Why Melting Ice Sheets is Easier than Freezing Them: The Surprising Reason Behind the 'Sponginess' of Ice

Breathing easily and taking a step back to understand the intricacies of our planet's ice sheets is vital in today's climate. Scientists have long known that it's easier to melt an ice sheet than to freeze it up again, but the reason behind this phenomenon has remained a mystery - until now. A recent study published in The Cryosphere sheds light on the 'sponginess' of ice, and it's changing the way we understand the behavior of ice sheets.

The Firn Factor

The study, led by Megan Thompson-Munson, uses a physics-based numerical model to assess the impacts of warming and cooling on firn, the porous layer between snow and glacial ice, over the entire Greenland Ice Sheet. Firn, which covers about 90 percent of the ice sheet, is porous and sponge-like, allowing water to pass through on its way to the solid ice layer below, where it can refreeze and add to the existing ice sheet instead of flowing to the ocean.

Researchers found that warming temperatures are rapidly changing how efficiently firn can store meltwater, and cooling temperatures may not help the firn fully recover as much as scientists might have hoped. This 'firn asymmetry' is a crucial piece of the puzzle in understanding why ice sheets can melt away quickly but take a long time to grow.

The Warming-Cooling Conundrum

The team used a computer model called SNOWPACK to hone in on the variable of temperature and its impact on firn. They found that the warming depletion of 'firn air content' or 'sponginess' is greater than the recovery of sponginess due to cooling. This means that the firn layer's ability to buffer sea level rise contribution is compromised, making it harder to preserve Arctic glaciers in a warming climate.

The study's findings raise important questions about geoengineering and our ability to reverse the Earth's warming. Any geoengineering concepts designed to decrease temperatures in the Arctic might not preserve ice and snow as efficiently as imagined, and the degree of cooling would have to exceed the degree of warming to help firn and glaciers return to normal.

Frequently Asked Questions

Q: What is firn?Firn is the porous layer between snow and glacial ice that covers about 90 percent of the Greenland Ice Sheet. It's porous and sponge-like, allowing water to pass through on its way to the solid ice layer below, where it can refreeze and add to the existing ice sheet instead of flowing to the ocean.

Q: Why is the 'sponginess' of ice important?The 'sponginess' of ice, or firn air content, is crucial in understanding how ice sheets respond to warming and cooling temperatures. It affects the firn layer's ability to buffer sea level rise contribution and preserve Arctic glaciers in a warming climate.

Q: What are the implications of this study?The study's findings raise important questions about geoengineering and our ability to reverse the Earth's warming. It highlights the need for more research into the complexities of ice sheet behavior and the importance of preserving Arctic glaciers in a warming climate.

Conclusion

In conclusion, the 'sponginess' of ice is a critical factor in understanding why melting ice sheets is easier than freezing them. As we continue to navigate the complexities of climate change, it's essential to delve deeper into the intricacies of ice sheet behavior and the role of firn in preserving Arctic glaciers. By doing so, we can work towards finding solutions to mitigate the devastating effects of climate change.

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