Arctic winter 2010/2011 at the brink of an ozone hole

Abstract

The Arctic stratospheric winter of 2010/2011 was one of the coldest on record with a large loss of stratospheric ozone. Observations of temperature, ozone, nitric acid, water vapor, nitrous oxide, chlorine nitrate and chlorine monoxide from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT are compared to calculations with a chemical transport model (CTM). There is overall excellent agreement between the model calculations and MIPAS observations, indicating that the processes of denitrification, chlorine activation and catalytic ozone depletion are sufficiently well represented. Polar vortex integrated ozone loss reaches 120 Dobson Units (DU) by early April 2011. Sensitivity calculations with the CTM give an additional ozone loss of about 25 DU at the end of the winter for a further cooling of the stratosphere by 1 K, showing locally near‐complete ozone depletion (remaining ozone <200 ppbv) over a large vertical extent from 16 to 19 km altitude. In the CTM a 1 K cooling approximately counteracts a 10% reduction in stratospheric halogen loading, a halogen reduction that is expected to occur in about 13 years from now. These results indicate that severe ozone depletion like in 2010/2011 or even worse could appear for cold Arctic winters over the next decades if the observed tendency for cold Arctic winters to become colder continues into the future.

MIPAS IMK/IAA CFC-11 (CCl3F) and CFC-12 (CCl2F2) measurements: accuracy, precision and long-term stability

“…In this particular case, strong stratospheric subsidence has led to extraordinarily low mixing ratios of CFCs. This uncommon atmospheric situation went along with substantial ozone destruction Sinnhuber et al, 2011).…”

“…The retrieval employs a nonlinear least-squares approach with a first-order Tikhonov-type regularization (von Clarmann et al, 2003(von Clarmann et al, , 2009. The simulation of the radiative transfer through the atmosphere is performed by the KOPRA (Karlsruhe Optimized and Precise Radiative transfer Algorithm) model (Stiller, 2000). In the comparisons, we consider data that were retrieved with the retrieval versions V5H_CFC-11_20 and V5H_CFC-12_20 for the FR period as well as V5R_CFC-11_220/221 and V5R_CFC-12_220/221 for the RR period (Kellmann et al, 2012).…”

“…Similar to the MIPAS data processing, the forward model KOPRA (Karlsruhe Optimized and Precise Radiative Transfer Algorithm; Stiller, 2000) and the inversion module KOPRAFIT (Höpfner et al, 2001), involving a first-order Tikhonov-type regularization, were used. The retrieval was performed sequentially, i.e., species with low spectral interference with other gases were retrieved first.…”

The contributions of chemistry and transport to low arctic ozone in March 2011 derived from Aura MLS observations

“…Adams et al [2012] and Lindenmaier et al [2012] both used an offline chemistry transport model simulation (SLIMCAT) carrying passive O 3 (no chemistry) and reported losses of 99-108 DU between 12 and 20 March. Sinnhuber et al [2011] report vortex losses of more than 140 DU by early April based on model calculations with a passive O 3 tracer. Their simulated vortex N 2 O, initialized with MIPAS data on 1 December, was 40 ppb too high compared to MIPAS by mid-February at 475 K. This indicates either insufficient descent, or sufficient descent but without vortex isolation.…”

“…Although recent cold Arctic springs, notably 1997Arctic springs, notably , 2000Arctic springs, notably , 2003Arctic springs, notably , and 2005, had a March vortex with sufficiently low temperatures to produce daily March minimum O 3 columns as low as~320 DU (averaged poleward of 63 o equivalent latitude), they did not have a period of polar stratospheric cloud (PSC) formation that lasted more than 3 months [WMO, 2011]. The lengthy period of low temperatures in 2011 led to a much greater degree of denitrification and subsequent ozone loss than has been previously diagnosed in the Arctic Sinnhuber et al, 2011].…”