Modelling the impact of global warming on the trophic state of the upper ocean

本研究的主要目的是定量评估全球变暖对上层海洋营养平衡的潜在影响。初级生产以及自养和异养呼吸都预计会随着温度的升高而增加，许多实验培养研究表明，呼吸的温度升高比生产的温度升高更为明显。这一观点在近期的生态系统研究中得到了进一步的证实。根据这些结果，全球变暖的一个预期直接影响是生物碳泵的减弱。与由环流和分层变化引起的间接影响相比，这种直接温度效应尚未在全球尺度上进行定量研究。利用一个中等复杂程度的地球系统模型，本研究将研究该模型的生物泵对温度对自养和异养过程影响的不同参数化的敏感性，每个参数化都由来自培养和中尺度研究的可用实验数据校准。不同参数化紧密再现生物地球化学示踪剂分布区域模式的能力将首先对工业化前的稳态解决方案进行评估。在第二步中，该模式将与21世纪ipcc型二氧化碳排放情景相结合，以估计直接温度效应对海洋生物群的影响，相对于通过环流和分层变化产生的间接影响。

The main aim of the proposed research is a quantitative evaluation of the potential impact of global warming on the trophic balance of the upper ocean. Primary production, as well as autotrophic and heterotrophic respiration are all expected to increase with temperature, and a number of experimental culture studies suggest that the increase with temperature is more pronounced for respiration than for production. This notion has been further confirmed on the ecosystem level in recent short-term mesocosm studies. According to these results, an expected direct effect of global warming is a weakening of the biological carbon pump. In contrast to indirect effects arising from changes in circulation and stratification, such a direct temperature effect has not yet been investigated quantitatively on a global scale. Using an Earth System Model of intermediate complexity, the proposed study will investigate the sensitivity of the model’s biological pump to different parameterisations of temperature effects on autotrophic and heterotrophic processes, each calibrated by available experimental data from culture and mesocosm studies. The ability of different parameterisations to closely reproduce regional patterns of biogeochemical tracer distributions will first be evaluated for pre-industrial steady-state solutions. In a second step, the model will be forced with IPCC-type CO2 emission scenarios over the 21st century in order to estimate the impact of direct temperature effects on the marine biota relative to indirect effects via changes in circulation and stratification.