Tetrafluoromethane in the deep North Pacific Ocean

Abstract

Dissolved tetrafluoromethane (CF4) has been measured for the first time in the North Pacific Ocean. Surface water collected during calm weather is near equilibrium with the modern atmosphere. Deep water, isolated from atmospheric exchange for centuries, is near equilibrium with the preindustrial atmosphere, after accounting for an expected 5% addition of this low-solubility gas due to air injection during high-latitude deep-water formation. These results strongly suggest that dissolved CF4 is conservative in seawater and that the oceanic imprint of anthropogenic increases in atmospheric CF4 can be used as a time-dependent tracer of ocean ventilation and subsurface circulation processes. Although the continental lithosphere is a source of natural atmospheric CF4, we find no evidence of an oceanic lithospheric CF4 input into deep Pacific waters. The estimated upper limit of a potential oceanic lithospheric CF4 flux to the global atmosphere is on th order of 4% of that from the continental lithosphere. Copyright 2008 by the American Geophysical Union.