Global Sea Level and Potential Future Decay of Ice Sheets in Response to Continued Warming
T. J. Hughes,
Climate Change Institute and Department of Earth Sciences

The Greenland and Antarctic ice sheets do not occupy their proper niche for the density-based layering of Earth's constituents. The proper niche for ice is between water and air, not land and air. Ice sheets seek to occupy their proper niche by flowing from land to the sea, and by pushing the land below sea level under the weight of ice. Climate warming increases surface melting in the "ablation zone" around the perimeter of the ice sheets and sinking of land under the ice sheets lowers the ice surface so the width of the ablation zone increases. It is now known that much of this surface meltwater in Greenland reaches the bed by way of water-filled surface crevasses. This meltwater then floods the bed, increasing the "floating fraction" of basal ice as bedrock bumps become progressively drowned. Drowning the bumps puts the ice sheet on the proverbial "banana peel" and allows it to slide faster into the sea, thereby raising sea level and releasing armadas of icebergs that cool surface water in the North Atlantic. In Antarctica, enhanced melting in the ablation zone occurs under the floating fringe of the Antarctic Ice Sheet, and water-filled bottom crevasses move upward to release gigantic icebergs into the Antarctic Ocean. Ice moving from land to sea allows the land under the ice sheets to rebound, and thereby act as a brake on deglaciation of the land, but rebound is a slow process compared to the rate at which ice moves to the sea. Short-term processes can destabilize climate. Long-term processes tend to restore stability.

The most immediate and dramatic climate change affecting New England and Maritime Canada would be a rapid rise in sea level and climate cooling, both resulting from rapid deglaciation of the island of Greenland and the continent of Antarctica. The rise in sea level could exceed 6 meters (which would submerge downtown Bangor), with an upper limit of 70 meters. Climate cooling would result from massive iceberg outbursts from the Greenland Ice Sheet that would radically cool the North Atlantic Current, which is the continuation of the warm Gulf Stream as it moves south of Greenland toward Europe. This could throw northeast North America and northwest Europe into a cold spell last felt during the Little Ice Age, with a full 90,000 year long Ice Age glaciation as the worst-case scenario. Ironically, this could be triggered by ongoing global warming.

glaciation as the worst-case scenario. Ironically, this could be triggered by ongoing global warming.