Does Antarctica Melt in Winter?

The summer sun causes temperatures in Antarctica to rise above zero for several months, causing snow atop the surface of the continent’s glaciers to melt away. However, new research undertaken by Utrecht University in the Netherlands has determined that this thaw isn’t limited to the summer months.

Even though there is no sunlight during winter and the interior of the continent remains freezing cold for months on end, the peripheral edges of Antarctica can enjoy warmer periods due to warm easterly winds from the western edge of the ice sheet.

Above zero even in winter

Scientists have long known that winter in Antarctica is a perfectly dark and freezing cold time of the year. With no solar light to heat the glacial surfaces, temperatures can plummet to as low as -80°C in the centre of the continent. Around its edges, they are normally significantly higher – around -25°C – but still far below melting point.

However, researchers were aware that snow was still melting during this period and so installed a weather station to find out why the ice was melting faster than they had previously assumed. The findings showed that one station recorded a high of 8°C during the dead of winter, something experts had previously believed impossible.

Warm winds

The culprit is believed to a temperate, arid wind which flows down from the mountains on the western edge of Antarctica every week. Known as a “foehn” wind (German for hairdryer), the breeze is capable of raising temperatures in its path by as much 15°C or even 20°C in just the space of a few hours.

“All of the winter heat comes from the foehn wind, there is no other heat source this period of year,” said Kuipers Munneke, lead author of the report. “During a strong foehn, so much snow can melt that it forms huge lakes on the surface of the ice. We had known about these lakes during the summertime, but apparently 20% to 25% of the meltwater from the past few years actually occurs in the winter instead.”

Potential consequences

This winter melt can lead to lakes forming on the top of glaciers, sometimes as long as a kilometre and as wide as 50m, with about a metre or two of depth. However, the water is believed to freeze back over before the end of winter, meaning it does not have a direct impact on rising sea levels. It does, however, sometimes cause the ice sheets to become unstable and so break off chunks into new glaciers.

Much like the enhanced nitrous oxide emissions found in the Arctic, these glaciers are more concerning for the potential consequences they could have than for their immediate ones. More unstable ice sheets could lead to more glaciers, which could have an impact on sea levels over a longer time. Furthermore, the problems of climate change mean that this phenomenon is only expected to deteriorate as we go forward, with warmer temperatures meaning warmer foehn winds, bigger ice lakes and more glaciers. As such, Antarctica melting in winter could be a real cause for concern for the future of the continent – and the planet – in the long run.