Introduction To Polar Ice Loss
The polar ice sheets of Greenland and Antarctica have been undergoing significant changes over the past half-century, resulting in substantial ice loss and contributing to global sea level rise. A recent study published in the journal Scientific Data has provided the most complete picture of ice loss from these regions to date, utilizing the longest satellite record ever assembled. The research, led by Dr. Inès Otosaka and Professor Andrew Shepherd at Northumbria University, combined 42 independent satellite surveys and drew on 27 satellite missions to assess ice loss from 1972 for Greenland and 1979 for Antarctica.
Mechanisms Of Ice Loss
The study found that Greenland and Antarctica have lost 11.3 trillion metric tons of ice since the 1970s, raising global sea level by more than 3 centimeters. Notably, 84% of the combined loss was driven by glaciers speeding up and pouring more ice into the ocean, with just 16% due to surface melting. This finding suggests that the dynamic response of the ice sheets to a warming ocean is the primary driver of ice loss, rather than surface melt caused by warmer air temperatures.
Satellite Data And Ice Sheet Mass Balance
The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) Team used satellite altimetry and other data to estimate the mass balance of the ice sheets. The team found that the ice sheets lost 11,309 billion metric tons of ice between 1979 and 2023, pushing global sea level up by 31.4 millimeters. Greenland accounted for the larger share of ice loss, contributing 18.1 millimeters to sea level rise, while Antarctica contributed 13.3 millimeters. The study also found that the rate of ice loss has been increasing over time, with Greenland's rate of loss rising from around 60 billion metric tons a year in the 1980s to 264 billion metric tons in the 2010s.
Implications And Future Outlook
The findings of this study have significant implications for our understanding of the role of polar ice sheets in global sea level rise. The fact that glaciers are flowing faster into the ocean, rather than melting at the surface, suggests that the ice sheets are responding to a warming ocean. This has important implications for sea level rise projections, as the dynamic response of the ice sheets to a warming ocean is a major source of uncertainty.
The study's authors note that the temporary slowdown in ice loss observed in recent years is likely a short-term fluctuation, and that the long-term trend of increasing ice loss is expected to continue.
Glacier Flow And Ocean-Ice Feedbacks
The study's findings also highlight the importance of glacier flow and ocean-ice feedbacks in driving ice loss. As glaciers flow faster into the ocean, they can trigger feedback loops that accelerate sea level rise. For example, the breakup of ice shelves in Antarctica can cause glaciers to accelerate, leading to increased ice loss.
Additionally, the thinning of glaciers can lead to marine ice cliff instability, where the ice face at the front of the glacier becomes too tall and collapses, driving further retreat.
Conclusion And Future Research Directions
In conclusion, the study provides a comprehensive understanding of ice loss from Greenland and Antarctica over the past half-century. The findings highlight the importance of glacier flow and ocean-ice feedbacks in driving ice loss, and suggest that the dynamic response of the ice sheets to a warming ocean is the primary driver of ice loss. Further research is needed to improve our understanding of these processes and to refine sea level rise projections. The study's authors note that the ice sheets are now responsible for around a quarter of all global sea level rise, and that their response to a warming climate is the single largest source of uncertainty in sea level projections.
Sources
This is an original synthesis by Qivorane based on reporting from the outlets below.
