Ice on the Okhotsk Sea has Decreased 20% in 30 Years

Ice on the Okhotsk Sea forms in the northwestern sea in November. After that, it spreads out so that by February to March it is at its largest area. By April, the ice reaches the shores of Hokkaido, and is gone by June. This is the typical cycle of ice in the Okhotsk. However, there are large year-to-year changes.

In 2006 marked the smallest recorded area of ice over the Okhotsk Sea. Since satellite observations began, the area of ice over the Okhotsk has decreased 20% in the last 30 years. The area of ice is gradually shrinking, but the annual fluctuations are great, such as in 2001, when the observed ice area was the largest on record.

Temperature Drops in the Northeastern Okhotsk and Sea Surface Temperatures to the Southeast of Kamchatka Hold the Key to Forecasting Sea Ice in the Okhotsk

One of the important elements in forecasting ice area over the Okhotsk, is how cold the northeastern part of the sea gets. “From the early ice (December) and the autumn (October and November) heat budget, we have determined that if the northeastern Okhotsk undergoes large cooling in the autumn, then ice forms earlier, and grows to a larger extent. In other words, the larger the heat loss, the earlier the first day of ice is.”

In addition to the relationship between the total heat loss and the first freezing day, another major factor is the sea temperatures to the southeast of Kamchatka. “We have found that there is a relationship between the maximum ice area in February and March, and the sea temperatures southeast of Kamchatka in November and December.”

When we forecast the sea ice area in the Okhostk for 2008 and 2009 according to Professor Oshima’s forecast algorithm, which is based on these relationships, it was predicted that the spread of ice in the Okhotsk was be limited. There was very little ice that actually reached the shores, and the actual conditions mirrored the predictions quite accurately.

“When focusing on Sakhalin and the shores of Hokkaido, then the East Sakhalin Current and northerly winds over the Okhotsk Sea become important factors in forecasting the ice area. The ice models can actually depict the movement of the ice. It is important to have a firm understanding of the ice movement in the winter.” In addition, by performing a simulation on the ice models, we can also see the path that oil flowing from Sakhalin takes, as well.

Ice on the Okhotsk Sea will not Disappear for Hundreds of Years

The Okhotsk is the southernmost limit of sea ice in the northern hemisphere. This is due to the strong arctic air coming down from northeast Russia, which is upwind from the Okhotsk.

It is also very susceptible to the effects of global warming. While the earth as a whole has shown a 0.65 degree temperature increase in the past 50 years, the northeastern area has shown a 2 degree increase. Although we do see a relationship between the change in temperature and the area of ice, the coldest day in northeastern Russia falls under 40 degrees below zero, one of the coldest areas in the northern hemisphere. In addition, the East Sakhalin Current, the cold current that carries the ice southward, also has a large effect. From these facts, Professor Oshima predicts: “Although there will be variations in when and how much ice is formed, it will not completely disappear over the next several hundred years.”

The Okhotsk Sea is the heart (pump) of the North Pacific Ocean. In areas where a lot of sea ice forms, heavy water is created, which then sinks to the middle levels in the ocean, and spreads out. This is how sea water moves. The Okhotsk Sea plays an important role in the creation of the vertical circulation of the currents in the North Pacific Ocean.

Weathernews provides service to support safe operations in the icy seas of the Okhotsk for LNG carriers headed toward Japan as part of the Sakhalin 2 Project. This autumn, WNI is planning to provide a sea ice outlook for the Okhotsk, and using Hokkaido University’s model and experience in analyzing sea current data, sharing technology and techniques, will support the safety of many vessels in the icy seas.