Abstract: The Southern Hemisphere Westerly Winds (SWW) have been suggested to exert a critical influence on global climate through wind-driven upwelling of deep water in the Southern Ocean and the potentially resulting atmospheric CO2 variations. The investigation of the temporal and spatial evolution of the SWW along with forcings and feedbacks remains a significant challenge in climate research. In this study, the evolution of the SWW under orbital forcing from the early Holocene (9 kyr BP) to pre-industrial modern times is examined with transient experiments using the comprehensive coupled global climate model CCSM3. Analyses of the model results suggest that the annual and seasonal mean SWW were subject to an overall strengthening and poleward shifting trend during the course of the early-to-late Holocene under the influence of orbital forcing, except for the austral spring season, where the SWW exhibited an opposite trend of shifting towards the equator.
Source: Supplement to: Varma, Vidya; Prange, Matthias; Merkel, Ute; Kleinen, Thomas; Lohmann, Gerrit; Pfeiffer, Madlene; Renssen, Hans; Wagner, Axel; Wagner, Sebastian; Schulz, Michael (2012): Holocene evolution of the Southern Hemisphere westerly winds in transient simulations with global climate models. Climate of the Past, 8(2), 391-402, https://doi.org/10.5194/cp-8-391-2012
Supplemental Information: Three transient experiments from early Holocene to pre-industrial modern times (9 kyr BP to 0 BP) under orbital forcing have been carried out using the low resolution version (T31) of the comprehensive global climate model CCSM3. By applying an acceleration (by a factor of 10) to the orbital forcing year, climate trends of the last 9000 yr, imposed by the external orbitally driven insolation changes, are represented in the experiments with only 900 simulation years. While the first transient run was initialized with the quasi-equilibrated 9 kyr BP state, the second and third transient runs used the 8.9 and 8.8 kyr BP climates from the first transient run as initial conditions at 9 kyr BP. Throughout the Holocene experiments, greenhouse gas concentrations as well as aerosol and ozone distributions were kept at pre-industrial values as prescribed by the protocol of the Paleoclimate Modelling Intercomparison Project (PMIP), Phase II (Braconnot et al., 2007, doi:10.5194/cp-3-261-2007). The data provided are the ensemble mean of the three transient runs given as decadal means.
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