WEKO3
アイテム
北海道東部太平洋海域における水塊分布と流れ場の構造に関する研究
https://fra.repo.nii.ac.jp/records/2010939
https://fra.repo.nii.ac.jp/records/2010939bd53450d-56d1-41b9-93c7-7aa1a4a2c5a0
| 名前 / ファイル | ライセンス | アクション |
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fra_k_43_1.pdf (18.9 MB)
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| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||||||||
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| 公開日 | 2024-10-02 | |||||||||||
| タイトル | ||||||||||||
| タイトル | 北海道東部太平洋海域における水塊分布と流れ場の構造に関する研究 | |||||||||||
| 言語 | ja | |||||||||||
| タイトル | ||||||||||||
| タイトル | Study on water mass distributions and current structures off the Pacific coast of eastern Hokkaido | |||||||||||
| 言語 | en | |||||||||||
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| 言語 | jpn | |||||||||||
| キーワード | ||||||||||||
| 言語 | en | |||||||||||
| 主題Scheme | Other | |||||||||||
| 主題 | Coastal Oyashio Water; Modified Soya Warm Current Water; Oyashio Water; Current structure; Volume transport | |||||||||||
| 資源タイプ | ||||||||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||||||||
| 資源タイプ | departmental bulletin paper | |||||||||||
| アクセス権 | ||||||||||||
| アクセス権 | open access | |||||||||||
| アクセス権URI | http://purl.org/coar/access_right/c_abf2 | |||||||||||
| 著者 |
日下, 彰
× 日下, 彰
WEKO
483
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| 抄録 | ||||||||||||
| 内容記述タイプ | Abstract | |||||||||||
| 内容記述 | The Doto area is a region off the Pacific coast of eastern Hokkaido between the Nemuro Peninsula and Cape Erimo. In the offshore area, Oyashio Water (OW) is distributed nearly throughout the year. In the shelf area, the lower temperature and salinity Coastal Oyashio Water (COW) is distributed along the coast during winter and spring, whereas the higher temperature and salinity Modified Soya Warm Current Water (M-SWCW) is distributed during summer and autumn. Although seasonal variations of hydrography in the Doto area have been clarified as stated above, the temporal evolution and modification processes of such representative water masses have not been fully examined in this area. In addition, direct current measurements have been limited because of difficulties associated with fishery activities, and the current structures have not been fully clarified in this area. The Doto area contains important fishing grounds, where sardine, saury, and salmon are caught by commercial fishing activities; it is also a nursery area for walleye pollock juveniles. Therefore, it is important to examine water mass distributions and current structures, which may affect these fish habitats. In Chapter 1, water masses and current structures off the Doto area were reviewed, and the purpose and structure of this study were stated. In Chapter 2, monthly climatology of hydrography for the Doto area was estimated based on long-term observational data over a 30-year period (1982–2011) using the flexible Gaussian filter method (Shimizu and Ito, 1996). Monthly variations in spatial and vertical distributions of hydrography, and temporal evolution and modification processes of representative water masses were examined with this climatology. In the offshore area, the OW was mainly distributed during January and May; and afterwards Surface OW (S-OW), which is warmer than the OW, was at the surface during June and December. On the other hand, there was a marked seasonal variability in hydrography in the shelf area. COW was distributed along the coast from January to May, when it was modified by relatively higher salinity water, which may have originated from the shelf area’s outer regions. Simultaneously, the COW warmed at the surface, mixed with fresh water from river discharges, such as the Tokachi River, and was modified to Surface COW (S-COW) during April and May. Thereafter, the S-COW spread offshoreward during May and June and stayed at the surface of the offshore area until October. Coastal density current structures were conspicuous in the shelf area from August to October because of the M-SWCW inflows between July and August. However, those structures weakened around November due to a developed surface mixed layer caused by surface cooling. Thus, such weakening led to weakening of higher salinity water inflows from upstream regions. The M-SWCW was replaced by COW during December and January with rapid salinity decreases, which suggest extremely lower salinity water inflows from the East Sakhalin Current Water. In Chapter 3, direct current measurements were conducted using a bottom mounted ADCP at a water depth of 82 m in the continental shelf region off the Akkeshi from July 2003 to July 2005. Simultaneous hydrographic observations with a CTD were also conducted at the A01 near this current measurement site, to examine temporal variations of current structures relative to water mass distributions. During summer and autumn, baroclinic flows intensified between July and August, accompanied by sudden saline and temperature increases because of horizontal density gradients caused by lighter water from the M-SWCW inflows piling on the shelf area. Such intensified baroclinic flows, however, weakened around November, which may be due to a developed surface mixed layer, as discussed in Chapter2 and decay of the Soya Warm Current (SWC) in the Okhotsk Sea. During winter and spring, Forerunner Coastal Oyashio Water (F-COW), which is warmer than the COW, intruded into the shelf area, and the barotropic flows intensified around December and January. These intensified barotropic flows weakened after February, while baroclinic flows were gradually predominant. In Chapter 4, direct current measurements using a shipboard ADCP and concurrent hydrographic observations with a CTD were conducted around the shelf area between January and May 2005 to estimate volume transport of the Coastal Oyashio (CO), and to examine temporal evolution of hydrography in response to the changes in volume transport. The volume transport of the CO (TCO) decreased from 0.79 Sv (1 Sv = 106 m3 /s) in January to 0.21 Sv in March, and it further decreased to 0.12 Sv in May. Moreover, the timing of the maximum TCO was not identical to the timing of the maximum COW extent. Such decreases in TCO led to shoreward shift of a surface-to-bottom density front accompanied with a baroclinic jet, and accordingly relatively offshore saline OW inflows into the shelf area. As a result, salinity increased mainly in a deeper part of the shelf area, forming horizontal salinity gradients. Considering that density around these periods depends on salinity, such salinity gradients cause density gradients in the shelf area, changing nearshore current structures from relatively barotropic to baroclinic during winter and spring, as shown in Chapter 3. In Chapter 5, the conclusion of this study was presented using schematic figures. The F-COW intrudes into the shelf area with rapid salinity decreases in December when barotropic flows are predominant. In the offshore area, the OW is distributed during January and May, while the COW is distributed along the coast. TCO decreases during this period, and offshore saline OW flows into the shelf area. As a result, horizontal salinity gradients are formed in the shelf area, and nearshore current structures change from relatively barotropic to baroclinic during winter and spring. In the offshore area, the S-OW is distributed after June, while the S-COW spreads offshoreward from the shelf area during May and June, and stays at the surface until October. In the shelf area, coastal density current structures are conspicuous from August to October due to the M-SWCW inflows between July and August, and saline water supplied from upstream regions. However, those structures start to weaken around October, and the decay of SWC in the Okhotsk Sea, accordingly leads to the weakening of higher salinity water inflows. As stated above, current structures in the Doto area are closely related to the distributions of representative water masses. | |||||||||||
| 言語 | en | |||||||||||
| bibliographic_information |
ja : 水産研究・教育機構研究報告 en : Bulletin of Japan Fisheries Research and Education Agency 巻 43, p. 1-46, ページ数 46, 発行日 2016-12 |
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| 出版者 | ||||||||||||
| 出版者 | 水産研究・教育機構 | |||||||||||
| 言語 | ja | |||||||||||
| 出版者 | ||||||||||||
| 出版者 | Japan Fisheries Research and Education Agency | |||||||||||
| 言語 | en | |||||||||||
| item_10002_source_id_9 | ||||||||||||
| 収録物識別子タイプ | PISSN | |||||||||||
| 収録物識別子 | 2432-2830 | |||||||||||
| item_10002_source_id_11 | ||||||||||||
| 収録物識別子タイプ | NCID | |||||||||||
| 収録物識別子 | AA12767505 | |||||||||||
| item_10002_relation_11 | ||||||||||||
| 識別子タイプ | EISSN | |||||||||||
| 関連識別子 | 2758-3953 | |||||||||||
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| 識別子タイプ | Local | |||||||||||
| 関連識別子 | fra_k_43_1 | |||||||||||
| 関連サイト | ||||||||||||
| 識別子タイプ | URI | |||||||||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010922969 | |||||||||||
| 関連名称 | 日本農学文献記事索引（AgriKnowledge） | |||||||||||
| 出版タイプ | ||||||||||||
| 出版タイプ | VoR | |||||||||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||||||||
