Hay River Falls
Alexandra Falls, Northwest Territories, Canada
Over this three-month period, seasonal warming sets in motion the greatest planetary transformations of the year. Winter has covered a great swathe of the northern hemisphere with snow. But now it's melting, receding to the edge of the Arctic Circle, where spring is about to arrive in dramatic fashion.
This is this the Hay River, which meanders North for 700 km through the Canadian tundra. Here in the North the river is still in the grip of winter ice. But upstream, to the south, the ice been cracked by the spring warmth. By the end of April the broken ice is on the move. At this point in its journey north, the river tumbles over a 35m drop, giving us this spectacular sight.
This is the Alexandra Falls. And you can see that the central flow is flowing strongly and does all winter but the majority of the falls are still frozen solid. For six months hardly anything at these falls has changed. Now, in the space of just a few hours a transformation has begun as the ice armada approaches from the warmer south.
Hay River Falls
But there is still not enough water in the river to force the ice over the falls, and it piles up any great ice dam. But eventually, it gives way. This is the moment we've been waiting for all day. All the ice has been backing up behind the waterfall and what needed to happen to shift it was for the water level just to come up. It's just mesmerising to watch the pouring jumble of mud and broken ice.
Alexandra Falls, Canada
This is spring Hay River style. It's violent, it's noisy and it's entirely speeded up by these warm meltwaters that have come from the south.