Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Processes Controlling Southern Ocean Shortwave Climate Feedbacks in CESM

TitleProcesses Controlling Southern Ocean Shortwave Climate Feedbacks in CESM
Publication TypeJournal Article
Year of Publication2014
JournalGeophysical Research Letters
Volume41
Pages616-622
Abstract / Summary

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°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 ~55°S, surface albedo reductions and increased cloud liquid water content (LWC) have competing effects on ASR changes. Equatorward of ~55°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°) 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°) 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.

DOI10.1002/2013GL058315
Journal: Geophysical Research Letters
Year of Publication: 2014
Volume: 41
Pages: 616-622
Publication Date: 01/2014

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°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 ~55°S, surface albedo reductions and increased cloud liquid water content (LWC) have competing effects on ASR changes. Equatorward of ~55°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°) 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°) 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.

DOI: 10.1002/2013GL058315
Citation:
Kay, JE, B Medeiros, Y- Hwang, A Gettelman, J Perket, and MG Flanner.  2014.  "Processes Controlling Southern Ocean Shortwave Climate Feedbacks in CESM."  Geophysical Research Letters 41: 616-622.  https://doi.org/10.1002/2013GL058315.