Ryo Fujita

Ship-based observations of atmospheric potential oxygen and regional air-sea O 2 flux in the northern North Pacific and the Arctic Ocean

Simultaneous observations of atmospheric potential oxygen (APO=O2+1.1×CO2) and air–sea O2 flux, derived from dissolved oxygen in surface seawater, were carried out onboard the research vessel MIRAI in the northern North Pacific and the Arctic Ocean in the autumns of 2012–2014. A simulation of the APO was also carried out using a three-dimensional atmospheric transport model that incorporated a monthly air–sea O2 flux climatology. By comparing the observed and simulated APO, as well as the observed and climatological air–sea O2 fluxes, it was found that the large day-to-day variation in the observed APO can be attributed to the day-to-day variation in the local air–sea O2 fluxes around the observation sites. It was also found that the average value of the observed air–sea O2 fluxes was systematically higher than that of the climatological O2 flux. This could explain the discrepancy between the observed and simulated seasonal APO cycles widely seen at various northern hemispheric observational sites in the fall season.

Long-term variations of the mole fraction and carbon isotope ratio of atmospheric methane observed at Ny-Ålesund, Svalbard from 1996 to 2013

Abstract We have conducted systematic observations of the CH4 mole fraction and its carbon isotope ratio (δ13C) at Ny-Ålesund, Svalbard (78°55′N, 11°56′E) using air samples collected weekly since 1991 and 1996, respectively. The CH4 mole fraction showed long-term increase until 1999, stagnation between 2000 and 2006, followed by an increase after 2006. On the other hand, δ13C showed monotonous increase until 2006 and decrease after 2006. By comparing the rates of change in the CH4 mole fraction and δ13C under the assumption that the atmospheric CH4 lifetime is constant, it is suggested that the temporal pause of the CH4 mole fraction observed at Ny-Ålesund is attributed to reductions of CH4 release from the microbial and fossil fuel sectors. On the other hand, the increase in CH4 after 2006 could be ascribed to an increase in microbial CH4 release. The CH4 and δ13C data presented in this paper would be useful for clarifying their temporal variations in the Arctic atmosphere, as well as providing additional constraints on the global CH4 budget.

Transit Characteristics of a Deformed Neutrophil Through a Moderate Constriction

This paper deals with the transit of a neutrophil through narrow capillary segments. In the segments are modeled by arc-shaped constrictions arranged in a straight pipeline. Initially the spherical cell deforms in transit through the first constriction. We focus on the transit time to the deformed cell through the second constriction. We investigate the effects of segment geometry on the transit time. Finally, it is shown that the transit time is independent of the shape of the first segment so long as it is organized by the entrance cell radius.Copyright