Antarctica’s melting ice shelves threaten global sea levels

Antarctica’s vast ice sheet, holding over half of Earth’s freshwater, plays a critical role in regulating the planet’s climate and sea levels. The continent’s ice shelves, large floating extensions of ice over the ocean, are of particular interest.

Observations show that many of these ice shelves are thinning due to melting from below, with profound implications for ocean dynamics and global sea levels.

Among these, the Filchner-Ronne Ice Shelf stands out. Spanning the Weddell Sea, it is one of Antarctica’s largest ice shelves. Fortunately, it remains relatively stable for now. Near-freezing currents circulating beneath the shelf provide a protective buffer.

However, climate models warn that warmer currents may reach this region in the future, potentially destabilizing the shelf.

Ice shelf dynamics in Antarctica

To predict the future of the Filchner-Ronne Ice Shelf, N. Steiger and colleagues from Sorbonne Université conducted a detailed analysis of ocean data collected between 2017 and 2021.

The team used sensors placed on the seafloor (moored instruments) and on floating devices beneath the water’s surface.

These tools recorded water temperature and velocity, providing a wealth of information about how ocean currents interact with the ice shelf.

Previous observations and limitations

Earlier research had identified a recurring phenomenon: in summer, warm seawater rises from middle ocean depths and flows along the Filchner Trough – a deep undersea valley – toward the edge of the ice shelf.

However, these studies were often limited to a single location or a short timeframe, which left gaps in understanding the broader system.

Warming of Antarctica’s ice shelves

The new study revealed a more intricate system of water movement. Warm water doesn’t only follow the main Filchner Trough but also uses a smaller, eastern trough. Importantly, the role of each pathway varies from year to year.

During years with higher-than-average temperatures, warm water moves faster and more extensively across the continental shelf. This increases the likelihood of warm water reaching the ice shelf and potentially contributing to its melting.

Steiger’s research highlights the importance of long-term and multi-site observations to grasp the complex interactions between ocean currents and Antarctic ice shelves. These insights improve predictions about how warming oceans may affect the stability of ice shelves and contribute to rising sea levels globally.

Warm summers and ice shelf changes

The researchers identified 2017 and 2018 as exceptional summers, characterized by unusually warm water flowing into the region and a significant reduction in floating sea ice. These conditions were crucial because sea ice acts as a barrier that influences ocean behavior.

When there is less sea ice, the ocean becomes more dynamic, enabling warm water from deeper layers to rise and spread across the continental shelf more easily.

Did the warm water reach the ice shelf?

Although it remains uncertain whether the warm water in 2017 and 2018 actually reached the edge of Antarctica’s Filchner-Ronne Ice Shelf, there is evidence from 2013 suggesting similar warm water flows did reach the shelf’s edge during that year.

In 2013, researchers linked this movement of warm water to specific wind patterns that likely drove the flow toward the ice shelf.

Implications of reduced sea ice

The lack of sea ice doesn’t just alter the flow of warm water; it also allows the warm water to interact more directly with the continental shelf and potentially with the ice shelf itself.

Understanding how these dynamics play out under varying conditions is critical for predicting future changes in Antarctic ice shelves and their contribution to rising sea levels.

Looking ahead

Identifying the drivers of warm water flow beneath Antarctic ice shelves remains a priority. As Steiger’s work shows, year-to-year variability in ocean currents and ice cover can significantly influence the shelf’s stability.

Continued observations and advanced modeling are crucial to predicting how these massive ice shelves will respond to shifting climate patterns.

This research emphasizes the need for continued monitoring and vigilance. The stability of Antarctica’s ice shelves holds the key to the planet’s future sea levels and climate health.

The study is published in the Journal of Geophysical Research: Oceans.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–