Abstract
Abstract. Floodplain forests, namely the Várzea and Igapó, cover an area of more than 97 000 km2. A key factor for their function and diversity is annual flooding. Increasing air temperature and higher precipitation variability caused by climate change are expected to shift the flooding regime during this century, and thereby impact floodplain ecosystems, their biodiversity and riverine ecosystem services. To assess the effects of climate change on the flooding regime, we use the Dynamic Global Vegetation and Hydrology Model LPJmL, enhanced by a scheme that realistically simulates monthly flooded area. Simulation results of discharge and inundation under contemporary conditions compare well against site-level measurements and observations. The changes of calculated inundation duration and area under climate change projections from 24 IPCC AR4 climate models differ regionally towards the end of the 21st century. In all, 70% of the 24 climate projections agree on an increase of flooded area in about one third of the basin. Inundation duration increases dramatically by on average three months in western and around one month in eastern Amazonia. The time of high- and low-water peak shifts by up to three months. Additionally, we find a decrease in the number of extremely dry years and in the probability of the occurrence of three consecutive extremely dry years. The total number of extremely wet years does not change drastically but the probability of three consecutive extremely wet years decreases by up to 30% in the east and increases by up to 25% in the west. These changes implicate significant shifts in regional vegetation and climate, and will dramatically alter carbon and water cycles.
Highlights
Amazonia plays a vital role for the global water and carbon cycles through enormous water and carbon stores and fluxes
Since the forcing from changing climate and land use appears to be nonlinearly related to the stability of the Amazonian ecosystem (Sitch et al, 2008; Nobre and De Simone Borma, 2009), this region has been identified as one of a set of global “tipping elements” susceptible to global change (Lenton et al, 2008)
We provide estimates on climate change induced shifts of inundation patterns, which comprises of time and duration of low/high water periods and the changing extent of the flooded area during those periods
Summary
Amazonia plays a vital role for the global water and carbon cycles through enormous water and carbon stores and fluxes. The Amazon catchment covers six million square kilometers and about 15 % of the world’s freshwater runoff is discharged by the Amazon River (Gaillardet et al, 1997). Dissolved in this water, about 33 Tg C yr−1 are thought to be exported to the Atlantic Ocean as organic carbon (Moreira-Turcq et al, 2003). Climate and land use change currently affect Amazonian forests substantially, leading to a reduction of biomass, biodiversity and ecosystem services (Fearnside, 2004; Foley et al, 2007; Nepstad et al, 2007; Betts et al, 2008). Since the forcing from changing climate and land use appears to be nonlinearly related to the stability of the Amazonian ecosystem (Sitch et al, 2008; Nobre and De Simone Borma, 2009), this region has been identified as one of a set of global “tipping elements” susceptible to global change (Lenton et al, 2008)
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