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| Titel |
Isolating the atmospheric circulation response to Arctic sea-ice loss in the coupled climate system |
| VerfasserIn |
Paul Kushner, Russell Blackport |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250152049
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| Publikation (Nr.) |
 EGU/EGU2017-16837.pdf |
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| Zusammenfassung |
| In the coupled climate system, projected global warming drives extensive sea-ice loss, but
sea-ice loss drives warming that amplifies and can be confounded with the global warming
process. This makes it challenging to cleanly attribute the atmospheric circulation response to
sea-ice loss within coupled earth-system model (ESM) simulations of greenhouse warming.
In this study, many centuries of output from coupled ocean/atmosphere/land/sea-ice
ESM simulations driven separately by sea-ice albedo reduction and by projected
greenhouse-dominated radiative forcing are combined to cleanly isolate the hemispheric scale
response of the circulation to sea-ice loss. To isolate the sea-ice loss signal, a pattern scaling
approach is proposed in which the local multidecadal mean atmospheric response is assumed
to be separately proportional to the total sea-ice loss and to the total low latitude ocean
surface warming. The proposed approach estimates the response to Arctic sea-ice loss with
low latitude ocean temperatures fixed and vice versa. The sea-ice response includes a high
northern latitude easterly zonal wind response, an equatorward shift of the eddy
driven jet, a weakening of the stratospheric polar vortex, an anticyclonic sea level
pressure anomaly over coastal Eurasia, a cyclonic sea level pressure anomaly over the
North Pacific, and increased wintertime precipitation over the west coast of North
America. Many of these responses are opposed by the response to low-latitude
surface warming with sea ice fixed. However, both sea-ice loss and low latitude
surface warming act in concert to reduce storm track strength throughout the mid and
high latitudes. The responses are similar in two related versions of the National
Center for Atmospheric Research earth system models, apart from the stratospheric
polar vortex response. Evidence is presented that internal variability can easily
contaminate the estimates if not enough independent climate states are used to construct
them.
References: Blackport, R. and P. Kushner, 2017: Isolating the atmospheric circulation
response to Arctic sea-ice loss in the coupled climate system. J. Climate, in press. Blackport,
R. and P. Kushner, 2016: The Transient and Equilibrium Climate Response to Rapid
Summertime Sea Ice Loss in CCSM4. J. Climate, 29, 401–417, doi: 10.1175/JCLI-D-15-0284.1. |
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