Antarctic ice shelves are much thinner than previously estimated

The stability of Antarctica’s ice shelves is more precarious than scientists previously believed, according to a study recently published in the Journal of Glaciology. 

Researchers from The Ohio State University discovered that Antarctic ice shelves, which are crucial for maintaining the stability of the Antarctic ice sheet and the global climate system, are nearly six percent thinner than previously assumed. 

Significant discovery 

This difference, equivalent to about 17 meters, may seem minor, but considering that typical ice shelves range from 50 to 600 meters in thickness, the implications are significant.

Study lead author Allison Chartrand is a recent doctoral graduate of the Byrd Polar and Climate Research Center.

“Because the Antarctic ice sheet is so big, a 1% misestimation in how fast it’s melting could mean inches or feet of sea level rise that we’re not accounting for,” said Chartrand. “So it’s really important to be as accurate as we can.”

How the research was conducted 

The research is the first large-scale study to compare ice shelf thickness data from ice-penetrating radar measurements with thickness data estimated from contemporary surface elevation measurements. 

Analyzing vast datasets of 20 of the 300 separate ice shelf systems that surround about 75% of the Antarctic ice sheet, the researchers found significant discrepancies in previous estimates. 

Although prior assumptions about ice shelf thickness were largely accurate on a broad scale, they varied greatly on a smaller scale, such as for individual structures like valleys or crevasses that are too narrow or small to be measured accurately.

Far-reaching consequences 

The consequences of even slight changes in the ice shelves’ size are far-reaching. Chartrand explained that minor displacements in the ice shelf could lead to the flow of thicker ice into the ocean, potentially causing some coastlines to retreat several feet. Such a scenario poses a significant threat to coastal communities worldwide.

Inconsistencies in prior research 

Chartrand and her co-author, glaciologist Ian Howat,  initiated the investigation into ice shelf thickness while studying basal channels. These are channels where warmer ocean water melts grooves into the bottom of the ice shelf, accelerating mass loss. 

They found that assumptions used in prior research sometimes exaggerated ice shelf thickness in certain areas while understating it in others.

“While many of these inconsistencies don’t take away much from the big picture, individually, these snapshots are vastly out of focus,” said Chartrand. 

“In comparing the thickness estimate with the radar estimate, we saw that the numbers we had on basal channels and other features like them could be different by up to hundreds of meters, which meant that we could potentially be underestimating or overestimating rates of change.”

Study implications 

The research highlights the need for more abundant and accurate data to better predict ice shelf loss in Antarctica. Ultimately, the researchers aim to improve observations of the processes contributing to sea level rise. 

“The ultimate goal of our work is to improve observations of the processes that contribute to sea level rise,” Chartrand concluded. This study marks a significant step towards that objective, shedding light on the urgent need for more precise measurements and predictions in the face of a rapidly changing climate.

More about the Antarctic ice sheet

The Antarctic ice sheet is the largest single mass of ice on Earth. It covers an area of almost 14 million square kilometers and contains 30 million cubic kilometers of ice. Around 60% of the world’s fresh water is stored in this ice sheet, which, if melted, would lead to a significant rise in sea levels, estimated to be around 60 meters or 200 feet.

Main components

The ice sheet is divided into two main components: the East Antarctic Ice Sheet (EAIS) and the West Antarctic Ice Sheet (WAIS). 

The EAIS is larger and sits on a landmass, while the WAIS is smaller and rests on a bed that lies below sea level. This makes the WAIS more vulnerable to melting from warm ocean water that can get underneath the ice sheet.

Formation

The ice sheet is formed by snowfall accumulating over thousands of years, compressing into ice, and flowing outward to the sea, forming floating ice shelves and glaciers. 

Climate change

These ice shelves act as a barrier, slowing down the flow of glaciers into the ocean. However, due to climate change, these ice shelves have been thinning and, in some cases, collapsing, which can lead to an acceleration of sea-level rise.

Sea levels

Melting of the Antarctic ice sheet is a major concern because of its potential impact on global sea levels. Ice loss from Antarctica has tripled over the past decade, contributing to a significant portion of the observed sea-level rise. 

This is due to a combination of warmer ocean temperatures melting the ice shelves from below, and warmer air temperatures melting the surface of the ice sheet.

Feedback loop

Furthermore, the melting of the Antarctic ice sheet contributes to a feedback loop. As the ice melts, it exposes darker ocean water, which absorbs more heat from the sun than the reflective ice, leading to further warming and more melting. This is known as the albedo effect.

Overall, the Antarctic ice sheet plays a crucial role in the Earth’s climate system, and its melting poses significant risks to coastal communities and ecosystems worldwide. 

Monitoring and understanding the changes in the Antarctic ice sheet is, therefore, critical for predicting future sea-level rise and for planning and adapting to the impacts of climate change.

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