SGER: Subantarctic Mode Water and Antarctic Intermediate Water: How Well Are They Represented in Climate Models?

南大洋的过程可在与全球气候变化有关的时间尺度上影响全球海洋环流和密度结构。因此，对美国气候模式中南大洋水团模拟的评估将有助于量化和减少预测全球温盐环流对大气中温室气体浓度增加的响应的不确定性。这项研究的目的是利用观测数据评估亚南极模式水(SAMW)和南极中间水(AAIW)在三个美国气候模式中的模拟：社区气候系统模式(CCSM)、地球物理流体动力学实验室(GFDL)模式和戈达德空间科学研究所(GISS)模式。这项研究有两个主要目的：(1)通过与2001年世界海洋地图集的观测资料的比较，评价海洋环流模式对SAMW和AAIW的模拟。分析将侧重于SAMW和AAIW的体积、温度和盐度，以及太平洋和大西洋南部边界经向断面的层结。(2)使用基于数据的倒箱模型估计的质量、热量和盐通量，评价对中间水的循环和修改的模拟。分析将侧重于流入太平洋和大西洋盆地的等周期通量，以及改变南大洋中间水性质的日周期通量。这些分析的结果将有助于确定OGCM模拟的SAMW和AAIW属性与观测属性之间的分歧来源。这项工作的更广泛影响是，它将有助于评估未来气候变化预测的不确定性，并将指导未来模型的开发。这对环境管理和决策活动很重要。

Processes in the Southern Ocean can influence global ocean circulation and density structure on the time scales relevant for global climate change. Evaluation of simulation of the Southern Ocean water masses in U.S. climate models will therefore assist in quantification and reduction of the uncertainty in predicting the response of the global thermohaline circulation to increasing concentration of greenhouse gases in the atmosphere. The goal of this study is to evaluate simulation of the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) in three U.S. climate Models: the Community Climate System Model (CCSM), the Geophysical Fluid Dynamics Laboratory (GFDL) model, and the Goddard Institute of Space Sciences (GISS) model, using observational data. The research has two main objectives: (i) To evaluate simulation of the properties of SAMW and AAIW by ocean general circulation models (OGCMs) through comparison with the observational data from the World Ocean Atlas 2001. The analysis will focus on the volume, temperature and salinity of SAMW and AAIW and on the stratification along meridional sections at the southern boundary of the Pacific and Atlantic oceans. (ii) To evaluate simulation of circulation and modification of the intermediate water using estimates of mass, heat and salt fluxes by a data-based inverse box model. The analysis will focus on the isopycnal fluxes into the Pacific and Atlantic basins, as well as on the diapycnal fluxes that modify properties of the intermediate water in the Southern Ocean. The results of these analyses will help to identify sources of disagreement between the OGCM-simulated and observed properties of SAMW and AAIW.The broader impacts of the work are that it will aid in assessing the uncertainty of the future climate change projections and will guide future model development. This is important for environmental management and decision-making activities.