Warm ocean water is accelerating the melting of Antarctic ice shelves, with new studies revealing the mechanisms behind this critical process and its implications for global sea level rise.
Warm Water Intrusion and Multi-Year Ocean Data
A study combining ship-based data and measurements from Argo floats has produced a 40-year monthly record of ocean conditions near Antarctica. The research, conducted by scientists at the University of Cambridge and the University of California, indicates that warm circumpolar deep water (CDW) has expanded and moved closer to the Antarctic continental shelf.
This CDW can melt ice shelves from below and push back the grounding line, which is the point where the ice shelf meets the bedrock. Professor Sarah Purkey of Scripps Institution of Oceanography characterized the process as a sustained influx of warm water. The researchers noted that the cause of this shift in CDW is uncertain and may involve a combination of natural climate variability and human-induced climate change.
"The process represents a sustained influx of warm water." — Professor Sarah Purkey
The study also reported that changes in heat distribution within the Southern Ocean could affect the global climate system, including a potential slowdown of the Atlantic Meridional Overturning Circulation (AMOC), which would have implications for sea levels and weather patterns.
Sub-Ice Channels and Localized Melting
A separate study published in Nature Communications examined the Fimbulisen Ice Shelf in East Antarctica. Researchers from the iC3 Polar Research Hub found that small channels on the underside of the ice shelf can trap warm water.
The research team used detailed maps of the ice shelf's underside and ocean cavity modeling to compare melting rates under smooth and channeled ice shelf conditions. The findings indicate that even small amounts of warmer water can substantially increase local melting rates within these channels.
"Small-scale melting processes should be included in future climate models to improve the accuracy of sea level rise projections."
The study's authors stated that the growth of these channels may weaken the ice shelf, potentially leading to its structural failure. Such a failure would allow land ice from the Antarctic continent to flow into the ocean, contributing to sea level rise. The researchers emphasized that these small-scale melting processes should be included in future climate models to improve the accuracy of sea level rise projections.