How to Safely Dive
an Iceberg

Every iceberg in Greenland began as snow on the Greenland Ice Sheet. Over thousands of years, that snow compressed into glacial ice and flowed toward the coast through outlet glaciers, where it broke off, or calved, into the sea. Where we find icebergs on any given day depends on the route, currents, prevailing winds and weather.

Northern Route: Disko Bay

Most of the icebergs in Disko Bay come from Sermeq Kujalleq (Jakobshavn Isbræ). Moving about 40 m (130 ft) a day, it is one of the fastest and most active glaciers in the world. It calves into the Ilulissat Icefjord, a UNESCO World Heritage Site, and produces about 10% of Greenland’s icebergs, more than any other glacier outside Antarctica. Many of the largest icebergs sit grounded at the mouth of the fjord before drifting out into Disko Bay.

Southern Route: Ice From the East Coast

Much of the ice we find in the south comes from Greenland’s east coast, where Helheim and Kangerlussuaq are the ice sheet’s highest-discharge glaciers after Sermeq Kujalleq. Thousands of large icebergs calve from east coast glaciers every year. The East Greenland Current carries them south around Cape Farewell, and the West Greenland Current brings some of them north along the southwest coast.

Most of an iceberg is underwater, and that’s where its most interesting features are. Here’s what to look for.

The Ice

Below the waterline, melting and current shape the surface of the ice. Look for scalloping, rows of shallow, rounded hollows carved as water flows along the ice, along with lines, ridges and layers. Color ranges from bright white to deep blue. Ice packed with tiny air bubbles scatters light and looks white. Dense ice with few bubbles absorbs red light and looks blue. Where the ice is thinner, sunlight passes through it and the ice appears to glow.

The Life

Where meltwater mixes with seawater, plankton gathers, and small animals follow. Look for:

• Sea angels (Clione limacina): small, translucent swimming sea slugs that hunt sea butterflies.
• Sea butterflies (Limacina helicina): tiny swimming snails, the sea angel’s main prey.
• Comb jellies (Mertensia ovum): rows of beating cilia that scatter light into a moving rainbow.
• Arctic jellies (Aglantha digitale): small, reddish jellyfish.
• Mysid shrimp, amphipods and drifting plankton.
• Near the seafloor: sculpins and Arctic shanny.

Tunnels and Caves

You may see tunnels and ice caves. We view and photograph them from outside. We never enter them.

Visibility

Visibility is often 10 to 15 m (30 to 50 ft). It’s lower deep in the fjords and better in open water, and it changes with meltwater sediment, nutrients, surrounding icebergs and water conditions. Visibility can be excellent on one side of an iceberg and noticeably lower on the other.

Icebergs are classified by shape, and shape tells us a lot about stability. Two risks matter most to a diver:

• Rolling: the iceberg shifts or turns over as melting changes its balance.
• Calving: a piece of ice breaks off the iceberg.

Ratings reflect how our team assesses each shape before a dive.

Why We Look for Low Tabular Icebergs

About 90% of an iceberg sits below the waterline. Its stability depends on how wide it is compared with its full height, above and below the surface. A tabular iceberg’s broad, flat profile keeps its center of gravity low, so it is the least likely to roll or calve.

Shape alone isn’t enough. A tall tabular iceberg can still be unstable, so we look for icebergs that are wide and low. As a rule of thumb, we want an iceberg several times wider than its height above the water. Occasionally a broad, low blocky iceberg meets that standard. Domes, wedges, pinnacles and dry-docks do not.

Rams

A ram is an underwater shelf of ice extending out from the base of an iceberg, sometimes visible as a pale “foot” just below the surface. It forms when the ice at the waterline melts and erodes faster than the ice below. A ram is buoyant ice held down only by its attachment to the iceberg. If it breaks off, it can rise quickly and with great force, and losing it can shift the iceberg’s balance enough to cause a roll. A ram’s full size also can’t be judged from the surface.

Cracks, Fissures and Overhangs

We also look for cracks and fissures, ice weakened by melting, overhangs and signs of recent change, such as fresh, clean fracture faces. These don’t automatically rule an iceberg out. A small overhang that looks solid can be noted in the briefing and avoided. Each one informs our decision, and a large overhang or a combination of warning signs means we move on.

Grounded Icebergs

An iceberg resting on the seafloor can look anchored and stable. In Greenland, it often isn’t. Tidal changes here are dramatic. As the tide drops, more of the iceberg sits above the water. Melting at the waterline can leave a grounded iceberg unstable, held in place only by the seafloor until a rising tide lifts it free. If a grounded iceberg rolls, a diver could be caught between the ice and the bottom. We treat grounded icebergs as less stable than those floating freely.

Finding the right iceberg is part of the diving and expedition experience. We sail among the icebergs looking for one that is safe to dive. It’s a team effort between the captain, crew and divers. The search can take some time, but the scenery alone is worth it.

1. Scan the horizon. We look for low tabular icebergs in open water.
2. Circle it. We inspect the iceberg from all sides. We study its shape above the water and look for rams, overhangs, cracks and anything else that could compromise the dive. Then we choose entry and exit points.
3. Check the neighbors. We assess surrounding icebergs that could drift, shift, roll or calve nearby. If a neighbor could become a hazard, we move on.
4. Check the weather. We don’t dive icebergs in storms or high wind. Wind and waves increase the chance of calving and rolling, and make diving near an iceberg unsafe. In poor weather, we look for protected water and a safe alternative, either another iceberg or a wall dive.
5. Check visibility. We assess water clarity from the surface before anyone gets in.
6. Brief the dive. Before every iceberg dive, we brief the iceberg’s contour, potential hazards, entry and exit points, team directions and signals. Small overhangs are identified and avoided. A large overhang can mean we don’t dive that iceberg at all.

Entry

Divers enter the water from the ship or a RIB (rigid inflatable boat), a short distance from the iceberg. Each team swims on the surface toward the iceberg, checks gas and equipment, and confirms its direction of travel. The team also notes its compass heading, so it can stay oriented to the ship. Then the team descends together, away from the iceberg, and approaches it underwater.

Distance

Stay about 3 m (10 ft) from the iceberg and don’t touch it. Maintain full situational awareness of your team, the iceberg and your surroundings: ahead, above and below.

Teams

Divers dive in teams of 3 to 4, including the dive guide, staying within 2 to 3 m (6 to 10 ft) of each other. Teams enter the water at intervals and split up around the iceberg: one or two swim clockwise, the other counterclockwise. Each team descends and ascends together.

Depth and Time

You don’t need to go deep to enjoy an iceberg. In polar water, and given the remote nature of our expeditions, we dive conservatively. Maximum depth on an iceberg dive is generally 20 m (65 ft), and most of the features worth seeing are between 5 and 15 m (15 and 50 ft). Maximum dive time is 60 minutes.

Ending the Dive

Each team ends its own dive. The team confirms it is ending the dive, then swims about 30 m (100 ft) away from the iceberg, on the side facing the ship. Deploy a surface marker buoy (SMB), one per team when the team is together, complete your safety stop and surface. Never ascend alongside the ice.

Exiting the Water

The RIBs wait between the iceberg and the ship and watch for SMBs. Track your direction and compass heading throughout the dive, so you surface where the crew can see you, between the ship and the iceberg.

Most divers know a halocline as a mostly still, visible layer where fresh and salt water meet. Around an iceberg, it behaves differently.

When air and water temperatures are above freezing, meltwater runs off the iceberg and into the sea. Sometimes you can see it from the surface. Often you can’t. Underwater, that fresh water mixes into the sea in plumes, and on a large iceberg the volume can be significant.

Fresh water is less dense than salt water, so moving between the two changes your buoyancy. Swim into a fresh water plume and you lose buoyancy and start to sink. Swim back into salt water and you gain buoyancy and start to rise. Near an iceberg, the change can be significant and come without warning, and you can pass from salt water into fresh water and back in a matter of seconds. Unless you’re watching the ice or another fixed reference, you may not notice. We recommend swimming with your dive computer in plain sight and checking it often.

For most divers, the first iceberg plume is a surprise. Be ready for it:

• Keep your computer in view and check your depth often.
• Be prepared to add or vent gas quickly in your drysuit or wing. You may swim out of the plume as quickly as you swam into it.
• Know your configuration. Your inflator and dump valve should be where your hands expect them. That’s true for all diving, and especially here.

Icebergs have a voice, and they often speak to divers. As the ice melts, air trapped in it thousands of years ago escapes as a steady fizz and crackle.

You may also hear a bang, or several. It may be the ice cracking or shifting inside. It’s not uncommon to hear them on our dives. Here’s what to do.

We choose icebergs that minimize the chance of a roll, and we prepare for one anyway. If you see the iceberg begin to move, remain calm and act as a team.

Like wrecks and caves, iceberg diving carries inherent risk. Careful selection, clear protocols and experience manage it. Our team dives icebergs every season, and every dive follows the same steps described here.

What you get in return is one of the most remarkable experiences in diving: hovering beside ice that fell as snow centuries or millennia ago, in light that seems to come from the ice itself.