Drift ice, or ice floes, which are large masses of sea ice that float in the ocean, have been a winter spectacle in the northern seas of Japan, particularly in the Sea of Okhotsk near Hokkaido. However, a recent study by Hokkaido University researchers has revealed alarming trends of dwindling drift ice coverage and a significant decrease in ice thickness over the past 30 years, attributed to the effects of climate change.
Researchers, led by experts like Kay Ohshima and Humio Mitsudera, have presented findings showing that drift ice in the southern Sea of Okhotsk has been thinning at a rate of 7.4 centimeters per decade, with an average 30 percent reduction in ice thickness from 1990 to 2020. This decline has surpassed previous estimations and raised concerns about the future of drift ice reaching Hokkaido's coast, impacting the marine ecosystem and fisheries.
The decrease in drift ice poses potential threats to the marine environment, as the ice contains essential nutrients like iron that support the growth of phytoplankton. The reduction in iron supply due to diminishing drift ice could disrupt the marine food chain, affecting species like zooplankton, fish, and other marine creatures that rely on phytoplankton for sustenance. This could lead to ecosystem changes not only in the Sea of Okhotsk but also in adjacent waters, impacting fisheries and marine resources in broader regions like the Oyashio areas.