Icebergs such as this ethereal blue sculpture are the culmination of a dynamic process eons in the making.
It’s easy to imagine glaciers as static – water interrupted, subject to thaw and melt, but otherwise frozen in space and time. In reality, they’re more like slow moving rivers, pulled down by gravity, pushed forward by the unimaginable tonnage of ice and snow in the icefields where the originate. A fast-moving glacier can travel at a rate of 20 meters a day or more.
Tidewater glaciers are among the most dynamic forms of ice in nature. Like the Blackstone Glacier (pictured below), they flow from icefields, much as a mountain stream might originate as the outflow from an alpine lake. What makes tidewater glaciers so fascinating is that they don’t gradually turn to water as they descend down a mountain valley, warming and thawing with the descent.
Instead, tidewater glaciers terminate when they reach the sea. The ice continues to flow, pushing the face of the glacier forward. If the face of the glacier is large enough, the combination of forward movement and warmer air and water temperatures can result in spectacular calving events, with massive pieces of ice sloughing off into the sea.
The Harding Ice Field, which gives birth to three dozen or more glaciers, stretches out like a vast, island-studed lake.
As soon as the freshly calved ice hits the water, it become part of sea’s ecosystem. Harbor seals (above) and black-legged kittiwakes (members of the gull family, below) use the frozen islands to rest, feed and stage hunts. The seals also use the ice as nurseries.