Abstract
Arctic column ozone reached record low values (∼310 DU) during March of 2011, exposing Arctic ecosystems to enhanced UV‐B. We identify the cause of this anomaly using the Oslo CTM2 atmospheric chemistry model driven by ECMWF meteorology to simulate Arctic ozone from 1998 through 2011. CTM2 successfully reproduces the variability in column ozone, from week to week, and from year to year, correctly identifying 2011 as an extreme anomaly over the period. By comparing parallel model simulations, one with all Arctic ozone chemistry turned off on January 1, we find that chemical ozone loss in 2011 is enhanced relative to previous years, but it accounted for only 23% of the anomaly. Weakened transport of ozone from middle latitudes, concurrent with an anomalously strong polar vortex, was the primary cause of the low ozone When the zonal winds relaxed in mid‐March 2011, Arctic column ozone quickly recovered.
Highlights
Model simulations of column ozone are in good agreement with the daily columns observed by satellite (GOME-2) as well as the Arctic-averaged column ozone for March over the 14-year period, 1998 through 2011
In 2011, the Arctic ozone deficit first appears in late January and reaches a maximum in the middle of March, before a breakdown of the vortex and mixing with mid-latitude air masses
Year 2011 represents a record low in late winter Arctic column ozone that was accompanied by increased ozone outside the Arctic region [Balis et al, 2011], a result shown by the Oslo CTM2
Summary
[2] A large deficit in column ozone relative to the previous 13 years of observations - was observed in the Arctic stratosphere during February- March of 2011. This low ozone resulted in record high UV-B exposure of the Arctic ecosystems in the early spring and thereby environmental damage [Callaghan et al, 2004; Solheim et al, 2006]. Even in terms of large-scale averages (60N–90N, month of March), this 2011 Arctic column ozone was about three standard deviations below the 1997– 2011 mean-sigma anomaly. 408 425 367 426 393 391 392 379 406 384 397 402 433 325 model – obs. model anomalyA
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