Particle-tracking experiments of coastal-origin sea ice that could induce high biological productivity in the Sea of Okhotsk

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.

Automated summary

In the southwestern Sea of Okhotsk, a large spring phytoplankton bloom occurs after the sea ice melts. It is believed that the sea ice, containing materials such as iron-containing sediment or ice algae, is transported from the north and melted, leading to a prominent bloom. This study suggests that the sea ice that enhances the spring bloom originates from active coastal polynyas in the upstream region. Using a particle-tracking method, the researchers simulated the transport of sea ice produced in the coastal polynyas and identified Terpenia Bay and Sakhalin polynyas as the main sources of sea ice in the western Kuril Basin. The study also highlights the importance of melt ice from the Terpenia Bay polynya in the frazil ice production.