OUR STORY
Cape Dension
The home of the blizzard
The title Douglas Mawson chose for his book about the AAE remains the most apt description of this bleak, windswept Antarctic coast. Cape Denison has long been acknowledged as one of the world’s windiest places.
Cecil Madigan’s meticulous weather records begin to reveal the chaos of Cape Denison’s weather: an hourly mean wind-speed over the AAE’s 22 months of over 71 km/h, a maximum 12-hour run, on 5–6July 1913, of 143.2 km/h, and a maximum hour’s run (5July 1913) of 154.5km/h.
Antarctica’s vast ice sheet is the source of the winds, called katabatics, that sweep over the continent’s coasts at frequent intervals. That, along with a trick of topography, has given Cape Denison its special notoriety.
Katabatics are formed in Antarctica’s icy hinterland. Dense, heavy, cold air from the high plateau slides down the slope toward the coast, gathering surface snow along the way. Behind Cape Denison, the valley that becomes Boat Harbour funnels the already-powerful wind into a blinding, hurricane-force blast sweeping all before it.
The chaos extends beyond the coast. A few metres from Boat Harbour’s shore, the katabatic whips the sea into a chop, with spume spreading ahead of it. Sea ice is blown out, which makes Cape Denison a relatively ice-free coastline.
Offshore from the Mertz Glacier, the winds are so fierce and relentless that the sea is kept free of ice year-round. As ice is blown away by the winds, new ice keeps forming on the exposed water. This high rate of ice production makes the region one of the primary sources of ‘Antarctic bottom water’ – heavy, salty, cold water that carries surface oxygen down to the deepest parts of the world’s oceans, bringing nourishment and life to an otherwise dead zone.
Cape Denison’s temperatures are not significantly different from other parts of Antarctica’s coast. Average midwinter temperatures (June to August) are often around minus 20ºC, while midsummer temperatures (December to February) are around zero degrees celcius. Sometimes at the height of summer it is warm enough for meltwater to flow into Boat Harbour. The cape also contains a number of small meltwater lakes formed from glacial action.
