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Determination of the freshwater origin of Coastal Oyashio Water using humic-like fluorescence in dissolved organic matter

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Title: Determination of the freshwater origin of Coastal Oyashio Water using humic-like fluorescence in dissolved organic matter
Authors: Mizuno, Yu Browse this author
Nishioka, Jun Browse this author →KAKEN DB
Tanaka, Takahiro Browse this author
Tada, Yuya Browse this author
Suzuki, Koji Browse this author →KAKEN DB
Tsuzuki, Yuta Browse this author
Sugimoto, Atsuko Browse this author
Yamashita, Youhei Browse this author →KAKEN DB
Keywords: Coastal Oyashio Water
Freshwater end-member
River water
Sea-ice melt water
Dissolved organic matter
Humic fluorescence
Issue Date: Oct-2018
Publisher: Springer
Journal Title: Journal of oceanography
Volume: 74
Issue: 5
Start Page: 509
End Page: 521
Publisher DOI: 10.1007/s10872-018-0477-x
Abstract: Coastal Oyashio Water (COW), defined as a water mass with a temperature lower than 2 degrees C and a salinity lower than 33.0, is distributed in the North Pacific Ocean off southeastern Hokkaido, Japan, from winter to spring. COW is rich in macronutrients and dissolved iron and is thus considered to affect the spring phytoplankton blooms in the Oyashio region. Although river water and sea-ice melt water have been considered freshwater end-members of COW, the contributions of these freshwater sources to COW have not been well described. In this study, the humic-like components in dissolved organic matter were first applied as a parameter to evaluate the freshwater end-members of COW in March 2015. Linear regressions with negative slopes were determined between the humic-like components and the salinity of COW. The intercepts of the regressions against the humic-like components were within the ranges of those observed for the local rivers of Hokkaido but were very different from those of sea ice. These findings suggest that river water contributed to the COW observed here as a freshwater end-member, although the contribution of sea-ice melt water to COW could not be evaluated. This novel approach also highlighted two different less-saline water masses in COW. The first was characterized by a lower temperature and relatively high levels of humic-like components, while the second was higher in temperature and had higher levels of humic-like components. It is suggested that these different characteristics are due to the contributions of water from different rivers and/or different effects of sea-ice melt water.
Rights: The final publication is available at Springer via
Type: article
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 山下 洋平

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