We analyzed the ability of the Estimating the Circulation and Climate of the Ocean – Phase II (ECCO2) reanalysis to represent the hydrographic properties and variability of Antarctic Bottom Water (AABW) in the Southern Ocean. We used a 20-year (1992–2011) observational database to perform comparisons of hydrographic properties and reanalysis output for the same time period. Four case studies based on current meter data and the AABW volume transport estimates previously reported in the literature were also evaluated. The opening and maintenance of an oceanic polynya in the Weddell Sea sector is observed after 2004 in the reanalysis product. Moreover, intense deep water production due to deep convection occurs, which leads to a scenario in which the Weddell Sea is flooded with AABW. For this reason, our analyses focused on the period that was identified as more reliable (1992–2004). The main Southern Ocean oceanographic features, as well as the characteristic shape of the regional potential temperature–salinity (θ–S) diagrams, are coincident with observations. However, the reanalysis output produces surface waters that are generally denser than observations due to the reproduction of waters that are generally saltier than expected, which probably resulted from the strong seasonality of sea ice concentrations. Bottom waters are warmer and less dense, while intermediate waters are statistically closest to the observations. The differences in bottom water properties are partially due to the inability of the reanalysis to properly reproduce the formation and export of dense waters from the shelf and the consequent absence of the densest AABW variety for most of the analyzed period. Despite differences in the absolute values, the upper AABW limit (γn ≥ 28.27 kg m?3) and AABW occupied area estimates are coincident with the observations in the World Ocean Circulation Experiment (WOCE) repeat sections SR2 and SR4. Moreover, the AABW volume export and current velocity variability are correlated with the observed time series in the most important region of dense water export (i.e., the Weddell Sea). Despite the consistency in terms of variability, the absolute volume transport and velocity estimates are underrepresented in all cases.
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机译：我们分析了估算海洋环流和气候的能力-II期再分析（ECCO2），以代表南大洋的南极底水（AABW）的水文特性和变异性。我们使用了一个为期20年（1992-2011年）的观测数据库，对同一时期的水文特性和重新分析输出进行了比较。还评估了基于电流表数据和先前文献中报道的AABW体积输运估算的四个案例研究。在2004年以后，再分析产品中观察到Weddell Sea地区的一个海洋性多年生鱼类的开放和维持。此外，由于深对流而导致大量的深水产生，这导致了ABBW淹没了韦德尔海的情况。因此，我们的分析集中于确定为更可靠的时期（1992年至2004年）。南部海洋的主要海洋学特征以及区域潜在温度-盐度（θ-S）图的特征形状与观测结果一致。但是，再分析输出所产生的地表水通常比观测值要浓，这是因为所繁殖的水通常比预期的要咸，这可能是由于海冰浓度的强烈季节性所致。底部水较温暖且密度较小，而中间水在统计上最接近观测值。底部水质的差异部分是由于无法进行重新分析，无法正确地重现架子中浓水的形成和出口，因此在大多数分析期间大部分都没有最稠密的AABW品种。尽管绝对值存在差异，但AABW上限（γ n ≥28.27 kg m ？3 ）和AABW占用面积估计值与世界海洋环流中的观测值一致实验（WOCE）重复SR2和SR4部分。此外，在浓水出口的最重要区域（即韦德尔海），AABW的体积出口和当前速度变化与观测到的时间序列相关。尽管在可变性方面具有一致性，但在所有情况下绝对体积输运和速度估计值均不足。
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