Kuroshio Impact
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Kuroshio Impact

Published
November 22, 2021
Category
Message in a Bottle

When scuba divers take a look at Japan on a map, there are some very obvious indicators that this island country likely has some amazing diving! I mean look at the endless coastline (29,751 kilometers to be exact). There is the Sea of Japan, the Sea of Okhotsk, the East China Sea, and the Pacific Ocean all surrounding the country. Not to mention all the islands that span over 300- kilometers! Japan might not advertise diving as a top reason to visit the country, but seasoned divers can imagine the waters of Japan must have a lot to offer.

The truth is, there is more going on in the waters of Japan than we could even imagine. There is a huge variety of diving from drift dives to shore dives, wreck dives to cave dives, and ice dives to tropical dives. Japan has it all! Much of the diversity in Japan is made possible by some interesting currents swirling around under the surface. Let’s take a deep dive into what makes Japan diving so unique!

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Types of Diving in Japan

As we mentioned, Japan has a little bit of everything when it comes to diving! That being said, it would be impossible to do all of this in one trip. The different kinds of diving you can do in Japan are spread throughout the country. When you’re looking into your next dive trip, check what time of year it is and what the best diving available is for that time frame.

Coral Diving: The warm waters of the Kuroshio Current have created the conditions for one of the highest latitude coral reefs in the world. It has created a home for tons of colorful, tropical fish. You can dive on fringing reefs, barrier reefs, and even one raised atoll. There are over 400 species of coral in Japan.

Cavern Diving: The Blue Cave is a popular diving and snorkeling destination that gets its name from the glowing blue color of the water. There are many other caverns in the surrounding areas of Miyako Island for divers to explore as well.

Wreck Diving: Check out one of Japan’s most popular dives at the USS Emmons Shipwreck. It was sunk after being destroyed by Japanese kamikaze. There are many other sunken ships from World War II in the waters of Japan that wreck enthusiasts can enjoy.

Ice Diving: If you’re willing to brave the cold, you can dive beneath the frozen sea off of Hokkaido’s Shiretoko Peninsula. The ice drifts south all the way from Russia! You’ll be able to spot some unique species here that are not found in other parts of Japan. You will have to dive in a dry suit thanks to the negative temperatures here.

Drift Diving: We’re going to discuss the currents that affect Japan in this article, so you won’t be surprised to find out there are drift dives available here. One drift dive in Yonaguni Island offers a drift dive to see school hammerheads!

The Biodiversity of the Waters of Japan

The sea life in Japan is just as diverse as the types of diving thanks to the hot and cold currents that converge off the northeast coast. The Kuroshio Current brings warmer-water fish to Japan from the south while the Oyashio Current brings cold-water species down from the north. Depending on the temperature of the waters and the location and depth of the dive site, there is a huge array of sea creatures that you might be able to encounter while scuba diving.

Okinawa is known to have some of the best diving in Japan thanks to its coral reefs and subtropical waters. Here you’ll find a variety of tropical fish and maybe larger species like schools of tuna, hammerheads, or whale sharks. At sites such as Miyako Island, you can swim with sea turtles. Head to Ishigaki Island and you can swim with many divers’ favorite, the manta ray. Dedicated divers can take the long ferry to Chichijima, known as the “Galapagos of the Orient.” If you’re lucky, you can see whales, dolphins, reef sharks, and rays.

The variety of sea life in Japan includes bioluminescent creatures, sea kelp, giant jellyfish, glowing jellyfish, basking sharks, giant squid, sea lions, seals, and even orcas. In fact, according to the Japan Agency for Marine-Earth Science and Technology, despite only making up a very small portion of the world’s oceans, you can find 14.6% of global marine species in Japan. Including everything from bacteria to mammals, 33,629 species have been reported.

Kuroshio Current

One of the biggest factors of the marine biodiversity and subtropical waters that you can find as far north as Japan is the Kuroshio Current. This major ocean current brings warmer water from the tropics further north at a rapid speed of about two meters per second, according to Eos. The current is so warm and void of nutrients that it creates a dark blue color which can be seen from satellite images. This current has a huge effect on the waters surrounding Japan as well as the entire North Pacific Ocean.

The warm, salty waters of the Kuroshio Current support one of the furthermost north coral reefs in the world. Large pelagic fish will hitch a ride north for spawning and migration purposes. The current, combined with the steep volcanic underwater topography, can cause upwellings that bring deep-sea creatures closer to the surface.

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Kuroshio’s Effect on Weather and Climate

The Kuroshio Current affects temperatures and humidity levels in Japan. The current distributes heat from the equator up through the Northern hemisphere. As the current brings warmer waters north, the heat of the ocean surface affects the air temperatures. It also affects precipitation patterns and typhoon paths thanks to the moisture that’s evaporating into the atmosphere.

There is also variability in the behavior of Kuroshio. Scientists believe that this variability is responsible for “climatic discomfort” in Tokyo. The major current has been known to stray from its original path, creating a “large meander” from 2004 to 2005 and again since 2017.

Because of the new path the current is taking, a greenhouse effect caused by the increased evaporation has resulted in a temperature increase in the Kanto district. According to TOHOKU University, summers with large meanders have a 160% increase in days of people experiencing discomfort due to temperature and humidity.

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Carbon Dioxide Absorption

According to Eos, recent studies show that the Kuroshio Extension absorbs carbon dioxide from the atmosphere and sends it deep into the ocean. This might be due to the warm waters being cooled as they head north, increasing their ability to absorb carbon dioxide. Others think it might be caused by the mass amounts of phytoplankton photosynthesis that takes place here. Regardless of what is causing this absorption, scientists will need to study and observe the overall effects on climate.

Other Currents Affecting the Japanese Waters

As the Kuroshio current reaches Japan, it splits into the Kuroshio Extension, which continues around the east side of the country to meet the Oyashio current, and part the Tsushima Current, which heads to the western coast of Japan. The extension eventually becomes the North Pacific West Wind Drift.

Another reason that Japan is such a hotbed of marine biodiversity is the Oyashio current which brings cold, nutrient-dense waters from the north to the south. The Oyashio Current is also known as the “parent current,” thanks to the life-giving nutrients it carries. The nutrients stem from it being an upwelling current which brings lots of nutrients up from the seafloor.

Both of these currents have a large effect on the ecosystems and climates of Japan. The area where they converge is known as the Kuroshio/Oyashio Transition Zone. This area of the ocean is extremely dynamic when looking at sea surface temperature, eddy activity, sea-surface heights, and heat loss.

Japan - A Unique Ecosystem Perfect for Diving

The unique system of currents that surrounds Japan mixed with the underwater topography caused by Japan’s volcanic nature has created a unique ecosystem different than anywhere else in the world. With a combination of the warm, saline Kuroshio current meeting the cool, nutrient Oyashio current, there’s biodiversity in Japan you likely won’t find anywhere else in the world.

Not only does Japan offer a diverse array of marine life, but there are also different types of dives available for all interests. There aren’t many places where you can dive a coral reef and underneath the ice in the same country! No matter what you’re into, whether it’s wrecks or caves or sharks, you’ll be able to find a dive site that will have you grinning from ear to ear! From new divers to experienced pros, you’ll love diving in Japan.

Further Reading

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