Abstract An understanding of the quality and accuracy of state-of-the-art time-varying salinity information is being established by comparing existing products against each other as well as against existing ocean reanalyzes and satellite retrieval. The focus the paper is on large-scale salinity structures and their temporal variations from the sea surface down to 700 m depth. Uncertainties are quantified through the spread between all existing estimates on various time scales including long-term trends. Results suggest that uncertainties of time mean climatological salinity estimates are as large as 0.3 within the first 50 m of high vertical salinity gradients and even larger in some boundary regions. Over the open (deep) ocean, a near-surface spread of 0.1 can be observed; below 300 m depth it stays below 0.03 over most part of the world ocean. Measuring salinity in near-costal and highly dynamic regions remains problematic and calls for a better integration of existing in situ and satellite capabilities there. There remain challenges in estimating the amplitude of the salinity seasonal cycle from the existing in situ database. This holds especially within the tropics, where the disagreement between the seasonal salinity amplitude estimated from individual situ data sets is typically around 30%, locally even up to 50%. Regarding interannual and longer-term salinity changes, inferred trend patterns agree well with the standard deviation of the decadal climatologies, suggesting that it remains difficult to obtain statistically significant estimates of long-term trends from the existing short data base over the world ocean. Overall, our results call for further improvements of ocean reanalysis products and their expanded use in studies of ocean variability and changes in the future.

中文翻译：

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我们对海洋盐度及其变化了解多少？

摘要 通过将现有产品相互比较以及与现有海洋重新分析和卫星检索，正在建立对最先进的时变盐度信息的质量和准确性的理解。论文的重点是大尺度盐度结构及其从海面到 700 m 深度的时间变化。不确定性通过包括长期趋势在内的各种时间尺度上所有现有估计值之间的差值进行量化。结果表明，时间平均气候盐度估计的不确定性在高垂直盐度梯度的前 50 m 内高达 0.3，在某些边界区域甚至更大。在开阔（深）海洋上，可以观察到 0.1 的近地表扩散；在 300 m 深度以下，它在世界海洋的大部分地区保持在 0.03 以下。在近海岸和高度动态区域测量盐度仍然存在问题，需要更好地整合现有的现场和卫星能力。从现有的原位数据库估计盐度季节周期的幅度仍然存在挑战。这尤其适用于热带地区，根据个别现场数据集估计的季节性盐度幅度之间的差异通常约为 30%，局部甚至高达 50%。关于年际和长期盐度变化，推断的趋势模式与年代际气候的标准偏差非常吻合，这表明从现有的世界海洋短期数据库中获得具有统计意义的长期趋势估计仍然很困难。全面的，