Bubbles: An estimate of their role in the global oceanic flux of carbon

Abstract

The amount of participate organic carbon (POC) formed annually via the scavenging of dissolved organic carbon (DOC) by bubbles is calculated to be 1.9 Gt C yr-1. In arriving at this estimate use was made of (1) published descriptions of the bubble spectrum associated with the alpha plumes beneath spilling wave crests, (2) the published relationship of stage A whitecap coverage to wind speed, (3) data on the scale depth of alpha plumes and on the rise velocity of bubbles coated with organic film, (4) published bubble scavenging efficiencies, and (5) recorded concentrations of DOC in oceanic surface waters. This rate of DOC scavenging by bubbles represents a 1.7% yr-1 turnover of the global oceanic DOC pool, and each year produces an amount of POC equal to 17% of the POC pool in the uppermost 300 m of the ocean. Bubble scavenging turns over the DOC present in the shallow layer of bubble influence once every 67 days. Moreover, within the depth of influence of large bubbles (uppermost 1.4 m of the water column), bubble scavenging represents an annual threefold turnover of the DOC pool and a POC production equivalent to thirtyfold of the POC pool. It is noted that the amount of DOC transformed into POC each year via bubble scavenging is equal to the amount of carbon present in the carbon dioxide estimated to be absorbed by the ocean each year from the atmosphere. Copyright 2001 by the American Geophysical Union.