Global ocean mixed layer depth and derived variables obtained from an energy-based methodology

A global monthly climatology of the mixed layer depth (MLD), obtained with a physically derived and energy-based methodology (EBM), is provided. This climatology defines the mixed layer as the energetically homogeneous upper ocean layer in which water parcels can move with little or no buoyancy work; the mixed layer is representative of seasonal timescales, without addressing the diurnal mixing cycle or the timescales in which mixing is currently active. This approach provides a robust criterion in determining the MLD, which is reliable across diverse ocean conditions, globally and temporally consistent, and easy to implement.
The available dataset contains the monthly climatology of mixed layer depth and derived variables over the global ocean, with a spatial resolution of 2° x 2°. This climatology is based on approximately 2 million in situ Argo profiles from January 2005 to December 2023. The MLD and derived variables were computed for each profile within a grid cell for each month in the long-term record; the resulting values were then averaged to obtain a representative value for that grid cell and month. The file contains the following variables, in addition to latitude, longitude, and month:
- mld: Global monthly climatology of the mixed layer depth calculated with the energy-based methodology.
- wb: Global monthly climatology of the threshold in the work done by buoyancy characterizing the EBM-MLD.
- rho: Global monthly climatology of the absolute differences in potential density from the reference depth of 10 m to the EBM-MLD.
- temp: Global monthly climatology of the absolute differences in conservative temperature from the reference depth of 10 m to the EBM-MLD.

本文提供了利用基于物理推导的能量法（energy-based methodology, EBM）获得的全球月尺度混合层深度（mixed layer depth, MLD）气候态数据。该气候态将混合层定义为能量均匀的上层海洋区域，其中水团的移动几乎不需要或完全不需要浮力功；此混合层代表季节时间尺度，未考虑日混合周期或当前活跃混合的时间尺度。该方法为MLD的确定提供了稳健的判据，在不同海洋条件下均可靠、具有全球和时间一致性，且易于实现。

可用数据集包含全球海洋的月尺度混合层深度及衍生变量气候态，空间分辨率为2°×2°。该气候态基于2005年1月至2023年12月期间约200万条原位Argo剖面数据。在长期记录中，针对每个网格单元和每个月份，计算了该单元内各剖面的MLD及衍生变量；随后对结果值取平均，得到该网格单元和月份的代表性值。数据集包含以下变量（除纬度、经度和月份外）：
- mld：采用能量法计算的全球月尺度混合层深度气候态。
- wb：表征EBM-MLD的浮力功阈值全球月尺度气候态。
- rho：从10米参考深度到EBM-MLD的位势密度绝对差值全球月尺度气候态。
- temp：从10米参考深度到EBM-MLD的保守温度（conservative temperature）绝对差值全球月尺度气候态。