Role of land-cover changes and precipitation trends in driving evapotranspiration changes in southeastern South America

ROMINA RUSCICA; SÖRENSSON, ANNA A.; LEANDRO B. DÍAZ; CAROLINA VERA; PHILLIPE PAPASTEFANOU; ANJA RAMMIG; LUIZ REZENDE; BORIS SAKSCHEWSKI ; KIRSTEN THONICKE ; NICOLAS VIOVY; CELSO VON RANDOW

Kigali

Conferencia; 2nd Open Science Conference of the World Climate Research Programme (WCRP).; 2023

World Climate Research Programme (WCRP)

Evapotranspiration plays a vital role in shaping climate variability, trends, and extremes meanwhile it is driven by precipitation and radiation, and constrained by land surface conditions. Despite their key role in the regional climate, variability and trends of evapotranspiration have been less explored and there are still open questions related to the drivers of their changes. Long-term dynamics of this variable is studied during 1950-2010 in three south-american regions which showed notable precipitation trends and variability and have undergone intense land-cover changes: the upper and lower La Plata Basin and the South Atlantic Convergence Zone. Evapotranspiration data was obtained from an ensemble of 24 south-american simulations - with and without land cover changes - from four stand-alone dynamic global vegetation models (inLand, LPJmL4, LPJ-GUESS, ORCHIDEE) driven by three atmospheric datasets (GLDAS, GSWP3, WATCH-WFDEI). This new ensemble was developed by an interdisciplinary team of climatologists and ecologists and it is a product of the CLIMAX project (http://www.climax-sa.org). It was found that the different evapotranspiration trends in each region could be attributed to different forcings in each region. In the upper La Plata Basin, land-cover changes forced a negative summer evapotranspiration trend. On the other hand, in the lower La Plata Basin, evapotranspiration was driven by precipitation variability showing a positive summer trend and marked seasonal anomalies influenced by ENSO and the activity of the leading pattern or regional precipitation variability (characterized by a dipole-like structure with anomalies of opposite sign located at the subtropics and tropics). In the South Atlantic Convergence Zone, the large uncertainty across ensemble members prevented obtaining meaningful results. Moreover, differences among models were important for the annual evapotranspiration cycle, which resulted to be more related to the model structure than to the atmospheric forcing dataset. On the contrary, evapotranspiration trends were found to be more dependent on the forcing datasets than on the models. Our study highlights the importance of the interaction between ecologists and climatologists in order to obtain better ensembles using multiple models and atmospheric forcings.