The phenomenon, known as the West Antarctic Peninsula ‘cold blob’, emerged in the early 1990s and is unusual when compared to the rapid warming seen elsewhere in the Southern Ocean.
To figure out why the cold blob has remained cold, researchers from the University of East Anglia (UEA) and the British Antarctic Survey (BAS) analysed 30 years of temperature and salinity measurements collected by autonomous floats deployed by the Argo profiling array.
They discovered that the cold blob is fed by a narrow jet of extremely cold water coming off the Larsen C Ice Shelf, which is about the size of Wales and is the fourth-largest ice shelf in Antarctica.
The findings are published in the journal Geophysical Research Letters.
Lead researcher Dr Inès O’Leary, from UEA’s School of Environmental Sciences, said: “The Southern Ocean is warming fast so we were surprised to see that the waters of the West Antarctic Peninsula have not warmed in 30 years.
“This is important, as the West Antarctic Peninsula is one of the most rapidly changing regions of Antarctica and hosts some of the fastest-changing ice sheets and glaciers in Antarctica.
“Using an array of autonomous floats that measure the ocean’s temperature and salinity every 10 days for 15 years, we found that the cold water feeding the cold blob originates from the melting ice in Larsen C.
“We used a computer model to simulate the circulation in the area and to look at how the ocean currents change in response to the increased melting of ice shelves and glaciers.
“Our results suggest that as more ice melts and fresh water is added to the ocean surface, the currents slow down, allowing more time for the ocean surface to release its heat to the atmosphere.”
In conclusion, the researchers say the cooling water could help explain why the ice sheet didn’t collapse following large cracks – or ‘mega-fractures’ – that have appeared on Larsen C in recent years.
Dr Alex Phillips, from BAS’s Polar Oceans team, said: “This is a region that has experienced repeated fracturing and collapse of its ice shelves in recent decades, so it’s important to understand the competing influences of a warmer ocean on the one hand, and colder subsurface water feeding into the region, on the other.
“Our findings support the idea that, even as the ocean warms around the edges of Antarctica, the addition of meltwater from the ice sheet could actually slow down the rate at which the ice shelves melt, and icebergs are produced.
“This study demonstrates the critical role of detailed observations from the ocean interior to fully understand the response of the ice sheet to climate change.”
