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La actual Mega-Sequía en Chile Central: Llegó el futuro?
René D. Garreaud + grupo de Sequía CR2Department of Geophysics, Universidad de ChileCenter for Climate and Resilience Research, CR2
IV Congreso Nacional de Oceanografía Fìsica y MeteorologíaPUCV 1u-Noviembre-2015
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La megasequía 2010-2015
• Moderada (20-40% déficit anual)• Larga (5-6 años) e ininterrumpida• Extensa (30-40°S)• Cálida (+0.5 – 1°C)• Alta demanda hídrica
Recurrencia en el siglo XX• 2-3 casos similares en centro-norte• 2-3 casos similares en centro-norte• <1 caso en centro-sur• También es inusual en reconstrucción Paleo
Impactos:• Hidrología sfc y subterranea• Vegetación natural• Regimen de incendios• Sociales y economicos
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La Megasequía 2010-2015
% con respectoa climatología
+40%
+20%
0
Norte Chico Centro Centro-sur
Período de retorno del año más seco durante la MS (años)
7 15 >30
Recurrencia de eventos secos (>30%) de 4 o mas años
4-6 2-3 1?
-20%
-40%
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1967-1970 2010-2014
Valparaiso
La Serena% con respectoa climatología
Grandes sequías contemporáneas
+40%
+20%
Concepción
Valdivia
0
-20%
-40%
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Una mirada al pasado
Reconstrucción dendroclimática (1000-2000 años d.C.) de la precipitación en Chile central
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Sequía y calor
Promedio anual de la temperatura máxima en Santiago (DMC)
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Impactos en Hidrología
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(a) Promedio (b) Anomalía MS
Copiapo
La Serena
Desierto
Índice de Vegetación Mejorada (EVI)Julio-Agosto-Septiembre
(b) Anomalía Megaseqia
0 – 55 – 1010 – 1515 – 3030 – 50
La Serena
Talca
Santiago
Salamanca
Nieve
Veg
etac
ión
+50
- 5Seq
ued
adFuente de datos: NASA (producto MODIS MOD13A3)
Mapas producidos por David Lopez, CEAZA
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DéficitPluviométrico(2010-2014)
DéficitPluviométrico(2010-2014)
La Megasequía 2010-2015
Gastos en Camiones Aljibes
(Mill$)
Gastos en Camiones Aljibes
(Mill$)
Seq
ued
ad
Apariciones en prensa escrita
(2014)
Apariciones en prensa escrita
(2014)
Seq
ued
ad
Deterioro vegetación
Agosto 2010-2015
Deterioro vegetación
Agosto 2010-2015
Incendios forestales de
magnitud
Incendios forestales de
magnitud
Transportede sedimentos
en invierno
Transportede sedimentos
en invierno
2008
2013
©GdG
No
dat
a
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La Megasequía 2010-2015:Una lección para el futuro
www.cr2.cl/megasequia
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Next Decade
100%
90%
80%
0%
10%
20%
Rai
nfa
ll an
om
aly
wrt
19
70
-20
00 R
ainfall d
eficit wrt
19
70????
Precipitación en Chile CentralEl desafío de la próxima década
1995 2005 2015 2025 2080
Far Future
RCP8.5
Mega
Drought
Recent
Past
80%
70%
20%
30%
Mid Future
RCP8.5
Rai
nfa
ll an
om
aly
19
70
-20
00
????
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100%
90%
80%
0%
10%
20%
Rai
nfa
ll an
om
aly
wrt
19
70
-20
00 R
ainfall d
eficit wrt
19
70
Next Decade
Precipitación en Chile CentralEl desafío de la próxima década
1995 2005 2015 2025 2080
Far Future
RCP8.5
Mega
Drought
Recent
Past
80%
70%
20%
30%
Mid Future
RCP8.5
Rai
nfa
ll an
om
aly
19
70
-20
00
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Rainfall (GCPC) Z500 (NNR) SST (NCEP-OI)
Drought Composite
Large-scale context for central Chile droughts
Cold
1967,68,64,73,76,85,96,87,03,07
-50 0 +50 m -1 0 +1°C-60 0 +60 mm/month
ColdHigh
Warm
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Large-scale context for central Chile droughts
Cen
tral
Chi
le w
inte
r ra
infa
ll an
omal
y
La Niña El Niño
r ≈ 0.6
MJJAS Niño3.4 index [°C]
Cen
tral
Chi
le w
inte
r ra
infa
ll an
omal
y
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Large-scale context for central Chile droughts
Cen
tral
Ch
ile R
ain
fall
An
om
aly
r ≈ -0.6
Cen
tral
Ch
ile R
ain
fall
An
om
aly
Z500 difference
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Drought compositeMean Z500 anomalies (contours)
Std Z500 anomalies (colors)
Large-scale context for central Chile droughts
Reduced variability downstream of anomalous ridge
Enhaned variability downstream of anomalous trough
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Rainfall Z500 SST
DroughtComposite
The 2010-2015 drought in Central Chile
ColdHigh
Warm
1967,68,64,73,76,85,96,87,03,07
2010-2014Average
-50 0 +50 m -1 0 +1°C-60 0 +60 mm/month
High
Warm
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Cen
tral
Chi
le w
inte
r ra
infa
ll an
omal
y
La Niña El Niño
The 2010-2015 drought in Central Chile
2010
2014
2013
2012
2011
2009
MJJAS Niño3.4 index [°C]
Cen
tral
Chi
le w
inte
r ra
infa
ll an
omal
y
+
2015????
Monte Carlo Experiment:5000 samples of 4 randomly chosen ENSO-neutral years
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Central Chile Rainfall Anomaly
The 2
01
0-2
01
5 d
rou
ght in
Cen
tral Ch
ile
r≈
0.6
Central Chile Rainfall Anomaly
Z50
0 d
ifference
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5800
5750
5700
5650
Subtropical box
NNRMMM
(hist+RC85)
Geo
po
ten
tial
hei
ght
[m]
The 2010-2015 drought in Central Chile
5300
5250
5200
5150
5000
5600
Midlatitude Box
MMM(hist+RC85)
NNR
Geo
po
ten
tial
hei
ght
[m]
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Evidence for anthropogenic forcing
Climate simulation family
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Attribution of the 2010-2015 mega drought
AMIP simulations: Global Circulation Model (GCM) forced by
• Observed SST
• Observed Sea Ice Distribution
• Observed or past Radiative Forcing (CO2, aerosols, O3,…)
Ensemble AMIP simulationsEnsemble AMIP simulations
• 10-30 “runs” of several decades long with slightly different initial conditions
• Ensemble mean reveals the SST forced response
• Ensemble spread reveals impact of internal variability (weather)
SST forcing includes natural variability (e.g., ENSO) but also anthropogenic impact
Ensemble mean with past radiative forcing excludes direct anthropogenic impact
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Rainfall deficit
CAM4 (20) ECHAM5 (30)
May-September, 2010-2014
-50 0 +50 %
GPCP
Observations AMIP (Obs .SST, Obs. Rad.Forc.)
Z500 anomaly
-50 0 +50 m
NNR
SST variability + Obs. Rad. Forcing during 2010-2014 accounts about half of theobserved Z and P anomalies. Remaining anomaly can due to “bad luck”
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(a) Nat-Hist forcing / Obs SST (b) Obs. Rad. Forcing / Obs. SST
Winter (MJJAS) rainfall anomaly 2010-2014LBNL CAM 5.1 AMIP simulations (50 runs)
-300 0 300 mm/year
-10% -20%
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Obs RF / Obs SST (AMIP)
Rai
nfal
l ano
mal
y [%
]
2010-2014 Winter rainfall anomaly in Central Chile
Past RF Obs SST(AMIP) Obs RF / Coupled ocean
ECHAM5 (30)CAM4 (20)
CAM5 (50)
Rai
nfal
l ano
mal
y [%
]
CMIP5 (20 models)
CAM5 (50)
Observations@ 35S, 71W
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The Next Decade Challenge
Next Decade
100%
90%
80%
0%
10%
20%
Rai
nfa
ll an
om
aly
wrt
19
70
-20
00 R
ainfall d
eficit wrt
19
70????
1995 2005 2015 2025 2080
Far Future
RCP8.5
Mega
Drought
Recent
Past
80%
70%
20%
30%
Mid Future
RCP8.5
Rai
nfa
ll an
om
aly
19
70
-20
00
????
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The Next Decade Challenge
100%
90%
80%
0%
10%
20%
*
**
Rai
nfa
ll an
om
aly
wrt
19
70
-20
00 R
ainfall d
eficit wrt
19
70
Next Decade
Unlikely
Unlikely
Likely
1995 2005 2015 2025 2080
Far Future
RCP8.5
Mega
Drought
Recent
Past
80%
70%
20%
30%
Mid Future
RCP8.5
MD Forcing
(*) Anthropogenic
(**) Natural (ENSO, PDO, Internal)
Rai
nfa
ll an
om
aly
19
70
-20
00
Very unlikely
Unlikely
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Conclusions
• Current multi-year drought (MD) in central Chile is a very infrequent event in the historical record (100 years) and paleo-record (1000 years). It occurs during the warmest decade on record and much increased water demands.
• The uninterrupted sequence of 5 (6) dry years occurred during mostly ENSO-neutral conditions, a very unlikely situation.mostly ENSO-neutral conditions, a very unlikely situation.
• Roughly speaking, half of the current MD rainfall deficit can be attributed to concurrent SST state (cold-phase of PDO).
• Thus, anthropogenic climate change, mediated by circulation anomalies, is already influencing central Chile hydro-climate.
• So, we are not fully into the “future”, but this is how it will be…warm and dry.
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Mea
n Q
N A
nn
ual
Pre
cip
itat
ion
[mm
/yea
r]
1900-10
1915-22
1926-42
1977-90
1991-2003
The error bars indicate the dispersion in the mean values when the initial or final year of each period is changed ±1 year
Warm PDO periodsCold PDO periods
The grey circles are 10-year synthetic PDO cold or warm periods
The blue circles are the composites using tree-rings reconstructions.
The 2010-2015 drought in Central Chile
Mean PDO Index
Mea
n Q
N A
nn
ual
Pre
cip
itat
ion
[mm
/yea
r]
1900-10
1942-57
1961-75
2007-2014
Long term mean
PDO Index
Year