Mid-depth freshening in the North Pacific subtropical gyre observed along the JMA repeat and WOCE hydrographic sections
Article first published online: 4 DEC 2007
Copyright 2007 by the American Geophysical Union.
Geophysical Research Letters
Volume 34, Issue 23, December 2007
How to Cite
2007), Mid-depth freshening in the North Pacific subtropical gyre observed along the JMA repeat and WOCE hydrographic sections, Geophys. Res. Lett., 34, L23608, doi:10.1029/2007GL031433., , , , , , and (
- Issue published online: 4 DEC 2007
- Article first published online: 4 DEC 2007
- Manuscript Accepted: 15 OCT 2007
- Manuscript Revised: 31 AUG 2007
- Manuscript Received: 24 JUL 2007
- mid-depth freshening;
- global warming
 We report a freshening at mid-depth in the North Pacific subtropical gyre by using long-term repeat hydrographic data along the 137°E section and one-time hydrographic data along the World Ocean Circulation Experiment Hydrographic Program (WHP) P2 and P3 sections. North of 15°N along the 137°E section, we estimated a linear freshening trend of 0.0015/yr between the main thermocline and the salinity minimum layer of the North Pacific Intermediate Water, mainly caused by isopycnal surface deepening due to warming, and by westward shifts of the salinity-minimum tongue due to strengthening of the subtropical gyre. Furthermore, along the WHP-P2 section, the linear freshening trend could be classified into several groups according to longitude. Such spatial differences in the freshening trend seem to reflect differences in the formation processes and mid-depth pathways of the salinity minimum waters.