Fate of ocean oxygenation in a warming world

氧气对所有高等生物的健康至关重要。自1960年以来，海洋中的溶解氧浓度下降了2%，并且由于人为的气候变化，预计未来将继续下降。未来的脱氧，沿着过度捕捞，威胁着具有重要经济意义的渔业和海洋生态系统的可持续性，并将影响全球生物地球化学循环。因此，我们必须对未来的情况有一个充分的了解。目前预测未来的模型模拟具有相当大的不确定性;它们并不都同意，并且严重低估了过去50年记录的下降。这表明模型缺少关键的相互作用，需要采取紧急行动和专门的和包容性的科学方法。FARGO通过解决为什么以及在什么程度上海水溶解氧浓度可能在变暖的世界中发生变化来提供这种方法。FARGO正在通过一个创新和专门的研究方案研究太平洋（目前海洋中最大的低氧水体）的溶解氧浓度，该方案采用了一种新颖的多代理方法，在关键的温暖时间间隔内为IPCC类型的气候模型模拟提供数据：i-美国海道关闭时的温暖气候（400 - 1500万年）;ii-气候变暖作为未来的模拟（上新世中期温暖期; 330万至300万年前，上新世早期间冰期; 400万至480万年前）;iii-更新世温暖期（最后一个世纪的间冰期）。FARGO在其头三年中取得了重要进展，利用有孔虫（微生物）改善了底层水和地下水氧气的重建。一些物种漂浮在海洋表面附近，称为浮游有孔虫，我们在如何利用浮游有孔虫的微量元素来了解海水氧气水平的变化方面取得了重大进展。生活在海洋底部沉积物上或沉积物中的物种被称为底栖有孔虫，可用于重建底层水氧浓度和通风。在这方面，我们也在取得重大进展，并正在推进各种校准。然而，FARGO的方法是多学科的，我们正在应用多代理方法来重建海水氧气水平以及驱动这一过程的过程。我们正在使用国际海洋发现计划的沉积物来确定在关键的温暖间隔期间，浅太平洋缺氧区（ODZ，例如氧气水平太低而无法支持有氧生活的地区）的自然范围和强度是否发生了变化。此外，FARGO正在进行模型模拟，帮助我们了解环境变化（温度，海洋环流）如何影响海水氧气，不仅是太平洋，而且是全球范围内。我们正在使用两个模型来测试模型结果的稳健性，并识别每个关键时间段的模型特定偏差。代理重建产生的时间序列将为IPCC类型的气候模型模拟提供数据，并提供稳健的测试，以调查模型模拟是否真实和正确，并确定改进模型模拟的路线。利用这些改进，FARGO将进行模拟未来，包括1.5和2度变暖的情景。为了提高对海洋脱氧的认识，FARGO有几个针对科学同行，政策制定者和特定公众的定制影响和参与活动。

Oxygen is critical to the health of all higher life. In the oceans dissolved oxygen concentrations have declined by 2% since 1960, and are expected to continue to decline into thefuture in relation to man-made climate change. Future deoxygenation, along with overfishing, threatens the sustainability of economically important fisheries and marineecosystems and will impact global biogeochemical cycles. It is therefore crucial that we obtain a well-informed view about what the future may hold.Current model simulations that predict the future carry considerable uncertainties; they do not all agree and grossly underestimate the documented decrease of the last 50 years. Thissuggests the models are missing key interactions, calling for urgent action and a dedicated and inclusive scientific approach.FARGO provides such an approach by addressing why, and to what extent, seawater dissolved oxygen concentrations may change in a warming world. FARGO is studyingdissolved oxygen concentrations in the Pacific Ocean, the largest low-oxic water body in the current ocean, through an innovative and dedicated research programmeincorporating a novel multi-proxy approach feeding IPCC-type climate model simulations across key warm time intervals:i- warmer climates across the closure of the American sea-way (4-15 million years);ii- warmer climates as future analogue (mid-Pliocene Warm Period; 3.3 to 3 million years ago, early Pliocene interglacials; 4.0-4.8 million years ago);iii- Pleistocene warm intervals (interglacials of the last ca. 800,000 years).During its first three years FARGO has made important advances to improve bottom water and subsurface water oxygen reconstructions using foraminifera (microorganisms). Some species float near the ocean surface, called planktonic foraminifera, we have made major advances in how trace elements of planktonic foraminifera may be used to understand changes in seawater oxygen levels. Species that live on or in sediments at the bottom of the ocean are termed benthic foraminifera and can be used to reconstruct bottom water oxygen concentrations and ventilation. Here we are also making major advancements, and are advancing various calibrations. FARGO's approach is however multidisciplinary, and we are applying a multiproxy approach to our reconstructions of seawater oxygen levels and also processes that drive this. We are using sediments from the International Ocean Discovery Program to determine if there have been changes in the natural extent and intensity of the shallow Pacific Ocean oxygen deficient zones (ODZ, e.g. areas where oxygen levels are too low to support aerobic life), during the key warm intervals. Furthermore FARGO is carrying out model simulations which help us understand how environmental changes (temperature, ocean circulation) impacted seawater oxygen not only for the Pacific, but also on a global scale. We are using two models to test the robustness of the model results and identification of model specific biases across each key time-period.The time-series generated by the proxy reconstructions will feed the IPCC-type climate model simulations and provide robust tests to investigate if the model simulations are realistic and correct for the specific time periods, and identify routes to improve the model simulations. Utilizing these improvements, FARGO will carry out simulations for future, including 1.5 and 2 degree warming scenarios.To raise awareness of ocean deoxygenation FARGO has several bespoke impact and engagement activities aimed at scientific peers, policy makers, and defined public audiences.