Why Antarctic ice shelves are losing their mass and how it leads to global sea level rise

Newswise — The Greenland ice cap (GIC) and Antarctic ice cap (AIC) greatly impact global mean sea level (GMSL) alterations, even though the seas adjacent to Antarctica such as the Bellinghausen-Amundsen Seas and the Indian Ocean sector experience considerably greater warming compared to other marginal seas. This warming has immediate noticeable impacts on the mass balance (net weight of the glacier primarily accounting for ice gained by snow and lost by melting and calving) of the AIC. The extent to which the AIC will contribute to the overall rise in sea level remains uncertain, and existing models differ significantly, leaving a crucial question about future sea levels unanswered. Advancing accurate modeling and technology to forecast the future state of the Earth's oceans and ice caps will aid in addressing these inquiries.

Research findings were published in Ocean-land-Atmosphere Research on May 9th.

"Zhaomin Wang, the study's first author and a professor, stated, 'In this paper, we outline crucial multiscale oceanic mechanisms accountable for transporting heat to the foundations of the Antarctic ice shelves and provide an overview of our current comprehension of these processes.'"

CDW, an abbreviation for circumpolar deep water, is one of the processes accountable for transporting heat.

CDW, a mixture of water masses from various ocean basins, forms a warm and saline mass in the Southern Ocean. It can rapidly penetrate the base of ice shelves, resulting in the formation of cavities or crevasses in the glaciers due to the presence of warm water currents. These cavities are then filled with warm-modified CDW and high salinity shelf water, ultimately leading to the detachment of ice chunks from the glacier's edge, known as "calving." The processes of CDW and cavity development, along with basal melting and calving, play a significant role in the loss of mass from the AIS and subsequently contribute significantly to the rise in GMSL.

The impacts of CDW on the melting of Antarctic ice shelves, as well as other mechanisms involved in warm air and water circulation, are generally acknowledged, although there is a lack of consistent and accurate modeling. This discrepancy may arise from limited comprehension of small-scale processes, particularly the influence of eddies (short-lived patterns of oceanic circulation) and the topography of glacier cavities on the melting process.

Wang commented, "Both eddies and the dynamic impacts of bottom topography have been suggested as crucial factors in the transportation of heat towards the ice shelf fronts, alongside heat transport facilitated by coastal currents."

These subtle topographical features aid in comprehending the transport of CDW and the intricate interactions between warm water currents, coastal currents, surface winds, and bottom pressure torque with glacial masses and ice sheets.

In summary, the process of ice melting due to warm water is more complex than it appears at first glance. Researchers have concluded that although advancements have been made in understanding the mechanisms through which oceanic warming impacts the AIS, there is a need for further improvement and innovation to assess the future implications of ongoing ice shelf melting in Antarctica on humanity. It is anticipated that retreating coastlines and a rise in GMSL will occur, but the precise extent of these changes is still poorly understood.

Researchers propose prioritizing several key areas, beginning with enhancing the understanding of cavity geometry, bathymetry (the measurement of water depth), and future projections of ice sheet mass balance. Devoting time to investigating small-scale processes could also yield valuable insights that contribute to the development of improved future models. Crucially, it is essential to determine the implications of AIS mass loss for atmospheric, oceanic, and sea ice circulations. By focusing on these priorities, researchers aim to gain a more comprehensive understanding of the effects of AIS melting and its broader impact on various Earth systems.

This research was made possible through funding from several sources, including the China National Natural Science Foundation Projects, The Independent Research Foundation of Southern Marine Science and Engineering Guangdong Laboratory, and the National Science Foundation of Jiangsu Province. The support provided by these funding agencies was instrumental in enabling the execution of the research.

This research involved the contributions of Zhaomin Wang, Chengyan Liu, and Chen Cheng from the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai). Additionally, Qing Qin, Liangjun Yan, Jiangchao Qian, and Chong Sun from the College of Oceanography at Hohai University, as well as Li Zhang from the School of Atmospheric Sciences at Sun Yat-sen University, made significant contributions to the study. Their collective expertise and efforts greatly contributed to the findings of this research.