Journal Article

The observed evolution of oceanic pCO2 and its drivers over the last two decades

Matear, Richard J., Roy, Tilla, Metzl, Nicolas, Sweeney, Colm, Kuchinke, Mareva, Sutherland, Stewart C., Takahashi, Taro, Tilbrook, Bronte, Lenton, Andrew

2012

نظرة عامة

We use a database of more than 4.4 million observations of ocean pCO2 to investigate oceanic pCO2 growth rates. We use pCO2 measurements, with corresponding sea surface temperature and salinity measurements, to reconstruct alkalinity and dissolved inorganic carbon to understand what is driving these growth rates in different ocean regions. If the oceanic pCO2 growth rate is faster (slower) than the atmospheric CO2 growth rate, the region can be interpreted as having a decreasing (increasing) atmospheric CO2 uptake. Only the Western subpolar and subtropical North Pacific, and the Southern Ocean are found to have sufficient spatial and temporal observations to calculate the growth rates of oceanic pCO2 in different seasons. Based on these regions, we find the strength of the ocean carbon sink has declined over the last two decades due to a combination of regional drivers (physical and biological). In the subpolar North Pacific reduced atmospheric CO2 uptake in the summer is associated with changes in the biological production, while in the subtropical North Pacific enhanced uptake in winter is associated with enhanced biological production. In the Indian and Pacific sectors of the Southern Ocean a reduced winter atmospheric CO2 uptake is associated with a positive SAM response. Conversely in the more stratified Atlantic Ocean sector enhanced summer uptake is associated with increased biological production and reduced vertical supply. We are not able to separate climate variability and change as the calculated growth rates are at the limit of detection and are associated with large uncertainties. Ongoing sustained observations of global oceanic pCO2 and its drivers, including dissolved inorganic carbon and alkalinity, are key to detecting and understanding how the ocean carbon sink will evolve in future and what processes are driving this change. Key Points Observationally, few regions have coverage to assess seasonal trends Drivers of oceanic pCO2 growth rate are unique in each ocean basin Investigation of trends seasonally is key to understanding CO2 sink evolution

• الناشر: Blackwell Publishing Ltd,American Geophysical Union
• موضوع: Alkalinity / Animal and plant ecology / Animal, plant and microbial ecology / Biological and medical sciences / Biological oceanography / Carbon dioxide / Carbon sinks / Chemical oceanography / climate change and variability / Climate variability / Dissolved inorganic carbon / Earth Sciences / Earth, ocean, space / Environmental Sciences / Exact sciences and technology / Fundamental and applied biological sciences. Psychology / General aspects / Geochemistry / Geophysics / Global Changes / observational pCO2 / ocean carbon uptake / pCO2 drivers / pCO2 growth rate / Physics / Sciences of the Universe / Sea surface temperature / Summer / Synecology / Winter