scholarly journals Horizontal distribution of Fukushima-derived radiocesium in zooplankton in the northwestern Pacific Ocean

2013 ◽  
Vol 10 (8) ◽  
pp. 5729-5738 ◽  
Author(s):  
M. Kitamura ◽  
Y. Kumamoto ◽  
H. Kawakami ◽  
E. C. Cruz ◽  
K. Fujikura
Keyword(s):  
Pacific Ocean ◽  
High Activity ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Fission Products ◽  
Tohoku Earthquake ◽  
Horizontal Distribution ◽  
Northwestern Pacific ◽  
Mode Water ◽  
Activity Concentrations

Abstract. The magnitude of the 9.0 Tohoku earthquake and the ensuing tsunami on 11 March 2011, inflicted heavy damage on the Fukushima Dai-ichi nuclear power plant (FNPP1). Fission products were emitted, falling over a broad range in the Northern Hemisphere, and water contaminated with radionuclides leaked into the ocean. In this study, we described the horizontal distribution of the Fukushima-derived radiocesium in zooplankton and in seawater in the western North Pacific Ocean (500–2100 km from the FNPP1) 10 months after the accident. 134Cs and 137Cs were detected in zooplankton and seawater from all the stations. Because of its short half-life, the 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was the same order of magnitude as it was one month after the accident, and average activity was one or two orders of magnitude higher than 137Cs activities observed before the accident around Japan. Horizontally, the radiocesium activity concentrations in zooplankton were high at around 25° N while those in surface seawater were high at around the transition area between the Kuroshio and the Oyashio currents (36–40° N). We observed subsurface radiocesium maxima in density range of the North Pacific Subtropical Mode Water and the occurrence of many diel vertical migratory zooplankton. These suggested that the high activity concentrations in the subtropical zooplankton at around 25° N were connected to the subsurface radiocesium and active vertical migration of zooplankton. However, the high activity concentrations of radiocesium in subsurface seawater did not necessarily correlate with the higher radiocesium activity in zooplankton. Activity concentrations of radiocesium in zooplankton might be influenced not only by the environmental radiocesium activity concentrations but also by other factors, which are still unknown.

scholarly journals Horizontal distribution of Fukushima-derived radiocesium in zooplankton in the northwestern Pacific Ocean

2013 ◽  
Vol 10 (4) ◽  
pp. 6143-6170 ◽  
Author(s):  
M. Kitamura ◽  
Y. Kumamoto ◽  
H. Kawakami ◽  
E. C. Cruz ◽  
K. Fujikura
Keyword(s):  
Pacific Ocean ◽  
High Activity ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Fission Products ◽  
Zooplankton Community ◽  
Horizontal Distribution ◽  
Northwestern Pacific ◽  
Mode Water ◽  
Activity Concentrations

Abstract. The magnitude of the 9.0 Tohoku earthquake and the ensuing tsunami on 11 March 2011, inflicted heavy damage on the Fukushima Dai-ichi nuclear power plant (FNPP1). Fission products were emitted, falling over a broad range in the northern hemisphere, and water contaminated with radionuclides leaked into the ocean. In this study, we described the horizontal distribution of the Fukushima-derived radiocesium in zooplankton and in seawater in the western North Pacific Ocean (500–2100 km from the FNPP1) 10 months after the accident. 134Cs and 137Cs were detected in zooplankton and seawater from all the stations. Because of its short half-lives, 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was same order of magnitude as that one month after the accident, and average activity was one or two orders of magnitude higher than 137Cs activities observed before the accident around Japan. Horizontally, the radiocesium activity concentrations in zooplankton were high at around 25° N while those in surface seawater were high at around the transition area between the Kuroshio and the Oyashio Currents (36–40° N). We observed subsurface radiocesium maxima in density range of the North Pacific Subtropical Mode Water and occurrence of many diel vertical migratory zooplanktons. These suggested that the high activity concentrations in the subtropical zooplankton at around 25° N were connected to the subsurface radiocesium and active vertical migration of zooplankton. However, the high activity concentrations of radiocesium in subsurface seawater did not necessarily follow the higher radiocesium activity in zooplankton. Biological characteristics of zooplankton community possibly influenced how large was contamination of radiocesium in the community but it is still unknown what kind of biological factors were important.

North Pacific Subtropical Mode Water Controlled by the Atlantic Multi-Decadal Variability

2020 ◽  
Author(s):  
Baolan wu ◽  
Xiaopei lin ◽  
Lisan yu
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Decadal Variability ◽  
Heat Content ◽  
Northwestern Pacific ◽  
Mode Water ◽  
Subtropical Mode Water ◽  
The North ◽  
Mean Temperature ◽  
The Pacific

<p><strong>The North Pacific Subtropical Mode Water (mode water hereafter) is a vertically homogeneous thermocline water mass, occupying the entire subtropical Western Pacific Ocean. By transporting mass, heat and nutrients from the surface into the subsurface ocean, it provides memory of climate variability and is a potential source of predictability. Previous studies attributed decadal variability of the mode water mean temperature to the Pacific Decadal Oscillation (PDO). Using available observations and reanalysis data, here we show that decadal to multi-decadal variability of the mode water mean temperature is controlled by the Atlantic Multi-Decadal Variability (AMV) instead. During an AMV positive phase, warm sea surface temperatures (SSTs) in the north Atlantic Ocean weaken the subtropical North</strong> <strong>Pacific westerlies, and the anomalous easterlies in the subtropical west Pacific drive an anomalous northward Ekman transport of warm water into the mode water formation area. </strong><strong>This increases the mode water temperature through subduction</strong><strong>, driving variability of the upper-layer ocean heat content and fish catches in the Northwestern Pacific. This mechanism is supported by a long pre-industrial model simulation with multiple AMV cycles and by a Pacemaker model experiment, in which the AMV forcing alone is shown to drive the variability of the mode water. Our finding suggests that the AMV is an important driver for decadal climate and ecosystem variability and provides memory for prediction in the Pacific Ocean.</strong></p>

Potential use of helminth parasites in stock identification of flying squid, Ommastrephes bartrami, in North Pacific waters

1991 ◽  
Vol 69 (4) ◽  
pp. 1124-1126 ◽  
Author(s):  
S. M. Bower ◽  
L. Margolis
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Parasite Fauna ◽  
Northwestern Pacific ◽  
Stock Identification ◽  
Helminth Parasites ◽  
Northwestern Pacific Ocean ◽  
Pacific Waters ◽  
Potential Use

A survey of helminth parasites in 68 flying squid (Ommastrephes bartrami) from off the west coast of North America (between latitudes 41°03′ and 48°23′ N and longitudes 129°49′ and 133°08′ W) revealed the presence of numerous juvenile nematodes and cestodes. Larval Hysterothylacium sp. and metacestodes of Phyllobothrium sp. were common (prevalence: 100 and 94.1%, respectively; mean intensity: 54.6 ± 28.1 and 6.4 ± 4.5, respectively). In addition, nine flying squid had a total of 11 Anisakis simplex larvae, and one metacestode of Tentacularia sp. (probably T. coryphaenae) was found in the sample bag that held one flying squid. The only adult helminths recovered were seven specimens of Rhadinorhynchus sp. (Acanthocephala) from three squid. The parasite fauna of these squid was sufficiently different from that previously reported for O. bartrami from the northwestern Pacific Ocean to suggest that parasites may prove useful as a tool to determine if intermixing of squid stocks from their feeding grounds in the eastern and western North Pacific Ocean occurs on the spawning grounds.

scholarly journals Geostrophic Circulation in the Tropical North Pacific Ocean Based on Argo Profiles

2014 ◽  
Vol 44 (2) ◽  
pp. 558-575 ◽  
Author(s):  
Dongliang Yuan ◽  
Zhichun Zhang ◽  
Peter C. Chu ◽  
William K. Dewar
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
World Ocean ◽  
North Equatorial Current ◽  
Northwestern Pacific ◽  
Argo Data ◽  
Vector Method ◽  
Geostrophic Currents ◽  
The North

Abstract Absolute geostrophic currents in the North Pacific Ocean are calculated from the newly gridded Argo profiling float data using the P-vector method for the period of 2004–11. The zonal geostrophic currents based on the Argo profile data are found to be stronger than those based on the traditional World Ocean Atlas 2009 (WOA09) data. A westward mean geostrophic flow underneath the North Equatorial Countercurrent is identified using the Argo data, which is evidenced by sporadic direct current measurements and geostrophic calculations in history. This current originates east of the date line and transports more than 4 × 106 m3 s−1 of water westward in the subsurface northwestern tropical Pacific Ocean. The authors name this current the North Equatorial Subsurface Current. The transport in the geostrophic currents is compared with the Sverdrup theory and found to differ significantly in several locations. Analyses have shown that errors of wind stress estimation cannot account for all of the differences. The largest differences are found in the area immediately north and south of the bifurcation latitude of the North Equatorial Current west of the date line and in the recirculation area of the Kuroshio and its extension, where nonlinear activities are vigorous. It is, therefore, suggested that the linear dynamics of the Sverdrup theory is deficient in explaining the geostrophic transport of the tropical northwestern Pacific Ocean.

Final mass balance of Fukushima released radiocaesium in our environment

2021 ◽  
Author(s):  
Michio Aoyama ◽  
Yayoi Inomata ◽  
Daisuke Tsumune ◽  
Takaki Tsubono
Keyword(s):  
Pacific Ocean ◽  
Mass Balance ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Marine Biota ◽  
Mode Water ◽  
The North ◽  
Final Mass ◽  
Direct Discharge ◽  
The North Pacific

<p>One of the greatest results obtained by analyzing seawater samples from the North Pacific Ocean was the estimation of the total amount of 137Cs in the North Pacific to be 15-18 PBq (Aoyama et al., 2016). This estimation has been validated by two methods described by Tsubono et al. (2016) and Inomata et al. (2016). Coastal modeling results gave the amount of 137Cs direct discharge from the FDNPP to coastal waters to be (3.5 ± 0.7) PBq (Tsumune et al., 2012) which was the first and the most accurate result. Since the amount of direct discharge was accurately determined, the amount of 137Cs released into the atmosphere was also properly determined by the mass balance consideration as discussed in Aoyama et al. (2016a). </p><p>For the calculation of the final mass balance, we did not include several results as they did not cover the whole region, or they included the amount of atmospheric fallout as part of the direct discharge. The total amount of radiocesium released to the atmosphere was estimated to be from 8.1 PBq (Yumimoto et al., 2016) to 36 PBq (Stohl et al., 2O12). Based on mass balance consideration we conclude that (15.2-20.4) PBq of the FDNPP-derived 137Cs might be a reasonable value for the total atmospheric release (supported by Aoyama et al., 2016a; Katata et al., 2015; Mathieu et al., 2012; Saunier et al., 2013; Winiarek et al., 2014). The estimated land deposition is (3.4–6.2) PBq (Aoyama et al., 2016). The estimated 137Cs inventories in the North Pacific are in the range (15.2–18.3) PBq, as obtained by Tsubono et al. (2016) and  Inomata et al. (2016), while only (3–6) PBq was the contribution from the direct discharge (consensus value, Aoyama et al., 2016), although our previous estimate was more precise, (3.5 ± 0.7) PBq. For atmospheric deposition to the North Pacific, the estimated values are in the range (11.7–14.8) PBq (Aoyama et al., 2016; Inomata et al., 2016; Tsubono et al., 2016).</p><p>The radiocesium inventories in the interior domains of the North Pacific Ocean have been estimated. The radiocesium inventory in the STMW (Subtropical Mode Water) is (4.2 ± 1.1) PBq (Kaeriyama et al., 2016), and (7.9 ± 1.4) PBq in the surface layer (Inomata et al., 2018b). In the CMW (Central Mode Water), the radiocesium inventory is (2.5 ± 0.9) PBq (Inomata et al., 2018b). The radiocesium sediment inventory is (0.20 ± 0.06) PBq (Otosaka, 2017). The inventory in marine biota might be less than 200 GBq (Aoyama et al., 2019).</p>

scholarly journals Rapid recirculation of FNPP1 derived radiocaesium suggesting new pathway of subtropical mode water in the western North Pacific to the Sea of Japan

2017 ◽  
Author(s):  
Yayoi Inomata ◽  
Michio Aoyama ◽  
Yasunori Hamajima ◽  
Masatoshi Yamada
Keyword(s):  
Pacific Ocean ◽  
Sea Of Japan ◽  
North Pacific ◽  
Western North Pacific ◽  
North Pacific Ocean ◽  
137Cs Activity ◽  
The Sea Of Japan ◽  
Mode Water ◽  
Western North Pacific Ocean ◽  
Subtropical Mode Water

Abstract. The rapid recirculation of 137Cs derived from the Fukushima Nuclear Power Plant Accident (FNPP1-137Cs) occurred in the Sea of Japan (SOJ) in several year timescale after released to the environment in March 2011. The recirculation of FNPP1-137Cs had started in 2012 and reached to the maximum in 2015/2016 in the East China Sea (ECS) and the western North Pacific Ocean. The recirculation of FNPP1-137Cs has been still continued in the coastal site of Sea of Japan in the year of 2016. The re-circulated FNPP1-137Cs activity concentrations showed subsurface peak in the seawater of which density correspond to the Subtropical Mode Water (STMW). These suggests that FNPP1-137Cs injected into the western North Pacific Ocean at south of Kuroshio were subducted into ocean interior just after the accident, then transported southward/southwestward. A part of FNPP1-137Cs in STMW entered into the ECS between Kyushu Island and Okinawa Islands. Then it obducted in the region west of Kyushu Island, north of the ECS, following then entered into the SOJ associated with northward transport with Tsushima Warm Current in several year time scale. This rapid pathway might be new finding of transport process from the western North Pacific Ocean to the SOJ. Almost same value of the 134Cs / 137Cs activity ratio in the coastal region of the Japanese islands (ECS, SOJ, and Ogasawara) also support this re-circulation route. The integrated amount of FNPP1137Cs entered in the SOJ until 2016 was estimated to be 0.21&thins;± 0.03 PBq, which corresponds to 5.1 (3.4–8.0) % of the total amount of FNPP1-137Cs in the STMW. The integrated amount of FNPP1-137Cs back to the North Pacific Ocean through the Tsugaru Straight in the surface layer was 0.1 ± 0.02 Bq, which corresponds to 0.6 (0.4–1.0) % of the total amount of FNPP1-137Cs in the STMW.

scholarly journals Transport of FNPP1-derived radiocaesium from subtropical mode water in the western North Pacific Ocean to the Sea of Japan

Ocean Science ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 813-826 ◽  
Author(s):  
Yayoi Inomata ◽  
Michio Aoyama ◽  
Yasunori Hamajima ◽  
Masatoshi Yamada
Keyword(s):  
Pacific Ocean ◽  
North Pacific ◽  
Activity Concentration ◽  
North Pacific Ocean ◽  
137Cs Activity ◽  
Fukushima Accident ◽  
The North ◽  
Activity Concentrations ◽  
Activity Ratios ◽  
The North Pacific

Abstract. This study investigated the spatio-temporal variations in activity concentrations in the Sea of Japan (SOJ) of 137Cs and these transport process from the North Pacific Ocean to the SOJ through the East China Sea (ECS) during 2012–2016. The 137Cs activity concentrations in the SOJ have been increasing since 2012–2013 and reached a maximum in 2015–2016 of approximately 3.4 Bq m−3, more than twice the pre-Fukushima accident 137Cs activity concentration of ∼1.5 Bq m−3. The 134Cs ∕ 137Cs activity ratios ranged from 0.36 to 0.51 in 2016. After taking into account radioactive decay and ocean mixing, we concluded that these 134Cs ∕ 137Cs activity ratios were evidence that the Fukushima accident caused the increase in the 137Cs activity concentrations. In the North Pacific south of Japan (NPSJ), the highest 137Cs activities in 2012–2013 were observed in water from a depth of 300 m, the potential water density anomaly (σθ) of which corresponded to subtropical mode water (STMW). In the ECS, a clear increase in the 137Cs activity concentration started at a depth of 140 m (σθ= 25.2 kg m−3) in April 2013, propagated to the surface layers at depths of roughly 0–50 m, reached a maximum in 2015 and decreased in subsequent years. In the ECS, the Fukushima-derived radiocaesium activity concentration in surface water reached a maximum in 2014–2015, whereas the concentration in the SOJ reached a maximum in 2015–2016. The propagation of Fukushima-derived radiocaesium in surface seawater from the ECS into the SOJ therefore required approximately 1 year. These temporal changes in 137Cs activity concentrations and 134Cs ∕ 137Cs activity ratios indicated that part of the 137Cs and 134Cs derived from the Fukushima accident (FNPP1-derived 137Cs and134Cs) was transported within several years to the ECS and then to the SOJ via STMW from the NPSJ. The integrated amount of FNPP1-derived 137Cs that entered the SOJ before 2016 was estimated to be 0.21±0.01 PBq, 5.0 % of the estimated total amount of FNPP1-derived 137Cs in the STMW. The integrated amount of FNPP1-derived 137Cs that returned to the North Pacific Ocean through the Tsugaru Strait was estimated to be 0.09±0.01 Bq, 43 % of the total amount of FNPP1-derived 137Cs transported to the SOJ and 2.1 % of the estimated total amount of FNPP1-derived 137Cs in the STMW.

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