Glaciers Advancing or Retreating?
When Vancouver explored the southeastern Alaska coast in 1794 he found Glacier Bay filled with ice. Today it is mostly ice-free, but glaciologist William 0. Field predicts that it may fill with ice again over a period of hundreds of years.
Though many Alaskan glaciers are retreating, quite a few others are advancing. Dr. Pield, still active after fifty years of glacial observation, cites examples of glaciers nearly side by side, some of which are retreating and others advancing. He concludes that factors other than climate change must be responsible.
Especially when glaciers spill into the sea, it appears that an unstable equilibrium exists. While the glacier ice always flows forward, the glacial snout advances and retreats, its position being determined by a complex interplay of snowfall, temperature through the year, deposition of rock debris and effects of ocean tides on iceberg calving rates.
Studies lasting many tens of years are necessary to unravel these effects, effects that can have serious consequences to coastal shipping and land transportation facilities in glaciated areas.