Processes controlling Southern Ocean shortwave climate feedbacks in CESM

TitleProcesses controlling Southern Ocean shortwave climate feedbacks in CESM
Publication TypeJournal Article
Year of Publication2014
AuthorsKay J.E, Medeiros B., Hwang Y.T, Gettelman A., Perket J., Flanner M.G
JournalGeophysical Research Letters
Date Published2014/01
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000332991000060
Keywords21st-century; budget; climate feedbacks; cloud biases; Clouds; community atmosphere model; evolution; hemisphere; hole; jet; ozone; poleward shift; radiation; sea ice; sea-ice; shortwave; Southern Ocean

A climate model (Community Earth System Model with the Community Atmosphere Model version 5 (CESM-CAM5)) is used to identify processes controlling Southern Ocean (30-70 degrees S) absorbed shortwave radiation (ASR). In response to 21st century Representative Concentration Pathway 8.5 forcing, both sea ice loss (2.6 W m(-2)) and cloud changes (1.2 W m(-2)) enhance ASR, but their relative importance depends on location and season. Poleward of similar to 55 degrees S, surface albedo reductions and increased cloud liquid water content (LWC) have competing effects on ASR changes. Equatorward of similar to 55 degrees S, decreased LWC enhances ASR. The 21st century cloud LWC changes result from warming and near-surface stability changes but appear unrelated to a small (1 degrees) poleward shift in the eddy-driven jet. In fact, the 21st century ASR changes are 5 times greater than ASR changes resulting from large (5 degrees) naturally occurring jet latitude variability. More broadly, these results suggest that thermodynamics (warming and near-surface stability), not poleward jet shifts, control 21st century Southern Ocean shortwave climate feedbacks.

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