McMurdo Sound - Winds Have Far Reaching Effects

Winds Have Far Reaching Effects

Polar winds are a driving force behind weather systems arising from three surface zones that converge at McMurdo Sound: the polar plateau and Transantarctic Mountains, the Ross Ice Shelf, and the Ross Sea. These surface zones create a range of dynamic weather systems. Cold, heavy air descending rapidly from the polar plateau at elevations of 10,000 feet (3,000 m) or more spawns fierce katabatic winds. These dry winds can reach hurricane force by the time they reach the Antarctic coast. Wind instruments recorded Antarctica’s highest wind velocity at the coastal station Dumont d'Urville in July 1972 at 199 mph (320 km/h) or 327 km/h (Australian Government Antarctica Division).

Prevailing winds spilling into McMurdo Sound shoot between mountain passes and other land formations, stirring up blizzards known locally as “Herbies.” Such blizzards can occur any time of year. Residents of McMurdo Station and Scott Base have dubbed the nearby White Island and Black Island as Herbie Alley due to winds that funnel blizzards between the islands (Field Manual for the U.S. Antarctic Program).

Overall the continent’s extreme cold air scarcely holds enough moisture for snowfall. Consequently, Antarctica’s blizzards are at times as much about wind stirring up existing snow as they are about new snowfall. For instance, the water equivalent from annual snow fall on Ross Island averages only 17.6 centimeters (National Science Foundation). Snowfall in Antarctica’s interior is far less at 2 inches (5 centimeters). Noted as well are the McMurdo Dry Valleys on the western shores of McMurdo Sound where snow seldom accumulates.

Antarctica's shortfall in new snow does not lessen the continent's striking polar climate. Antarctica essentially doubles in size during the winter as the surrounding sea water freezes (Antarctic Connection). The subsequent annual summer melt of the estimated 7,000,000 square miles (18,000,000 km2) of ice that rings Antarctica creates the planet’s largest seasonal climate event (USA Today). The result is a vertical circulation driven by a massive heat and energy exchange between ice, ocean, and atmosphere.

McMurdo Sound provides an important component in Antarctica’s global effects upon climate. A key factor is the polar winds that can drive the sound’s pack ice into the Ross Sea summer or winter. Frigid katabatic winds rake subsequent exposed water causing sea ice to form. Freezing surface water excludes salt from the water below; leaving behind heavy, cold water that sinks to the ocean floor. This process repeats itself along Antarctica’s coastal areas, spreading cold sea water outward into the world’s ocean basins (Australian Government Antarctic Division).

According to an interview with a climatologist Gerd Wendler published in the National Science Foundation’s Antarctic Sun, one could dive to the ocean floor anywhere in the world and encounter water from the coast of Antarctica. "Seventy five percent of all the bottom water, wherever you are, comes from Antarctica."