Antarctic Atmospheric Rivers Expected to Double by 2100, Study Reveals

A recent study published in *Nature Communications* reveals that the frequency of atmospheric rivers impacting Antarctica is projected to double by the end of this century. This increase, driven by global warming, may significantly alter precipitation patterns and contribute to rising sea levels. Led by Dr. Michelle Maclennan of the British Antarctic Survey, the research utilized a high-resolution climate model to assess the future of these crucial weather phenomena in Antarctica under a high greenhouse gas emission scenario.

Atmospheric rivers are vast corridors of moisture that can transport more water than the Amazon River. They form over warm oceans and move towards polar regions, releasing their moisture as rain or snow. While these systems have been studied extensively in mid-latitudes, their specific impacts in Antarctica have remained less understood. According to Dr. Maclennan, "This is the first study to consider how these extreme weather events in Antarctica might change in response to human-induced warming this century."

The researchers found that not only will the number of atmospheric rivers increase, but the moisture content they carry could rise by as much as 2.5 times. This phenomenon is attributed to the capacity of warmer air to hold more water vapor, leading to a significant elevation in integrated water vapor levels over Antarctic coastal areas.

The implications of these findings are profound. Atmospheric rivers, under colder conditions, can lead to increased snowfall, which may temporarily slow down sea-level rise. However, under warmer conditions, they can bring rainfall, resulting in the melting of ice shelves. This melting is concerning since ice shelves play a crucial role in stabilizing the Antarctic ice sheet. If these shelves fracture, it could accelerate the flow of glaciers into the ocean, thereby contributing to higher sea levels.

A notable observation from the study indicates that while total precipitation from atmospheric rivers could nearly triple under high-emission scenarios, most of this precipitation is expected to fall as snow, particularly in regions like Dronning Maud Land and West Antarctica. However, vulnerable areas, such as the Antarctic Peninsula, may experience significant increases in rainfall, complicating the mass balance of the ice sheet.

The study also highlights the variability that atmospheric rivers introduce to Antarctica’s surface mass balance—the balance between snow gained and ice lost. Today, intense storms can offset weeks of melting, but with the anticipated increase in storm frequency and intensity, these fluctuations are expected to grow. This variability poses challenges for future sea-level rise predictions, which often rely on multi-decadal averages. Dr. Maclennan and her team warn that extreme years may become the norm rather than the exception.

Moreover, changing wind patterns due to climate change may enhance the frequency of atmospheric rivers reaching critical sectors like the Amundsen Sea and Ross Sea, where warm ocean waters are already undermining ice shelves. As the polar jet stream shifts, it may steer more atmospheric rivers into these vulnerable regions, further complicating the dynamics of ice loss.

The findings underscore the urgent need for better climate modeling that incorporates the complexities of atmospheric rivers and their impacts on Antarctic ice dynamics. Future projections of sea-level rise must consider the dual role of atmospheric rivers in potentially adding snow while also increasing melt from ice shelves. As Dr. Maclennan emphasizes, "Understanding the future patterns of these atmospheric rivers is crucial to projecting Antarctica’s contribution to sea-level rise." The choices made regarding greenhouse gas emissions in the coming years will have lasting consequences, shaping the behavior of atmospheric rivers and their impacts on global coastlines.