The Southern Westerly Winds throughout the Holocene in climate model simulations
Abstract
Atmospheric circulation at hemispheric scale integrates large-scale features from tropical, subtropical, midlatitudes and polar regions, including the Hadley and Ferrel Cell, as well as the subtropical anticyclones and in the Southern Hemisphere (SH), the Southern Westerly Winds (SWW). The SWW in particular have been a central element in understanding past, present and future climate in the SH and at global scale, due to their importance in the global carbon cycle via its coupling with the southern ocean.
We analyse three transient model simulations of the Holocene to investigate the evolution of the SH westerly wind system. The Holocene, the last 11,700 years of Earth history, is usually depicted as a relatively stable climate period in which human civilization has developed; its climate evolution has been driven mainly by slowly varying insolation forcing and is therefore a prime setting for disentangling external and internal modes of variability in our climate system. A better understanding of natural climatic variations in the SH will help quantify the contribution of both anthropogenic and natural variations to current and future climatic changes in this region. In the present climate, we know that at the seasonal scale mayor latitudinal changes are found in the Pacific Ocean, and to a smaller degree in the Atlantic Ocean, whereas in the Indian Ocean and the Australian / NZ sector the seasonal shift is minimal. In terms of strength, strongest winds are found in the Indian Ocean sector. On the other hand, at upper levels over the Pacific, the subtropical jet features a split jet. These characteristics are reproduced by the models for present climate and throughout the Holocene. In addition the models show millennial trends in wind strength that follow the insolation forcing, but also multi-centennial variability. Important seasonal variations are found.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A43I..08R
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3319 General circulation;
- ATMOSPHERIC PROCESSESDE: 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSES