The impact of a changing southern hemisphere annular mode on Antarctic Peninsula summer temperatures
Marshall, G.J.; Orr, A.; van Lipzig, N.; King, J.C. (2006). The impact of a changing southern hemisphere annular mode on Antarctic Peninsula summer temperatures. J. Clim. 19(20): 5388-5404. http://dx.doi.org/10.1175/JCLI3844.1 In: Journal of Climate. American Meteorological Society: Boston, MA. ISSN 0894-8755; e-ISSN 1520-0442, more |   |
| Keyword | | | Author keywords | Temperature, Ice shelves, Annular mode |
| Authors | | Top | - Marshall, G.J.
- Orr, A.
- van Lipzig, N.
- King, J.C.
| | |
| Abstract | Since the mid-1960s, rapid regional summer warming has occurred on the east coast of the northern Antarctic Peninsula, with near-surface temperatures increasing by more than 2°C. This warming has contributed significantly to the collapse of the northern sections of the Larsen Ice Shelf. Coincident with this warming, the summer Southern Hemisphere Annular Mode (SAM) has exhibited a marked trend, suggested by modeling studies to be predominantly a response to anthropogenic forcing, resulting in increased westerlies across the northern peninsula.Observations and reanalysis data are utilized to demonstrate that the changing SAM has played a key role in driving this local summer warming. It is proposed that the stronger summer westerly winds reduce the blocking effect of the Antarctic Peninsula and lead to a higher frequency of air masses being advected eastward over the orographic barrier of the northern Antarctic Peninsula. When this occurs, a combination of a climatological temperature gradient across the barrier and the formation of a föhn wind on the lee side typically results in a summer near-surface temperature sensitivity to the SAM that is 3 times greater on the eastern side of the peninsula than on the west. SAM variability is also shown to play a less important role in determining summer temperatures at stations west of the barrier in the northern peninsula (~62°S), both at the surface and throughout the troposphere. This is in contrast to a station farther south (~65°S) where the SAM exerts little influence. |
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