The Way of an Iceberg

Imagine you are standing on the Greenland ice cap about 10,000 years ago. Snow is falling. The cold is penetrating. In fact, over a full year, it’s so cold that the snow accumulates faster than it melts, and hence the icefield grows. If you could see this in time-lapse over thousands of years, you would see the icefield thicken and spread. Where the outer edge of the icefield meets with lower ground, the ice creeps downhill as a glacier.

This slow-moving ice river gradually slips down through a valley, eventually meeting the ocean. There, the toe of this glacier forms a thick overhang undercut by the sea, making this one a tide-water glacier. Other glaciers that melt away before reaching the sea don't produce icebergs. Pressure from the weight of the ice above, wave action from the sea, and warm temperatures in the summer cause the ice to break off in an explosive event called calving.

Finally, an iceberg is born, about 10,000 years after the snow first fell around your feet at the ice cap. It floats low in the water, with eighty to ninety percent beneath the surface. (Hence the expression, “That’s just the tip of the iceberg!”) Pushed by wind and current, its seaward journey now begins.

In west Greenland, most icebergs are produced by Sermeq Kujalleq, a hyperactive glacier that meets the sea near the town of Ilulissat. It produces about ten percent of all Greenland’s icebergs—more than any other site in the Northern Hemisphere. The bergs calve into a fifty-five-kilometre-long fjord that terminates with a shallow, undersea moraine, which acts like a dam to the bergs. The biggest ones run aground blocking the passage of all the others behind, so the fjord fills up with gigantic blocks of ice.

Only when these largest ones at the fjord’s mouth melt enough, or when the pressure from behind is great enough, do they break up and float over the moraine into Disko Bay. The whole phenomenon is so singular and compelling that the Ilulissat Icefjord has been designated as a UNESCO World Heritage Site.

The icebergs that calve into the waters off west Greenland first float north, carried by the dominant current. As they reach the north end of Baffin Bay, they are swept westward into Canadian waters, picked up by the southward flowing current, and gradually move down the coast of the Arctic islands, Labrador, and eventually Newfoundland. The full journey might take two or three years, with the bergs freezing into the ice pack each winter.

About nine out of ten icebergs that reach Newfoundland waters, in the area known as iceberg alley, come from west Greenland, while the rest originate from the Canadian Arctic. Once in warmer waters, the icebergs melt and eventually disappear, but usually this is not a quiet and gentle process like the melting of the ice-cubes in your summer libation.

The submerged ice generally melts faster than that above the waterline. As it melts, the centre of gravity shifts, which disrupts the forces holding the berg together. It might tip, then rock, and sometimes flip over entirely. It can even explode, sending great shards of ice into the air as though the iceberg was just hit by the shell of a giant cannon.

The whole process is called foundering, at least in Newfoundland and Labrador. Even if you were standing on land many kilometres away from an iceberg, you would hear the tell-tale, thunder-like boom and know an iceberg has foundered.

Many icebergs are so large that they become grounded even in water that is tens of metres deep. They become stuck until they melt away or break up further and then drift off again. The Grand Banks off Newfoundland, anywhere from fifteen to ninety metres deep, is scoured with criss-crossing trenches as though ploughed by a drunken farmer, caused by large icebergs running aground.

Sometimes you see an iceberg with remarkable, turquoise bands running through it. They might be a few centimetres wide or even a metre or more. These formed when the iceberg was still within the glacier and meltwater ran into cracks. When that water refroze, it had no air in it—unlike the surrounding body of the glacier, which contains a lot of air because it formed from compressed snowflakes.

Some icebergs are mostly blue. As the ice builds up in a glacier, the bottom layers are so highly compressed by the weight of ice above that the air is squeezed out. This ice will appear blue because there are no air bubbles left in it. This is very old ice from near the bottom of the glacier.

The detailed texture of an iceberg surface can be fascinating. Often a series of narrow, parallel furrows appears as though the berg has been scraped by a set of teeth or prongs. Sometimes these can be drag marks where the underside has been scratched by the sea bottom, but they can also be bubble tracks that form as the compressed air in the iceberg escapes below the waterline and rises in straight lines to the surface.

If you are close enough, it sounds like seltzer. Over time, they etch the parallel tracks into the ice. If the iceberg tips or rolls, then these bubble tracks appear above sea level and each forms a little valley for melt water that etches deeper into the surface.

After a berg has been floating for a while, the seawater melts the ice from below, creating a small shelf parallel to the water level. If the centre of gravity changes, the iceberg tips and this shelf will then run at an oblique angle to the water level, as another shelf begins to form in the new position. In this way, you will sometimes see icebergs with a number of straight ridges running at a slight angle to one another. These indicate the former water line and tell you that the berg has tipped from an earlier position on water.

Icebergs come in all sizes, starting with growlers that are up to about two metres across and about a metre above water, so named because they can come very close to the shoreline where you could hear them scrape along the bottom. Next up are bergy bits about the size of a small cottage. From there on, you have the unimaginatively named small, medium, large and extra-large, which can be anything over seventy-five metres tall and two hundred metres across.

But even that does not hint at the biggest icebergs that can be larger than some Caribbean islands. Christened B-15, the world’s largest iceberg (so far) broke from Antarctica’s Ross Ice Shelf in 2000 and was over 10,000 square kilometres, about twice the size of Prince Edward Island.

As icebergs come in many sizes, so too do they have many shapes and associated names. They fall into two broad categories: tabular and non-tabular. Tabular icebergs calve from ice shelves, so they are flat-topped with roughly vertical sides. Non-tabular bergs are irregularly shaped, having calved from tide-water glaciers. Pinnacle icebergs have one or more spires, while dome-shaped icebergs are rounded, usually from having spent a long time in the water.

Bergs can be blocky, arched, wedge-shaped, and even have an eroded slot or channel, often called a dry-dock iceberg. You might think of icebergs as lifeless blocks, but they create mini ecosystems around their floating bases. Bergs that calve from the bottom of a glacier bring gravel and soil from the land into the sea, thus adding nutrients. Their physical movement scrapes the seabed, stirring nutrients into the water column. Melting freshwater from the iceberg, as well as the movement of the berg itself, generate small upwelling currents.

All this water movement creates an environment good for phytoplankton and zooplankton that then become food for plankton-feeding fish. In areas where icebergs are large and plentiful, like the Ilulissat Icefjord, whales and seals are attracted to the surrounding waters because they can herd and corral fish against the submerged walls of ice—all the better to get a good mouthful.

From Greenland to Canada’s Arctic islands, from Labrador to Newfoundland, all are great places to witness the spectacle of icebergs from their genesis to their final melt. Much like whales, the sight of them never gets old. To cruise alongside a glimmering iceberg in a Zodiac, always at a respectful distance, is simply one of life’s great moments.

I’ve seen thousands upon thousands, but when a new one comes into view, I’ll be one of the first on deck so as not to miss it. It’s always an emotional experience, stirring up both awe and humility, when one thinks about how these spectacular, gargantuan beauties were formed by gently falling snowflakes thousands of years ago.