Hydroclimatic Changes in the South American Altiplano During the Last Millenium D.A. Christie, M.S. Morales, R. Villalba, M. Vüille, J. Li, B. Francou Framework Central • Water availability is the main limiting factor in the Andes Altiplano region for both, the ecological and socioeconomic dynamics • The Central Andes (Altiplano) acts as regional “water towers” and are characterized by low annual precipitation with a high interannual variability • There is a need to better understand the hydroclimatic dynamics from interannual to millennial time-scale The Altiplano • High elevation plateau ~ 4,000 m a.s.l. Central Andes (15°-22°S) • Limit of Pacific (dry) and Atlantic influence (humid) • Atmospheric circulation ~ ENSO variability • Precipitation recharges the Atacama aquifer 18° - Tropical lowlands 22° - Atacama Desert Future Precipitation in the Altiplano % of reduction Thibeault et al. (2010) J. Geophys. Res. Minvielle & Garreaud (2011) J. Clim. ? Polylepis tarapacana The world’s highest elevation tree-ring records (Queñoa) (4,000-5,200 m a.s.l.) Cross-dating and chronology development Polylepis tarapacana (Queñoa) • Wide distribution across the Altiplano (16° - 23°S) • Tree growth is moisture limited • Lifespan of > 700 años • Subfossil wood • High coherence of tree growth at regional scale • Natural archive P. tarapacana tree-ring sites , and Precipitation stations Regional chronology from 353 tree-ring series Observed and Tree-ring reconstructed annual precipitation (Nov–Oct) across the Altiplano Tree-ring reconstruction of annual precipitation in the Altiplano region for the period 1300–2006 Correlation field between the precipitation reconstruction and gridded SST for the interval 1948-2006 Comparisons between the main oscillatory modes of ENSO (N3.4 SST) and the Precipitation reconstruction N3.4 SST / Preciptation Reconstruction 1 r = - 0.53 -1 0 0 -1 (a) 8.5 - 13 yr 1 r = - 0.51 ? 1 -1 0 0 Amplitude -1 (b) 5 - 6.7 yr 1 1 r = - 0.65 -1 0 0 -1 (c) 3 - 4.7 yr 1 1880 1900 1920 1940 1960 1980 2000 Year Year Tree-ring based ENSO reconstruction from 2,222 PanPacific sites 2 1 0 -1 SSTA (C°) SSTA -2 -3 1300 1400 1500 1600 1700 1800 1900 2000 Calendar years Future directions Comparisons between Tree-Rings and Glacier Mass Balances Photo: B. Francou 1940 1996 1994 2005 2009 Chacaltaya Glacier 3 Mass balance (Nov-Jun) Zongo Tree-rings 2 r = 0.55 (P <0.05) 1 0 -1 Zongo Glacier -2 3 Mass balance (Nov-Dec) 2 Tree-rings Normalized values Normalized r = 0.72 (P <0.01) 1 0 -1 Chacaltaya -2 1992 1994 1996 1998 2000 2002 2004 2006 Year Spectral comparisons between the Polylepis Tree-Rings and the Quelccaya Ice-Core for future for multiproxy hidroclimatic reconstructions Year 1200 1300 1400 1500 1600 1700 1800 1900 2000 Calendar year Year Tree-rings / Quelccaya 1920 1935 1950 1965 1980 1995 - 11200 1300 1400 1500 1600 1700 1800 1900 2000 1 Period (years) 75 Observed / Reconstructed 4 0.8 0 80 yr SSA: 16 0 0.5 % 32 Coherence 64 -1 10 yr (r = - 0.36) -1 % 0.2 -75 128 r = 0.70 (n = 77, p<0.001) F = 34.9 / RE = 0.45 2 Tree-rings / Quelccaya R = 0.48 80 - 1 adj 1 40 0 0 1st differences cm) ( 0 -1 10 yr (r = - 0.44) -1 Titicaca Titicaca lake level 1600 1650 1700 1750 1800 1850 1900 1950 2000 -40 Year -80 1200 1300 1400 1500 1600 1700 1800 1900 2000 Calendar year FINAL REMARKS • Our precipitation reconstruction points out that century-scale dry periods are a recurrent feature in the Altiplano climate, and exhibit an unprecedented negative trend since the 1930´s in the context of the last 700 yr. • Next step will be to develop glacier mass balance reconstructions. • The similarity between Tree-rings and Ice-core records demonstrated the feasibility to develop multiproxy hidroclimatic reconstructions in the region to evaluate and detect climate changes • Water resource managers must anticipate these changes to adapt to future climate scenarios, reduce vulnerability and provide water equitably to all users. Gracias! Comparison between low frequency of the Precip reconstruction and it interannual variabiliy Low frequency (35 yr spline 50%) versus Interannual variability (25 yr running variance) Spatial patterns of Polylepis tarapacana tree-growth (1890-1999 AD period) EOF-1 (55.3%) EOF-2 (12.1%) EOF-3 (7.1%) 17° 0.6 0.6 0.7 0.4 -0.2 0.3 0.2 0.1 19° 0.8 -0.1 0.4 -0.1 S Bolivia -0.2 0.3 -0.3 0.2 21° 0.8 0.8 Chile 0.1 -0.1 -0.4 23° Argentina 70° 68° 66° 70° 68° 66° 70° 68° 66° W High coherence in the spatio-temporal growth patterns .