Tema Vulnerabilidade das Áreas Costeiras Palestra: Luiz Drude de Lacerda, Labomar/UFC

Transcrição

1 Tema Vulnerabilidade das Áreas Costeiras Palestra: Luiz Drude de Lacerda, Labomar/UFC

2 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

3 The Semi-arid of Brazil is one of the largest (nearly 870,000km 2 ) and most populous in the world. At the Ceará coast it reaches the sea. The semi-arid reaches the coast at the Northeastern oriental littoral A few rivers, including the Jaguaribe River (75,000 km 2 basin) run entirely under a semi-arid climate

4 The semiarid coast of Brazil Contas R. Characteristics Location: ~ o S Climate: Tropical semi-arid mm.a -1 (Koppen BS) Extension: ~1,300 km Fluvial Flux : ~< 1,000 m 3.s -1 Tide: 2-4 m Mangrove Area: ~34,000 ha

5 Possible environmental proxies of global climate change Sand dune displacement Erosion/sedimentation in estuaries Mangrove extension changes

6 Driver 1: Precipitation anomalies and reducing continental runoff Global precipitation and runoff anomalies from Dai et al. (2009) Brazil s semi-arid coast

7 Driver 2: Sea level change (c.f. Monteiro, 2009) (c.f. Schettini, 2010)

8 Proxy 1: Dune displacement Rainfall (mm) Wind velocity (m/s) J F M A M J J A S O N D Less rain results in larger displacement (Jimenez et al., 1999; Claudino Salles et al., 2002; Levin et al., 2009).

9 N Cuspidate marks from Jericoacoara (CE) dune field (c.f. Levin et al., 2009) 0 m 500 m

10 Driver 1: Increasing the intensity of ENSO events: High confidence scenario (IPCC 2007)

11 El Niño effects on dune displacement at Jericoacoara (Maia et al., 2005) Dune

12 Unfortunately... 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)..

13 (Moncunill, 2006) Evolution Trend ( ) in annual precipitation over Ceará. (5,3 mm.yr -1 reduction)

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

15 Annual rainfall at the Jaguaribe River Basin, CE (Lacerda, 2010)

16 Rainfall (mm) Rainfall (mm) Dry season rainfall in the Jaguaribe Basin Aracati mm 4.4 mm Year Limoeiro do Norte mm mm Year

17 Rainfall and fluvial flow of the Jaguaribe River, CE Total Rain (mm) Medium Flow (m³/s) Dam opening

18 Sedimentation/erosion of estuaries 1997 Farol do Cabeço, São Francisco river (c.f. Medeiros, 2010)

19 Average erosion of 0.88 m/yr at the left margin of the Jaguaribe River (Gentil, 2007) Na margem esquerda da foz houve uma taxa média de erosão de 0,83 m/ano.

20 Average accretion of 0.77 m/yr at the right margin of the Jaguaribe River (Gentil, 2007)

21 Loss of beach volume at the Jaguaribe river mouth y = x R² = Profile Volume (m 3)

22 Erosion of Jaguaribe River margins: ± 100 m from 1988 and 2008 (Godoy, 2010)

23 Erosão de sedimentos e remobilização de metais Concentração de metais (µg/g) 2x 4x 6x 8x? Metal A Metal B RIO

24 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) Pires & Lacerda (2007)

25 Range (m) Range (m) Range (m) Flow velocity (ADCP) in humid system Rio de Contas, Itacaré, BA Always a positive flux to the ocean Contour Variable: Velocity - Direction Contour Variable: Velocity - Direction Enchente (deg) Vazante (deg

26 Range (m) Range (m) Range (m) Flow velocity (ADCP) in semiarid system Mostly a negative flux to the ocean Rio Jaguaribe, Fortim, CE Contour Variable: Velocity - Direction Contour Variable: Velocity - Direction Enchente Profile Number (deg) Direction (deg) 10 Vazante 20 Profile Number (deg)

27 Changes in island area in the Jaguaribe River estuary between 1988 and 2008 (Godoy, 2010) No. Islands Total area (sq. km) % Change Total period

28 Island area change at the Jaguaribe River estuary

29 2.69 ha Enlargement of fluvial beaches Island formation 3.84 ha Morphological changes at the Pacotí Estuary (CE) Menezes et al. (2007)

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31 Jaguaribe River, CE October, 2009 August, 2010

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33 Erosão na foz Estuário do Rio Jaguaribe, CE, NE Brasil Crescimento no interior

34 Maia et al. (2006), Mangrove Atlas of Northeastern Brazil. ( Piauí Herz Estado 2004 atual Ceará Rio Grande do Norte Paraíba Pernambuco Parametro km 2 % Área Total de Mangues em Área Total de Mangues em Crescimento Maia et al. (2006)

35 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 New mangrove areas Engineering works Without human intervention Dams

36 Origins of alterations identified in 27 estuaries of the semiarid littoral of northeast Brazil. Comparing Landsat, SPOT & Quickbird data from 1999 to 2006 Engineering works New mangrove areas 25% 16% 29% Without human intervention Dams 30%

37 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. = INCT-TMCOcean Transferência de Materiais Continente-Oceano

38 delta(d) delta(d) Dry Season Plataforma Rio The dancing estuary Estuário Pluma ,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 delta(o-18) Rainy Season delta(o-18) Plataforma Rio Estuário Pluma A salty river choked during 8 months

39 Long TR Short TR Choking the estuary increases water residence time, augmenting reactivity and bioavailability of substances INCT-TMCOcean Transferência de Materiais Continente-Oceano

40 Days WTR Dry Season WTR Wet Season

41 Concentration A lesson from the Arctic; Mackenzie River Estuary Hg-Org Icing Ice Freshet River Delta Sea

42 Global Climate Change Sediment depth (cm) 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? Hg (ng/l) Hg-Org DGM HgII-react Hg-org Hg-total Tidal choking & water residence time Reactivity & bioavailability Human exposure INCT-TMCOcean Transferência de Materiais Continente-Oceano

43 Obrigado!