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The impact of topographically forced stationary waves on local ice-sheet climate
Stockholm University, Faculty of Science, Department of Meteorology .
Stockholm University, Faculty of Science, Department of Meteorology .
2010 (English)In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 56, no 197, 534-544 p.Article in journal (Refereed) Published
Abstract [en]

A linear two-level atmospheric model is employed to study the influence of ice-sheet topography on atmospheric stationary waves. In particular, the stationary-wave-induced temperature anomaly is considered locally over a single ice-sheet topography, which is computed using the plastic approximation. It is found that stationary waves induce a local cooling which increases linearly with the ice volume for ice sheets of horizontal extents smaller than 1400 km. Beyond this horizontal scale, the dependence of stationary-wave-induced cooling on the ice volume becomes gradually weaker. For a certain ice-sheet size, and for small changes of the surface zonal wind, it is further shown that the strength of the local stationary-wave-induced cooling is proportional to the basic state meridional temperature gradient multiplied by the vertical stratification in the atmosphere. These results are of importance for the nature of the feedback between ice sheets and stationary waves, and may also serve as a basis for parameterizing this feedback in ice-sheet model simulations (e.g. through the Pleistocene glacial/interglacial cycles).

Place, publisher, year, edition, pages
2010. Vol. 56, no 197, 534-544 p.
National Category
Meteorology and Atmospheric Sciences
Identifiers
URN: urn:nbn:se:su:diva-49151DOI: 10.3189/002214310792447824ISI: 000280930000014OAI: oai:DiVA.org:su-49151DiVA: diva2:376216
Note
authorCount :2Available from: 2010-12-10 Created: 2010-12-10 Last updated: 2017-12-11Bibliographically 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.
Keyword
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
Identifiers
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)
Opponent
Supervisors
Note
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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