[A-CG44] Future global ocean observation system: complementarity of autonomous and shipboard observations

[ACG44-P04] Changes in oceanographic vertical structure in Mixed Water Region from unsupervised clustering results

*Fumika Sambe¹, Toshio Suga^1,2 (1.Graduate School of Science, Tohoku University, 2.JAMSTEC)

Keywords:Mixed Water Region, Argo float, Unsupervised Clustering, Oceanographic Vertical Structure, Data-driven Science

In the mid-latitude northwest Pacific Ocean, the transport, stirring and mixing of subtropical and subarctic water occur, resulting in multiple ocean domains characterized by various unique oceanographic vertical structures. Among them, the area east of Japan up to about 155°E is called Mixed Water Region (MWR), where subtropical and subarctic waters are intensely mixed and take on a complex distribution of vertical structures. Vertical structures have so far been investigated mainly based on shipboard observation data. With the expansion of the Argo observation network and the full spatiotemporal availability of a large amount of vertical structure data, we have been working on classifying Argo profiles using unsupervised clustering. As a result, we were able to classify the temperature and salinity vertical profiles of the mid-latitude Northwest Pacific into five classes in a manner consistent with existing knowledge. Of these five classes, Classes 2 and 3 were distributed overlapping in MWR. Compared to Class 3, Class 2 shows more subtropical and subarctic characteristics in the upper and the lower layer, respectively, and a deeper salinity minimum. Since this study is expected to lead to a detailed understanding of the vertical structure formation process in MWR, we investigated the temporal changes of the distribution and vertical structure of Classes 2 and 3 in this study.
In the range 35°N-45°N, 140°E-170°E, the distribution of Class 2 increased from fall to winter and that of Class 3 increased from spring to summer. In contrast to this variation, the seasonal change in the latitude of the southern limit and the mean latitude of the Oyashio showed a weak positive correlation with a two-month leading time. Other interannual changes were observed in the zonal location of Classes 2 and 3 distributions and trends in vertical profiles within each class (high and low of temperature and salinity). This talk will discuss the details of these variations and the physical processes in the MWR that emerge from them.