N₂O and CH₄ variations during the last glacial epoch: Insight into global processes

Greenhouse gas measurements along polar ice cores provide important insight into the former composition of the atmosphere, its natural variations, and the responses to fast climatic changes in the past. We present high‐resolution nitrous oxide (N 2 O) and methane (CH 4 ) records measured along two ice cores from central Greenland covering part of Marine Isotope Stages 3 and 4 in the last glacial epoch. The N 2 O data confirm the hypothesis that N 2 O shows variations in phase to fast climatic changes observed in the Northern Hemisphere, the so‐called Dansgaard‐Oeschger (D‐O) events. Variations exist not only for events with a long duration (1500 years and more) but also for the shorter ones. The comparison with CH 4 unveils interesting differences between the response of CH 4 and N 2 O to D‐O events. While the average amplitudes of CH 4 oscillations associated with D‐O events are similar to those of the Northern Hemisphere summer insolation, the magnitude of the N 2 O concentration change instead correlates with the duration of the D‐O events. The records give further insight into the timing of concentration changes at the beginning of D‐O events. They show that for long‐lasting events the N 2 O concentration starts to increase before both the sharp increase in the CH 4 concentration and the temperature reconstructed for Greenland.