Gale force winds promote air-sea carbon dioxide (CO2) exchange over the Southern Ocean during research cruise JR239 on the RRS James Clark Ross. Shipboard surface water CO2 measurements are the backbone of data-based ocean CO2 sink estimates. Credit: Dorothee Bakker

Earth’s oceans are thought to have taken up about one quarter of the carbon dioxide (CO2) that humans pumped into the atmosphere in the past 2 decades. The CO2 drives acidification and has consequences for sea life, but it also moderates the rate of climate change.

Researchers studying how the rate of CO2 uptake has changed over time using ship observations have mostly relied on ocean carbon measurements from only a few regions. Landschützer et al. set out to create a global model of CO2 uptake using fine-scale observations on a global scale.

The team used the Surface Ocean CO2 Atlas to create monthly maps of CO2 concentration at sea surface. Between 1998 and 2011, they found strong interannual variations, with the Pacific Ocean dominating the global flux variability. There, the El Niño–Southern Oscillation was the primary driver.

The researchers’ model also showed that the ocean had absorbed increasing amounts of carbon during the period they studied, but the short timescale makes it impossible to draw conclusions about what may happen over the course of decades. In addition, by isolating the amount of carbon taken up by the ocean and comparing it to anthropogenic emissions, they determined how much carbon had been absorbed on land. (Global Biogeochemical Cycles, doi:10.1002/2014GB004853, 2014)

—Eric O. Betz, Writer

Citation: Betz, E. O. (2014), Ocean carbon uptake more variable than previously thought, Eos Trans. AGU, 95(49), 472, doi:10.1002/2014EO490011.

© 2014. American Geophysical Union. All rights reserved.

© 2014. American Geophysical Union. All rights reserved.