People usually think of the ocean as this bottomless, terrifying void. We’ve all seen the documentaries about the Mariana Trench where weird, bioluminescent fish float through crushing pressure. But when you ask how deep is the arctic ocean, the answer is actually a bit of a curveball. It’s the smallest and shallowest of the world's five major oceans. In fact, if you compared it to the Pacific, it’s basically a wading pool.
That doesn't mean it’s shallow like a lake, though. Not even close.
The Arctic Ocean covers about 5.4 million square miles. That is roughly the size of Russia. While it is technically the "shallowest" ocean, it still drops down into some seriously dark, icy territory that we are only just beginning to map with any real accuracy. Most of the water sits over the continental shelf, which is why the average depth is only about 3,953 feet (1,205 meters). For context, the Atlantic Ocean is more than double that on average.
It’s a weird place. Honestly, the geography of the Arctic floor looks less like a smooth basin and more like a crumpled-up rug. You have massive underwater mountain ranges, like the Lomonosov Ridge, which literally split the ocean floor in half.
Getting Specific: How Deep is the Arctic Ocean at Its Lowest Point?
If you want to find the deepest spot, you have to head toward the Fram Strait. This is the gap between Greenland and Svalbard. Down there, hidden under layers of shifting sea ice, is the Molloy Hole.
It’s deep.
The Molloy Hole hits a depth of roughly 18,210 feet (5,550 meters). To put that in perspective, if you dropped the tallest building in the world—the Burj Khalifa—into the Molloy Hole, you’d need to stack nearly seven of them on top of each other just to reach the surface. It’s a bathymetric anomaly. Most of the surrounding area is nowhere near that deep, but this one specific trench just plunges.
Victor Vescovo, an explorer who basically makes a living diving into the deepest parts of the planet, reached the bottom of the Molloy Hole in 2019 during the Five Deeps Expedition. Before his dive, we had some rough sonar data, but we didn’t really know what was down there. It’s a desolate, silty basin where the water is near freezing.
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Beyond the Molloy Hole, the Arctic is divided into two main basins:
- The Eurasian Basin, which is the deeper side.
- The Amerasian Basin, which is a bit shallower and more complex.
These two are separated by that Lomonosov Ridge I mentioned earlier. This ridge is a 1,100-mile-long underwater mountain range. It’s a point of huge geopolitical tension right now because Russia, Canada, and Denmark all claim it’s an extension of their continental shelves. Why? Because whoever owns the ridge might own the rights to the massive oil and gas reserves buried under the seabed.
The Continental Shelf: Why the Arctic is Mostly "Shallow"
So, why do we call it the shallowest ocean? It’s because of the shelves.
The Arctic has the largest continental shelf of any ocean on Earth. Specifically, the Siberian Shelf is massive. It extends nearly 900 miles out from the coast of Russia. In many parts of the Siberian Shelf, the water is only 100 to 650 feet deep. You could almost say the Arctic Ocean is like a very deep bowl with a massive, flat rim.
This shallow rim is where all the action happens.
Because it’s shallow, sunlight can sometimes reach closer to the bottom in certain areas, fueling a burst of life during the summer months when the ice retreats. It’s also where the sea ice interacts most heavily with the land. When we talk about how deep is the arctic ocean, we’re often talking about these massive expanses of relatively shallow water that are incredibly sensitive to climate change.
If the water were deeper, it might be more stable. But because it’s shallow, small changes in water temperature can have massive effects on the permafrost buried beneath the seafloor. There’s a lot of methane trapped down there. If that methane escapes because the "shallow" water is warming up, it’s bad news for the global climate.
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Understanding the Layers
The Arctic isn’t just one big bucket of cold water. It’s layered like a cake.
- The Surface Layer: This is the top 150 to 200 feet. It’s the least salty because of all the melting ice and the massive rivers from Russia and Canada pumping fresh water into it.
- The Halocline: Below the surface, there’s a layer where salinity increases rapidly. This acts as a barrier, preventing the warmer, deeper water from rising up and melting all the sea ice.
- The Deep Water: This is the stuff that sits in the basins. It’s incredibly cold, very salty, and hasn’t seen the surface in hundreds of years.
The Challenges of Measuring Depth in the High North
Mapping the depth of the Arctic is a nightmare. Truly.
In the Pacific or Atlantic, you can just sail a ship with a multibeam echosounder and map the floor. In the Arctic, there is a giant, moving lid of ice in the way. For decades, our best data came from Cold War-era submarines. These subs would cruise under the ice, using sonar to make sure they didn't crash into underwater mountains (seamounts).
We’re still finding things.
Just a few years ago, researchers discovered a "hidden" field of hydrothermal vents in the deep Arctic. These are essentially underwater volcanoes that spew mineral-rich water at 600 degrees Fahrenheit. It’s wild to think that in an ocean we’ve "mapped," we’re still finding giant volcanic structures.
The International Bathymetric Chart of the Arctic Ocean (IBCAO) is the gold standard for this data. They’re constantly updating it. The latest versions show that the ridges and valleys are far more rugged than we previously thought. It’s not just a flat mud floor. It’s a landscape of jagged peaks and deep, narrow canyons.
Why Depth Matters for Modern Travel and Shipping
You might be wondering why anyone except a scientist cares about how deep is the arctic ocean.
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The answer is shipping.
As the ice melts, the "Northern Sea Route" along the Russian coast is becoming a viable shortcut for ships traveling between Europe and Asia. But because the Arctic is so shallow—especially along those continental shelves—large tankers have to be incredibly careful. One wrong move and they hit the bottom.
There are "choke points" where the water depth is barely enough for a modern cargo ship.
Furthermore, cruise ships are now venturing further north than ever before. In 2016, the Crystal Serenity was the first large luxury cruise ship to traverse the Northwest Passage. These ships rely on depth charts that are, in some cases, still based on data from the 1800s or early 1900s. It’s risky. Exploring the Arctic is still very much a "frontier" activity, even with modern GPS.
Final Practical Takeaways on Arctic Depth
If you're looking for the "too long; didn't read" version of Arctic bathymetry, here it is.
The Arctic is a basin of extremes. You have the Molloy Hole at 18,210 feet, which is terrifyingly deep, but you also have millions of square miles of water that wouldn't even cover a skyscraper.
- Average Depth: 3,953 feet.
- Deepest Point: Molloy Hole (approx. 5.5 km deep).
- Primary Feature: The Lomonosov Ridge (divides the ocean into two).
- Shallowest Feature: The Siberian Shelf (the widest continental shelf on Earth).
Understanding these depths is the only way to predict how the ocean will react to a warming world. The less water there is (shallowness), the faster it heats up.
If you're planning on following Arctic exploration or even looking into an Arctic cruise, keep an eye on the bathymetry. The seafloor here isn't just mud—it's the foundation of a global climate system and a burgeoning trade route. To get a better sense of this, check out the latest maps from the Intergovernmental Oceanographic Commission (IOC). They provide the most detailed visual representations of where the deep basins actually lie.
Start by looking at the Fram Strait. It’s the primary gateway where the deep Atlantic water meets the Arctic, and it’s arguably the most important few hundred miles of water on the planet right now. Monitor the bathymetric updates from the Nippon Foundation-GEBCO Seabed 2030 project, which aims to have the entire Arctic floor mapped in high resolution by the end of the decade.