Tracking the Variable North Atlantic Sink for Atmospheric CO 2

The fluxes of CO 2 between the atmosphere and ocean are large and variable, and understanding why the concentration of atmospheric CO 2 changes as it does, depends on accurately determining the details of those fluxes. One of the major obstacles in the way of quantifying this exchange is that there are too few measurements available, both temporally and geographically. Watson et al. (p. 1391 ) report results from a happy marriage of science and commerce—data collected by instruments fitted onto commercial ships plying the waters of the North Atlantic Ocean—that has generated the largest and most comprehensive set of measurements of ocean pCO 2 ever collected. These data allow the oceanic CO 2 sink to be monitored with unprecedented accuracy and will help researchers precisely map regional interannual air-sea fluxes. Data from instrumented commercial ships reveal substantial interannual variations of carbon dioxide flux between the ocean and the air. The oceans are a major sink for atmospheric carbon dioxide (CO 2 ). Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO 2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO 2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%. This approach offers the prospect of accurately monitoring the changing ocean CO 2 sink for those ocean basins that are well covered by shipping routes.