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
Date Published01/2014
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
Date Published: 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.