The current Mega Drought in Central Chile: Is the future now?

René D. Garreaud Department of Geophysics, Universidad de Chile Center for Climate and Resilience Research, CR2

Outline

• Where is Chile? • Climate projections • The current Mega drought • Dynamical analysis

26th General Assembly of the International Union of Geodesy and Geophysics (IUGG) Praga, July 2015

Central Chile: subtropical (30-40°S) west coast of South America, bounded by the Andes cordillera (3-5 km). MAP from 100 to 1500 mm/year. Strongly impacted by ENSO

SLP & MAP 850 hPa winds & SAT

L Cold

Warm

500 hPa

Precipitation in central Chile is largely caused by the passage of frontal systems rooted in extratropical depression

embedded in the South Pacific westerly wind belt

Stronger westerlies associated with more frequent and intense storms → more precipitation

Cold

Warm

High

Dry

Seco

Dry

Húmedo

Global context for central Chile droughts

Rainfall SST

SLP Zonal wind 300 hPa

2013

1998 1924 1968

2012 2011

2010

1997

1987

1982

Niño3.4 [°C] MJJAS

Win

ter (

MJJA

S) ra

infa

ll in

San

tiago

(33S

)

19°C 20° 21°C TSM en región Niño 3.4

El Niño La Niña

Wet

Dry

Multimodel average SLP and sfc wind difference betweenA2 (2070-2100) and BL (1970-2000)

Over open ocean ∆v in geostrophic balance with ∆SLP. Near the coast ∆v more controlled by along-coast ∆SLP

Annual mean

© IPCC 2007: WG1-AR4 (2007)

+50%

+25%

0% -25% -50%

100*[P(A2)-P(BL)]/P(BL) Annual mean

*

Far future Heavy GEI scenario

Annual Precipitation 33°S-71°W

Base line Near future dP/Po = 11%

Far future dP/Po = 24%

Sim. Histórica Sim. RCP8.5

25 Individual models from CMIP-5

Year

Prec

ipita

ción

Ann

ual /

Pre

cipi

taci

ón M

edia

Anu

al

Central Chile current mega-drought (2015 very dry so far)

0.7*Pmedia

Pmedia Hist

Central Chile current mega-drought (2015 very dry so far)

Mega Drought: 2010-2013

Norte Chico Centro Centro-

sur

Ret. Period driest year within MD (year) 7 15 >30

Recurrence of 4 year drought (per 50 years) 4-6 2-3 1?

Annual rainfall in Santiago [mm/year]

18.5 18 17.5 17 16.5 16

Salto Climático

Santiago (Quinta Normal) +0.15°/década

Antofagasta (Cerro Moreno) -0.18°/década

Prom

edio

Anu

al T

empe

ratu

ra (°

C)

Prom

edio

Anu

al T

empe

ratu

ra (°

C)

Año

EN

EN

EN

LN

Increasing temperatures in central Chile… Impacts on evapo-transpiración y snow-cover

Year

GRAC

E TW

S [m

m] f

or lo

n:-7

0.84

/lat:-

33.1

1/ra

d:35

0km

TWSt = SMt + SNWt + SWt + GWt ≈ GWt

Central Chile current mega-drought (2015 very dry so far)

Rad

ial g

row

th [m

m]

Monte Oscuro - Maule foothills Nothofagus obliqua (Roble)

41 isolated trees + 81 surrounded trees

Wet versus dry periods

• 40% less precipitation (1630 → 1602 mm/yr) • 25% less radial growth ( 1.7 → 1.3 mm/yr) • 11% less volume growth ( 7.1 → 6.2 m3/ha) → ∆CO2 Sequestration?

P. Corvalán, M. Galleguillos, J. Hernández, R. Garreaud

Santiago

Talca

Constitución

Curicó

60 km

MODIS-TERRA 08 Enero 2014

11:55 Hora Local

Neutro Niño

Niño Niña

Central Chile current mega-drought (2015 very dry so far)

SST (colors) and SLP (contours) anomalies

2010

2014

2013

2012

2011

2009

MJJAS Niño3.4 index [°C]

Cen

tral C

hile

win

ter r

ainf

all a

nom

aly

La Niña El Niño

+

Monte Carlo Experiment: 5000 samples of 4 randomly chosen ENSO-neutral years

Central Chile current mega-drought (2015 very dry so far)

2015????

Mean PDO Index

Mea

n Q

N A

nnua

l Pre

cipi

tatio

n [m

m/y

ear]

1900-10

1915-22

1926-42

1977-90

1991-2003

1942-57

1961-75

2007-2014

Long term mean

PDO Index

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 periods Cold PDO periods

Year

Precipitation distribution in Quinta Normal during cold and warm PDO periods

The grey circles are 10-year synthetic PDO cold or warm periods

Hist RPC 8.5

Altura Geopotencial en 250 hPa, 35S-100W

Evidence for anthropogenic forcing (?)

Preindustrial Reco

1850-1950

1950-2000

2000-2050

1000 500

200 100 50

20 1

Climate simulation family

Megadrought recurrence rate (years)

Mea

n an

nual

rain

fall

rela

tive

to 1

970-

2000

(%)

Preindustrial 850-1750

Histórica 1850-1950

Histórica 1950-2000

RCP8.5 2010-2050

RCP8.5 2050-2100

Reco.

Obs.

Evidence for anthropogenic forcing (?)

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.

• Roughly speaking, half of the current MD rainfall deficit can be attributed to concurrent cold-phase of PDO (transitioning now?).

• 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.