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Abstract This study quantifies the contribution to Arctic winter surface warming from changes in the tropospheric energy transport (Ftrop) and the efficiency with whichFtropheats the surface in the RCP8.5 warming scenario of the Community Earth System Model Large Ensemble. A metric for this efficiency,Etrop, measures the fraction of anomalousFtropthat is balanced by an anomalous net surface flux (NSF). Drivers ofEtropare identified in synoptic‐scale events during whichFtropis the dominant driver of NSF.Etropis sensitive to the vertical structure ofFtropand pre‐existing Arctic lower‐tropospheric stability (LTS). In RCP8.5, winter‐meanFtropdecreases from 95.1 to 85.4 W m−2, whileEtropincreases by 5.7%, likely driven by decreased Arctic LTS, indicating an increased coupling betweenFtropand the surface energy budget. The net impact of decreasingFtropand increasing efficiency is a positive 0.7 W m−2contribution to winter‐season surface heating.
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The Arctic Surface Heating Efficiency of Tropospheric Energy Flux Events
Abstract This paper examines the processes that drive Arctic anomalous surface warming and sea ice loss during winter-season tropospheric energy flux events, synoptic periods of increased tropospheric energy flux convergence ( F trop ), using the NASA MERRA-2 reanalysis. During an event, a poleward anomaly in F trop initially increases the sensible and latent energy of the Arctic troposphere; as the warm and moist troposphere loses heat, the anomalous energy source is balanced by a flux upward across the tropopause and a downward net surface flux. A new metric for the Arctic surface heating efficiency ( E trop ) is defined, which measures the fraction of the energy source that reaches the surface. Composites of high-, medium-, and low-efficiency events help identify key physical factors, including the vertical structure of F trop and Arctic surface preconditioning. In high-efficiency events ( E trop ≥ 0.63), a bottom-heavy poleward F trop occurs in the presence of an anomalously warm and unstratified Arctic—a consequence of decreased sea ice—resulting in increased vertical mixing, enhanced near-surface warming and moistening, and further sea ice loss. Smaller E trop , and thus weaker surface impacts, are found in events with anomalously large initial sea ice extent and more vertically uniform F trop . These differences in E trop are manifested primarily through turbulent heat fluxes rather than downward longwave radiation. The frequency of high-efficiency events has increased from the period 1980–99 to the period 2000–19, contributing to Arctic surface warming and sea ice decline.
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- Award ID(s):
- 2026863
- PAR ID:
- 10387909
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 35
- Issue:
- 18
- ISSN:
- 0894-8755
- Page Range / eLocation ID:
- 5897 to 5913
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/JCLI-D-21-0852.1
