North Pole Drifting Ice Station NP-35: Stratospheric Ozone Measurements
Ozone sonde at a meteorological balloon
Polar stratospheric clouds (mother of pearl clouds) above Kiruna.
The discovery of the Antarctic ozone hole in 1985 led to intensified international research on the polar ozone layer. The ozone layer, which is mainly located in the stratosphere at altitudes of about 15-25 km above the ground, protects the biosphere from harmful ultraviolet (UV) radiation from the sun. Initial research focused on the chemical processes that drive ozone loss in polar regions. Much of this is now understood and anthropogenic emissions of chlorofluorocarbons (CFCs) were identified as main reason for the ozone loss. Due to the presence of Polar Stratospheric Clouds (PCSs) in the ozone layer breakdown products of the CFC are converted from benign species into aggressive molecules, which destroy ozone rapidly. PSCs can form in the winter polar stratosphere when temperatures fall to very low values.
Similar to the Antarctic - although less intense - ozone loss take place in some of the Arctic winters. The Arctic is much closer to populated areas than the Antarctic. Arctic ozone loss led to reductions in the thickness of the ozone layer over Europe - an effect that already contributed to higher levels of harmful UV radiation in Europe and North America. So far ozone loss over the Arctic has been less severe than over the Antarctic and the degree of ozone loss is very variable from year to year. The known ozone chemistry can explain only 50% of the observed annual variability of the Arctic ozone layer in spring. Dynamical mechanisms that are not well understood are as important for the variability of the ozone layer in the Arctic as the chemical loss of ozone.
At the Arctic station of the AWI in Ny-Ålesund on Spitsbergen (79° N) a strong and systematic multi-annual variation of the abundance of ozone is observed at altitudes of 25 to 30 km, which appear to be related to solar variability and which cannot be explained by the known chemical or dynamical processes. If indeed caused by solar variability, the observed 30% amplitude of the effect would be by far the strongest signal of solar variability on the lower atmosphere ever found.
The reasons for these unexplained variations will be studied in the project.
Scheme of the polar vortex
In each winter a pronounced low pressure system forms in the Arctic stratosphere - the so called polar vortex. It plays a key role for the dynamical processes in the stratosphere that contribute to variability of Arctic ozone. Particularly dynamical processes and transport of ozone during the initial setup of the vortex are poorly known.
The ozone soundings in the central Arctic during fall and winter have two goals:
(1) to study the dynamical processes and ozone transport while the Arctic polar vortex forms.
(2) to contribute to the quantification of chemical ozone loss - the station on the ice floe will participate in a so-called Match campaign that will isolate chemical ozone loss from dynamical changes and will precisely measure the rate of ozone destruction.
Electrochemical ozonesonde
The vertical distribution of ozone will be measured with electrochemical cells at a very high vertical resolution. Such measurements are regularly performed at various stations worldwide. But so far the region north of 82° N, the central Arctic - a key region for Arctic ozone variability - is a blind spot in the observational system. We will measure the first high vertical resolution ozone profiles in this region and close an essential gap in high resolution global maps of the ozone layer.
Ozone sonde station net in the Arctic and mid-latitudes with example trajectory
This unique data set will be combined with data records of ozone profiles from other areas of the Arctic and sub-Arctic that exist. Computations of air movements (trajectories) and the use of chemical models will contribute to a better understanding of the seasonal and interannual variability of stratospheric ozone in the Arctic.