Perturbation to the nitrogen cycle during rapid Early Eocene global warming

Area of Science:

• Paleoceanography
• Geochemistry
• Marine Ecology

Background:

• Ocean deoxygenation impacts marine community function, but the extent remains unclear.
• The Paleocene-Eocene Thermal Maximum (PETM) was a period of rapid global warming driven by increased greenhouse gases.
• Studying past warming events like the PETM can illuminate future ocean changes.

Purpose of the Study:

• To investigate the effects of the PETM on marine nitrogen cycling.
• To analyze nitrogen isotope data from the Eastern Peri-Tethys Ocean during the PETM.
• To understand the reorganization of marine nitrogen cycles under rapid warming and deoxygenation.

Main Methods:

• Stable nitrogen isotope analysis of sediments.
• Paleoceanographic reconstruction of the Eastern Peri-Tethys Ocean.
• Correlation of geochemical data with paleoclimate events.

Main Results:

• A significant shift in the nitrogen cycle was detected at the onset of the PETM.
• Sediment nitrogen isotopic composition decreased by approximately 6‰, reaching as low as -3.4‰.
• These changes indicate a major reorganization of the marine nitrogen cycle.

Conclusions:

• The PETM triggered a transition in the nitrogen cycle within the Eastern Peri-Tethys Ocean.
• Warming, altered ocean circulation, and deoxygenation drove this transition.
• The observed conditions resemble those of Mesozoic Oceanic Anoxic Events, highlighting the severity of PETM impacts.