Long-lasting floods buffer the thermal regime of the Pampas

NOSETTO, MARCELO; BARRUCAND, MARIANA; KUPPEL, SYLVAIN; ORICCHIO, PATRICIO; JOBBÁGY ESTEBAN; HOUSPANOSSIAN JAVIER; DIBELLA, CARLOS; RUSTICUCCI, MATILDE

Theoretical and Applied Climatology

Springer

Año: 2016

The presence of large water masses influences thethermal regime of nearby land shaping the local climate ofcoastal areas by the ocean or large continental lakes. Largesurface water bodies have an ephemeral nature in the vastsedimentary plains of the Pampas (Argentina) where nonfloodedperiods alternate with flooding cycles covering up toone third of the landscape for several months. Based on temperaturerecords from 17 sites located 1 to 700 km away fromthe Atlantic coast and MODIS land surface temperature data,we explore the effects of floods on diurnal and seasonal thermalranges as well as temperature extremes. In non-floodedperiods, there is a linear increase of mean diurnal thermalrange (DTR) from the coast towards the interior of the region(DTR increasing from 10 to 16 K, 0.79 K/100 km, r2 = 0.81).This relationship weakens during flood episodes when theDTR of flood-prone inland locations shows a decline of 2 to4 K, depending on surface water coverage in the surroundingarea. DTR even approaches typical coastal values 500 kmaway from the ocean in the most flooded location that westudied during the three flooding cycles recorded in the studyperiod. Frosts-free periods, a key driver of the phenology ofboth natural and cultivated ecosystems, are extended by up to55 days during floods, most likely as a result of enhancedground heat storage across the landscape (~2.7 fold changein day-night heat transfer) combined with other effects on thesurface energy balance such as greater night evaporation rates.The reduced thermal range and longer frost-free periods affectplant growth development and may offer an opportunity forlonger crop growing periods, which may not only contributeto partially compensating for regional production lossescaused by floods, but also open avenues for flood mitigationthrough higher plant evapotranspirative water losses