
Climate change has made Greenland’s massive ice sheet permanently and irreversibly melt. This phenomenon was demonstrated by researchers through a new study using simulations identifying two tipping points on the Greenland Ice Sheet.
When about 1,000 gigatonnes of carbon are emitted, most of the massive ice sheet will melt permanently. According to the study, 500 gigatons have been emitted so far. (Ultram) When about 1,000 gigatonnes of carbon were emitted into the atmosphere, the southern portions of the massive ice sheet melted and disappeared permanently.
The Greenland Ice Sheet covers 1.7 million square kilometers in the Arctic. If it melted completely, global sea levels would rise by about 7 meters, but scientists aren’t sure how fast the permafrost could melt. Air and water temperature, ocean currents, precipitation and other factors all determine how quickly permafrost melts and where it loses ice.
Those factors influence each other, along with the long timeframe scientists need to consider to melt an ice sheet this large. That makes it difficult to predict how the ice sheet will respond to different climate scenarios and carbon emissions.
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Höning’s new study for the first time uses complex models of the entire Earth system to discover how the response of ice sheets to climate might evolve over time.
Scientists first used constant-temperature simulations to find the its equilibrium state. Then they ran a series of simulations over 20,000 years with carbon emissions ranging from 0 to 4,000 gigatonnes of carbon.
From these simulations, the researchers obtained a critical point of 1,000 gigatonnes of carbon for melting of the southern portion of the ice sheet and an even more dangerous 2,500 gigatonnes of carbon for the loss of almost the entire sheet.
As the permafrost melts, its surface will be at lower altitudes, exposed to warmer air temperatures. Warmer air temperatures speed up melting, making it sink and warmer. Therefore, global air temperatures must remain elevated for hundreds of years or even longer for this feedback to be effective.
If ice crosses a threshold, it will surely continue to melt. Even if atmospheric carbon dioxide were reduced to pre-industrial levels, it would not be enough to allow the permafrost to grow back substantially.
Source: nationalgeographic.grid.id