《Unsupervised clustering of Southern Ocean Argo float temperature profiles》

  • 来源专题:物理海洋学知识资源中心
  • 编译者: cancan
  • 发布时间:2019-01-08
  • 摘要:The Southern Ocean has complex spatial variability, characterized by sharp fronts, steeply tilted isopycnals, and deep seasonal mixed layers. Methods of defining Southern Ocean spatial structures traditionally rely on somewhat ad‐hoc combinations of physical, chemical, and dynamic properties. As a step towards an alternative approach for describing spatial variability in temperature, here we apply an unsupervised classification technique (that is, Gaussian mixture modelling or GMM) to Southern Ocean Argo float temperature profiles. GMM, without using any latitude or longitude information, automatically identifies several spatially coherent circumpolar classes influenced by the Antarctic Circumpolar Current. In addition, GMM identifies classes that bear the imprint of mode/intermediate water formation and export, large‐scale gyre circulation, and the Agulhas Current, among others. Because GMM is robust, standardized, and automated, it can potentially be used to identify structures (such as fronts) in both observational and model datasets, possibly making it a useful complement to existing classification techniques.

    全文链接:https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JC014629?af=R

  • 原文来源:https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018JC014629?af=R
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  • 《The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program》

    • 来源专题:物理海洋学知识资源中心
    • 编译者:cancan
    • 发布时间:2018-11-14
    • Roemmich D, Gilson J. The 2004–2008 mean and annual cycle of temperature, salinity, and steric height in the global ocean from the Argo Program. 来源: Progress in Oceanography, 2009, 82(2):81-100. 摘要: The Argo Program has achieved 5 years of global coverage, growing from a very sparse global array of 1000 profiling floats in early 2004 to more than 3000 instruments from late 2007 to the present. Using nearly 350,000 temperature and salinity profiles, we constructed an upper-ocean climatology and monthly anomaly fields for the 5-year era, 2004–2008. A basic description of the modern upper ocean based entirely on Argo data is presented here, to provide a baseline for comparison with past datasets and with ongoing Argo data, to test the adequacy of Argo sampling of large-scale variability, and to examine the consistency of the Argo dataset with related ocean observations from other programs. The Argo 5-year mean is compared to the World Ocean Atlas, highlighting the middle and high latitudes of the southern hemisphere as a region of strong multi-decadal warming and freshening. Moreover the region is one where Argo data have contributed an enormous increment to historical sampling, and where more Argo floats are needed for documenting large-scale variability. Globally, the Argo-era ocean is warmer than the historical climatology at nearly all depths, by an increasing amount toward the sea surface; it is saltier in the surface layer and fresher at intermediate levels. Annual cycles in temperature and salinity are compared, again to WOA01, and to the National Oceanography Center air–sea flux climatology, the Reynolds SST product, and AVISO satellite altimetric height. These products are consistent with Argo data on hemispheric and global scales, but show regional differences that may either point to systematic errors in the datasets or their syntheses, to physical processes, or to temporal variability. The present work is viewed as an initial step toward integrating Argo and other climate-relevant global ocean datasets. 全文网址:https://www.sciencedirect.com/science/article/pii/S0079661109000160
  • 《Argo observations of the Deep Mixing Band in the Southern Ocean: A salinity modeling challenge》

    • 来源专题:物理海洋学知识资源中心
    • 编译者:cancan
    • 发布时间:2018-11-28
    • 摘要:The Southern Ocean plays an important role in mediating oceanic uptake of CO2 and heat due to a strong meridional overturning circulation. Gridded Argo float data for 2004–2017 were used to evaluate subsurface processes at the mixed layer depth (MLD) that occur in a narrow deep mixing band. Shifts in the value of the Turner Angle at the MLD indicate that early in the season the MLD deepens slowly as it encounters and is stabilized by a subsurface salt maximum. By September mixing has penetrated this salinity feature and the rate of deepening is faster once the MLD is deeper than the depth where the maximum salinity occurs (~150–200 m). This distinctive salinity layer is the result of surface Ekman transport of fresh water from the south and subsurface advection of high-salinity water from the north. Two configurations of the Community Earth System Model (CESM) ocean-ice forced hindcast experiments—one with 1° and the other with 0.1° horizontal resolution (Parallel Ocean Program low and high resolutions [POP-LR and POP-HR], respectively)—are compared with the Argo data for 2005–2009. POP-LR has a shallow MLD bias common to many Fifth Coupled Models Intercomparison Project (CMIP5) models, while POP-HR has a mix of deep and shallow MLD biases. While both models were able to replicate the large-scale processes leading to formation of a high-salinity layer, the salinity feature in POP-HR is too strong and deep. Neither model was able to replicate the vertical mixing processes leading to penetration of the subsurface salt maximum 全文链接:https://agupubs.pericles-prod.literatumonline.com/doi/pdf/10.1029/2018JC014275