Delayed recovery of Atlantic meridional ocean circulation threatens Europe-wide gross primary productivity under positive and negative CO2 emissions

Abstract

Abstract Climate change mitigation through negative CO2 emissions has been recognized as a crucial strategy to combat global warming. However, its potential effects on terrestrial carbon uptake and agricultural productivity, particularly in Europe, remain uncertain. In this study, we utilized large ensemble simulations with an Earth system model of full complexity to investigate the response of Gross Primary Production (GPP) in the region. Our findings reveal a significant asymmetry in the GPP response to CO2 ramp-up and symmetric ramp-down model experiments, indicating that GPP at lowering atmospheric CO2 levels is more efficiently reduced than those at raising CO2. Remarkably, during the CO2 removal period, the North Atlantic Sea surface temperature (NASST) experienced cooling due to a delayed recovery of Atlantic Meridional Overturning Circulation (AMOC). This cooling led to precipitation and soil moisture deficits, resulting in a rapid reduction in GPP. This asymmetry in GPP response holds consistent across multi-model simulations. These results underscore the potential implications of delayed recovery in ocean circulation, which could unexpectedly accelerate terrestrial GPP reduction. These insights are crucial for policymakers, aiding them in projecting agricultural activity and formulating targeted GPP control policies specific to the European region.