Role of Physical Processes in the Southern Ocean CO2 Sink

CMIP5，即耦合模式比对项目（第五阶段），促进了一套标准的地球系统模式气候模拟，以便：1)评估我们的模式在模拟近期气候方面的现实程度；2)提供两个时间尺度上的未来气候变化预估，一个是短期（到2035年左右），一个是长期（到2100年及以后）；3)了解导致模式预估差异的一些因素，包括量化一些关键反馈，如涉及云和碳循环的反馈。该项目旨在分析CMIP5模式的输出，以评估影响地表水二氧化碳分压变化和海气二氧化碳吸收的南大洋物理过程的影响。系统的模式间比较将解决三个主要问题：1)整个南大洋表层海洋二氧化碳分压的地带性变化有多显著，因此，南大洋其他地区德雷克通道的esm条件有多大代表性？2)南大洋表层二氧化碳分压的增加速率是否与锋面以南海洋表面上涌的总溶解无机碳（DIC）的增加一致？3)在8个可用esm中，有一半在极锋附近发现了过量的地表水pCO2浓度，哪些物理过程可以解释？提高对未来气候变化的认识符合美国的利益。

CMIP5, the Coupled Model Intercomparison Project (Phase 5) promotes a standard set of earth system model climate simulations in order to: i) evaluate how realistic our models are in simulating climate of the recent past, ii) provide projections of future climate change on two time scales, one near term (out to about 2035) and one long term (out to 2100 and beyond), and iii) understand some of the factors responsible for differences in model projections, including quantifying some key feedbacks such as those involving clouds and the carbon cycle. This project aims to analyse CMIP5 model output to assess the impacts of physical processes in the Southern Ocean that influences surface water pCO2 variation, and air-sea CO2 uptake.Systematic model intercomparisons will be carried out to tackle three main questions: 1) How significant are the zonal variationsin surface ocean pCO2 throughout the entire Southern Ocean, hence, how representative are conditions in Drake Passage of ESMs in other areas of the Southern Ocean? 2) Does the rate of pCO2 increase in the surface waters of the Southern Ocean concur with the increase of total Dissolved Inorganic Carbon (DIC) upwelled to the ocean surface south of the fronts? 3) What physical processes can explain the excessive surface water pCO2 concentrations found near the Polar Front in half of the eight available ESMs?Increased knowledge of future climate change is in the interest of the US.