Offshore Surface 419 Sea of Okhotsk vicinity

Basic Information References

Reason(s) for selection Criteria

Characteristics References

These waters are the lowest-latitude waters in the world where seasonal sea ice forms, and the only icy waters in Japan. The cold East Sakhalin Current flows south along the east coast of Sakhalin. The Soya Warm Current, coming from the Tsushima Current, flows in through the La Pérouse Strait, flowing as far as the vicinity of the Shiretoko Peninsula along Hokkaido's Sea of Okhotsk coast. When seasonal sea ice forms in the northern Sea of Okhotsk during winter, low-temperature, high-salinity sea water rich in nutrients sinks, forming the cold intermediate layer of the Sea of Okhotsk. This cold intermediate layer spreads in the intermediate later from the Sea of Okhotsk to the northwestern North Pacific as a mass of nutrient-rich water, supporting abundant biological production beginning with the massive proliferation of phytoplankton in the spring. Ice algae grow thickly on the bottom surfaces of seasonal sea ice, and when they sink they serve as feed for creatures living on the sea floor (mainly filter feeders). Like the waters of the Oyashio Current, krill, copepods and other large zooplankton are abundant here, and these serve as feeding waters for cod, flounder, crab, and other useful sea creatures that feed on these, as well as sea birds, pinnipeds, and cetaceans. While from winter to spring these waters are dominated by cold-water marine organisms resembling those of the ice edge ecosystems of the polar regions (cod and other bottom fish, sea eagles, and pinnipeds that breed on the ice surface), from summer to fall, migratory fish from the surface layers of warm currents migrate here.