This document summarizes a study examining how the Quasi-Biennial Oscillation (QBO) can modulate the atmospheric response to projected Arctic sea ice loss. The study uses the Whole Atmosphere Community Climate Model to simulate different phases of the QBO and responses to historical and future sea ice conditions. It finds that a weaker early winter polar vortex occurs during the QBO's easterly phase, leading to constructive wave interference. A North Atlantic Oscillation-like response is seen in the QBO's westerly phase, while Siberian cold extremes occur in the easterly phase. The results suggest the QBO can influence both stratospheric and tropospheric/surface responses through the Holton-

1. Linking the Quasi-Biennial Oscillation and
projected Arctic sea-ice loss to
stratospheric variability in early winter
Zachary M. Labe
Gudrun Magnusdottir, Yannick Peings
Department of Earth System Science at UC Irvine
10 January 2019
@ZLabe

2. Atmospheric response to
sea-ice loss may be
sensitive to background
state and stratospheric
pathway
Polar Amplification Model
Intercomparison Project
(PAMIP; Smith et al. 2018,
Geosci. Model Dev.)
SMITH ET AL. 2017, JCLI
MOTIVATION

3. 1. Composite atmospheric responses by QBO phase (westerly,
neutral, easterly) – approximately 67 years per phase
2. Assess Holton-Tan effect (QBO-E minus QBO-W)
3. Does the QBO modulate the atmospheric response to sea-ice
loss? (Future minus Historical)
Assess the role of the Quasi-biennial Oscillation
(QBO) on the atmospheric response to Arctic sea-
ice loss

4. WACCM4
Whole Atmosphere
Community Climate
Model version 4 –
Specified Chemistry
“high top”
chemistry-climate
atmosphere
model
Physical
parameterizations
from CAM4
• 66 vertical levels – extending to 5
x 10-6 hPa (140 km)
• 1.9° latitude x 2.5° longitude
• QBO prescribed from radiosonde
observations
• Improved representation of
sudden stratospheric warming
(SSW) events
• fixed radiative forcings from year
2000

5. NAME SEA ICE FORCING DURATIO
N
Historical Average 1976-2005 LENS SIT
Average 1976-2005 LENS SIC
ONDJFM;
200 members
Future Future 2051-2080 LENS SIT
Future 2051-2080 LENS SIC
ONDJFM;
200 members
All experiments have average 1976-2005 LENS SST*
Atmospheric General Circulation Model
Experiments

6. SEAICE

7. HEATFLUX
Longwave
+ Turbulent (latent,sensible)

8. Large-Scale
Response

9. December

10. December

11. December

12. LABEETAL.2018,GRL

13. LABEETAL.2018,GRL

14. December
Pacific vs. Atlantic
jets

15. December
N(AO) response
differences

16. December
500hPaHEIGHTS
QBO-EQBO-W
Upper level ridge
extends over Siberia
NAO-like response

17. December
Constructive
interference

18. GEOPOTENTIAL

19. Mechanisms

20. Nov-Dec
PLUMBFLUX

21. Nov-Dec
PLUMBFLUX

22. Nov-Dec
Plumb Flux QBO-E at 150 hPa
Anomalous WAFz
over Siberia

23. LINEARINTERFERENCE
Nov-Dec

24. Surface
Response

25. December
COLDEXTREMES
Thermal advecti
response

26. 1) Simulations reproduce shift in zero-
wind line and polar vortex response in
each QBO phase (albeit weaker)
2) Weaker early winter polar vortex in
QBO-E, constructive linear wave
interference
3) NAO-like response = QBO-W, Siberian
cold extremes = QBO-E
SUMMARY
• Holtan – Tan
mechanism
• Stratospheric
response
• Tropospheric
and surface
response

27. 1) Simulations reproduce shift in zero-
wind line and polar vortex response in
each QBO phase (albeit weaker)
2) Weaker early winter polar vortex in
QBO-E, constructive linear wave
interference
3) NAO-like response = QBO-W, Siberian
cold extremes = QBO-E
SUMMARY
• Holtan – Tan
mechanism
• Stratospheric
response
• Tropospheric
and surface
response

28. 1) Simulations reproduce shift in zero-
wind line and polar vortex response in
each QBO phase (albeit weaker)
2) Weaker early winter polar vortex in
QBO-E, constructive linear wave
interference
3) NAO-like response = QBO-W, Siberian
cold extremes = QBO-E
SUMMARY
• Holtan – Tan
mechanism
• Stratospheric
response
• Tropospheric
and surface
response

29. zlabe@uci.edu
@ZLabe
Zachary Labe
QUESTIONS
QBO can modulate atmospheric response to
sea-ice loss in an AGCM
– Importance of background state