May 29, 2023
Study identifies new cause of melting Antarctic ice shelves

Study identifies new cause of melting of Antarctic glaciers

Norwich (England), December 26

Researchers have identified a technique that may help melt Antarctic ice sheets.

A multinational team of scientists has discovered that the instability of one ice reef can affect others downstream.

The study, which was conducted by the University of East Anglia in the UK, also found that the proximity of the Thwaites Ice Shelf to a small ocean gyre, or system of circulating ocean currents, can affect how much meltwater flows underneath. More warm water can enter the areas below the ice shelf when the gyre is weaker, which causes the ice to melt.

The Thwaites Ice Shelf is one of the largest ice sheets in West Antarctica and supports the eastern side of the Thwaites Glacier, which has been retreating rapidly over the past 20 years and is the largest contributor to global sea-level rise among Antarctic glaciers.

Using a unique dataset collected by sensors installed beneath the Thwaites Ice Shelf — which has also thinned and weakened significantly in recent decades — the researchers observed that the shallow layers of the ocean beneath it warmed significantly over the period from January 2020 to March 2021.

Most of this warming came from waters with a large volume of glacial melt originating from the Pine Island Ice Shelf, further east, flowing into the area beneath the Thwaites Ice Shelf.

Glacial meltwater mixes with saltwater when the ocean melts the base of ice shelves and can form a floating layer of water that is warmer than the surrounding waters. This lighter, relatively fresher and warmer water brings heat that melts the base of the Thwaites Ice Shelf.

Lead author Dr Tiago Dotto, of the Center for Ocean and Atmospheric Sciences at UEA, said: “We have identified another process that could affect the stability of ice shelves, revealing the importance of local ocean circulation and sea ice.” “Circumpolar Deep Water, a warm variety of Antarctic waters, is a key factor in melting the base of ice shelves. However, in this study, we show that a large amount of heat in shallow layers beneath an ice shelf can be provided by the water that comes from other ice sheets melting nearby. So what happens on one ice shelf can affect the adjacent ice shelf and so on,” he said.

“This process is important for areas with high ice melting, such as the Amundsen Sea, because one continental shelf is next to another, and heat extraction from one continental shelf can reach the next via ocean circulation,” he added.

Dr. Dotto added, “These atmosphere-sea-ice-ocean interactions are important because they can prolong warm periods beneath the ice shelves by allowing warm, melt-enriched water to enter adjacent ice sheet cavities.” “The gyres potentially present in other regions around Antarctica may also predispose a greater number of ice shelves to intense basal melting associated with prolonged warm conditions and as a result further contribute to global sea level rise,” he said. .

In January 2020 colleagues from the US drilled holes in the ice and installed sensors that monitor temperature, salinity and ocean current under the Thwaites Ice Shelf.

For more than a year these sensors have been sending back, via satellite, data used to track ocean fluctuations, for example how the temperature and content of meltwater vary. From these observations, the researchers suspected that the excess heat could not be originating locally in the Thwaites Ice Shelf because they did not see strong melting in the locations where the sensors were installed.

Combining the information with computer simulations to determine the origin of this heat, they discovered that water leaving the Pine Island Ice Shelf may be accessing the areas beneath the Thwaites Ice Shelf.

The mechanism that explains how these waters access the Thwaites Ice Shelf was identified using model simulations and data collected from tags attached to seals. Both showed that a gyre near the Thwaites Ice Shelf weakens in winter, which allows more heat to reach shallow areas beneath the ice shelf.

Satellite images also showed that the 2020/2021 Southern Hemisphere summer was unusual in that it had a high concentration of sea ice in areas near the Thwaites Ice Shelf.

Based on simulations and previous research, the team hypothesized that the gyre was even weaker, so excess meltwater from adjacent ice shelves could not be swept away from this region by currents and instead entered the ice shelf. Thwaites.

This further reduced the strength of this gyre, which allowed the inflow of water with higher concentrations of glacial melt below the ice shelf.

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