Impact of oceanic circulation changes on atmospheric δ¹³ CO₂

δ¹³ CO₂ measured in Antarctic ice cores provides constraints on oceanic and terrestrial carbon cycle processes linked with millennial-scale changes in atmospheric CO₂. However, the interpretation of δ¹³ CO₂ is not straight-forward. Using carbon isotope-enabled versions of the LOVECLIM and Bern3D models, we perform a set of sensitivity experiments in which the formation rates of North Atlantic Deep Water (NADW), North Pacific Deep Water (NPDW), Antarctic Bottom Water (AABW), and Antarctic Intermediate Water (AAIW) are varied. We study the impact of these circulation changes on atmospheric δ¹³ CO₂ as well as on the oceanic δ¹³ CO₂ distribution. In general, we find that the formation rates of AABW, NADW, NPDW, and AAIW are negatively correlated with changes in δ¹³ CO₂: namely, strong oceanic ventilation decreases atmospheric δ¹³ CO₂. However, since large-scale oceanic circulation reorganizations also impact nutrient utilization and the Earth’s climate, the relationship between atmospheric δ¹³ CO₂ levels and ocean ventilation rate is not unequivocal. In both models atmospheric δ¹³ CO₂ is very sensitive to changes in AABW formation rates: increased AABW formation enhances the transport of low δ¹³ CO₂ waters to the surface and decreases atmospheric δ¹³ CO₂. By contrast, the impact of NADW changes on atmospheric δ¹³ CO₂ is less robust and might be model dependent. This results from complex interplay between global climate, carbon cycle, and the formation rate of NADW, a water body characterized by relatively high δ¹³ CO₂.

Denying the foreseeability of an event as a means of self-protection. The Impact of Self-Threatening Outcome Information on the Strength of the Hindsight Bias

The hindsight bias represents the tendency of people to falsely believe that they would have predicted the outcome of an event, once the outcome is known. Two experiments will be presented that show a reduction or even reversal of the hindsight bias when the outcome information is self-threatening for the participants. Participants read a report of an interaction between a man and a woman that ended with different outcomes: The woman was raped vs. the woman was not raped vs. no outcome information was given. Results of the first experiment indicated that especially female participants, who did not accept rape myths, showed a reversed hindsight bias, when they received the rape outcome information. The more threatening the rape outcome had been, the lower was their estimated likelihood of rape. Results of the second experiment confirmed those of the first. Female participants, who did not accept rape myths and perceived themselves highly similar to the victim, showed a strong reversed hindsight bias, when threatened by the rape outcome, whereas female participants, who did believe in rape myth and were not similar to the victim, showed a classical hindsight bias. These effects were interpreted in terms of self-serving or in-group serving functions of the hindsight bias: Participants deny the foreseeability of a self-threatening outcome as a means of self-protection even if they are not personally affected by the negative information, but a member of their group.