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On the edge of the Arctic circle spring has us guessing

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Stephen Marsh Stephen Marsh | 12:49 UK time, Tuesday, 3 May 2011

d ~ 316'454'400: day 123

The 23 Degrees team are heading back out to Northern Canada on the edge of the Arctic Circle. The last time we were out there it was mid-winter and it was 35 degrees below zero. That's seriously cold. On that trip we were learning why Yellowknife was the coldest city in America, and why mid-January is the coldest period in the northern hemisphere. This time we are there to discover what happens when the Sun warming rays finally reach this northern territory.

Frozen stream, northern territories

For most of the northern hemisphere spring arrives gently, think of beautiful flowers blooming, blossom bursting, trees greening and animals starting to mate. But the 23 Degrees team are about to learn that up in the northern territories spring comes with a bang.

We are travelling to the Hay River which flows towards the Great Slave Lake. During winter the Hay river is a major highway linking Yellowknife with the outside world. The frozen river becomes a three-lane highway for the ice road truckers to ship in supplies. But from April the days are getting longer and more and more solar energy is arriving, warming the ice. Now for most rivers this is not a big deal, the ice melts and the river flows. But not the Hay River because unusually it flows south to north, and that makes a big difference. Because of the planet's tilt the warming Sun's rays hit the headwaters of the river in the south first, while downstream in the north there's little sun so it stays really cold. This means that the upstream part of the river thaws first while the downstream section of the river stays frozen.

Once the ice upstream melts and breaks up it starts to flow north towards the Great Slave Lake. When it gets there the great lumps of ice smash into the frozen lake - sometime creating huge pile-ups of ice. If these ice dams are big enough they can block off the flow of water, which then spreads into the surrounding tundra. That can be very bad news for the inhabitants of Hay River, the last time it happened the town was flooded.

Kate Humble and the Team are going filming with scientists and local experts who are monitoring the break up of the ice in an attempt to see if there will be a flood. One indicator of how bad the ice break up is going to be is the Alexandra Falls. Right now the 35-metre waterfall is frozen solid but soon it's going to melt, with a serious crash.

Hay river, northern territories

In a brief moment hundreds of tonnes of ice will splinter and fall, and the whole waterfall will collapse. The incredible cascade of water and ice will only last for a short time but it signals the start of a tense period for the locals and the scientists. For the next few days they will closely monitor the ice break up to assess how much ice will hit the Slave Lake and how much flooding might occur.

The 23 Degrees team will be there watching the break up and relaying back updates on this incredible spectacle.


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