The life of an iceberg begins thousands or even tens of thousands of years before it reaches the ocean

 

I saw my first iceberg in 2004 on a voyage into the Southern Ocean. It was a pristine experience that I will never forget. The entire trip included South Georgia Island, the Falkland Islands, and Antarctica. I was so enthralled that I did it all over again in 2007.  The iceberg, to me, is a symbol of the wonderful adventures I experienced in the Southern Ocean.

To describe icebergs, one must first talk about coastal glaciers. A glacier is a massive land-based slab of ice and snow that can be hundreds of miles long and thousands of feet thick. The life of an iceberg begins thousands or even tens of thousands of years before it reaches the ocean. Glaciers build layer upon layer of ice – compressing the deeper ice into a particularly dense form.

Glaciers “flow” downhill at a very slow rate under the force of their own weight. A coastal glacier can eventually reach the ocean. At the coast, the ice extends out beyond the land, floating on the water and forming an ice shelf. The weight of the ice combines with tidal motions raising and lowering the shelf to create fissures in the ice. Eventually, a chunk of ice will separate from the glacier, a process known as calving. The calved ice, called an iceberg, can have very irregular shapes, like mountains of ice, or they can be flat with steep sides, like a plateau of ice. Once it calves, an iceberg can live for three to six years.

Ice is unique among solids in that it is the only solid that’s less dense than the liquid phase of the same material. This reduces the density of ice. That is why icebergs float.

Icebergs generate their own mobile ecosystems. Many connections in Nature are evident through the food chains that develop. For example, young icefish hide in small iceholes to avoid predators. A variety of invertebrates, like jellyfish and siphonophores , congregate near the iceberg. Many of these organisms come to feed on tiny shrimp-like creatures called krill. Snow petrels nest on the icebergs and feed on the sea life nearby.

Icebergs can have a negative impact on ocean and animal life as well. When massive Antartctic  ice bergs get stuck in certain areas, they block the migration  path of Emperor penguins. The penguins need to get to the ocean to feed. With too many icebergs in the way, they have to walk much farther. In areas where oceanic currents bring many icebergs, the ocean floor is often blasted clear of all life. The huge ice chunks extend deep under water, scraping and gouging the sea floor. Over the course of many years, these impacts render the sea floor almost completely lifeless.

The story of icebergs, then, is a story of connections in Nature that start with the sun’s energy driving Earth’s atmosphere to form snow. Over many years, the connected pathways include the harboring of life and end when the iceberg melts and water molecules are returned to the ocean and the atmosphere.

Worth Your Extra Attention 

Why do scientists study icebergs? (Quoted from the National Snow and Ice Data Center).

Climate scientists study icebergs as they break up for clues to the processes that cause ice shelf collapse. Scientists have noticed that the way icebergs break up when they reach warmer waters mirrors the disintegration of Antarctic ice shelves. By studying the factors that cause icebergs to break up, researchers hope to better understand the influences that lead to ice shelf breakup, and to better predict how ice shelves will respond to a warming climate.

Oceanographers follow icebergs because the cold freshwater they contribute to the sea can influence currents and ocean circulation far away from their origins.

Biologists study icebergs to find out how they influence ocean life.  As icebergs melt, they leak nutrients into the ocean around them. Recent studies have shown that the water surrounding icebergs teems with plankton, fish, and other sea life.

To learn more about a recent NSIDC study on iceberg breakup, see the IceTrek Web site

 

Why Do I Write These Essays?

 

  

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