Interannual to Decadal Variations of Submesoscale Motions around the North Pacific Subtropical Countercurrent

The outputs from a submesoscale permitting hindcast simulation from 1990 to 2016 are used to investigate the interannual to decadal variations of submesoscale motions. The region we focus on is the subtropical Northwestern Pacific including the subtropical countercurrent. The submesoscale kinetic energy (KE) is characterized by strong interannual and decadal variability, displaying larger magnitudes in 1996, 2003, and 2015, and smaller magnitudes in 1999, 2009, 2010, and 2016. These variations are partially explained by those of the available potential energy (APE) release at submesoscale driven by mixed layer instability in winter. Indeed, this APE release depends on the mixed layer depth and horizontal buoyancy gradient, both of them modulated with the Pacific Decadal Oscillation (PDO). As a result of the inverse KE cascade, the submesoscale KE variability possibly leads to interannual to decadal variations of the mesoscale KE (eddy KE (EKE)). These results show that submesoscale motions are a possible pathway to explain the impact associated with the PDO on the decadal EKE variability. The winter APE release estimated from the Argo float observations varies synchronously with that in the simulation on the interannual time scales, which suggests the observation capability to diagnose the submesoscale KE variability

Spreading of Antarctic Bottom Water examined using the CFC-11 distribution simulated by an eddy-resolving OGCM

We have investigated the spreading and pathway of Antarctic Bottom Water(AABW) using the simulated distribution of chlorofluorocarbons(CFCs) in a global eddy-resolving(1/10°) OGCM. Our goal is understanding of the processes and pathways determining the distribution of CFCs in the Southern Ocean, where much of this tracer is entrained by formation of deep and bottom water. The simu- lated high CFC-11 water reveals the newly formed AABW around the Antarctic Continent. The main source regions of AABW in the model are in the Weddell Sea(60°- 30°W ), offshore of Wilkes Land(120°- 160°E ) and in the Ross Sea(170°E -160°W ). In our model, spreading of simulated CFC-11 in the deep Southern Ocean from the newly formed AABW regions is more similar to the observed distribution than in coarse-resolution models. In the Weddell Sea, the high CFC-11 water spreads eastward with the Antarctic Circumpolar Current(ACC) and flows northward to the Argentine Basin. The high CFC-11 water from Wilkes Land joins with the high CFC-11 water from the Ross Sea. Some of the high CFC-11 water from Wilkes Land flows northward toward New Zealand. The high CFC-11 water from the Ross Sea flows eastward with the ACC along the Mid Ocean Ridge and northward to the Southeast Pacific Basin

Impact of oceanic-scale interactions on the seasonal modulation of ocean dynamics by the atmosphere

Ocean eddies (with a size of 100–300 km), ubiquitous in satellite observations, are known to represent about 80% of the total ocean kinetic energy. Recent studies have pointed out the unexpected role of smaller oceanic structures (with 1–50 km scales) in generating and sustaining these eddies. The interpretation proposed so far invokes the internal instability resulting from the large-scale interaction between upper and interior oceanic layers. Here we show, using a new high-resolution simulation of the realistic North Pacific Ocean, that ocean eddies are instead sustained by a different process that involves small-scale mixed-layer instabilities set up by large-scale atmospheric forcing in winter. This leads to a seasonal evolution of the eddy kinetic energy in a very large part of this ocean, with an amplitude varying by a factor almost equal to 2. Perspectives in terms of the impacts on climate dynamics and future satellite observational systems are briefly discussed

Variability of Kuroshio nitrate flux and transport in the western North Pacific: A model study

ACG06-04発表要旨 / 日本地球惑星科学連合2013年大会（2013年5月19日～5月24日, 幕張メッセ国際会議場） / 日本惑星科学連合の許諾に基づき本文ファイルを掲

Sixteen-year phytoplankton biomass trends in the northwestern Pacific Ocean observed by the SeaWiFS and MODIS ocean color sensors

Using multisensor/platform biophysical data collected from 1997 to 2013, we investigated trends of the concentrations of phytoplankton biomass (Chl) in the northwestern Pacific Ocean (NWPO) and the probable responsible factors. The trend of rising sea surface temperature (SST) was the main factor maintaining phytoplankton positive net growth and resulted in a trend of increasing Chl at high latitudes in all seasons. At latitudes of 36-46°N, east of 160°E, the trend of rising SST was accompanied by a trend of declining Chl, markedly in spring and fall, which could be ascribed to strengthened stratification. The trends of environmental variables in the Oyashio area have modified conditions in a way detrimental to phytoplankton growth, the result being a trend of declining Chl from spring to fall. Chl south of roughly 36°N exhibited different trends in different seasons because of the different trends of vertical stratification. Whereas the observed 16-year Chl trends were not primarily influenced by interannual climate variability, to some degree they were likely modified by decadal variability associated with a weakened Aleutian Low pressure. This work prompts further comprehensive studies to investigate the probable ecological consequences of the observed Chl trend for high-trophic-level marine organisms in the NWPO

Body Mass Index and Diabetes in Asia: A Cross-Sectional Pooled Analysis of 900,000 Individuals in the Asia Cohort Consortium

10.1371/journal.pone.0019930PLoS ONE66