New results on joint classification of vertical structure of ocean properties at a global scale

Ocean temperature, salinity, and electric conductivity are essential ocean properties. Their structure and changes directly impact physical, chemical and biological processes in oceans. Since the 1970s, numerous researches have focused on the morphological analysis of vertical profiles in oceanography. However, due to the complexity of an ocean environment, most of them are conducted at local scales or only focus on single elements, e.g., ocean temperature or salinity. This work aims to achieve the joint classification of the vertical structure of ocean properties at a global scale and present two-dimension regional characteristics. Based on 150 seawater profiles from the National Oceanographic Data Center, this work explores such characteristics of ocean temperature, salinity and electric conductivity in the deep sea and achieves global-scale joint classification. We demonstrate that their vertical features have clear regional characteristics and can be classified into four types, i.e., bidirectional gradient, homo-dromous contravariant, homo-dromous gradient, and homodromous gradient (salinity) ones. In addition, our results prove that there exist the power-law distributions of these three factors in intermediate water, which may be explained through the self-organization theory. Moreover, the 'up-tail' phenomenon is widely discovered in the vertical structure of electric conductivity, and it may be considered as a combined effect caused by temperature, pressure, and salinity.