Deep ocean oxygen concentrations and efficiency of the biological pump

深海氧气浓度和生物泵效率

• 批准号: NE/I020563/1
• 负责人: Babette Hoogakker
• 金额: $ 41.55万
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI020563%2F1
• 关键词: Deep; ocean; oxygen; concentrations; efficiency

Oxygen forms a major component of our atmosphere (20%) and is produced by plant photosynthesis. Photosynthesis uses carbon dioxide, water and energy from sunlight to make organic carbon. Respiration and the decay of organic carbon consumes oxygen. The amount of dissolved oxygen in seawater is much smaller than the amount of oxygen in the atmosphere, and is related to temperature-controlled solubility and respiration of organic carbon. The distribution of dissolved oxygen in the oceans is not uniform. In deep waters (deeper than 1.5 km) the remineralization of organic carbon through respiration causes a decrease in dissolved oxygen concentrations from the North Atlantic Ocean (where deep waters are formed) en route to the Pacific Ocean. Warmer seawater temperatures, increased sinking of organic carbon produced in surface waters and respiration of this organic carbon, as well as a reduction in deep water formation, are all mechanisms that lead to a reduction in deep ocean dissolved oxygen concentrations. Several recent studies have suggested that global seawater dissolved oxygen concentrations will decline by 30% by the year 3000 as a result of global warming. Knowledge of natural variations of dissolved oxygen concentrations is therefore crucial to advance future predictions and an important research question. During ice ages (glacial times) there is mounting evidence that the oceans sequestered about 30% of the carbon dioxide that is (naturally) present during warm climates (interglacials) in our atmosphere. This carbon sequestration was caused by a variety of biological (respiration), physical (temperature, ocean circulation) and chemical (carbonate buffering through preservation and dissolution of calcium carbonate microfossils) mechanisms. The contribution of each of these mechanisms is poorly quantified, and we do not fully know where in the oceans the atmospheric carbon was stored. Production of organic material by photosynthesis, and respiration deeper down the water column will isolate carbon dioxide from the atmosphere for some time. An increase in organic material production and export and remineralization at depth (e.g. stronger biological pump) is one mechanism that is proposed to have acted as a carbon dioxide sequestration mechanism. As oxygen solubility is mainly temperature controlled, we can calculate the amount of total consumed oxygen (through remineralization of organic material) of a water mass by subtracting the initial saturated dissolved oxygen concentration from the measured dissolved oxygen concentration. From this we can then calculate the amount of sequestered carbon in that water mass. I have developed a novel technique to measure deep and intermediate ocean oxygen concentrations using benthic organisms (microfossils) obtained from deep sea sediment samples. For this fellowship I propose to generate historical (glacial-interglacial) records of deep and intermediate ocean oxygen concentration and test whether changes in atmospheric carbon dioxide are directly related to biological carbon sequestration. I am then going to use earth system models to test several hypothesis of why there was more biologically sequestered carbon in the glacial ocean.

氧气是我们大气的主要成分（20%），由植物光合作用产生。光合作用利用二氧化碳、水和来自阳光的能量来制造有机碳。呼吸和有机碳的衰变消耗氧气。海水中的溶解氧含量远小于大气中的含氧量，与有机碳的温度控制溶解度和呼吸作用有关。海洋中溶解氧的分布是不均匀的。在深沃茨（1.5公里以下），有机碳通过呼吸作用的再矿化作用导致从北大西洋（形成深沃茨的地方）到太平洋的溶解氧浓度下降。海水温度升高、表层沃茨中产生的有机碳下沉和这种有机碳的呼吸作用增加以及深水形成减少，都是导致深海溶解氧浓度降低的机制。最近的几项研究表明，由于全球变暖，到3000年，全球海水溶解氧浓度将下降30%。因此，溶解氧浓度的自然变化的知识是至关重要的，以推进未来的预测和一个重要的研究问题。在冰河时代（冰川时代），越来越多的证据表明，海洋隔离了大约30%的二氧化碳，这些二氧化碳在温暖的气候（间冰期）中（自然）存在于我们的大气中。这种碳固存是由各种生物（呼吸作用）、物理（温度、海洋环流）和化学（通过碳酸钙微化石的保存和溶解来缓冲碳酸盐）机制造成的。这些机制中的每一个的贡献都很难量化，我们也不完全知道大气中的碳储存在海洋的什么地方。光合作用产生的有机物质，以及水柱深处的呼吸作用，将使二氧化碳在一段时间内与大气隔离。有机物质生产和出口的增加以及深海生物化（例如，更强的生物泵）是被认为是二氧化碳封存机制的一种机制。由于氧的溶解度主要受温度控制，我们可以通过从测量的溶解氧浓度中减去初始饱和溶解氧浓度来计算水体的总消耗氧量（通过有机物质的分解）。由此，我们可以计算出水团中封存的碳的数量。我开发了一种新的技术，利用从深海沉积物样品中获得的底栖生物（微化石）来测量深海和中层海洋的氧浓度。对于这个奖学金，我建议产生的历史（冰川间冰期）记录的深和中间的海洋氧浓度和测试是否在大气中的二氧化碳的变化是直接相关的生物碳封存。然后，我将使用地球系统模型来测试为什么在冰川海洋中有更多的生物隔离碳的几个假设。

项目成果

Millennial changes in North Atlantic oxygen concentrations

北大西洋氧气浓度的千年变化

• DOI: 10.5194/bgd-12-12947-2015
• 发表时间: 2015
• 作者: Hoogakker B

I/Ca in epifaunal benthic foraminifera: A semi-quantitative proxy for bottom water oxygen in a multi-proxy compilation for glacial ocean deoxygenation

表层底栖有孔虫中的 I/Ca：冰川海洋脱氧多代理汇编中底层水氧的半定量代理

• DOI: 10.1016/j.epsl.2019.116055
• 发表时间: 2020
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Lu, Wanyi;Rickaby, Rosalind E.M.;Hoogakker, Babette A.A.;Rathburn, Anthony E.;Burkett, Ashley M.;Dickson, Alexander J.;Martínez-Méndez, Gema;Hillenbrand, Claus-Dieter;Zhou, Xiaoli;Thomas, Ellen
• 通讯作者: Thomas, Ellen

Glacial expansion of oxygen-depleted seawater in the eastern tropical Pacific

• DOI: 10.1038/s41586-018-0589-x
• 发表时间: 2018-10-18
• 期刊: NATURE
• 影响因子: 64.8
• 作者: Hoogakker, Babette A. A.;Lu, Zunli;Galbraith, Eric
• 通讯作者: Galbraith, Eric

Foraminifera Iodine to Calcium Ratios: Approach and Cleaning

有孔虫碘钙比例：方法和清洁

• DOI: 10.1029/2021gc009811
• 发表时间: 2021
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Winkelbauer H

Glacial-interglacial changes in bottom-water oxygen content on the Portuguese margin

• DOI: 10.1038/ngeo2317
• 发表时间: 2015-01-01
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Hoogakker, Babette A. A.;Elderfield, Henry;Rickaby, Rosalind E. M.
• 通讯作者: Rickaby, Rosalind E. M.