Tema Vulnerabilidade das Áreas Costeiras

Palestra:

Luiz Drude de Lacerda,

Labomar/UFC

Proxies of global climate change at the continent-ocean interface in the semi-arid coast of

Northeastern Brazil

Luiz Drude de Lacerda

Instituto Nacional de Ciência e Tecnologia de Transferência de Materiais Continente-Oceano

&

Laboratório de Biogeoquímica Costeira, Universidade Federal do Ceará

The semi-arid reaches the coast at the North-eastern oriental littoral

A few rivers, including the Jaguaribe River (75,000 km2 basin) run entirely under a semi-arid climate

The Semi-arid of Brazil is one of the largest (nearly

870,000km2) and most populous in the world. At the

Ceará coast it reaches the sea.

Characteristics

Location: ~ 3.5-8.0 oS

Climate: Tropical semi-arid

500-800 mm.a-1 (Koppen

BS)

Extension: ~1,300 km

Fluvial Flux : ~< 1,000 m3.s-1

Tide: 2-4 m

Mangrove Area: ~34,000 ha

The semiarid coast of Brazil

Contas R.

Possible environmental proxies of global climate change

Sand dune displacement

Erosion/sedimentation in estuaries

Mangrove extension changes

Global precipitation and runoff anomalies from Dai et al. (2009)

Brazil’s semi-arid coast

Driver 1: Precipitation anomalies and reducing continental runoff

(c.f. Monteiro, 2009)

(c.f. Schettini, 2010)

Driver 2: Sea level change

Proxy 1: Dune displacement

0

50

100

150

200

250

300

350

400

J F M A M J J A S O N D

Rainfall (mm) Wind velocity (m/s)

Less rain results in

larger displacement

(Jimenez et al., 1999;

Claudino –Salles et

al., 2002; Levin et al.,

2009).

N

0 m 500 m

“Cuspidate”

marks from

Jericoacoara (CE)

dune field

(c.f. Levin et al.,

2009)

Driver 1: Increasing the intensity of ENSO events: High

confidence scenario (IPCC 2007)

Dune

El Niño effects on dune displacement at

Jericoacoara (Maia et al., 2005)

… residual dune ridges that form behind

migrating dunes due to the rise and fall of

water levels can be modeled well using

climatic time series of rainfall, potential

evaporation and wind power.

The model succeeded in predicting the width

and height of RDRs as well as the spacing

between them. As time passes, however,

RDRs are usually flattened and may

disappear entirely.

… the potential for serving to reconstruct the

palaeo-climate of wind regime on a yearly

basis or to identify past El-Niño events seems

to be quite limited

…because of: (i) occasionally there are

years with low rainfall when no RDR forms;

(ii) the RDRs do not retain their original shape

and change in shape and size with time

because of natural erosion processes and the

ecological succession of plants on them (Levin

et al., 2009)..

Unfortunately.....

Evolution Trend (1961 – 2008) in annual precipitation over Ceará. (5,3 mm.yr-1

reduction)

(Moncunill, 2006)

Annual rainfall and river fluxes at the Gongogi sub-basin, Contas River Basin, BA (Amon, 2009)

Annual rainfall at the

Jaguaribe River Basin, CE

(Lacerda, 2010)

0

10

20

30

40

50

60

70

80

Ra

infa

ll(m

m)

Year

Aracati

0

5

10

15

20

25

30

Ra

infa

ll(m

m)

Year

Limoeiro do Norte

Dry season rainfall in the Jaguaribe Basin

12.6 mm

4.4 mm

3.6 mm

1.9 mm

0

200

400

600

800

1000

1200

1400

1600

Total Rain (mm) Medium Flow (m³/s)

Dam

opening

Rainfall and fluvial flow of the Jaguaribe River, CE

Sedimentation/erosion of estuaries

Farol do Cabeço, São Francisco river

(c.f. Medeiros, 2010)

1997

Na margem esquerda da foz houve uma taxa média de erosão de 0,83 m/ano.

Average erosion of 0.88

m/yr at the left margin of

the Jaguaribe River

(Gentil, 2007)

Average accretion of 0.77

m/yr at the right margin of the

Jaguaribe River (Gentil, 2007)

y = -0.1224x + 4710.9R² = 0.558

0

50

100

150

200

250

300

350

400

450

500

Pro

file

Vo

lum

e (

m3)

Loss of beach volume at the

Jaguaribe river mouth

Erosion of Jaguaribe River

margins: ± 100 m from 1988 and

2008 (Godoy, 2010)

RIO

Erosão de sedimentos

e remobilização de

metais

Concentração de metais (µg/g)

2x 6x4x 8x ?

Metal A Metal B

Pires & Lacerda (2007)

Piritas framboidais formadas

em sedimentos de mangue

liberam metais em seguida a

oxidação (e.g. através da

erosão de sedimentos ou

aumento de energia de ondas)

1.0

1.5

2.0

2.5

3.0

3.5

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5.0

Ra

ng

e (

m)

10Profile Number

20Profile Number

1.0

1.5

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4.5

5.0

Ra

ng

e (

m)

40Direction (deg)

60Direction (deg)

80Direction (deg)

100Direction (deg)

120Direction (deg)

140Direction (deg)

40

60

80

100

120 140

Dir

ectio

n (

de

g)

90

100

110

120

130

140 150

Sig

Am

p (

co

un

ts)

Contour Variable: Velocity - Direction

40

60

80

100

120

140(deg) 1.0

1.5

2.0

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Ra

ng

e (

m)

10Profile Number

20Profile Number

30Profile Number

40Profile Number

1.0

1.5

2.0

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3.5

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5.5

Ra

ng

e (

m)

0Direction (deg)

50Direction (deg)

100Direction (deg)

150Direction (deg)

200Direction (deg)

250Direction (deg)

300Direction (deg)

0

50

100

150

200

250 300

Dir

ecti

on

(d

eg

)

60

80

100

120

140

Sig

Am

p (

co

un

ts)

Contour Variable: Velocity - Direction

0

50

100

150

200

250

300(deg)

Enchente Vazante

Flow velocity (ADCP) in humid system

Rio de Contas, Itacaré, BA

Always a positive flux to the ocean

Flow velocity (ADCP)

in semiarid system

Rio Jaguaribe,

Fortim, CE

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

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Ra

ng

e (m

)

10Profile Number

20Profile Number

30Profile Number

40Profile Number

1.0

1.5

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Ra

ng

e (m

)

0Direction (deg)

50Direction (deg)

100Direction (deg)

150Direction (deg)

200Direction (deg)

250Direction (deg)

300Direction (deg)

0

50

100

150

200

250 300

Dir

ectio

n (d

eg

)

60

80

100

120

140

Sig

A

mp

(co

un

ts)

Contour Variable: Velocity - Direction

0

50

100

150

200

250

300(deg) 1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Ra

ng

e (m

)

10Profile Number

20Profile Number

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Ra

ng

e (m

)

40Direction (deg)

60Direction (deg)

80Direction (deg)

100Direction (deg)

120Direction (deg)

140Direction (deg)

40

60

80

100

120 140

Dir

ectio

n (d

eg

)

90

100

110

120

130

140 150

Sig

A

mp

(co

un

ts)

Contour Variable: Velocity - Direction

40

60

80

100

120

140(deg)

Enchente

Vazante

Mostly a negative flux to the ocean

0

2

4

6

8

10

12

14

1988 1992 2003 2008 Total period

No. Islands Total area (sq. km) % Change

Changes in island area in the Jaguaribe River estuary

between 1988 and 2008 (Godoy, 2010)

Island area change at the Jaguaribe River estuary

2.69 ha

3.84 ha

Island

formation

Enlargement of

fluvial beaches

Menezes et al. (2007)

Morphological changes at the Pacotí Estuary (CE)

October, 2009

August, 2010

Jaguaribe

River, CE

1988

1958

Estuário do Rio Jaguaribe, CE, NE Brasil

Erosão na foz

Crescimento no interior

Maia et al. (2006), Mangrove Atlas of Northeastern Brazil.

(www.institutomilenioestuarios.com.br)

29.94

140.43

108.19

68.88

96.61

40.40

182.25

129.71

96.31

161.39

0.00 50.00 100.00 150.00 200.00

Piauí

Ceará

Rio Grande do Norte

Paraíba

Pernambuco

Herz - 1978

Estado atual2004

Parametro km2 %

Área Total de Mangues em 1978 448

Área Total de Mangues em 2004618

Crescimento 179 37

Maia et al. (2006)

Origins of alterations identified in 51 estuaries of the semiarid littoral of northeast Brazil. Comparing radar data from 1980 to

Landsat, SPOT & Quickbird data from 2006

Without human intervention

Dams

Engineering works

New mangrove areas

29%

30%

25%

16%

Origins of alterations identified in 27 estuaries of the semiarid littoral of northeast Brazil. Comparing Landsat, SPOT &

Quickbird data from 1999 to 2006

Without human intervention

Dams

Engineering works

New mangrove areas

=

INCT-TMCOcean

Transferência de Materiais

Continente-Oceano

Temporal and spatial distribution of continental water masses

combining multi-tracers analysis and simultaneous sampling

grids in river, estuary, plume and continental shelf, show

freshwater plume during the rainy season and penetration of

Tropical Waters (Oceanic) into the shelf.

Dry Season

0

2

4

6

8

10

12

14

16

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

delta(O-18)

delt

a(D

)

Plataforma

Rio

Estuário

Pluma

Rainy Season

-20

-15

-10

-5

0

5

10

15

20

25

30

-4 -2 0 2 4 6 8

delta(O-18)

delt

a(D

)

Plataforma

Rio

Estuário

Pluma

The

dancing

estuary

A salty

river

choked

during 8

months

INCT-TMCOcean

Transferência de Materiais

Continente-Oceano

Lo

ng

TR

Sh

ort

TR

Choking the estuary increases water residence time,

augmenting reactivity and bioavailability of substances

WTR Wet SeasonWTR Dry Season

14

12

10

8

6

4

2

0

Days

Hg-Org

Icing Ice Freshet

River Delta Sea

A lesson from the Arctic; Mackenzie

River EstuaryC

on

centr

ation

INCT-TMCOcean

Transferência de Materiais

Continente-Oceano

Global Climate Change

The Arctic Paradox: what arctic and semi-arid rivers

have in common when they reach the sea? How it will

respond to global climate changes?

0 1 2 3 4

5

15

30

50

Se

dim

en

t d

ep

th (

cm

)

Hg (ng/l)

DGM HgII-react Hg-org Hg-total

Tidal choking & water

residence timeReactivity &

bioavailability Human exposure

Hg-Org

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