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Accueil > Grands équipements > La plateforme tournante Coriolis > Projets de recherche > Archives 2004

A low level explanation for the recent large warming trend over the western Antarctic Peninsula involving blocked winds and changes in zonal circulation

Orr A., D. Cresswell, G. J. Marshall, J. C. R. Hunt, J. Sommeria, C. G. Wang, M. Light, Geophys. Res. Lett. 31, L06204 (2004)

We demonstrate a mechanism whereby the impact of
stronger circumpolar westerly winds on the mountains of
the Antarctic Peninsula contributes significantly to the
enhanced warming trend observed over its western side in
the last 50 years. Numerical and laboratory meteorological
modelling demonstrate how, when westerly winds impinge
on this side, warm air below the height (1.5–2.0 km) of the
Peninsula is advected in a southerly direction. The strength
of the annual mean westerly winds has increased by about
15–20% since the 1960s, while the modelling results
indicate that contemporaneously the air advected to its
western side originates from an increasingly northerly (and
warmer) location. This gives rise to increased northerlies
and a greater transport of warm air into this region.
Consequently there is a reduction in the sea-ice extent,
further amplifying the local warming. This ‘low-level’,
orographic mechanism for the local climate trend is
supported by observational evidence.