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

Inomata, Yayoi; Aoyama, Michio; Hamajima, Yasunori; Yamada, Masatoshi

doi:https://doi.org/10.5194/os-14-813-2018

Articles | Volume 14, issue 4

https://doi.org/10.5194/os-14-813-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/os-14-813-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 4

Research article

|

24 Aug 2018

Research article |

| 24 Aug 2018

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

Yayoi Inomata, Michio Aoyama, Yasunori Hamajima, and Masatoshi Yamada

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Final revised paper (published on 24 Aug 2018)
Supplement to the final revised paper
Preprint (discussion started on 29 Nov 2017)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review of "Rapid recirculation of FNPP1 derived radiocaesium suggesting new pathway of subtropical mode water in the western North Pacific to the Sea of Japan" by Inomata et al.', Eitarou Oka, 30 Dec 2017
- AC1: 'Reply to reviewer, Prof. Oka', Yayoi Inomata, 08 Mar 2018
RC2: 'Review of the manuscript OS-2017-90', Anonymous Referee #2, 17 Jan 2018
- AC2: 'Replay to reviewer 2', Yayoi Inomata, 08 Mar 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Yayoi Inomata on behalf of the Authors (08 Mar 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (14 Mar 2018) by Matthew Hecht

RR by Anonymous Referee #2 (27 Mar 2018)

RR by Eitarou Oka (31 Mar 2018)

Suggestions for revision or reasons for rejection

While the original manuscript insisted that the observed transport of radiocaesium suggests a new pathway of STMW circulation, the revised manuscript is more descriptive, focusing mainly on the radiocaesium transport from the East China Sea to the Japan Sea. I felt that this revision was adequate and suggest further revision to concentrate on the ECS to JS transport processes, because the authors are not showing any analysis nor discussion on the transport processes from the North Pacific to the ECS, particularly in Sec. 3.3.

The schematic in Fig. 8 still needs to be revised. The Kuroshio path is too much simplified. Its pathway from the ECS to the NP via the Tokara Strait is not expressed at all. STMW is formed as deep winter mixed layers north of ~28N and is subducted southward across the mixed layer front at ~28N. Then, it is transport westward and reaches the western boundary at ~25N or further south (e.g., Oka, 2009). As I commented to the original manuscript, I believe that STMW with radiocaesium does NOT “enter the ECS from the region between Kagoshima and Tokara” (p.7, l.14-15) as shown by blue arrows in Fig. 8. If the authors insist so, please show the evidence.

Other comments:

Title: What does “rapid” mean? Given the timescale of 2-3 years for STMW circulation shown by previous studies, I think the time period for radiocaesium transport shown by the present study is reasonable but not “rapid”.

p.1, l.16-18, “A time lag of the maximum .. in the SOJ.”: I do not understand what each sentence mean and do not understand the relation between the two sentences.

p.2, l.31-32, “The SOJ is connected to the Pacific Ocean at its southwest through the Tsushima Straits”: This is incorrect. The SOJ is connected to the East China Sea.

p.2, l.33, “this current splits into three paths.”: Please add references.

In the last paragraphs of Sec. 1, the authors need to explain more clearly what advances from the preliminary study of Aoyama et al. (2017) the authors are going to show in this study.

p.5, l.20: The wording “the southern Japan (SJPN)” does not make sense. I would call the region “North Pacific south of Japan (NPSJ)”.

p.5, l.34-35, “Fig. 7 displays the latitude-time cross-sections … along the eastern TWC.”: How did the authors distinguish the eastern and western TWC? Please explain.

p.6, l.6: What does “the other layers” mean?

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ED: Reconsider after major revisions (13 Apr 2018) by Matthew Hecht

AR by Yayoi Inomata on behalf of the Authors (25 May 2018)

ED: Referee Nomination & Report Request started (22 Jun 2018) by Matthew Hecht

RR by Eitarou Oka (27 Jun 2018)

ED: Publish subject to minor revisions (review by editor) (09 Jul 2018) by Matthew Hecht

AR by Yayoi Inomata on behalf of the Authors (19 Jul 2018) Author's response Manuscript

ED: Publish as is (03 Aug 2018) by Matthew Hecht

AR by Yayoi Inomata on behalf of the Authors (10 Aug 2018) Author's response Manuscript

Short summary

Analysing increased ¹³⁷Cs and ¹³⁴Cs / ¹³⁷Cs ratio derived from the Fukushima Nuclear Power Plant accident in the Sea of Japan and its marginal sea, we found a rapid transport process associated with subduction in the subtropical mode water (STMW) formation region and obduction in the north East China Sea. The integrated amount of FNPP1 ¹³⁷Cs entering the Sea of Japan until 2016 was estimated to be 0.21 ± 0.03 PBq, which corresponds to 5.1 (3.4–8.0) % of the total amount of FNPP1 ¹³⁷Cs in the STMW.