May 5, 2021
By Scott K. Johnson...The influence of sea ice (click here) on the Earth is not just regional; it’s global. The white surface reflects far more sunlight back to space than ocean water does. (In scientific terms, ice has a high albedo.) Once sea ice begins to melt, a self-reinforcing cycle often begins. As more ice melts and exposes more dark water, the water absorbs more sunlight. The sun-warmed water then melts more ice. Over several years, this positive feedback cycle (the ice-albedo feedback) can influence global climate....
...The first study—led by Robert DeConto (click here) at the of Massachusetts Amherst—describes the latest version of that worrisome Antarctic model we mentioned at the start. The model attempts to account for the spontaneous collapse of excessively tall cliffs of ice at the front of glaciers, as well as the pressure-driven expansion of deep cracks that fill with meltwater. The effect of these processes can be amplified in settings like the West Antarctic Ice Sheet, where significant areas of glacial ice sit on bedrock that drops in elevation as you move inland—ultimately dropping well below sea level. Once ice in this situation destabilizes, water can get under it, and it can retreat unstoppably until the bedrock slopes up again.
The model was fed several greenhouse gas-emissions scenarios relevant to recent international talks: futures in which warming is halted at 1.5°C, 2°C, and 3°C (which current pledges have us roughly on track for). The model was also fed a scenario in which unabated warming crosses 4°C before the end of this century. Interestingly, it also includes a series of scenarios where growing emissions halt and suddenly flip into active removal of atmospheric CO2 in 2030, 2040, or 2050, and so on....
...The first study—led by Robert DeConto (click here) at the of Massachusetts Amherst—describes the latest version of that worrisome Antarctic model we mentioned at the start. The model attempts to account for the spontaneous collapse of excessively tall cliffs of ice at the front of glaciers, as well as the pressure-driven expansion of deep cracks that fill with meltwater. The effect of these processes can be amplified in settings like the West Antarctic Ice Sheet, where significant areas of glacial ice sit on bedrock that drops in elevation as you move inland—ultimately dropping well below sea level. Once ice in this situation destabilizes, water can get under it, and it can retreat unstoppably until the bedrock slopes up again.
The model was fed several greenhouse gas-emissions scenarios relevant to recent international talks: futures in which warming is halted at 1.5°C, 2°C, and 3°C (which current pledges have us roughly on track for). The model was also fed a scenario in which unabated warming crosses 4°C before the end of this century. Interestingly, it also includes a series of scenarios where growing emissions halt and suddenly flip into active removal of atmospheric CO2 in 2030, 2040, or 2050, and so on....
