In the context of climate change, it is common to speak of melting glaciers, but scientists have noted that some large accumulations of ice on the Antarctic Peninsula have grown markedly over the past 20 years. Changes in atmospheric circulation and redistribution of the mass of Antarctic ice closer to shore may be to blame.
The enormous masses of ice in the southernmost continent hold much of the water, and this water is perfectly fresh. However, as global warming continues, many Antarctic glaciers are melting fast, causing sea levels to rise. Scientists have been watching their decline since the mid-20th century, and since the 1960s, including through satellite imagery.
To understand how an ice continent works, it is important to bear in mind that local glaciers are dynamic: constantly building up in some parts and melting in others. Meanwhile, huge masses of ice are literally, albeit very slowly, flowing from the centre to the edges of Antarctica, out over the coastline and breaking away. The result is what is known as floating ice, which then sets off on its own journey. Curiously, in English this process is called "ice calving" - literally "ice calving".
The outermost and thinnest part of the ice shell of Antarctica, located in the warmest part of the continent (near the coast), are the so-called ice shelves. They are particularly important for preserving Antarctica's enormous ice reserves, as they serve as 'backstops' that limit the movement of ice masses into the ocean.
This is why glaciologists, climatologists and other scientists keep a close eye on the complex dynamics of glaciers on the Antarctic Peninsula. It is the northernmost part of the frozen continent, extending 1,300 kilometres towards South America. The peninsula accounts for almost four per cent of Antarctica, with glaciers occupying 80 per cent of its land area.
In 1995 and 2002, scientists noted a catastrophic decline in the glaciers called Larsen A and Larsen B. This caused a dramatic acceleration in the flow of ice towards the coast and contributed to rising ocean levels.
In a new study published in Nature Geoscience, a team of scientists from the UK and New Zealand used satellite image data and information on atmospheric and ocean changes.
As a result, they were able to gain detailed insights into the state of the Antarctic Peninsula's glaciers and their dynamics. Surprisingly, 85% of the area's ice shelves have increased in size since the early 2000s. Some of the ice has not gone this deep into the sea since the 1960s, the first time satellite observations have been made. This contrasts sharply with the rapid decline of glaciers in the previous two decades, in the 1980s and 1990s.
The researchers attribute this unexpected change to the dynamics of air circulation - it is likely that the winds are now carrying more ice from inland areas towards the coast. The authors concluded that sea ice is also important in protecting the ice cover from rapid breakup.
"We found that changes in sea ice can both prevent and trigger the separation of icebergs from large Antarctic ice shelves," shared one of the authors, Dr Frazer Christie of the Scott Institute for Polar Research at the University of Cambridge, UK. - Regardless of how the ice around Antarctica may change with a warming climate, our study highlights the particular importance of the often neglected dynamics of sea ice to the health of the Antarctic ice sheet.