Session: Last Millennium & Past2K
Author: Alexander Koch / firstname.lastname@example.org / University College London
Co-author: Chris Brierley, University College London;
Simon Lewis, University College London;
Agricultural activity was widespread over the American continent before Europeans arrived. Following European contact, Old World diseases, warfare and slavery led to an indigenous population loss of up to 90% and a near-cessation of agriculture. Several studies argue that the additional carbon uptake from the following reforestation event had an substantial impact on the global carbon cycle and is partially responsible for the CO2 minimum observed around 1610 CE in Antarctic ice cores. This hypothesis is supported by a d13C-CO2 signal pointing towards an increased terrestrial sink for this period.
Modelling studies suggest that depopulation-induced land use changes could have a magnitude ranging from near-zero to accounting for the full magnitude of expected carbon sink. These results are partially down to the choice of land use datasets with different magnitudes of forcing, but may easily be model-dependent.
Here we outline and present initial results from a new approach to estimate the effect of the land use change following European conquest of the Americas. We are performing an ensemble of simulations spanning the period from initial European contact until 1750 with an Earth System Model (CESM 1.2; T31 resolution, interactive carbon cycle). We compare the effects of the three available land use forcing datasets (PO10, HYDE 3.2 & KK10) and a best guess land use estimate based on available archaeological data. This approach should allow us to reliably detect variations in the carbon cycle response to different land use forcing at 1500 CE, one focus point of the Landcover6k initiative. Furthermore we should be able to constrain the contribution of land use change on the decline in atmospheric CO2 seen at 1610 CE and address the question whether humans had an impact on the carbon cycle and climate immediately prior to the Industrial Revolution.