Climate sensitivity to wetlands and wetland vegetation in mid-Holocene North Africa

Wetland regions are important components of the local climate, with their o wn characteristic surface energy and moisture budgets. Realistic representa tion of wetlands, including the important Vegetation component, may therefo re be necessary for more accurate simulations of climate and climate change . However, many land-atmosphere coupled models either ignore wetlands or tr eat wetlands as bare, water-saturated soil, neglecting the vegetation prese nt within wetland environments. This study investigates the possible respon se of the mid-Holocene climate of North Africa to changes in orbital forcin g, both with and without the presence of wetlands. The location of these we tlands is guided by analysis of paleovegetation and wetland distribution. I n this study, the wetland regime in the land surface component of a climate model was modified to incorporate vegetation. Field measurements have show n that vegetation affects water loss associated with evaporation (including transpiration) within a wetland area. Comparisons between non-vegetated we tland and vegetated wetland revealed an increase in local albedo that produ ced an associated decrease in net radiation, evaporation and precipitation in the vicinity of the wetlands regions. Based on an analysis of the model surface water balance, the calculated area of mid-Holocene wetland coverage for North Africa closely matches the observed. For the North African regio n as a whole, the effects of adding vegetation to the wetland produced rela tively small changes in climate, but local recycling of water may have serv ed to help maintain paleo wetland communities.