Roach and Bindoff Global Temperature, Salinity and Oxygen Atlas (Shipboard Data 1955-2018) V1.0

This atlas uses all of the available full water column profiles of oxygen, salinity and temperature available as part of the World Ocean Atlas released in 2018. Instead of optimal interpolation we use the Data Interpolating Variational Analysis (DIVA) approach to map the available profiles onto 108 depth levels between the surface and 6800 m, covering more than 99% of ocean volume. This 1/2° x 1/2° degree atlas covers the period 1955 to 2018 in 1 year intervals. The DIVA method has significant benefits over traditional optimal interpolation. It allows the explicit inclusion of advection and boundary constraints thus offering improvements in the representations of oxygen, salinity and temperature in regions of strong flow and near coastal boundaries. We demonstrate these benefits of this mapping approach with some examples from this atlas. We can explore the regional and temporal variations of oxygen in the global oceans. Preliminary analyses confirm earlier analyses that the oxygen minimum zone in the eastern Pacific Ocean has expanded and intensified. Oxygen inventory changes between 1970 and 2010 are assessed and compared against prior studies. We find that the full ocean oxygen inventory decreased by 0.84% ± 0.42%. For this period temperature driven solubility changes explain about 21% of the oxygen decline over the full water column, in the upper 100 m solubility changes can explain all of the oxygen decrease, for the 100-600 m depth range it can explain only 29%, 19% between 600 m and 1000 m, and just 11% in the deep ocean.

本图集采用了2018年版《世界海洋图集》（World Ocean Atlas）中公开的所有完整水柱溶解氧、盐度与温度剖面数据。本研究未采用传统最优插值方法，而是采用数据插值变分分析（Data Interpolating Variational Analysis, DIVA）方法，将现有剖面数据插值至表层至6800米深度间的108个深度层，覆盖了全球99%以上的海洋体积。该图集的空间分辨率为0.5°×0.5°，时间跨度为1955年至2018年，时间间隔为1年。相较于传统最优插值方法，DIVA方法具备显著优势：其可显式纳入平流与边界约束条件，从而在强流区域及近岸边界区域的溶解氧、盐度与温度场模拟中实现更精准的表征。本图集通过若干实例验证了该插值方法的上述优势，借此可开展全球海洋溶解氧的区域与时间变化特征研究。初步分析结果印证了此前的研究结论，即东太平洋低氧区已发生扩张与强化。本研究评估了1970年至2010年间的海洋氧储量变化，并与已有研究结果进行对比。研究发现，全球海洋总氧储量下降了0.84%±0.42%。在该时段内，温度驱动的溶解度变化可解释全水柱约21%的氧含量下降；在表层100米以浅海域，溶解度变化可完全解释氧含量的降低；在100~600米深度区间，该因素仅能解释29%的氧含量下降，600~1000米区间为19%，而在深海海域仅为11%。