A conceptual framework linking Heinrich events and Dansgaard–Oeschger cycles

Abstract. Dansgaard–Oeschger (D–O) events and Heinrich events represent the dominant modes of millennial-scale climate variability during the last glacial period, yet their physical linkage remains incompletely understood. Here we propose a conceptual framework in which abrupt glacial variability emerges from the interaction of Atlantic Meridional Overturning Circulation (AMOC) dynamics, atmosphere–ocean CO₂ exchange, and dust-driven biogeochemical feedback operating within an orbitally modulated climate state. During stadial phases, enhanced dust transport and iron fertilization in the tropical Atlantic strengthen the biological pump and promote gradual atmospheric CO₂ drawdown, while reduced ocean ventilation facilitates the accumulation of respired carbon and heat in the ocean interior. Heinrich events represent extreme stadial states that amplify these imbalances through freshwater forcing, sea-ice expansion, and atmospheric circulation changes. The resulting buildup of subsurface heat and carbon may precondition the stratified North Atlantic for abrupt AMOC reinvigoration, releasing stored CO₂ and producing rapid interstadial warming. This framework provides a unified conceptual perspective on the asymmetry and recurrence of D–O cycles and suggests that orbital forcing modulates the probability of Heinrich events by influencing the background stability of the climate system.