East Siberian Sea

• 1. Introduction

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  The East Siberian Sea sits at the top of the world, a vast stretch of Arctic water pressed between the coast of Siberia to the south and the open Arctic Ocean to the north. Its name was only officially fixed on the 27th of June 1935, by decree of the Soviet Government. Before that, the sea had floated through Russian records under a scatter of names: Indigirskoe, Kolymskoe, Severnoe, Sibirskoe, Ledovitoe. No single label had stuck. That uncertainty about what to call the place says something about what the sea actually is: one of the least studied bodies of water in the entire Arctic. Its ice fields fully melt only in August and September. Its tides barely top 25 centimetres. Its largest city, Pevek, holds just over five thousand people and carries the distinction of being the northernmost city on the Russian mainland. What happens in a sea this remote, this cold, and this overlooked? The answers reach back thousands of years of indigenous life, forward through labour camps and nuclear reactors, and outward across one of the longest coastlines on earth.

• 2. Shape of the Sea

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  Kolyma Bay, Kolyma Gulf, and Chaunskaya Bay all crowd the southern limits of the sea, which opens toward the Arctic Ocean with no large islands blocking the middle. The entire island area within the sea adds up to only 80 square kilometres, and some of those islands are composed largely of sand and ice, slowly wearing away into the water. The coastline runs for 3,016 kilometres, bending deeply inland in places and splitting into two very different personalities east and west of the Kolyma River. West of the river, the shore is low and uniform, giving way to marshy tundra dotted with small lakes. East of the Kolyma, the coastline turns mountainous, with steep cliffs dropping into the water. The seabed beneath all of this is a gently sloping plain running from southwest to northeast, covered in a mixture of silt, sand, and stones. About 70 percent of the sea sits shallower than 50 metres, with depths of 20 to 25 metres dominating. The greatest depths, around 915 metres, are found in the northeastern corner. Northeast of the mouths of the Kolyma and Indigirka rivers, there are deep trenches on the seabed that geologists trace back to ancient river valleys, now drowned beneath the sea. The sea itself rests on what was once the Verkhoyansk Sea, an ancient body of water that covered much of this region during the Permian period.

• 3. Climate and Ice

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  January temperatures average around minus 30 degrees Celsius, driven down by south-westerly winds blowing cold air off the Siberian continent at 6 to 7 metres per second. Atlantic cyclones push those temperatures briefly upward while Pacific cyclones bring storms and blizzards. Summer offers only modest relief. Northerly winds keep the open sea between 0 and 1 degree Celsius in July, warming slightly to 2 or 3 degrees along the coast. The western part of the sea becomes one of the most storm-prone stretches on the northern Russian coast by August, when winds strengthen to between 10 and 15 metres per second. Fogs blanket the coast for 90 to 100 days per year, with 68 to 75 of those fog days concentrated in summer. Annual precipitation runs between 100 and 200 millimetres, low even by Arctic standards but still exceeding evaporation. Ice governs the sea's calendar more than any other factor. Freezing begins between October and November; breakup comes between June and July. Near the coast, stationary ice reaches 2 metres thick by the end of winter. Further out, drifting ice runs 2 to 3 metres thick. South winds in winter push the drifting ice northward, opening polynyas near the sea centre. There are no icebergs. Melting typically starts in May, first around the delta of the Kolyma River, and the ice fields do not fully clear until August and September.

• 4. Rivers and Water

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  Seven rivers are singled out as the most significant contributors to the sea: the Indigirka, Alazeya, Chukochya, Kolyma, Rauchua, Chaun, and Pegtymel. The Kolyma River alone delivers 132 cubic kilometres of fresh water each year. The Indigirka contributes 59 cubic kilometres. Together, the rivers send about 250 cubic kilometres into the sea annually, which amounts to only 10 percent of the total river runoff across all the Arctic seas of Russia. Ninety percent of that runoff arrives in summer, concentrated near the coast where weak currents keep it from spreading far. The result is a sharp gradient in salinity. Near the Kolyma and Indigirka deltas in winter and spring, the surface reads as low as 4 to 5 parts per thousand. Toward the northern outskirts of the sea, salinity climbs to 31 to 32 parts per thousand. Snow melt in summer drops salinity across the sea by roughly 5 parts per thousand. Surface currents run from west to east but are weak enough that winds can temporarily reverse them. Storms in the western sea generate waves reaching 3 to 5 metres. Those storms last 1 to 2 days in summer, but winter storms can stretch to 3 to 5 days. The annual outflow to the Chukchi Sea alone runs to 6,600 cubic kilometres, more than double what flows back in.

• 5. Peoples of the Coast

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  Yukaghirs and Chukchi lived along these shores for thousands of years before any outside group arrived, surviving through fishing, hunting, and reindeer husbandry. Reindeer sleds were the essential tool of both transportation and hunting across the frozen terrain. Around the second century, Evens and Evenks joined and absorbed those earlier groups. Then, between the ninth and the fifteenth centuries, the much more numerous Yakuts moved in from further south, pressing northward from the Lake Baikal area to avoid confrontations with Mongols. All of these groups practised shamanism, even as they spoke entirely different languages. Russian sea-farers entered the picture in the seventeenth century, moving from river mouth to river mouth in their kochs. In 1648, Semyon Dezhnev and Fedot Alekseev sailed the full stretch of the East Siberian coast from the Kolyma River to the Anadyr River, which drains into the Bering Sea. Systematic mapping expeditions followed in waves: 1735 to 1742-1820 to 1824, 1822, 1909, and 1911 to 1914. The settlements that exist today are few and small, with most holding fewer than one hundred people. The exception is Pevek, which serves as the regional centre and the only true city on this coast.

• 6. Gulag and Industry

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  Ambarchik, a coastal settlement at the Kolyma River delta, became a transit point in the 1930s for prisoners being moved deeper into the Gulag system. Those prisoners were put to work building the port infrastructure and unloading supply ships. Shallow waters eventually made Ambarchik impractical for larger vessels, and shipping was shifted upstream to Chersky. The old port was abandoned and now houses only a meteorological station run by a handful of staff. Near Pevek, two more camps followed: Chaunlag, which operated from 1951 to 1953, and Chaunchukotlag, which ran from 1949 to 1957. Each held about ten thousand inmates assigned to mine and construction work. The mines around Pevek extracted gold and tin, though the tin operations closed in the 1990s. That closure triggered an outflow of population. The settlement of Logashkino, once a functioning East Siberian Sea port, was abolished altogether in 1998. Gold mining continues near Leningradsky and Pevek, and the port of Pevek handles the bulk of cargo moving along this stretch of the Northern Sea Route. Fish production in 2005 logged specific catches: Muksun at 2,800 tonnes, broad whitefish at 2,700 tonnes, Bering cisco at 2,200 tonnes, Arctic cisco at 1,800 tonnes, and sardine at 1,600 tonnes, alongside other species.

• 7. Nuclear Power at the Edge

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  In 1944, the Chaunskaya Thermal Power Plant came online to supply electricity to Pevek and the wider Chukotka region, drawing on coal-burning facilities with a combined capacity of 30 megawatts. Decades of ageing and the high cost of shipping fuel to such a remote location eventually pushed planners toward a different solution. The Bilibino Nuclear Power Plant, located inland from the sea, brought its first stage online in 1974 and its second in 1976. It ran four EGP-6 reactors, each rated at 12 megawatts of electrical output. The EGP-6 design, whose Russian name translates roughly as the Energy Heterogeneous Loop Reactor, was a scaled-down version of the RBMK design, using graphite as a moderator and light water for cooling via natural circulation, a configuration suited to remote permafrost locations. By the time all four units shut down in January 2026, the plant had accumulated more than 190 reactor-years of operation and had delivered over 11.6 terawatt-hours of electricity. The decision to close was approved in March 2016. Unit 1 came down in 2018; the others followed. Replacing it is the Akademik Lomonosov, a floating nuclear power plant moored in Pevek that began commercial operation in May 2020. It carries two small reactors generating 35 megawatts each. In January 2026, it supplied its first billion kilowatt-hours to the Chaun-Bilibino grid. As of 2026, it accounts for over 60 percent of power generation in that isolated grid and can feed up to 70 megawatts into the town's onshore supply when no heat is being diverted to shore. FNPP Deputy Director Natalia Tarasova noted in 2025 that the plant had been refuelled for the first time, calling out the particular difficulty of doing so in Arctic conditions.