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Interactions between topographically and thermallyforced stationary waves: implications on ice-sheetevolution
Stockholm University, Faculty of Science, Department of Meteorology .
(English)Article in journal (Refereed) Submitted
Abstract [en]

This study examines mutual interactions between stationary waves and ice sheets using a dry atmospheric primitive-equation model coupled to a three-dimensional thermomechanical ice-sheet model. The emphasis is on how nonlinear interactions between thermal and topographical forcing of the stationary waves influence the ice-sheet evolution through the ablation. Simulations are conducted in which a small ice cap, on an idealised Northern Hemisphere continent, evolves to an equilibrium continental-scale ice sheet. In the absence of stationary waves, the equilibrium ice sheet arrives at symmetric shape with a zonal equatorward margin. In isolation, the topographically-induced stationary waves have essentially no impacton the equilibrium features of the ice sheet. The reason is that the response is nonlinearimplying that the temperature anomalies are located far from the equatorward ice margin. When forcing due to thermal cooling is added to the topographical forcing, thermally-induced perturbation winds amplify the topographically-induced stationary-wave response, which serves to increase the equatorward extent of the ice sheet. Hence, the present study suggests that, if the topographically-induced stationary-wave response is nonlinear, it can be substantially amplified by the high albedo of the ice-sheet surface.

National Category
Meteorology and Atmospheric Sciences Climate Research
Research subject
Atmospheric Sciences and Oceanography
URN: urn:nbn:se:su:diva-55552OAI: diva2:405095
Available from: 2011-03-21 Created: 2011-03-21 Last updated: 2011-04-01Bibliographically approved
In thesis
1. The mutual interaction between the time-mean atmospheric circulation and continental-scale ice sheets
Open this publication in new window or tab >>The mutual interaction between the time-mean atmospheric circulation and continental-scale ice sheets
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Geomorphological evidence of glaciations exist for the Last Glacial Maximum (about 20 kyr ago). At this time, both North America and Eurasia were covered by extensive ice sheets which are both absent today. However, the temporal and spatial evolution of the ice sheets from the previous interglacial up to the fully-glaciated conditions at LGM is still unresolved and remains a vexing question in climate dynamics.

The evolution of ice sheets is essentially controlled by the prevailing climate conditions. On glacial time-scales, the climate is shaped the by the orbital variations of the Earth, but also by internal feedbacks within the climate system. In particular, the ice sheets themselves have the potential to change the climate within they evolve. This thesis focuses on the interactions between ice sheets and the time-mean atmospheric circulation (stationary waves). It is studied how the stationary waves, which are forced by the ice-sheet topography, influence ice-sheet evolution through changing the near-surface air temperature.

In this thesis, it is shown that the degree of linearity of the atmospheric response controls to what extent the stationary waves can reorganise the structure of ice sheet. Provided that the response is linear, the stationary waves constitute a leading-order feedback, which serves to increase the volume and deform the shape of ice sheets. If the stationary-wave response to ice-sheet topography is nonlinear in character, the impact on the ice-sheet evolution tends to be weak. However, it is further shown that the amplitude of the nonlinear topographical response, and hence its effect on the ice-sheet evolution, can be significantly enhanced if thermal cooling over the ice sheets is taken into account.

Place, publisher, year, edition, pages
Stockholm: Department of Meteorology, Stockholm University, 2011. 35 p.
Atmospheric stationary waves, Paleo ice sheets, Ice-sheet ablation, Atmosphere-ice sheet modelling
National Category
Climate Research Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences and Oceanography
urn:nbn:se:su:diva-55931 (URN)978-91-7447-271-4 (ISBN)
Public defence
2011-04-29, Högbomsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted. Available from: 2011-04-07 Created: 2011-03-30 Last updated: 2011-04-01Bibliographically approved

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