Modulation of the North Atlantic deoxygenation by the slowdown of the nutrient stream

• Published in: Biogeosciences
• Main Authors: Tagklis, Filippos, Ito, Takamitsu, Bracco, Annalisa
• Format: Text
• Language: English
• Published: 2020
• Subjects: Pacific; North Atlantic
• Online Access: https://doi.org/10.5194/bg-17-231-2020; https://www.biogeosciences.net/17/231/2020/

Western boundary currents act as transport pathways for nutrient-rich waters from low to high latitudes (nutrient streams) and are responsible for maintaining midlatitude and high-latitude productivity in the North Atlantic and North Pacific. This study investigates the centennial oxygen ( O 2 ) and nutrient changes over the Northern Hemisphere in the context of the projected warming and general weakening of the Atlantic Meridional Overturning Circulation (AMOC) in a subset of Earth system models included in the CMIP5 catalogue. In all models examined, the Atlantic warms faster than the Pacific Ocean, resulting in a greater basin-scale solubility decrease. However, this thermodynamic tendency is compensated by changes in the biologically driven O 2 consumption which dominates the overall O 2 budget. These changes are linked to the slowdown of the nutrient stream in this basin, in response to the AMOC weakening. The North Atlantic resists the warming-induced deoxygenation due to the weakened biological carbon export and remineralization, leading to higher O 2 levels. Conversely, the projected nutrient stream and macronutrient inventory in the North Pacific remain nearly unchanged.