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Material transport by sea ice plays an important role in the biological production of spring blooms. We conducted backward-tracking simulations to estimate the origins of the sea ice in the southern part of the Sea of Okhotsk and examine the relationship between the origin of sea ice and biological production, the concentration of iron, and the frazil ice fraction. The simulation of the sea ice melted in areas, where the net community production (NCP) was estimated shows that the sea ice that melted in areas with high NCP tended to originate in coastal areas, mostly the Terpenia Bay and Sakhalin polynyas, where ice production is high and sea ice can incorporate the seafloor sediments. This result supports the hypothesis that the incorporation of sedimentary particles into sea ice and their release during ice melt are key factors in high biological production. The simulation of the sea ice floes sampled by the icebreaker Soya off Hokkaido coast suggests that the samples collected over the shelf with depths of less than 500 m or so were formed over the shelf around the southern tip of Sakhalin Island, whereas the samples, including that with high iron concentration, collected over the shelf slope at greater depths were likely transported from the northern area up to Terpenia Bay but not further north. The simulation also suggests that the sea ice floes with a high fraction of frazil ice could be formed anywhere in the southern part of the Sea of Okhotsk. [ABSTRACT FROM AUTHOR]

This study provides formulae for monthly estimates of the Soya Warm Current (SYC) transport from the sea-level difference (SLD) across the Soya Strait and along the current, and creates a 50-yr data set of the SYC transport. The formulae are based on the dynamical balance both across the strait and along the current by considering the barotropic and baroclinic components. It is suggested that the barotropic and baroclinic components in transport variability are comparable in summer, whereas the barotropic component is dominant in winter. We compared the 50-year time series of the SYC transport with those of the Tsushima (TSC) and Tsugaru Warm Currents estimated from the SLDs from the viewpoint of the Japan Sea Throughflow (JSTF) system. The variabilities of the SYC and TSC transports are mostly shared for any season, showing relatively high coherence at periods of 2–5 years as well as 1 year. The winter variability of the JSTF transport originates partly from that of the SYC transport caused by the winter monsoon variability in the Sea of Okhotsk. The SYC transport is significantly correlated with the transport through the eastern channel of the TSC, but not that through the western channel. We found difficulty in extracting variability and relationships at periods longer than 5 years among the three transports estimated from the SLDs, probably due to incomplete correction of the ground movements for the sea-level data. [ABSTRACT FROM AUTHOR]

In the southwestern Sea of Okhotsk, a large spring phytoplankton bloom occurs after the sea ice melts. A suggested scenario is that sea ice with materials such as iron-containing sediment or ice algae is transported from the north and melted with release of them, inducing a prominent bloom. We hypothesize that sea ice containing materials that could enhance spring bloom originates from active coastal polynyas in the upstream region. To verify this hypothesis and identify which coastal areas generate sea ice that is further transported to the bloom area, we simulated the transport of sea ice produced in the coastal polynyas by a particle-tracking method. Sea ice production and drift velocity were derived from satellite microwave data. For regions near the coast, where ice drift data derived from the satellite are inaccurate, we combined ice drift data derived from the wind using the wind factor and the turning angle obtained from mooring data. Further, we used the apparent wind factor that expresses enhancement of the alongshore component of ice drift by the ocean current. The simulations suggest that most of the sea ice that melts in the western Kuril Basin originates from the Terpenia Bay and Sakhalin polynyas. The area where high net community production occurs after the sea ice melts corresponds well to the area where sea ice originating from these polynyas melts. The simulation of frazil ice suggests the importance of melt ice originating from the Terpenia Bay polynya with a higher rate of frazil ice production. [ABSTRACT FROM AUTHOR]