scholarly journals Direct observation of <sup>134</sup>Cs and <sup>137</sup>Cs in surface seawater in the western and central North Pacific after the Fukushima Dai-ichi nuclear power plant accident

2013 ◽  
Vol 10 (6) ◽  
pp. 4287-4295 ◽  
Author(s):  
H. Kaeriyama ◽  
D. Ambe ◽  
Y. Shimizu ◽  
K. Fujimoto ◽  
T. Ono ◽  
...  
Keyword(s):  
Power Plant ◽  
Particle Tracking ◽  
North Pacific ◽  
Nuclear Power ◽  
Kuroshio Extension ◽  
Horizontal Distribution ◽  
Surface Seawater ◽  
The North ◽  
The North Pacific ◽  
Central North Pacific

Abstract. The horizontal distribution of radioactive cesium (Cs) derived from the Fukushima Dai-ichi nuclear power plant (FNPP) in the North Pacific is still unclear due to the limitation of direct measurement of the seawater in the open ocean. We present the result of direct observation of radioactive Cs in surface seawater collected from a broad area in the western and central North Pacific in July 2011, October 2011 and July 2012. We also conducted a simple particle tracking experiment to estimate the qualitative spatial distribution of radioactive Cs in the North Pacific. 134Cs was detected at 94 stations out of 123 stations, and 137Cs was detected at all stations. High 134Cs and 137Cs concentrations more than 10 m Bq kg−1 were observed in the area of the northern part of Kuroshio Extension at 144° E and 155° E in July 2011, in the area 147–175° E around 40° N in October 2011, and the northern part of Kuroshio Extension at 155° E and 175°30´ E in July 2012. Combining the result of direct observations and particle tracking experiment, the radioactive Cs derived from the FNPP had been dispersed eastward to the central North Pacific during 2011. It was considered from the horizontal distribution that radioactive Cs was dispersed not only eastward but also north- and southward in the central North Pacific. Pronounced dilution process of radioactive Cs from the FNPP during study period is suggested from temporal change in the activity ratio of 134Cs / 137Cs, which was decay-corrected on 6 April 2011, and relationships between radioactive Cs and temperature.

scholarly journals Direct observation of <sup>134</sup>Cs and <sup>137</sup>Cs in surface seawater in the western and central North Pacific after the Fukushima Dai-ichi nuclear power plant accident

2013 ◽  
Vol 10 (2) ◽  
pp. 1993-2012 ◽  
Author(s):  
H. Kaeriyama ◽  
D. Ambe ◽  
Y. Shimizu ◽  
K. Fujimoto ◽  
T. Ono ◽  
...  
Keyword(s):  
Power Plant ◽  
Particle Tracking ◽  
North Pacific ◽  
Nuclear Power ◽  
Kuroshio Extension ◽  
Horizontal Distribution ◽  
Surface Seawater ◽  
The North ◽  
The North Pacific ◽  
Central North Pacific

Abstract. The horizontal distribution of radioactive cesium (Cs) derived from the Fukushima Dai-ichi Nuclear Power Plant (FNPP) in the North Pacific is still unclear due to the limitation of direct measurement of the seawater in the open ocean. We present the result of direct observation of radioactive Cs in surface seawater collected from broad area in the western and central North Pacific in July, October 2011 and July 2012. We also conducted a simple particle tracking experiment to estimate the qualitative spatial distribution of radioactive Cs in the North Pacific. 134Cs were detected at 94 stations out of 123 stations and 137Cs was detected at all stations. The high 134Cs and 137Cs concentrations more than 10 mBq kg−1 were observed in the area where the northern part of Kuroshio extension at 144° E and 155° E in July 2011, in the area 147° E–175° E around 40° N in October 2011, and the northern part of Kuroshio extension at 155° E and 175° 30´ E in July 2012. Combining the result of direct observations and particle tracking experiment, the radioactive Cs derived from FNPP had been dispersed eastward to the central North Pacific during 2011. It was considered from the horizontal distribution that radioactive Cs was dispersed not only eastward but also north- and southward in the central North Pacific. Pronounced dilution process of radioactive Cs from FNPP during study period is suggested from temporal change in the activity ratio of 134Cs/137Cs which was decay corrected at 6 April 2011, and relationships between radioactive Cs and temperature.

scholarly journals Cesium-134 and 137 activities in the central North Pacific Ocean after the Fukushima Dai-ichi Nuclear Power Plant accident

2013 ◽  
Vol 10 (9) ◽  
pp. 6045-6052 ◽  
Author(s):  
J. Kameník ◽  
H. Dulaiova ◽  
K.O. Buesseler ◽  
S. M. Pike ◽  
K. Št'astná
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Pacific Ocean ◽  
North Pacific ◽  
Nuclear Power ◽  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Hawaiian Islands ◽  
Surface Seawater ◽  
The Kuroshio

Abstract. Surface seawater 134Cs and 137Cs samples were collected in the central and western North Pacific Ocean during the 2 yr after the Fukushima Dai-ichi Nuclear Power Plant accident to monitor dispersion patterns of these radioisotopes towards the Hawaiian Islands. In the absence of other recent sources and due to its short half-life, only those parts of the Pacific Ocean would have detectable 134Cs values that were impacted by Fukushima releases. Between March and May 2011, 134Cs was not detected around the Hawaiian Islands and Guam. Here, most 137Cs activities (1.2–1.5 Bq m–3) were in the range of expected preexisting levels. Some samples north of the Hawaiian Islands (1.6–1.8 Bq m–3) were elevated above the 23-month baseline established in surface seawater in Hawaii indicating that those might carry atmospheric fallout. The 23-month time-series analysis of surface seawater from Hawaii did not reveal any seasonal variability or trends, with an average activity of 1.46 ± 0.06 Bq m–3 (Station Aloha, 18 values). In contrast, samples collected between Japan and Hawaii contained 134Cs activities in the range of 1–4 Bq m–3, and 137Cs levels were about 2–3 times above the preexisting activities. We found that the southern boundary of the Kuroshio and Kuroshio extension currents represented a boundary for radiation dispersion with higher activities detected within and north of the major currents. The radiation plume has not been detected over the past 2 yr at the main Hawaiian Islands due to the transport patterns across the Kuroshio and Kuroshio extension currents.

Transport of the Cs-134 activity derived from Fukushima Dai-ichi Nuclear Power Plant in the North Pacific Ocean

2020 ◽  
Author(s):  
Takaki Tsubono ◽  
Kazuhiro Misumi ◽  
Daisuke Tsumune ◽  
Michio Aoyama ◽  
Katsumi Hirose
Keyword(s):  
Surface Layer ◽  
Power Plant ◽  
Nuclear Power Plant ◽  
North Pacific ◽  
Intermediate Layer ◽  
Nuclear Power ◽  
North Pacific Ocean ◽  
Abundance Ratio ◽  
The North ◽  
The North Pacific

&lt;p&gt;We conducted the ensemble simulation of Cs-134 activity in the North Pacific Ocean (NPO) water after the Fukushima Dai-ichi Nuclear Power Plant (1F NPP) by setting four different passive tracers corresponding to the fluxes of the Cs-134 activity; 1. Cs_DD for Cs-134 activity directly discharged from the coast of the 1F NPP (Tsumune et al., 2013), 2. Cs_ADN for the activity derived from the atmospheric deposition (Aoyama et al, 2015) northern from 36&amp;#176;N, 3. Cs_ADKE for that in the Kuroshio Extension area from 32&amp;#176;N or 36&amp;#176;N, 4. Cs_ADS for that southern from 32&amp;#176;N. The totals of the Cs_DD, Cs_ADN, Cs_ADKE and Cs_ADS in the NPO in May 2011 are 5.6, 8.7, 1.0 and 0.6 PBq respectively, suggesting that the impact was dominant northern from 36&amp;#176;N in the NPO. The sum of four tracers showed comparable to the Cs-134 activity from all the fluxes in previous study with the correlation coefficient of 0.99 and the RMS of 5 Bq m$^{-3}$ in 2011 and 0.99 and 0.1 Bq m$^{-3}$ in 2012, except for the area of Japanese coast near the 1F NPP in which the rapid increase in the direct discharge flux produced the different negative values due to the dispersive error of the difference scheme. Since the Cs-134 activity diminishes in time due to the short half life of about 2 years, the abundance ratio was calculated for the investment of the meridional and vertical transport. The abundance ratio of the whole Cs-134 activities showed that although almost all the Cs-134 activity existed in the surface layer above 200m depth after the accident, the ratio in the intermediate layer from 200m to 600m depth increased and exceeded 50 percent since 2017. Moreover the ratio in the intermediate layer southern from 32&amp;#176;N exceeded the 25 percent since 2017, suggesting that more than 25 percent of the Cs-134 activity in the surface layer northern to the 36&amp;#176;N in early period after the accident were transported to the southern and deep in 2017. While the abundance ratio of Cs_DD and Cs_ADN in the intermediate layer showed an increase like a logarithmic function shape, the ratio of the Cs_DD, 60 percent, was larger than that of the Cs_ADN, 50 percent, in 2021. Moreover, the abundance ratio in 2011 showed the 70 percent of Cs_DD and Cs_ADN existed in the intermediate layer southern to the 32 &amp;#176;N, suggesting a large amount of both the Cs_DD and Cs_ADN were transported southern and deep in 2021.&lt;/p&gt;

scholarly journals Cesium-134 and 137 activities in the central North Pacific Ocean after the Fukushima Dai-ichi nuclear power plant accident

2013 ◽  
Vol 10 (3) ◽  
pp. 5223-5244 ◽  
Author(s):  
J. Kameník ◽  
H. Dulaiova ◽  
K.O. Buesseler ◽  
S. M. Pike ◽  
K. Št'astná
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Pacific Ocean ◽  
North Pacific ◽  
Nuclear Power ◽  
North Pacific Ocean ◽  
Kuroshio Extension ◽  
Hawaiian Islands ◽  
Surface Seawater ◽  
The Kuroshio

Abstract. Surface seawater 134Cs and 137Cs samples were collected in the central and western North Pacific Ocean during the 1.5 yr after the Fukushima Dai-ichi nuclear power plant accident to monitor dispersion patterns of these radioisotopes towards the Hawaiian Islands. In the absence of other recent sources and due to its short half-life only those parts of the Pacific Ocean would have detectable 134Cs that were impacted by Fukushima releases. Between March and May 2011, 134Cs was not detected around the Hawaiian Islands and Guam. Here, most 137Cs activities (1.2–1.5 Bq m−3) were in the range of expected preexisting levels. Some samples north of the Hawaiian Islands (1.6–1.8 Bq m−3) were elevated above the 18-month baseline established in surface seawater in Hawaii indicating that those might carry atmospheric fallout. The 18-month time-series analysis of surface seawater from Hawaii did not reveal any seasonal variability or trends, with an average activity of 1.46 ± 0.06 Bq m−3 (Station Aloha, 17 values). In contrast, samples collected between Japan and Hawaii contained 134Cs activities in the range of 1–4 Bq m−3 and 137Cs levels were about 2–3 times above the preexisting activities. We found that the southern boundary of the Kuroshio and Kuroshio extension currents represented a boundary for radiation dispersion with higher activities detected within and north of the major currents. The radiation plume has not been detected over the past 1.5 yr at the main Hawaiian Islands due to the transport patterns across the Kuroshio and Kuroshio extension currents.

scholarly journals On the Relationship between Synoptic Wintertime Atmospheric Variability and Path Shifts in the Gulf Stream and the Kuroshio Extension

2009 ◽  
Vol 22 (12) ◽  
pp. 3177-3192 ◽  
Author(s):  
Terrence M. Joyce ◽  
Young-Oh Kwon ◽  
Lisan Yu
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Western Boundary ◽  
Atmospheric Variability ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Coherent, large-scale shifts in the paths of the Gulf Stream (GS) and the Kuroshio Extension (KE) occur on interannual to decadal time scales. Attention has usually been drawn to causes for these shifts in the overlying atmosphere, with some built-in delay of up to a few years resulting from propagation of wind-forced variability within the ocean. However, these shifts in the latitudes of separated western boundary currents can cause substantial changes in SST, which may influence the synoptic atmospheric variability with little or no time delay. Various measures of wintertime atmospheric variability in the synoptic band (2–8 days) are examined using a relatively new dataset for air–sea exchange [Objectively Analyzed Air–Sea Fluxes (OAFlux)] and subsurface temperature indices of the Gulf Stream and Kuroshio path that are insulated from direct air–sea exchange, and therefore are preferable to SST. Significant changes are found in the atmospheric variability following changes in the paths of these currents, sometimes in a local fashion such as meridional shifts in measures of local storm tracks, and sometimes in nonlocal, broad regions coincident with and downstream of the oceanic forcing. Differences between the North Pacific (KE) and North Atlantic (GS) may be partly related to the more zonal orientation of the KE and the stronger SST signals of the GS, but could also be due to differences in mean storm-track characteristics over the North Pacific and North Atlantic.

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