How the McMurdo Dry Valleys Stay Bare
On the edge of Antarctica’s Ross Sea, the McMurdo Dry Valleys look less like the continent’s familiar ice fields than a stark, rocky desert. Their snowlessness is not simply a result of receiving little snowfall. The landscape is shaped by a combination of sheltering mountains and winds that remove moisture before it can settle.
Mountains Block the Ice; Winds Do the Rest
The Transantarctic Mountains stand between the valleys and the vast East Antarctic ice sheet. They keep much of that ice from flowing into the lowlands. Meanwhile, powerful, cold downslope winds—called katabatic winds—spill from the high interior toward the coast. As the air descends, it speeds up and can warm slightly, making it harder for snow to persist. The winds also sweep loose snow off exposed ground and help turn surface ice directly into water vapor, a process called sublimation.
Together, these effects make it difficult for snow to accumulate. The valleys are therefore among the driest places on Earth, even though they are surrounded by a continent dominated by ice.
A Desert That Still Has Ice and Water
“Snow-free” does not mean entirely without frozen water. Glaciers occupy parts of the valleys, and some lakes remain beneath thick ice. In the brief austral summer, meltwater from glaciers can flow through channels, leaving narrow ribbons of life and activity amid the rock and frozen ground.
The result is a landscape preserved by an unusual balance: mountains limit the ice that can arrive, while dry, forceful winds keep much of the remaining snow from staying put. That combination helps explain how these valleys have remained largely bare for more than two million years.
