Researchers have found that forty percent of Antarctica’s ice shelves are melting due to warm ocean temperatures and changing wind patterns. In their article on a new Antarctic study published in Science Advances, the Guardian lede summarizes it like this.
More than 40% of Antarctica’s ice shelves have shrunk since 1997 with almost half showing “no sign of recovery”, a study has found, linking the change to the climate breakdown.
According to the study, forty percent of ice shelves shed trillions of tons of freshwater into the Southern Ocean.
Scientists at the University of Leeds have calculated that 67tn tonnes of ice was lost in the west while 59tn tonnes was added to the east between 1997 and 2021, resulting in a net loss of 7.5tn tonnes.
Warm water on the western side of Antarctica has been melting ice, whereas in the east, ice shelves have either stayed the same or grown as the water is colder there.
The ice shelves sit at the end of glaciers and slow their rate of flow into the sea. When they shrink, glaciers release larger amounts of freshwater into the sea which can disrupt the currents of the Southern Ocean.
The study is most interesting for those of us who follow the changing climate in Antarctica:
Here is a portion of the study Introduction.
Ice shelves fringe the majority of the fast-flowing parts of the Antarctic Ice Sheet (AIS) (1) and exert a critical control on the rate of ice discharge into the ocean through a process known as “buttressing” (2, 3). Ice shelf thinning (4, 5) or retreat (6–9) can reduce the buttressing force provided by the ice shelf, leading to an increase in the speed of the upstream grounded ice (10) and an increase in the ice sheet contribution to global sea level rise. For example, in the Amundsen Sea Embayment of West Antarctica, decadal variations in ice shelf basal melt rates and consequent changes in ice shelf thickness have caused large increases in grounding line discharge (11–15), which has been exacerbated in recent years by a sequence of major calving events at Pine Island Ice Shelf (8). The disintegrations of the Larsen B, Larsen A, and Prince Gustav Channel ice shelves were followed by a multiyear acceleration and thinning of their tributary glaciers (10, 16–19). At the ice sheet scale, the observed spatial patterns of grounded ice speed change in recent decades can be reproduced by ice flow models that are forced only by the observed change in ice shelf thickness (4, 5). Modeling studies have also examined hypothetical scenarios including complete ice shelf loss, which results in large-scale ice sheet destabilization (20, 21), confirming the importance of ice shelves for stabilizing large portions of the AIS.Ice shelves are one of the most vulnerable parts of the AIS to changes in atmospheric and ocean conditions. They are low-elevation plains that experience widespread and often intense surface melting (22–26). Vertical drainage of ponded surface meltwater can cause ice shelf flexure (27, 28) and drove, in combination with other factors, the rapid fragmentation and collapse of the Larsen B Ice Shelf in 2002 (18, 29). Ice shelf surface melting is projected to intensify this century (30), which may lead to more widespread and more frequent meltwater ponding, potentially increasing the risk of ice shelf disintegration (31). Ice shelves also have large ice-ocean interfaces where basal melting and refreezing occur (32), which can affect ice shelf stability and enhance calving (33, 34). Changes in sea ice conditions, combined with ocean swell, currents, tides, and ocean surface slope, can lead to calving from or disintegration of ice shelves (35, 36).The export of solid and liquid freshwater from ice shelves affects water column hydrography (37, 38), sea ice extent (39), and bottom water formation (40, 41), with feedback on the ice shelf (42). Some estimates of ice shelf freshwater export exist (1, 33, 43); however, these generally provide only temporal snapshots or short time series of freshwater export and have limited accounting of ice shelf area changes (7, 33). Therefore the magnitude, timing, spatial distribution, and phase of these freshwater inputs are not known in detail, resulting in widely varying approaches to represent freshwater perturbations in ocean circulation models and consequently diverging conclusions regarding the effect of Antarctic meltwater on, for example, sea ice extent (39, 44).Each of the factors outlined above makes ice shelves a key pillar in ice sheet–climate interactions. In recognition of the importance of ice shelves, there is a burgeoning literature documenting and investigating ice shelf thickness changes (15, 45–49), ice shelf area changes and calving (7, 50–52), changes in grounding line discharge (13, 53, 54), or grounding line migration (55, 56) at one or many ice shelves. Despite these efforts, the components of ice shelf change have rarely been viewed together to provide a clear and coherent picture of ice shelf mass changes during the satellite era (7, 46), which hinders efforts to model the processes that drive ice shelf mass change and their impact on grounded ice (20, 57, 58). Therefore, it is essential to better quantify ice shelf freshwater export, ice shelf mass changes, and its components and importance for buttressing of grounded ice. Here, we make use of high-resolution satellite datasets to produce an annual record of ice shelf mass balance and its constituent components for all Antarctic ice shelves from 1997 to 2021.