open access

https://hdl.handle.net/2115/97568

High-turbidity bottom mixed-layer water on the shelf off Hokkaido in the Okhotsk Sea: distribution, seasonal variations, and spreading

英語

Identification of Soya Strait origin waters

2025

Springer

Journal of oceanography

The Okhotsk Sea coast of Hokkaido and the Kuril Basin exhibit high primary production, supported by nutrient supply through material circulation. As part of this circulation, we focused on high turbidity water in the bottom mixed layer (BML) on the shelf off Hokkaido and its spreading. Our observations in spring and autumn showed a thick, high-turbidity BML across the shelf, originating mostly from the Soya Strait and flowing toward the Shiretoko Peninsula and into the Kuril Basin. Analysis of past observation data and an ocean model output revealed that the thick BML was present year-round, suggesting the continuous supply of high-turbidity waters. BML thickness and density were highest in spring and lowest in winter and peaked offshore of the Soya Warm Current. Using the model output, we conducted Lagrangian tracking of BML water. BML waters with low density mostly flowed into the North Pacific quickly through shallow straits near Hokkaido, whereas higher-density BML waters spread into the Kuril Basin, remaining there longer before eventually flowing into the North Pacific through deep straits. We also showed seasonal variations primarily driven by density variations, interannual changes associated with flow field variation, and sensitivity to sinking rates for sinking particles. The results suggest that high-turbidity bottom waters off Hokkaido in the Okhotsk Sea are transported to the Kuril Basin and North Pacific, potentially impacting material circulation and ecosystems. In particular, high-turbidity waters lighter than 26.7 sigma theta may be entrained into the euphotic zone by winter mixing, contributing to the next spring bloom.

学術雑誌論文

Accepted Manuscript

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: http://dx.doi.org/10.1007/s10872-025-00755-x

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