Collaborative Research: Changes in Ocean Circulation, Productivity & Carbon Cycling during Heinrich Events

根据该奖项，PI将测试冰消期海洋翻转环流的重组从深海释放CO2的假设，从而解释了大气CO2的大部分冰消期上升。他们发现，蛋白石埋藏率的峰值发生在冰消期的南大洋和赤道东太平洋。他们认为，这与此时深层沃茨的重新通气以及向地表沃茨供应的溶解硅的相应增加是一致的。因为这发生在海因里希事件1期间，当时北大西洋深水地层被认为已经崩溃，他们推断深水通风的更新是由南极洲周围的底层水形成驱动的。他们建议测试从这些发现中得出的两个假设：H1：冰川时期深海分层的增加减少了溶解硅向赤道上涌地区的供应; H2：冰川边界条件的深海分层特征在每次海因里希事件中被打破。 为了检验这些假设，他们将重建蛋白石在南大洋沉积物中的积累速率，并评估蛋白石通量以及赤道太平洋沉积物中某些浮游植物类群的生物标志物相对丰度的变化。他们预测，油菜甾醇（硅藻代理）/烯酮（coccolithophorid代理）的浓度比较低，在末次冰盛期比全新世在赤道太平洋沉积物。 进一步的预测是，油菜甾醇/烯酮的比例，像蛋白石通量，增加在冰川消退，并在每个海因里希事件，相对于冰川基线条件。他们将使用常规的古海洋学方法来测试这些预测。 他们希望这项工作将导致对未来海洋吸收人为二氧化碳的更明智的预测。 这项工作将支持一名年轻女性阿富汗裔美国人的博士研究。P：\MGG\IPAs\Core Program\MG G May 2005\Abstracts

Under this award the PIs will test the hypotheses that reorganization of the oceans overturning circulation during deglaciation released CO2 from the deep sea, thereby accounting for a large part of the deglacial rise of atmospheric CO2.They found that peak opal burial rates occurred around the Southern Ocean and in the eastern equatorial Pacific Ocean during deglaciation. They believe that this is consistent with a reinvigorated ventilation of deep waters at this time and a corresponding increase in supply of dissolved Si to surface waters. Because this occurred during Heinrich Event 1, when North Atlantic Deep Water formation is believed to have collapsed, they infer that the renewal of deep water ventilation was driven by bottom water formation around Antarctica. They propose to test two hypotheses derived from these findings: H1: Increased stratification of the deep ocean during glacial times reduced the supply of dissolved Si to equatorial upwelling regions; and H2: Deep ocean stratification characteristic of glacial boundary conditions broke down during each Heinrich Event. In order to test these hypotheses they will reconstruct opal accumulation rates in Southern Ocean sediments, and evaluate opal fluxes together with changes in the relative abundance of biomarkers diagnostic of certain phytoplankton taxa in equatorial Pacific sediments. They predict that brassicasterol (diatom proxy)/alkenone (coccolithophorid proxy) concentration ratios were lower during the Last Glacial Maximum than during the Holocene in equatorial Pacific sediments. A further prediction is that brassicasterol/alkenone ratios, like opal fluxes, increased during deglaciation, and during each Heinrich event, relative to glacial baseline conditions. They will test these predictions using routine paleoceanographic methods. They hope that this work will lead to more informed predictions about the oceans uptake of anthropogenic CO2 in the future. The work will support the PhD research of a young female Afghani-American. P:\MGG\IPAs\Core Program\MG&G May 2005\Abstracts