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

中更新世过渡（MPT）标志着气候和冰量变化从41 kyr到100 kyr周期的过渡，而轨道强迫模式没有变化。大气pCO 2降低约30 ppm（Wolff等人，2010年，Hönisch等人，2009年）。有孔虫碳同位素在0.9 Ma左右显示出显著的最小值，这是第一个主要的100 kyr周期出现的时间（Raymo等人，我们计划检验海洋生物生产力的提高是否在MPT的气候事件中发挥了作用这一假设。已经表明，高纬度地区增加的灰尘输入（Martinez-Garcia等人，2011）在陆地干旱增加的时期（de Menocal，1995年，Dupont等人，2001年），导致了在亚南极洲南大西洋的ODP站点1090的生产力的提高。在这里，我们测试全球范围内提高生产力的程度。具体而言，我们要求：1）不同气候和水文区域的地点在pCO 2大气压期间是否表现出伴随的生产力增加。下降（~0.9 Ma）？ 2)12 C从大陆转移到海洋可以解释较低的海洋d13 C值吗？（与中新世晚期的发现相当（Diester-Haass等人，我们（即我的合作伙伴K.Billups（美国）和C. Lear（GB）和I）提出了一种多指标方法来评估MPT期间古生产力的变化及其与冷-暖阶段和底栖有孔虫d13 C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率（BFAR），并推导出由Herguera（2000年）开创并由Diester-Haass等人（2013年和本文参考文献）应用的gC/cm² x ky值。我们还将采用一个相对较新的替代指标，南极有孔虫U/Ca比值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本中构建海底有孔虫d13 C值的平行记录，以监测深层沃茨溶解无机碳的d13 C，以评估深层沃茨的原位呼吸与有机碳输入的联系程度。底栖有孔虫d18 O值将提供一个大规模气候变化的记录，生产力代理将耦合。这些替代物将使我们能够确定在这段时间内出口生产力对气候变化的作用。我们将通过XRF数据（以及Marum-Bremen的新测量）和古植物学研究（例如Dupont等人，2001年; Schefuillet al.，2005; Clarke等人，2006年）。

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 ).