Surprising Discovery of Meltwater Storage in Greenland Ice Sheet

A recent study published in *Nature* reveals a significant finding: a large amount of meltwater is temporarily stored within the Greenland Ice Sheet during the summer months. This research marks the first time an international team of scientists has been able to quantify meltwater using positioning data, challenging existing models of how ice sheets contribute to global sea level rise. Currently, the Greenland Ice Sheet is the largest single contributor to global sea-level rise, with the potential to raise mean sea levels by as much as seven meters if it were to completely melt.

Despite extensive studies on the melt processes of the ice sheet, a key question remained: how does the storage of meltwater evolve within the ice sheet throughout the summer melt season? The study introduces a novel approach that provides an unprecedented view of meltwater movement and storage. Jiangjun Ran, an associate professor at Southern University of Science and Technology, explains, "During the melt season, we found that a significant fraction of meltwater mass is stored temporarily within the ice sheet. This water buffering effect peaks in July and slowly recedes in the following weeks."

Utilizing data from the Greenland GPS Network (GNET), which consists of numerous stations around Greenland that continuously provide positioning data, the research team developed an innovative method to interpret the vertical displacements of the bedrock. These displacements occur as the mass of melting water pushes the bedrock down, allowing for a clearer understanding of how water is stored and released within the ice sheet.

The implications of this discovery are substantial for climate models, which often underestimate the complexity of water storage in ice sheets. During warmer years, models predicting water runoff toward the ocean may easily overlook this process, potentially requiring scaling adjustments of up to 20% for the warmest years. Michiel van den Broeke, a professor at Utrecht University, emphasizes, "These findings are crucial for improving forecasts of the Greenland Ice Sheet's contribution to future sea-level rise. With climate change making the Arctic warmer than ever, accurate predictions are essential for preparing coastal regions for potential sea-level rise."

The study is the culmination of years of preparation and challenging expeditions to some of the most remote locations on Earth. Shfaqat Abbas Khan, a professor at the Technical University of Denmark, notes, "The work we've done not only enhances our understanding of ice sheet dynamics but also opens the door to new measurement techniques and campaigns. This study highlights the importance of international collaboration in addressing one of the planet's most pressing environmental challenges.