Drifting Ice Stories on the Sea of Japan's World Natural Heritage — Japan Underwater Odyssey

Hello everyone, I'm Ishino, an underwater photographer. Starting last month, I launched a series called "Diving Journey through the Japanese Archipelago." In the first episode, I traveled to Ishigaki in southwestern Japan in search of manta rays. In February, I ventured to the "edge of the world" in northeastern Japan — the Shiretoko Peninsula.

Cape Puyuni in Utoro, Shiretoko, near where the drift ice comes to rest

Shiretoko is one of Japan's five UNESCO World Natural Heritage Sites and is the southernmost point in the Northern Hemisphere where drift ice reaches. Its World Heritage designation stems from the area's intact ecosystem, where sea, rivers, and forests form a complex food chain and energy cycle driven by the drift ice. However, with changing environmental conditions, there are growing concerns that drift ice may no longer reach Shiretoko in the future.

Over the past four years, I have been returning to Shiretoko, hoping to document the drift ice before it disappears. Every year from late January to early March, I spend about five weeks continuously photographing this ever-changing sea ice. Diving in Shiretoko is a battle against the bitter cold — water temperatures drop to -2°C, causing diving equipment such as the regulator to freeze up, and even the camera buttons can ice over. So why do I keep coming back to dive here under such grueling conditions?

The Spectacular World Beneath the Drift Ice

One of the most captivating aspects of ice diving is, without a doubt, the sheer scale of these ice sheets. They originate in the Sea of Okhotsk and drift along on wind and ocean currents. Along the way, the ice floes collide and grow larger, eventually reaching Shiretoko. The drift ice often piles up and overlaps, forming spectacular pressure ridges.

Diving beneath these enormous ridges is an absolutely thrilling experience. For me, one of the most rewarding things is photographing divers under the drift ice.

Lush Forests of Kelp

In the northern waters, dense kelp forests grow in abundance. Because kelp can absorb large amounts of carbon dioxide, it plays an important role in the concept of blue carbon. Beyond that, it serves as habitat, spawning ground, and feeding area for many fish species, supporting a rich marine ecosystem.

As someone who usually dives in southern waters, I feel an immense sense of excitement every time I descend into these kelp-filled seas. When ice diving, you even have the chance to capture drift ice and kelp together in a single frame — a truly unique and precious experience.

Ice Crystals

In the extreme cold of -2°C, some astonishing and beautiful natural phenomena occur. One of them is the formation of ice crystals; these crystals can take on needle-like or dendritic shapes, attaching themselves to drift ice, kelp, or other surfaces to create breathtaking scenes.

Beneath the drift ice, diatoms known as Ice Algae are also trapped within the ice. As spring approaches and sunlight intensifies, these algae photosynthesize and multiply rapidly. The drift ice, once a pale blue, gradually turns brown, completely transforming the underwater landscape.

Within the drift ice itself, highly saline water known as brine is also present. As it melts and seeps through the ice, it forms distinctive channels. If you're lucky enough to witness droplets falling from the tips of these channels, you'll have witnessed a truly rare miracle. These phenomena arise from a combination of specific conditions and are not visible at any given time, which adds to their mystique. Unfortunately, this year I was not able to capture this phenomenon on camera.

Marine Life Living in the Cold Seas

Although the cold northern seas may appear barren, they actually nurture an extraordinarily rich ecosystem. The Smooth lumpsucker and Lumpfish are prime examples. And I have a particular fondness for plankton — the northern waters are home to many fascinating creatures. Let me introduce a few:

Sea Angel (Clione)

The most beloved is the Sea Angel, often called the "ice angel of the sea." Its "wings" flutter as it drifts along the currents, creating an utterly charming sight.

Sea Butterfly (Limacina helicina)

Like the Sea Angel, the Sea Butterfly is also a planktonic drifter — and it happens to be the Sea Angel's favorite prey. However, the Sea Butterfly is among the first organisms to be highly sensitive to ocean acidification, which in turn makes survival increasingly difficult for the Sea Angel as well.

Brownbanded Moon Jelly

This jellyfish is primarily found in northern waters and can even be spotted in the deep sea. One of the largest jellyfish species, it can grow up to 25 cm across. It has previously undergone population blooms that caused problems for fisheries.

Lion's Mane Jellyfish

The bell of this jellyfish can reach up to 40 cm in diameter and features 16 lobes, eight of which are petal-shaped. It is highly venomous and will even attack and consume other jellyfish.

Drift Ice That Constantly Changes — As Though Alive

From the time the drift ice arrives until it melts spans about one month, and the transformations it undergoes during this period are truly astonishing. For example, as Ice Algae absorb sunlight and multiply en masse, the color of the drift ice shifts from blue to yellow, and eventually to a deep ochre-red.

In this photo, the yellow section at the top is Ice Algae — trapped within the drift ice, these algae absorb sunlight to photosynthesize and reproduce. As nutrients increase, large numbers of zooplankton such as copepods begin to appear, and the underwater world comes alive once more. These plankton attract fish such as salmon, which are in turn eaten by seabirds. Beyond that, salmon also migrate upriver, where they are consumed by forest animals; the nutrients are carried into the forest through their waste. And as salmon spawn and die, they are broken down by microorganisms in the river, cycling nutrients directly back into the sea.

The drift ice doesn't just change in color — its shape evolves too. When it first arrives, the surface is rough and jagged, but after prolonged exposure to sunlight, it gradually melts and becomes more rounded and smooth.

The drift ice also takes on entirely different appearances depending on the weather and temperature. When the air temperature plunges extremely low, beautiful ice crystals form on its surface. On sunny days, sunlight filters through the gaps in the drift ice and spills down to the seafloor in a spectacular display. When it snows, the snowflakes settle on the surface of the sea without melting — because the water temperature is lower than that of the snow — adding a pure white blanket over everything.

By staying for an extended period, you can witness a diverse range of phenomena; depending on when during the ice diving season you visit, you will encounter completely different scenes.

Things to Know Before Ice Diving

During ice dives, water temperature is around -2°C, and air temperatures can drop below -10°C — an extremely harsh environment. To stay warm, divers must wear heavy thermal undergarments, and weights must be increased accordingly, making movement both in the water and on land considerably more difficult.

Participating in ice diving requires at least 100 dives in a drysuit. If you have no prior experience, it is very important to receive professional instruction in advance — in particular, choose a dive shop that specializes in drift ice diving.

According to research from the Institute of Low Temperature Chemistry, drift ice will increasingly lose contact with the Shiretoko Peninsula; due to climate change, it may eventually no longer reach Shiretoko at all.

For that reason, I will continue to capture this magnificent sea on camera for as long as the drift ice remains.