riley x. brady€¦ · riley x. brady . university of colorado at boulder . coauthors: ryan...
Post on 15-Aug-2020
2 Views
Preview:
TRANSCRIPT
Emergence of Anthropogenic Trends in California Current Upwelling in the Presence of Natural Climate Variability
Riley X. Brady University of Colorado at Boulder
Coauthors: Ryan Rykaczewski (U. South Carolina)
Michael Alexander (NOAA ESRL)
CESM Workshop June 23rd, 2016
Breckenridge, CO
A mechanism exists whereby global greenhouse warming could . . . lead to acceleration of coastal upwelling. (Bakun, 1990)
Source: Rykaczewski & Checkley 2008 Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
“. . . we still cannot attribute coastal wind intensification in EBUS to global warming because we cannot discount the role of multi-decadal climate variability in the observed trends.”
Garcia-Reyes, et al. 2015
“Summertime winds near poleward boundaries of climatological upwelling zones are projected to intensify, while winds near equatorward boundaries are projected to weaken."
Rykaczewski, et al. 2015
By holding the model and emissions scenario constant, we can attribute disparities entirely to internally-generated climate variability.
Modified from Kay et al. 2015
1850 Control Member 1
Observations Members 2-35
Generated ensemble with 10-14K air
temperature differences
Forced with RCP8.5 emissions scenario
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
The California Current was split into three distinct regions based on coastal geography.
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Nor
th
Cent
ral
Sout
h
These regions display distinct seasonal cycles in both vertical velocity and alongshore wind stress.
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Vert
ical
Vel
ocity
at 5
0m D
epth
(cm
/s x
10-3
)
Area
-Wei
ghte
d Al
ongs
hore
Win
d St
ress
(dyn
e/cm
2 )
North
Central
South
Ensemble Historical Coastal Upwelling (1920 – 2005)
Ensemble Historical Alongshore Wind Stress (1920 – 2005)
Model Data Observational Data
Coastal Grid-Cell
A Signal-to-Noise Ratio quantifies the relative strength of anthropogenic climate change.
Signal (S) = ∆𝒘𝒘 Noise (N) = 𝝈𝝈∆𝒘𝒘
N = 35
1∘
1∘
∆𝑤𝑤𝜎𝜎∆𝑤𝑤
≡ 𝑆𝑆𝑁𝑁
> 𝟐𝟐 is considered a significant emergence of the signal.
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Long-term changes in upwelling and wind stress vary by season and location.
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Forced Change in Alongshore Wind Stress (dyne/cm2)
Forced Change in Vertical Velocity (cm/s x 10-3)
RCP
8.5
(2
041-
2100
– 1
941-
2000
) SNR >= 1
SNR >= 2
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Chan
ge in
Ver
tical
Vel
ocity
(cm
/s x
10-3
)
July
Tot
al C
hang
e in
Ver
tical
Vel
ocity
(2
041-
2100
– 1
941-
2000
)
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Chan
ge in
Ver
tical
Vel
ocity
(cm
/s x
10-3
)
Ensemble Mean (Forced Signal)
July
Tot
al C
hang
e in
Ver
tical
Vel
ocity
(2
041-
2100
– 1
941-
2000
)
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Chan
ge in
Ver
tical
Vel
ocity
(cm
/s x
10-3
)
July
Nat
ural
Com
pone
nt o
f Cha
nge
in V
ertic
al V
eloc
ity
(204
1-21
00 –
194
1-20
00)
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Run
5 Ru
n 23
Total Natural Forced
Chan
ge in
Ver
tical
Vel
ocity
(cm
/s x
10-3
)
Summary
Spring intensification and summer weakening could be driven by different mechanisms.
The sign of change in upwelling may vary meridionally and intra-annually.
Natural variability can largely impact the magnitude of change in California Current Upwelling.
Upwelling Large Ensemble Regions Historical Upwelling SNR Deltas Natural Variability Summary
Supplemental Slides
Frac
tiona
l Cha
nge
Rela
tive
to H
ist. M
ean
Frac
tiona
l Cha
nge
Rela
tive
to H
ist. M
ean
Supplemental Slides
top related