The drag coefficient is very important parameter that is used to calculate the air-sea momentum flux. Although the many estimation models of the drag coefficient have been proposed and discussed (conditions with extreme wind, wind wave, swell, etc.), the agreement has not reached yet. Comparison and evaluation of the model’s characteristics have been performed. However, assessment related climate change has not been done. For a global phenomenon associated with climate change due to change in wind speed, we focused on the El Nino and La Nina phenomenon. In this study, using the sea surface wind data, we investigated the influence of the air-sea momentum flux estimation for the year when the phenomenon occurred and did not occur. CCMP (Cross-Calibrated Multi-Platform) of NASA was used the sea surface wind data. The period is from January to December of El Nino phenomenon, La Nina phenomenon, and normal period. Studies of Charnock (1955) and Takagaki et al. (2012) (consider the extreme wind speed range) were used for the drag coefficient model. The annual mean global air-sea momentum flux showed that the maximum and minimum air-sea momentum flux value corresponded the normal period and the El Nino phenomenon, respectively. And the difference was as small as 7.4% and 7.0% in both models. In every month, it showed the maximum and minimum is the normal period and the El Nino phenomenon in both models, and the difference was as big as approximately 13.9% and 13.8%. We also investigated the difference of the air-sea momentum flux for each phenomena in 10 degree latitude bands and the proposed seven sea areas. As a results, the difference between the maximum and the minimum value corresponded to the La Nina and El Nino phenomenon showed approximately 18% from the north latitude 50° to the north latitude 60° in the high wind speed region. The wind speed in the North Atlntic showed that sea wind speed is a very large value for the El Nino and La Nina phenomenon. Therefore, in this region, the value of air-sea momentum flux corresponding to the El Nino and La Nina phenomenon was larger than that corresponding to the other phenomena.
Lake Takahoko, the brackish lake located in Aomori Prefecture, Japan, is connected to the Pacific Ocean in the east through a channel, which has narrow mouths at both ends. The lake is partitioned almost at the center into west and east sides by a levee with water gates, and one of which is usually opened. In order to clarify the inflow and outflow rate of water and salinity, and seawater exchange rate in the lake, the salinity, water current and water level were observed at stations set up at sea side (St. B) and lake side mouth (St. C) of channel and the water gates of levee (St. G) from August to November 2014. Mean inflow rate of water at Sts. B, C, and G were estimated at 6.4 × 105, 1.8 × 105 and 8.7 × 104 m3 d–1, respectively. The inflow rate of water at Sts. B and C periodically varied with large amplitude during spring tide and small amplitude during neap tide, while that at St. G did not show such periodicity. Means of daily seawater exchange rate at Sts. C and G were estimated at 0.40 (variation value 0.04–0.61) and 0.33 (variation value 0.12–0.53).
The purpose of this study is to analyze the relationship between high turbidity and sulfur, and transfer of a blue tide after upwelling. We achieved ship observations of a blue tide at 24th August 2015 on the inner part of Tokyo Bay. There was a definite positive correlation between turbidity and sulfur from analysis of water samples. Therefore, high turbidity indicates the particulate sulfur element in a blue tide. Upwelling water of the blue tide outflowed to the middle layer for analyzing a composition of the blue tide water. It was considered that a density of upwelling water decreased slightly due to mix with around surface water. The blue tide water drifted on a pycnocline for wind driven current and density current.
The effect of iron and iron hydroxide on sedimentary hydrogen-sulfide release was studied with laboratory incubation method using intact sediment cores sampled from Mikawa Bay, Japan. As a preliminary investigation, the experimental setup was reassessed to clarify the effect of agitation of the overlying water on the material balances at the sediment-water interface. Laboratory incubation experiment using intact sediment cores was conducted varying the agitation intensity to monitor sedimentary oxygen demand. The results showed that sedimentary oxygen demand was positively affected by flow velocity. As such physical control is common mechanism for dissolved materials, we briefly summarize that the hydrodynamic control is indispensable to sediment-core-incubation procedure. Based on the preliminary investigation, the same experimental procedure was employed to investigate the effect of iron and iron hydroxide on sedimentary hydrogen-sulfide release. In the procedure, intact sediment cores were incubated under anoxic condition for 5 days with addition of iron and iron hydroxide powder on the sediment surface and hydrogen sulfide concentration in the overlying water was monitored. The results showed that sedimentary hydrogen-sulfide-release was clearly suppressed by addition of 1.55 mg/cm2-iron powder and of 1.38 mg/cm2-iron hydroxide powder, respectively. The experimental results were also compared with an existing numerical diagenetic-model and discussed.
We examined the tolerance of greasyback shrimp Metapenaeus ensis to hypoxia and H2S exposure under controlled laboratory conditions. Larvae and juveniles were exposed to normoxic or to hypoxic water (dissolved oxygen concentration <0.5 mg/L) with or without un-ionized H2S (concentrations, 0.09 to 0.62 mg/L). One-hour exposure experiments revealed ontogenetic changes in the shrimp’s tolerance to hypoxia and H2S exposure: tolerance to hypoxia was high in larvae at nauplius (survival rate, 100%) and protozoea stages (79%), but was attenuated significantly in larvae at mysis and postlarval stages as well as in juvenile stage (0% for these stages). Presence of H2S of the concentration >0.1 mg/L enhanced decrease in the survivability after the one-hour exposure even in the hypoxic-tolerant nauplius and protozoea stages. Larvae and juveniles ceased swimming behavior and sank to the bottom soon after the initiation of exposure to hypoxic water with H2S, followed by death within 24 hours. These results suggest that mass mortality of larvae and juveniles of greasyback shrimp could occur by exposure to hypoxia and H2S in the field.