17:15 〜 18:30
[ACG29-P06] Mechanism of the warming of the North Pacific subtropical mode water from 1901 to 2010 in a regional ocean model
The present study examines mechanism of warming of the subtropical mode water in the North Pacific from 1901 to 2010 using a regional ocean model. The warming trend of the subtropical mode water in the model was about +1.2ºC/100yr, consistent with the previous observational study. In addition, this trend and interannual to decadal variability of the mode water temperature well corresponded to those of the sea surface temperature in the formation region, south of the Kuroshio Extension region. On the other hand, the thickness of the subtropical mode water did not show a significant trend. Consistently, the mixed layer depth in the formation region in winter also did not have a significant trend. It is revealed from two sensitivity experiments of the model that the warming of the subtropical mode water was mainly caused by the warming of atmospheric temperature. However, this warming of atmospheric temperature induced the shallowing of the mixed layer depth in winter in the formation region. Interestingly, this shallowing of the mixed layer depth by the atmospheric warming was canceled out by wind stress forcing, which induced the deepening trend of the mixed layer depth.