The complex relationship between antarctic ice melt and oceanic warming

The melting of the Greenland ice sheet (GIS) and the Antarctic ice sheet (AIS) has a significant impact on global mean sea level (GMSL) rise. However, recent studies have shown that the seas surrounding Antarctica, such as the Bellinghausen-Amundsen Seas and the Indian Ocean sector, are experiencing much greater warming compared to other marginal seas. This warming has immediate and noticeable effects on the mass balance of the AIS, which refers to the net weight of the glacier considering ice gained from snow and lost through melting and calving.

The precise contribution of the AIS to future sea level rise remains uncertain, as current models vary widely, leaving a major question unanswered. To address this issue, accurate modeling techniques and advanced technology are needed to predict the future state of Earth’s oceans and ice sheets.

A research paper published in Ocean-Land-Atmosphere Research highlights key oceanic processes responsible for delivering heat to the bases of Antarctic ice shelves. The lead author, Professor Zhaomin Wang, discusses these processes and our current understanding of them.

One such process is circumpolar deep water (CDW), which is a mixture of water masses from different ocean basins, resulting in a warm and salty mass of water in the Southern Ocean. CDW can rapidly penetrate the base of ice shelves, creating cavities or cleaves in the glacier due to warm water currents. These cavities then fill with warm-modified CDW and high salinity shelf water, leading to the loss of ice chunks from the glacier, known as “calving.”

CDW and cavity development, along with basal melting and calving, significantly contribute to the mass loss of the AIS and, consequently, to the rise in GMSL.

The impacts of CDW on melting Antarctic ice shelves, as well as other mechanisms contributing to warm air and water circulation, are generally understood. However, they are poorly represented in models due to a lack of understanding of small-scale processes, particularly the effects of eddies (short-lived oceanic circulation patterns) and the topography of cavities on melting.

“Both eddies and the dynamic effects of bottom topography have been proposed to be crucial in heat transport toward the fronts of ice shelves, in addition to heat transport by coastal currents,” explains Wang.

Understanding the transport of CDW and the interactions between warm water currents, glacial masses, and ice sheets requires considering these topographical complexities, as well as coastal currents, surface winds, and bottom pressure torque.

In summary, the process of ice melting due to warm water is more complex than it initially appears. While progress has been made in understanding how oceanic warming affects the AIS, there is a need for improvement and innovation to assess the future implications of ongoing ice shelf melting in Antarctica. Anticipated consequences include retreating coastlines and rising GMSL, but the specific levels remain poorly understood.

The researchers recommend prioritizing the improvement of cavity geometry, bathymetry (measuring water depth), and future projections of ice sheet mass balance. Furthermore, investigating small-scale processes may provide valuable insights for the development of more accurate models. Understanding the mass loss of the AIS is crucial for comprehending atmospheric, oceanic, and sea ice circulations and their broader implications for humanity.

Source: Ocean-Land-Atmosphere Research (OLAR)

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