The Tsushima Warm Current (TWC) along the west of Hokkaido gradually dissipates from winter through spring because of vertical mixing of the surface layers. In summer and autumn, it extends northward accompanied by a local clockwise meandering off Ishikari Bay. In order to understand such seasonal changes of TWC flow pattern, XCTD and XBT surveys were carried out in May or June from 2005 to 2008. Cold (< 6°C) water mass was found below the seasonal thermocline around Musashi Rise, which we call "Musashi Rise Mode Water (MRMW)" in this study. Because of stronger winter cooling during 2006 and 2008, the thickness of MRMW was larger in those years than in 2005 and 2007. In May and June, when the path of TWC changes, the MRMW seems to play a role in causing the bifurcation of the northward flow of TWC. The onshore branch of TWC forms a small warm eddy off Ishikari Bay, and then flows along the shelf edge west of Hokkaido. The offshore branch flows clockwise along the offshore edge of MRMW.

Argo, the global observing network of numerous profiling floats, provides a lot of hydrographic data which have enabled to quantify the ocean warming and the sea level rise more precisely than ever. Some previous studies suggested that (a part of) Argo data might contain pressure biases. Japan Agency for Marine-Earth Science and Technology has tackled the issue since 2003 incorporation with Japan Meteorological Agency. Investigations by the International Argo have clarified that the pressure biases are caused by many factors; degradation of pressure sensors, defects of a type of float and inconsistencies between float/sensor hardware and data processing procedures in floats. Especially, artificial inconsistencies in data processing at Argo data centers are more serious than expected. Here, we explain the details of the previously-identified pressure biases and the present status of their correction in Argo (as of March 2009). We also discuss potential pressure biases in pre-Argo float data. In order to meet requirements by recent studies on the changes of oceanic heat content and steric height due to the global warming, elimination of systematic pressure biases is the most important and a random error of ±5 dbar should be a future target that Argo should attain in pressure measurement, which enables us to estimate the upper ocean heat content and the sea level with the accuracy of ±0.5 x 10²² J and ±3 mm, respectively. The inconsistency between sea level trend derived by satellites and that by hydrographic measurements since 2003 is likely to be reduced by corrections of the pressure biases in Argo dataset.

The relation between the human interaction and the biodiversity in the coastal sea (Sato-umi) is discussed based on some examples. We can understand that the human interaction to make many kinds of habitats may raise the biodiversity in the coastal sea. On the other hand, the human interaction to stop the trend to the extreme condition of flora may raise the biodiversity in the forest (Sato-yama).