Researchers have identified key multiscale oceanic processes responsible for delivering heat to the bases of Antarctic ice shelves.
The researchers from Hohai University and other Chinese institutes also said that it is yet unknown how much the Antarctic ice sheet (AIS) will contribute to the overall increase in sea level and that current models varied drastically.
They describe these oceanic processes in a paper published in the journal Ocean-land-Atmosphere Research.
One of these processes responsible for heat delivery, the researchers said, is circumpolar deep water (CDW), which is a mix of the ocean's water masses from different ocean basins and culminates in a warm, salty mass of water in the Southern Ocean, or the southern waters surrounding Antarctica.
They said that this CDW can cut through the base of ice shelves rapidly, leading to "cavities", or cleaves in a glacier due to warm water currents, which get filled with warm-modified CDW and high salinity shelf water.
This eventually leads to loss of chunks from the tip of the glacier, known as "calving".
CDW and cavity development, the researchers said, are substantial processes, along with basal melting and calving, contributing to a rise in global mean sea level changes.
While the effects of CDW on AIS melting and other mechanisms contributing to warm air and water circulation are generally understood, they said that they are poorly modelled, possibly due to a lack of understanding of small-scale processes, particularly when it comes to the effects eddies, or short-lived oceanic circulation patterns, and the topography of cavities in the glacier have 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," Zhaomin Wang, first author of the study.
These topographical subtleties help with understanding the transport of CDW and how coastal currents, surface winds, and bottom pressure torque all play into the interactions of these warm water currents with glacial masses and ice sheets, the researchers said.
They suggested investigating small-scale processes that may provide valuable information and lead to better future models being developed, and critically, determining what the mass loss of the AIS meant for atmospheric, oceanic, and sea ice circulations.
