The Mid Pleistocene transition: did marine biological productivity lead to pCO2 changes?"

中更新世转变（MPT）标志着气候和冰量变化周期从41 kyr转变为100 kyr，而轨道强迫模式没有改变。大气co2分压降低了约30ppm （Wolff et al. 2010, Hönisch et al., 2009）。有孔虫碳同位素在大约0.9 Ma，即第一个主要100 kyr旋回出现的时间，显示出明显的最小值（Raymo et al., 1998）。我们计划验证海洋生物生产力的提高是否在MPT的气候事件中起作用。研究表明，在陆地干旱加剧时期（de Menocal, 1995, Dupont et al., 2001），高纬度地区（Martinez-Garcia et al., 2011）增加的粉尘输入导致南大西洋亚南极ODP站点1090的生产力增加。在这里，我们测试生产率提高的全球程度。具体而言，我们的问题是：1)不同气候和水文区域的站点在pCO2atm期间是否显示出伴随的生产力增加。减小（~0.9 Ma）？2) 12C从大陆向海洋的转移能否解释海洋d13C值较低的原因？(可与中新世晚期的发现相比较（Diester-Haass et al., 2006）。我们（即我的合作伙伴K.Billups（美国）和C. Lear（英国）和我）提出了一种多代理方法来评估MPT期间古生产力的变化及其与冷暖阶段和底栖有孔虫d13C值变化的关系。为了估计古生产力，我们将测量底栖有孔虫积累速率（BFARs），并得出以gC/cm²x ky为单位的值，该方法由Herguera（2000）首创，并由Diester-Haass等人（2013年及本文引用文献）应用。我们还将采用一种相对较新的替代方法，即浮游有孔虫U/Ca比率，作为沉积物氧化还原状态和古生产力的指标（Mawbey和Lear， 2013）。我们还将从这些相同的样品中构建底栖有孔虫d13C值的平行记录，以监测深水溶解无机碳的d13C，以评估深水原位呼吸与有机碳输入的联系程度。底栖有孔虫d18O值将提供大规模气候变化的记录，生产力代用指标将与之耦合。这些代理将使我们能够确定出口生产率在这段时间内对气候变化的作用。我们将利用基于XRF数据（以及在马鲁姆-不来梅的新测量）和古植物学研究（例如Dupont等人，2001年；Schefuß等人，2005年；Clarke等人，2006年）的陆地输入（特别是作为生产力驱动因素的铁输入）的文献信息来增强这些重建。

The Mid Pleistocene transition (MPT) marks a transition from 41 kyr to 100 kyr cycles in climate and ice volume changes without change in the mode of orbital forcing. Atmospheric pCO2 decreased by about 30 ppm (Wolff et al. 2010, Hönisch et al., 2009). Foraminiferal carbon isotopes display a marked minimum at around 0.9 Ma, the time of emergence of the first major 100 kyr cycles (Raymo et al., 1998).We plan to test the hypothesis whether or not enhanced marine biological productivity played a role in the climatic events of the MPT. It has been shown that enhanced dust input in high latitudes (Martinez-Garcia et al., 2011) during a period of increase in terrestrial aridity (de Menocal, 1995, Dupont et al., 2001) has led to an increase productivity at ODP Site 1090 in the subantarctic South Atlantic. Here we test the global extent of enhanced productivity. Specifically, we ask: 1) Do sites from different climatic and hydrographic regions show concomitant productivity increases during the period of pCO2atm. decrease (~0.9 Ma)? 2) Can transfer of 12C from the continents to the ocean explain the lower marine d13C values? (comparable to findings in the late Miocene (Diester-Haass et al., 2006).We (i.e. my cooperation partners K.Billups (USA) and C. Lear (GB) and I) propose a multiproxy approach to assess changes in paleoproductivity during the MPT and their relation to cold-warm stages and to variations in benthic foraminiferal d13C values. To estimate paleoproductivity, we will measure benthic foraminiferal accumulation rates (BFARs) and derive values in gC/cm² x ky as pioneered by Herguera (2000) and applied by, for example, Diester-Haass et al. (2013 and references herein). We will also employ a relatively new proxy, planktonic foraminiferal U/Ca ratios as an indicator of the sediment redox state of the sediments and paleoproductivity (Mawbey and Lear, 2013). We will also construct parallel records of benthic foraminiferal d13C values from these same samples in order to monitor the d13C of dissolved inorganic carbon of the deep waters, to assess the degree to which the in situ respiration in deep waters can be linked to organic carbon inputs. Benthic foraminiferal d18O values will provide a record of large-scale climate change to which the productivity proxies will be coupled. Together these proxies will allow us to determine the role of export productivity on climate change during this interval of time.We will augment these reconstructions with literature based information about terrestrial input (especially Fe input as a driver of productivity) from XRF data (and new measurements at Marum-Bremen) and from paleobotanical studies (e.g. Dupont et al., 2001; Schefuß et al., 2005; Clarke et al., 2006 ).