A study from Copernicus reports that the effect of sea ice ( fast ice connected to land ) as a buttressing force against land ice is negligible. The study area was the Larsen B ice shelf, which has collapsed since 2002 and is effectively gone after a major collapse in 2022.
We observe the evacuation of 11-year-old landfast sea ice in the Larsen B embayment on the East Antarctic Peninsula in January 2022, which was in part triggered by warm atmospheric conditions and strong offshore winds. This evacuation of sea ice was closely followed by major changes in the calving behaviour and dynamics of a subset of the ocean-terminating glaciers in the region. We show using satellite measurements that, following a decade of gradual slow-down, Hektoria, Green, and Crane glaciers sped up by approximately 20 %–50 % between February and the end of 2022, each increasing in speed by more than 100 m a−1. Circumstantially, this is attributable to their transition into tidewater glaciers following the loss of their ice shelves after the landfast sea ice evacuation. However, a question remains as to whether the landfast sea ice could have influenced the dynamics of these glaciers, or the stability of their ice shelves, through a buttressing effect akin to that of confined ice shelves on grounded ice streams. We show, with a series of diagnostic modelling experiments, that direct landfast sea ice buttressing had a negligible impact on the dynamics of the grounded ice streams. Furthermore, we suggest that the loss of landfast sea ice buttressing could have impacted the dynamics of the rheologically weak ice shelves, in turn diminishing their stability over time; however, the accompanying shifts in the distributions of resistive stress within the ice shelves would have been minor. This indicates that this loss of buttressing by landfast sea ice is likely to have been a secondary process in the ice shelf disaggregation compared to, for example, increased ocean swell or the drivers of the initial landfast sea ice disintegration.
In the Southern Hemisphere summer of 2002, scientists monitoring daily satellite images of the Antarctic Peninsula watched in amazement as almost the entire Larsen B Ice Shelf splintered and collapsed in just over one month. They had never witnessed such a large area—3,250 square kilometers, or 1,250 square miles—disintegrate so rapidly.
Scientists are still investigating the reason for the breakup, but the early clearing of seasonal sea ice along the Antarctic Peninsula suggests that the austral summer has been warm and wet. Scientist Rajashree Tri Datta of University of Colorado, Boulder, noted that foehn winds, influenced by a large atmospheric river, helped destabilize the ice pack. The phenomenon is apparent in this animation composed with images from NOAA’s GEOS-16 satellite.
AI research from the University of Cambridge has mapped slush on the surface of Antarctic Ice shelves for the first time. It is yet another threat to the Antarctic continent. This time, the damage is on the ice sheet instead of the large swathes of decay from the underbelly of the massive ice platforms around Antarctica. Using NASA satellite imagery, it was determined that meltwater lakes and slush are a threat due to their weight, and surface meltwater has the potential to cause hydrofracture and collapse.
Slush—water–soaked snow—makes up more than half of all meltwater on the Antarctic ice shelves during the height of summer, yet it is poorly accounted for in regional climate models.
Researchers led by the University of Cambridge used artificial intelligence techniques to map slush on Antarctic ice shelves and found that 57% of all meltwater is held in the form of slush, with the remaining amount in surface ponds and lakes.
As the climate warms, more meltwater is formed on the surface of ice shelves, the floating ice surrounding Antarctica which acts as a buttress against glacier ice from inland. Increased meltwater can lead to ice shelf instability or collapse, which in turn leads to sea level rise.
The researchers also found that slush and pooled meltwater leads to 2.8 times more meltwater formation than predicted by standard climate models, since it absorbs more heat from the sun than ice or snow. The results, reported in the journal Nature Geoscience, could have profound implications for ice shelf stability and sea level rise.
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“Since slush is more solid than meltwater, it won’t cause hydrofracture in the same way that water from a lake does, but it’s definitely something we need to consider when attempting to predict how or whether ice shelves will collapse,” said Willis.
In addition to the potential implications of slush on hydrofracture, it also has a large effect on melt rates. Since slush and lakes are less white than snow or ice, they absorb more heat from the sun, causing more snowmelt. This extra melt is currently unaccounted for in climate models, which may lead to underestimates in projections of ice sheet melting and ice shelf stability.
The study can be found in the Nature Geoscience.
Bob Berwyn writes in Inside Climate News:
Earlier this week, a separate study in the same journal also showed the increasing vulnerability of Antarctica’s ice shelves to melting from below, with the findings suggesting that a warming ocean is likely to lead to “runaway melting.”
Thwaites glacier damage continues in the deep of winter. In the Amundsen Sea Embayment, year-round melting is occurring with open water present.
For Further Reading:
Damage to Astrolabe Glacier (Adélie Coast, Antarctica) ice tongue.
From Daily Kos blogger Denise Oliver Velez.
Caribbean Matters: The devastating aftermath of Hurricane Beryl