GISP2 ice core N2O data

Paleoatmospheric records of trace-gas concentrations recovered from ice cores provide important sources of information on many biogeochemical cycles involving carbon, nitrogen, and oxygen. Here, we present a 106,000-year record of atmospheric nitrous oxide (N2O) along with corresponding isotopic records spanning the last 30,000 years, which together suggest minimal changes in the ratio of marine to terrestrial N2O production. During the last glacial termination, both marine and oceanic N2O emissions increased by 40 ± 8%. We speculate that our records do not support those hypotheses that invoke enhanced export production to explain low carbon dioxide values during glacial periods.

Neogene ice-rafted debris record of ODP Hole 120-751A

One of the primary objectives of Leg 120 was to obtain a high-resolution Neogene stratigraphic section from the Kerguelen Plateau. Site 751, located in the central part of the Raggatt Basin on the Southern Kerguelen Plateau in 1633.8 m of water (57°43.56'S; 79°48.89'E), was selected as the dedicated Neogene site for this objective. High-resolution sampling at Site 751 was used to delineate in detail the Neogene ice-rafted debris (IRD) occurrences on the Kerguelen Plateau. The oldest IRD found at Site 751 was approximately 9.9 Ma, and it was not until approximately 8.5 Ma that significant concentrations of IRD were detected. The first major IRD event at this site occurred in the uppermost Miocene between 6.0 and 5.5 Ma. During this time period, a general climatic cooling and glacial expansion occurred on Antarctica. The late Miocene IRD event was followed by a continuous episode of elevated IRD deposition in the lowermost Pliocene between 4.5 and 4.1 Ma. The 0.4-m.y. duration and the timing of the early Pliocene IRD event on the Kerguelen Plateau corresponds with IRD fluxes observed on the Falkland Plateau and in the Weddell Abyssal Plain. This correspondence of data indicates that a major global climatic event occurred during the early Pliocene. The East Antarctic Ice Sheet may have experienced deglaciation between 4.5 and 4.1 Ma and, as a result, released large volumes of sediment-laden ice into the Southern Ocean.