Weerwoord | Re : Tijd om nieuw klimaat onderzoek

Natuurlijk wordt die vraag gesteld. Laat me er even dieper op in gaan voor het zuidelijk halfrond. Sta me toe te kopiëren uit een kladversie voor een artikel dat ik aan het schrijven ben voor Climate Dynamics. Onderaan het stuk kunt u wat uitleg vinden.

As discussed in previous studies (Fyfe et al., 1999; Marshall et al., 2004; Arblaster and Meehl, 2006; Fyfe and Saenko, 2006), the Southern Annular Mode (SAM) is projected to move towards a more positive phase, i.e. a lower pressure at high latitudes and a higher pressure in mid-latitudes during the 21st century.

Zoals gezegd in dit stukje is er een grotere neiging tot lagedrukgebieden rond 65°S (en zuidelijker) en hogedrukgebieden rond 40°S wat aanleiding geeft tot sterkere westenwinden in het tussengebied. Ik citeer verder (uit Lefebvre et al., 2004):

When the SAM is in its positive phase, ... The pressure pattern associated with the SAM induces meridional winds which advect warmer air in the Weddell Sea and around the Antarctic Peninsula and colder air in the Amundsen and Ross Seas. This implies a dipole response of sea ice to the SAM, with on average a decrease in ice area in the Weddell Sea and around the Antarctic Peninsula and an increase in the Ross and Amundsen Seas during years with a high SAM index.

Die veranderingen geven dus aanleiding tot specifieke gevolgen voor bepaalde regio's.
Ik citeer nu even uit Marshall et al., 2006:

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 modelling studies to be predominantly a response to anthropogenic forcing, resulting in increased westerlies across the northern Peninsula.
We utilize observations and reanalysis data to demonstrate that the changing SAM has played a key role in driving this local summer warming. We propose that the stronger summer westerly winds reduce the blocking effect of the 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 temperature sensitivity to the SAM that is three times greater on the eastern side of the Peninsula than on the west. SAM variability is also shown to play a lesser 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.

wat aantoont dat er heel specifieke gevolgen kunnen zijn van zo'n situaties.

Zo'n onderzoeken bestaan voor Europa ook, maar met minder duidelijk resultaat.

Wouter

Referenties:

Lefebvre W, Goosse H, Timmermann R and Fichefet T, Influence of the Southern Annular Mode on the sea ice--ocean system, J. Geophys. Res., 109, C09005, doi:10.1029/2004JC002403, 2004.

Lefebvre W. and Goosse H., Analysis of the projected regional sea ice changes in the Southern Ocean during the 21st century, in preparation.

Marshall GJ, Orr A, van Lipzig NPM and King JC, The impact of a changing Southern Hemisphere Annular Mode on Antarctic Peninsula summer temperatures, J. of Climate, 19, 5388-5404, 2006.