11B.1 Learning from Antarctica: Climate variability and change, stable boundary-layers and chemistry, and a few surprises on the high plateau (2008

11B.1

Learning from Antarctica: Climate variability and change, stable boundary-layers and chemistry, and a few surprises on the high plateau

William Neff, NOAA/ESRL-PSD, Boulder, CO

Antarctica is one of the most dramatic topographic features on the face

of the Earth extending over half an atmospheric scale height into the

troposphere with a horizontal extent exceeding the Rossby Radius of

deformation. Dynamically, it is the closest analogue in the atmosphere

to a seamount in the ocean. While a history of the Earth's climate and

chemical composition over 800,000 years resides in 3000-m deep ice cores

from the high plateau, intensive observation of atmospheric and chemical

processes affecting the continent only began with the IGY in late 1957.

In recent decades, it has received recognition for hosting massive

springtime ozone depletion in its stratospheric vortex and some of the

Earth's most rapid surface warming on its Peninsula. However, from the

heroic era of exploration to the present, the surface winds over

Antarctica have dominated the human experience with remarkable

persistence over the interior, strength on the coast, as well as a

seemingly straightforward dynamical explanation. With new acoustic

probing of the boundary layer beginning in the 1970s at the South Pole,

this picture has changed, revealing unexpected complexity (even in the

absence of a diurnal insolation cycle) and sensitivity of the boundary

layer, on daily to decadal time scales, to the circulation in the

upper-troposphere/lowermost stratosphere. Among the surprises, recent

studies of reactive nitrogen exchanges with the snow surface have

revealed unexpectedly high concentrations of nitric oxide (>900 pptv)

and shown the dominant role of the stable boundary layer in mediating

these exchanges in concert with changes in the upper tropospheric

circulation. More importantly, recent work examining trends in

geopotential height over the South Pole in comparison with coastal sites

over the last five decades has revealed surprising seasonal and

geographical asymmetries as well as decadal to multi-decadal variability

in these trends, perhaps as a result of the warming of the tropical oceans.

Session 11B, Walter Orr Roberts Lecture
Wednesday, 23 January 2008, 1:30 PM-2:30 PM, 217-218