转换方程求取了古海水温度, 并将二者进行了对比, 旨在探讨盐度因素对Mg/Ca温度计的影响。结果显示, 在表层水温大约28℃以下, 两个方程获得的结果几乎一致, 平均差异为0.07℃; 在表层水温28℃以上, 二者平均相差大约1℃。此外, 表层海水盐度越低, 包含盐度信息的转换方程获得的古海水氧同位素的值越大。上述结果揭示盐度对该地区有孔虫Mg/Ca比值的影响效应不明显。
Foraminiferal Mg/Ca-thermometer is one of the key methods in reconstructing past ocean temperatures. Increasing evidence, however, revealed that precision of Mg/Ca-thermometer is influenced by various factors in addition to seawater temperature. Of these factors, salinity is in particular highlighted. This study measured and collected an amount of more than one thousand Holocene (since about 11 ka B.P.) foraminiferal Mg/Ca ratios from sediment cores recovered from the Indo-Pacific warm pool. These Mg/Ca ratios were converted into temperatures using two conventional equations, with and without salinity involved. Estimated temperatures were then compared to reveal salinity effects on Mg/Ca-thermometer used for samples from the Indo-Pacific warm-pool region. It is shown that values resulted from the two equations are very similar, with a difference of 0.07℃ on average in the case that the estimated temperature is lower than 28℃. In contrast, difference is up to 1℃ when the estimated temperature is higher than 28℃. Moreover, it is also revealed that less saline water and larger seawater oxygen isotope were estimated using the equation involving salinity. These findings imply that salinity likely had little influence on foraminiferal Mg/Ca in this region.
[1]李建如. 2005. 有孔虫壳体的Mg/Ca比值在古环境中的应用[J]. 地球科学进展, 20 (8): 815-822.
[2]徐建. 2010. 壳体大小对浮游有孔虫生物地球化学记录的影响[J]. 矿物岩石地球化学通报, 29 (2): 109-118.
[3]ANAND P, ELDERFIELD H, CONTE M H. 2003. Calibration of Mg/Ca thermometry in planktonic foraminifera from a sediment trap time series[J]. Paleoceanography, 18(2): 1050. doi: 10.1029/2002PA000846.
[4]ANTONOV J I, SEIDOV D, BOYER T P, et al. 2010. World Ocean Atlas 2009, Volume 2: Salinity[M]//LEVITUS S. NOAA Atlas NESDIS 69. Washington D C: U.S. Government Printing Office: 1-184.
[5]ARBUSZEWSKI J, DEMENOCAL J, KAPLAN A, et al. 2010. On the fidelity of shell-derived δ18Oseawater estimates[J]. Earth Planet Sci Lett, 300: 185-196. doi: 10.1016/j.epsl. 2010. 10.035.
[6]BARKER S, GREAVES M, ELDERFIELD H. 2003. A study of cleaning procedures used for foraminiferal Mg/Ca paleothermometry[J]. Geochem Geophy Geosy, 4: doi: 10.1029/2003GC000559.
[7]BARKER S, CACHO I, BENWAY H, et al. 2005. Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum[J]. Quaternary Sci Rev, 24: 821-834. doi: 10.1016/j.quascirev.2004.07.016.
[8]BEMIS B E, SPERO H J, BIJIMA J, et al. 1998. Reevaluation of the oxygen isotopic composition of planktonic foraminifera: Experimental results and revised paleotemperature equations[J]. Paleoceanography, 13(2): 150-160.
[9]BOLLIET T, HOLBOURN A, KUHNT W, et al. 2011. Mindanao Dome variability over the last 160 kyr: Episodic glacial cooling of the West Pacific Warm Pool[J]. Paleoceanography, 26: PA1208. doi: 10.1029/2010PA001966.
[10]BOUSSETTA S, BASSINOT F, SABBATINI A, et al. 2011. Diagenetic Mg-rich calcite in Mediterranean sediments: Quantification and impact on foraminiferal Mg/Ca thermometry[J]. Mar Geol, 280: 195-240. doi: 10.1016/ j.margeo.2010.12.011.
[11]DANG H, JIAN Z, BASSINOT F, et al. 2012. Decoupled Holocene variability in surface and thermocline water temperatures of the Indo-Pacific Warm Pool[J]. Geophys Res Lett, 39: L01701. doi: 10.1029/2011GL050154.
[12]DEKENS P S, LEA D W, PAK D K, et al. 2002. Core top calibration of Mg/Ca in tropical foraminifera: Refining paleotemperature estimation[J]. Geochem Geophy Geosy, 3(4): 1022. doi: 10.1029/2001GC000200.
[13]DUENAS-BOHORQUEZ A, DA ROCHA R E, KUROYANAGI A, et al. 2009. Effect of salinity and seawater calcite saturation state on Mg and Sr incorporation in cultured planktonic foraminifera[J]. Mar Micropaleontol, 73: 178-189. doi: 10. 1016/j.marmicro.2009.09.002.
[14]FERGUSON J E, HENDERSON G M, KUCERA M, e al. 2008. Systematic change of foraminiferal Mg/Ca ratios across a strong salinity gradient[J]. Earth Planet Sci Lett, 265: 153-166. doi: 10.1016/j.epsl.2007.10.011.
[15]HOOGAKKER B A A, KLINKHAMMER G P, ELDERFIELD H, et al. 2009. Mg/Ca paleothermometry in high salinity environments[J]. Earth Planet Sci Lett, 284: 583-589. doi: 10. 1016/j.epsl.2009.05.027.
[16]HOLBOURN A, KUHNT W, XU J, 2011. Indonesian Throughflow variability during the last140 ka: the Timor Sea outflow[J]. Geol Soc London, Special Publications 355: 283-303. doi: 10.1144/SP355.14.
[17]HUANG K F, YOU C F, LIN H L, et al. 2008. In situ calibration of Mg/Ca ratio in planktonic foraminiferal shell using time series sediment trap: A case study of intense dissolution artifact in the South China Sea[J]. Geochem Geophy Geosy, 9: Q04016. doi: 10.1029/2007GC001660.
[18]KISAKÜREK B, EISENHAUER A, BÖHM F, et al. 2008. Controls on shell Mg/Ca and Sr/Ca in cultured planktonic foraminiferan, Globigerinoides ruber (white)[J]. Earth Planet Sci Lett, 273: 260-269. doi: 10.1016/j.epsl.2008.06.026.
[19]LEA D W, PAK D K, SPERO H J. 2000. Climate impact of late Quaternary Equatorial Pacific sea surface temperature variations[J]. Science, 289: 1719-1724.
[20]LEA D W. 2003. Elemental and isotopic proxies of past ocean temperatures[M]//HOLLAND H D, TUREKIAN K K. The Oceans and Marine Geochemistry Vol. 6: Treatise on Geochemistry. Oxford: Elsevier-Pergamon: 365-390.
[21]LOCARNINI R A, MISHONOV A V, ANTONOV J I, et al. 2010. World Ocean Atlas 2009, Volume 1: Temperature[M]//LEVITUS S. NOAA Atlas NESDIS 68. Washington D C: U.S. Government Printing Office: 1-184.
[22]MATHIEN-BLARD E, BASSINOT F. 2009. Salinity bias on the foraminifera Mg/Ca thermometry: Correction procedure and implications for past ocean hydrographic reconstructions[J]. Geochem Geophy Geosy, 10: Q12011. doi: 10.1029/2008 GC002353.
[23]MORIMOTO M, ABE O, KAYANNE H. et al. 2002. Salinity records for the 1997-98 El Niño from Western Pacific corals[J]. Geophys Res Lett, 29(11): 1540. doi: 10.1029/2001GL 013521.
[24]REGENBERG M, NUERNBER D, STEPH S, et al. 2006. Assessing the effect of dissolution on planktonic foraminaferal Mg/Ca ratios: Evidence from Caribbean core tops[J]. Geochem Geophy Geosy, 7: Q07P15. doi: 10.1029/2005 GC001019.
[25]ROSENTHAL Y, OPPO D W, LINSLEY B K. 2003. The amplitude and phasing of climate change during the last deglaciation in the Sulu Sea, western equatorial Pacific[J]. Geophys Res Lett, 30(8): 1428. doi: 10.1029/2002GL016612.
[26]ROSENTHAL Y, PERRON-CASHMAN S, LEAR C H, et al. 2004. Interlaboratory comparison study of Mg/Ca and Sr/Ca measurements in planktonic foraminifera for paleoceanographic research[J]. Geochem Geophy Geosy, 5(4): Q04D09. doi: 10.1029/2003GC00650.
[27]SADEKOV A, EGGINS S M DE DECKKER P, et al. 2009. Surface and subsurface seawater temperature reconstruction using Mg/Ca microanalysis of planktonic foraminifera Globigerinoides ruber, Globigerinoides sacculifer, and Pulleniatina obliquiloculata[J]. Paleoceanography, 24: PA3201. doi: 10.1029/2008PA001664.
[28]SAGAWA T, YOKOYAMA Y, IKEHARA M, et al. 2012. Shoaling of the western equatorial Pacific thermocline during the last glacial maximum inferred from multispecies temperature reconstruction of planktonic foraminifera[J]. Palaeogeogr Palaeoclimatol Palaeoecol: 346-347, 120-129. doi: 10.1016/j.palaeo.2012.06.002.
[29]SCHLITZER R, 2013. Ocean Data View[CP/OL]. Version 4.5.6.[2013-06-20]. http://odv.awi.de.
[30]STEINKE S, KIENAST M, GROENEVELD J, et al. 2008. Proxy dependence of the temporal pattern of deglacial warming in the tropical South China Sea: Toward resolving seasonality[J]. Quaternary Sci Rev, 27: 688-700. doi: 10.1016/j.quascirev. 2007.12.003.
[31]STEINKE S, GLATZ C, MOHTADI M, et al. 2011. Past dynamics of the East Asian monsoon: No inverse behaviour between the summer and winter monsoon during the Holocene[J]. Glob Planet Ch, 78: 170-177. doi: 10.1016/j. gloplacha. 2011.06.006.
[32]STOTT L, TIMMERMAN A, THUNELL R. 2007. Southern Hemisphere and deep-sea warming led deglacial atmospheric CO2 rise and tropical warming[J]. Science, 318: 435-438. doi: 10.1126/science.1143791.
[33]VISSER K, THUNELL R, STOTT L. 2003. Magnitude and timing of temperature change in the Indo-Pacific warm pool during deglaciation[J]. Nature, 421: 152-155.
[34]XU J, HOLBOURN A, KUHNT W, et al. 2008. Centennial Changes in the Thermocline Structure of the Indonesian Outflow during Terminations Ⅰ and Ⅱ[J]. Earth Planet Sci Lett, 273: 152-162. doi: 10.1016/j.epsl.2008.06.029.
[35]XU J, KUHNT W, HOLBOURN A, et al. 2010. Indo-Pacific Warm Pool variability during the Holocene and Last Glacial Maximum[J]. Paleoceanography, 25: PA4230. doi: 10.1029/ 2010PA001934.
