NASA Uncovers Surprising Insights into Antarctic Ice Loss

Recent studies on Antarctica, which includes the first-ever mapping of iceberg calving, have doubled earlier estimates regarding ice shelf loss and provide insights into how the continent is evolving.

The primary uncertainty in predicting global sea level increase revolves around the acceleration of ice loss in Antarctica as the climate heats up. Two investigations released on Aug. 10, spearheaded by scientists at NASA’s Jet Propulsion Laboratory in Southern California, present surprising new data concerning the mass loss of the Antarctic Ice Sheet in recent years.

One investigation, published in the journal Nature, illustrates how iceberg calving – the separation of ice from a glacier’s edge – has altered the Antarctic shoreline in the past 25 years. The researchers discovered that the perimeter of the ice sheet is losing icebergs at a pace that exceeds the rate of ice replenishment. This unexpected finding has led to a doubling of prior estimates of ice loss from Antarctica’s floating ice shelves since 1997, increasing from 6 trillion to 12 trillion metric tons. The loss of ice due to calving has compromised the ice shelves, thereby allowing Antarctic glaciers to flow more swiftly into the ocean, thus increasing the rate of global sea level rise.

The other study, published in Earth System Science Data, provides unprecedented insight into how the thinning of Antarctic ice, caused by ocean water melting it, has extended from the continent’s outer edges into its core, nearly doubling in the western regions of the ice sheet over the last decade. Together, these complementary reports offer the most comprehensive understanding of the transformations taking place on the frozen continent.

“Antarctica is disintegrating at its borders,” states JPL scientist Chad Greene, the main author of the calving study. “As ice shelves diminish and weaken, the continent’s massive glaciers typically accelerate, thus increasing global sea level rise.”

Most Antarctic glaciers flow into the sea, where they terminate in floating ice shelves that can reach up to 2 miles (3 kilometers) thick and extend 500 miles (800 kilometers) wide. Ice shelves function as supports for glaciers, preventing the ice from collapsing directly into the ocean. When stable, ice shelves maintain a natural cycle of calving and replenishment, sustaining their size over the long run.

However, in recent decades, the warming ocean has put pressure on Antarctica’s ice shelves by melting them from beneath, making them thinner and more fragile. Satellite altimeters track this thinning process by measuring changes in the height of the ice, but prior to this research, a thorough evaluation of how climate change might influence calving around the continent has not been conducted.

This is partly due to the complex nature of interpreting satellite imagery. “For instance,” remarked Greene, “consider looking at a satellite image and attempting to distinguish between a white iceberg, a white ice shelf, white sea ice, and even a white cloud. That has always posed a challenge. However, we now possess sufficient data from various satellite sensors to gain a clear understanding of how Antarctica’s coastline has shifted in recent years.”

For the new research, Greene and his colleagues compiled satellite images of the continent utilizing visible, thermal infrared (heat), and radar wavelengths since 1997. By incorporating these measurements with insights into ice flow derived from an ongoing NASA glacier-mapping project, they delineated the edges of ice shelves along approximately 30,000 linear miles (50,000 kilometers) of the Antarctic shoreline.

The losses incurred from calving have surpassed natural growth of ice shelves to such an extent that the researchers believe it is improbable that Antarctica can revert to its pre-2000 condition by the close of this century. In fact, the findings imply that greater losses are on the horizon: all of Antarctica’s largest ice shelves seem to be advancing toward significant calving events within the next 10 to 20 years.

In the complementary study, JPL scientists amalgamated nearly 3 billion data points from seven spaceborne altimetry devices to create the longest uninterrupted data series on the fluctuating height of the ice sheet – an indicator of ice loss – dating as far back as 1985. They employed radar and laser measurements of ice elevation, precise to within centimeters, to produce monthly maps of ice loss with the highest resolution ever created.

The exceptional detail in this new dataset illustrates how long-term patterns and annual weather variations impact the ice. It even indicates the rise and fall of the ice sheet as subglacial lakes frequently fill and drain miles beneath the surface. “These subtle alterations, combined with enhanced understanding of long-term trends from this dataset, will assist researchers in grasping the mechanisms influencing ice loss, leading to better future predictions of sea level rise,” stated JPL’s Johan Nilsson, the principal author of the study.

The endeavor of synthesizing and analyzing the extensive archives of measurements into a singular, high-resolution dataset required years of effort and thousands of hours of computing time on NASA’s servers. Nilsson asserts that the effort was entirely worthwhile: “Condensing the data into a format that is more broadly applicable may bring us closer to the significant breakthroughs necessary for a deeper understanding of our planet and to better prepare us for the future ramifications of climate change.”

Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307 / 626-379-6874
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov

Authored by Carol Rasmussen

2022-118