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The lessons of Arctic ice floes

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Mark Robinson
Meteorologist

Sunday, April 6, 2014, 2:18 PM -


UNEARTHED: Catch tonight's premiere episode of "Unearthed" at 7 p.m. Eastern.


I sat in the very end of the bow of the Zodiac as it drove up and onto the floe. 

The massive chunk of ice bowed down slightly, almost as if it welcomed the sudden intrusion, but just as quickly rose back up and forced me to hop fast to avoid getting tossed off and into the icy water.  

As my boots hit the snow that lay in semi-compacted mass on top of the sea ice, I realized that I was suddenly at the mercy of the Arctic Ocean and whatever this chunk of frozen water decided to do. 

If the ice wasn’t bottom heavy enough it could easily roll over as my weight changed its balance. And that meant a sudden and icy swim for me. I’m a good swimmer, but getting back onto the Zodiac while immersed in water just above freezing is one of those things that isn’t high on the list of easy things to do.

Ice defines the polar regions. Everywhere you look in both the Arctic and Antarctic, the movement, creation, and destruction of ice shape the landscape. 

Sea ice builds up on the oceans as winter closes in; building up into sheets so thick even the most powerful ships in the world cannot break through. 

Across the land, snowflakes settle on high ground and slowly turn into the vast icy blue sheets that we call glaciers.  As spring arrives and the temperature rises, meltwaters run across the land, scouring out valleys and building deltas into the ocean. 

Across the rest of the planet, ice may not seem critical and yet, by some definitions, our Earth is still in the midst of an ice age. 

Greenland and the Antarctic continent still have permanent ice caps. Mountain ranges also retain their icy headdresses throughout the year and these glaciers are often important sources of water for civilizations downstream. Some of the largest river systems in the world have their headwaters being directly fed by glaciers (this includes the Amazon).

However, it’s the polar regions that are most associated with ice and here we can divide that ice into two main categories; sea and glacial. 

Both are frozen water, but they are formed in two vastly different ways and have strikingly different characteristics.

The ice that threatened to tip me over in the ocean was a block of sea ice, formed as salty ocean water froze during the dark, cold winter. 

In the far north and south, because even the summers tend to be cold, much of this ice survives as floes and small chunks even late into August.  

We again divide this ice into a couple of categories.  First year ice is new ice that forms in a given year while multi-year ice is comprised of the ice that survives the polar summer and undergoes another freeze cycle.  Most of the ice that we encountered was first year and was generally thin and broken into pieces that ranged from massive chunks the size of the Academic Ioffee to tiny pieces that we could drag on our Zodiac.  

Sea ice bleeds salt. Ok, not quite bleeds, but as the sea water freezes, the salt is squeezed out of it. The process is somewhat complicated, but essentially of it is that as the sea ice freezes, it pushes the salt out of the ice crystals. 

The salt forms a dense, cold brine that sinks downwards through the ice and into the open water below. An interesting aspect of this slat brine is that the saltier it becomes, the colder the temperatures that are needed to freeze it. In some cases, the water has to be below -20C before it freezes into ice.  

This dense, cold water continues sinking towards the bottom of the ocean and when applied on a vast scale it has critical implications for the climate of earth. As the cold water sinks, it moves along the bottom of the ocean and can create vast, deep currents of cold water.  When this occurs along the ice sheets off Antarctica, the volume of moving water dwarfs the flow of every river system on earth and is critical for moving energy across the planet.  This in turn drives the climate and weather systems everywhere. 

Sea ice, especially multi-year ice is critical to the ecosystems of the polar regions. 

In the north, the basis of much of the food web is concentrated around the sea ice. 

Algae grows underneath the water on the ice, which is in turn eaten by simple crustaceans, which are consumed by fish, which are fed upon by seals, and then finally the seals are predated upon by polar bears. As multi year ice becomes more rare, this ecosystem is easily disrupted with the resulting loss of even top predators in the web.

Glacial ice is formed in a completely different and much slower manner than sea ice.  Snowflakes, pressure and time are the key ingredients needed for glacial ice.  Most importantly, glaciers only form in places that remain below freezing through the summer months.  Thus, the Arctic, Antarctic and high mountain tops are now the only places on the planet in which glaciers can form. 

As layers of snow build up year after year, the lower layers become increasingly compressed by the weight of the snow above.  

After a long period of time, this mass of slowly forming ice becomes more and more dense, eventually culminating in massive, basketball sized crystals of dense, blue ice. Given enough time (in the thousands of years), the depth of ice can range into the hundreds of feet.

Glaciers are not static. In fact, to understand how they move, they must be looked at as if they were flowing rivers. Which is pretty much exactly what they are; vast, slow moving rivers of ice. 

And these rivers do the same erosion job on the landscape that liquid water does, but much more slowly.  Glaciers carve out massive U-shaped valleys, transport gigantic boulders hundreds of miles from their starting point and deposit huge amounts of gravel and sand to the very tip of the ice river. 

The resulting landscape is familiar to anyone who has spent time in areas even as far south as Southern Ontario.

However, ice is fragile and we are watching fundamental changes happen far quicker than anything we can find in the recent geological record. 

The rapid shift in the climate of the planet is having a drastic effect on the ice in the Arctic region, especially sea ice. As the Arctic ocean warms, multi-year ice is becoming more rare as less and less ice survives from year to year. The resulting change in the ecosystems is having an effect on everything from krill right to up to the Inuit who still rely on hunting to provide day-to-day nourishment. 

The rapid melting of glaciers threatens the agricultural systems of huge numbers of people in Asia and even North America. And these changes are happening fast. The big question is whether or not we can adapt to the change and loss of these critical systems.

All of these changes were less distant that you might have imagined as I stood on that ice floe in the Arctic Ocean.   

All around me I could hear the steady dribble of water into the sea as the sun beat down on the ice and snow around me. Even though the ice never did flip over and send me into the icy blue, that trickle reminded me that it was really only a matter of time before my platform disappeared back into the water from where it came. And that eventually, even the vast ice sheets of the polar regions could suffer the same fate. 

And there won’t be a Zodiac there to rescue our civilization before the ice is gone.

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